ASN RSS https://amnat.org/ Latest press releases and announcements from the ASN en-us Thu, 21 Nov 2019 06:00:00 GMT 60 “Body size, light intensity, and nutrient supply determine plankton stoichiometry in mixotrophic plankton food webs” https://amnat.org/an/newpapers/Apr-Ho.html Pei-Chi Ho, Chun-Wei Chang, Fuh-Kwo Shiah, Pei-Ling Wang, Chih-hao Hsieh, and Ken H. Andersen (Apr 2020) Our field observations and model extend the light-nutrient theory determining plankton C:N with body size dependency Read the Article (Just Accepted) Plankton are tiny organisms that compose the base of aquatic food webs and critically support the growth of large animals such as fish and whales. Plankton are categorized into plant-like phytoplankton and animal-like zooplankton. Heterotrophic zooplankton usually have higher N and P body mass and their stoichiometry (C:N:P ratio) is less variable than photoautotrophic phytoplankton, and thus zooplankton face stoichiometric imbalance and decrease of assimilation efficiency consuming phytoplankton. Other than heterotrophic zooplankton and photoautotrophic phytoplankton, mixotrophs that can both photosynthesize and feed on prey may have stoichiometry between phytoplankton and zooplankton. In both freshwater and marine plankton communities, body size is the key trait that regulates trophic strategy and potentially stoichiometry. However, we lack the field studies that reveal the relationship between stoichiometry and plankton body size. Furthermore, the mechanisms determining the variation of stoichiometry with body size within a plankton community are yet to be explored. Ho et al. investigated the stoichiometry of subtropical freshwater and marine plankton and found that plankton C:N ratio is a unimodal function of body size, with the maximal C:N ratio occurring at 50 μm. Plankton C:N ratio also increases with light intensity and decreases with nutrient supply, which supports the light-nutrient hypothesis of ecological stoichiometry. To explain the unimodal pattern, they constructed a mixotrophic food web model in which the affinities of light harvest, inorganic nutrient uptake, and prey consumption depend on body size. Model simulations indicate that increasing C:N ratio of photoautotrophs smaller than 50 μm is due to the increase of photosynthetic C assimilation relative to inorganic N uptake as cell size increases. The C:N ratio of mixotrophs and heterotrophs larger than 50 μm decreases with body size, and it is mainly caused by low photosynthetic C assimilation and respiratory C loss. This study gives insights on how plankton stoichiometry is determined by body size, and extends the classical light-nutrient hypothesis to explain the variation of the stoichiometry of diverse plankton. Abstract Trophic strategy determines stoichiometry of plankton. In general, heterotrophic zooplankton have lower and more stable C:N and C:P ratios than photoautotrophic phytoplankton whereas mixotrophic protists, which consume prey and photosynthesize, have stoichiometry between zooplankton and phytoplankton. As trophic strategies change with cell size, body size may be a key trait influencing eukaryotic plankton stoichiometry. However, the relationship between body size and stoichiometry remains unclear. Here, we measured plankton size-fractionated C:N ratios under different intensities of light and nutrient supply in subtropical freshwater and marine systems. We found a unimodal body size-C:N ratio pattern with a maximum C:N ratio at ~50 μm diameter in marine and freshwater systems. Moreover, the variation in C:N ratios is mainly explained by body size, followed by light intensity and nutrient concentration. To investigate the mechanisms behind this unimodal pattern, we constructed a size-based plankton food web model in which the trophic strategy and C:N ratio is an emerging result. Our model simulations reproduce the unimodal pattern with C:N ratio of photoautotrophs ≤ 50 μm increasing with body size due to increase of photosynthetic carbon, whereas C:N ratios of organisms > 50 μm decreases with size due to decreasing photoautotrophic but increasing heterotrophic uptake. Based on our field observations and simulation, we extend the classic “light-nutrient” theory that determines plankton C:N ratio to include body size and trophic strategy dependency. We conclude that body size and size-dependent uptake of resources (light, nutrients and prey) determine plankton stoichiometry at various light and nutrient supplies. More forthcoming papers &raquo; <p>Pei-Chi Ho, Chun-Wei Chang, Fuh-Kwo Shiah, Pei-Ling Wang, Chih-hao Hsieh, and Ken H. Andersen (Apr 2020) </p> <p><b>Our field observations and model extend the light-nutrient theory determining plankton C:N with body size dependency </b></p> <p><i><a href="https://dx.doi.org/10.1086/707394">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>lankton are tiny organisms that compose the base of aquatic food webs and critically support the growth of large animals such as fish and whales. Plankton are categorized into plant-like phytoplankton and animal-like zooplankton. Heterotrophic zooplankton usually have higher N and P body mass and their stoichiometry (C:N:P ratio) is less variable than photoautotrophic phytoplankton, and thus zooplankton face stoichiometric imbalance and decrease of assimilation efficiency consuming phytoplankton. Other than heterotrophic zooplankton and photoautotrophic phytoplankton, mixotrophs that can both photosynthesize and feed on prey may have stoichiometry between phytoplankton and zooplankton. In both freshwater and marine plankton communities, body size is the key trait that regulates trophic strategy and potentially stoichiometry. However, we lack the field studies that reveal the relationship between stoichiometry and plankton body size. Furthermore, the mechanisms determining the variation of stoichiometry with body size within a plankton community are yet to be explored. Ho et al. investigated the stoichiometry of subtropical freshwater and marine plankton and found that plankton C:N ratio is a unimodal function of body size, with the maximal C:N ratio occurring at 50 μm. Plankton C:N ratio also increases with light intensity and decreases with nutrient supply, which supports the light-nutrient hypothesis of ecological stoichiometry. To explain the unimodal pattern, they constructed a mixotrophic food web model in which the affinities of light harvest, inorganic nutrient uptake, and prey consumption depend on body size. Model simulations indicate that increasing C:N ratio of photoautotrophs smaller than 50 μm is due to the increase of photosynthetic C assimilation relative to inorganic N uptake as cell size increases. The C:N ratio of mixotrophs and heterotrophs larger than 50 μm decreases with body size, and it is mainly caused by low photosynthetic C assimilation and respiratory C loss. This study gives insights on how plankton stoichiometry is determined by body size, and extends the classical light-nutrient hypothesis to explain the variation of the stoichiometry of diverse plankton. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>rophic strategy determines stoichiometry of plankton. In general, heterotrophic zooplankton have lower and more stable C:N and C:P ratios than photoautotrophic phytoplankton whereas mixotrophic protists, which consume prey and photosynthesize, have stoichiometry between zooplankton and phytoplankton. As trophic strategies change with cell size, body size may be a key trait influencing eukaryotic plankton stoichiometry. However, the relationship between body size and stoichiometry remains unclear. Here, we measured plankton size-fractionated C:N ratios under different intensities of light and nutrient supply in subtropical freshwater and marine systems. We found a unimodal body size-C:N ratio pattern with a maximum C:N ratio at ~50 μm diameter in marine and freshwater systems. Moreover, the variation in C:N ratios is mainly explained by body size, followed by light intensity and nutrient concentration. To investigate the mechanisms behind this unimodal pattern, we constructed a size-based plankton food web model in which the trophic strategy and C:N ratio is an emerging result. Our model simulations reproduce the unimodal pattern with C:N ratio of photoautotrophs ≤ 50 μm increasing with body size due to increase of photosynthetic carbon, whereas C:N ratios of organisms > 50 μm decreases with size due to decreasing photoautotrophic but increasing heterotrophic uptake. Based on our field observations and simulation, we extend the classic “light-nutrient” theory that determines plankton C:N ratio to include body size and trophic strategy dependency. We conclude that body size and size-dependent uptake of resources (light, nutrients and prey) determine plankton stoichiometry at various light and nutrient supplies. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 21 Nov 2019 06:00:00 GMT “Factors that can affect the spatial positioning of large and small individuals in clusters of sit-and-wait predators” https://amnat.org/an/newpapers/Apr-Scharf.html Inon Scharf (Apr 2020) The spatial distribution of large and small predators living in clusters is not random but depends on various factors Read the Article (Just Accepted) Not all predators chase after their prey but instead simply choose an ambush site and then sit and wait for prey to enter their detection range. Such predators usually live in clusters and are restricted to the type of area that provides the best conditions for ambush. In many of these clusters, the best positions are in the periphery, because prey arrive there first. Those predators in the central positions, therefore, catch less prey, as most prey are already intercepted by the predators in peripheral positions. Consequently, whether small or large, all predators should prefer peripheral locations in the cluster. It is common, nonetheless, to observe a difference in the positions within a cluster of small and large predators. A simulation model presented the spatial arrangement of such sit-and-wait predators. Small predators only occupied the cluster periphery under certain conditions, such as high prey abundance or low predator density. The reason is that such conditions moderate their need to frequently relocate, as too frequent relocation generally pushes the small predators away from the favorable peripheral positions. Large predators, in contrast, do not relocate so frequently, even when they are located in the cluster’s center, because they are able in any case to capture more prey than small predators. Moreover, any condition that triggers more relocation by large predators will bring them closer to the periphery. The model provides a possible mechanism for the distinct positions within the cluster of small and large predators. The model should be easily testable in systems of sit-and-wait predators, such as pit-building antlion larvae, which construct pit-traps in sand and ambush ants. Abstract Shadow competition, the interception of prey by sit-and-wait predators closest to the source of prey arrival, is prevalent in clusters of sit-and-wait predators. Peripheral positions in the cluster receive more prey and should thus be more frequently occupied. Models predicting spatial positioning in groups, however, usually ignore variability among group members. Here, I used a simulation model to determine conditions under which small and large sit-and-wait predators, which differ in their attack range, should differ in their spatial positions in the cluster. Small predators occupied peripheral positions more frequently than large predators at the simulation beginning, while the opposite held true as time advanced. Due to the large and small attack range of large and small predators respectively, small predators mistakenly relocated away from peripheral positions, while large predators did not relocate fast enough from inferior central positions. Any factor that moderated the frequent relocations of small predators or had the opposite effect on large predators assisted small or large predators respectively to reach the more profitable peripheral positions. Furthermore, any factor elevating shadow competition led to longer occupation of the periphery by large predators. This model may explain why sit-and-wait predators are not homogenously distributed in space according to size. More forthcoming papers &raquo; <p>Inon Scharf (Apr 2020) </p> <p><b>The spatial distribution of large and small predators living in clusters is not random but depends on various factors </b></p> <p><i><a href="https://dx.doi.org/10.1086/707392">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">N</span>ot all predators chase after their prey but instead simply choose an ambush site and then sit and wait for prey to enter their detection range. Such predators usually live in clusters and are restricted to the type of area that provides the best conditions for ambush. In many of these clusters, the best positions are in the periphery, because prey arrive there first. Those predators in the central positions, therefore, catch less prey, as most prey are already intercepted by the predators in peripheral positions. Consequently, whether small or large, all predators should prefer peripheral locations in the cluster. It is common, nonetheless, to observe a difference in the positions within a cluster of small and large predators. A simulation model presented the spatial arrangement of such sit-and-wait predators. Small predators only occupied the cluster periphery under certain conditions, such as high prey abundance or low predator density. The reason is that such conditions moderate their need to frequently relocate, as too frequent relocation generally pushes the small predators away from the favorable peripheral positions. Large predators, in contrast, do not relocate so frequently, even when they are located in the cluster’s center, because they are able in any case to capture more prey than small predators. Moreover, any condition that triggers more relocation by large predators will bring them closer to the periphery. The model provides a possible mechanism for the distinct positions within the cluster of small and large predators. The model should be easily testable in systems of sit-and-wait predators, such as pit-building antlion larvae, which construct pit-traps in sand and ambush ants. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>hadow competition, the interception of prey by sit-and-wait predators closest to the source of prey arrival, is prevalent in clusters of sit-and-wait predators. Peripheral positions in the cluster receive more prey and should thus be more frequently occupied. Models predicting spatial positioning in groups, however, usually ignore variability among group members. Here, I used a simulation model to determine conditions under which small and large sit-and-wait predators, which differ in their attack range, should differ in their spatial positions in the cluster. Small predators occupied peripheral positions more frequently than large predators at the simulation beginning, while the opposite held true as time advanced. Due to the large and small attack range of large and small predators respectively, small predators mistakenly relocated away from peripheral positions, while large predators did not relocate fast enough from inferior central positions. Any factor that moderated the frequent relocations of small predators or had the opposite effect on large predators assisted small or large predators respectively to reach the more profitable peripheral positions. Furthermore, any factor elevating shadow competition led to longer occupation of the periphery by large predators. This model may explain why sit-and-wait predators are not homogenously distributed in space according to size. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 21 Nov 2019 06:00:00 GMT “Maintenance of fertility in the face of meiotic drive” https://amnat.org/an/newpapers/Apr-Meade.html Lara Meade, Sam Finnegan, Ridhima Kad, Kevin Fowler, and Andrew Pomiankowski (Apr 2020) Males with meiotic drive have enlarged testes to maintain high fertility despite the destruction of half their sperm Read the Article (Just Accepted) Meiotic drive genes are selfish genetic elements that cause the destruction of sperm that do not carry the selfish gene. The consequent loss imposes a severe fertility disadvantage on males which carrying the drive gene (“drive males”). Dr. Lara Meade, Professor Andrew Pomiankowski and colleagues at University College London have uncovered an entirely novel response to meiotic drive. In the Malaysian stalk-eyed fly, Teleopsis dalmanni, X-linked meiotic drive causes the destruction of all Y-sperm. Surprisingly the fertility of males carrying the drive gene is not reduced. This is even the case when males are challenged to mate with large numbers of females over a short period of time. Drive and wildtype sperm delivery is identical. This highly unusual finding has a simple explanation. On dissection, the authors found that drive males have greatly enlarged testis size—the organ that produces sperm. Faced with sperm destruction, drive males compensate by increasing sperm production, bringing their fertility up to the level of wildtype males. Increased testis size comes at a cost. Drive males have small eyespan—the highly sexually selected trait females use in their mate choice. Drive males also have small accessory glands—organs that produce essential components of the ejaculate. The authors suggest these patterns of trait development are connected. Small eyespan means drive males are unattractive and gain few mating opportunities. So, investment in accessory gland (which enables higher mating rates) gives a low return. It is better to divert resources into testis. This allows drive males to deliver sufficient sperm to compete under the conditions of high sperm competition seen in stalk-eyed flies. Bizarrely, these responses to drive not only improve individual male fitness, but also intensify the transmission of the drive gene itself. The authors suggest that this may contribute to the persistence of this selfish gene in natural populations of stalk-eyed flies. Abstract Selfish genetic elements that gain a transmission advantage through the destruction of sperm have grave implications for drive male fertility. In the X-linked SR meiotic drive system of a stalk-eyed fly, we found that drive males have greatly enlarged testes and maintain high fertility despite the destruction of half their sperm, even when challenged with fertilizing large numbers of females. Conversely, we observed reduced allocation of resources to the accessory glands that probably explains the lower mating frequency of SR males. Body size and eyespan were also reduced, which are likely to impair viability and pre-copulatory success. We discuss the potential evolutionary causes of these differences between drive and standard males. More forthcoming papers &raquo; <p>Lara Meade, Sam Finnegan, Ridhima Kad, Kevin Fowler, and Andrew Pomiankowski (Apr 2020) </p> <p><b>Males with meiotic drive have enlarged testes to maintain high fertility despite the destruction of half their sperm </b></p> <p><i><a href="https://dx.doi.org/10.1086/707372">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>eiotic drive genes are selfish genetic elements that cause the destruction of sperm that do not carry the selfish gene. The consequent loss imposes a severe fertility disadvantage on males which carrying the drive gene (“drive males”). </p><p>Dr. Lara Meade, Professor Andrew Pomiankowski and colleagues at University College London have uncovered an entirely novel response to meiotic drive. In the Malaysian stalk-eyed fly, <i>Teleopsis dalmanni</i>, X-linked meiotic drive causes the destruction of all Y-sperm. Surprisingly the fertility of males carrying the drive gene is not reduced. This is even the case when males are challenged to mate with large numbers of females over a short period of time. Drive and wildtype sperm delivery is identical. This highly unusual finding has a simple explanation. On dissection, the authors found that drive males have greatly enlarged testis size—the organ that produces sperm. Faced with sperm destruction, drive males compensate by increasing sperm production, bringing their fertility up to the level of wildtype males. </p><p>Increased testis size comes at a cost. Drive males have small eyespan—the highly sexually selected trait females use in their mate choice. Drive males also have small accessory glands—organs that produce essential components of the ejaculate. The authors suggest these patterns of trait development are connected. Small eyespan means drive males are unattractive and gain few mating opportunities. So, investment in accessory gland (which enables higher mating rates) gives a low return. It is better to divert resources into testis. This allows drive males to deliver sufficient sperm to compete under the conditions of high sperm competition seen in stalk-eyed flies. </p><p>Bizarrely, these responses to drive not only improve individual male fitness, but also intensify the transmission of the drive gene itself. The authors suggest that this may contribute to the persistence of this selfish gene in natural populations of stalk-eyed flies. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>elfish genetic elements that gain a transmission advantage through the destruction of sperm have grave implications for drive male fertility. In the X-linked SR meiotic drive system of a stalk-eyed fly, we found that drive males have greatly enlarged testes and maintain high fertility despite the destruction of half their sperm, even when challenged with fertilizing large numbers of females. Conversely, we observed reduced allocation of resources to the accessory glands that probably explains the lower mating frequency of SR males. Body size and eyespan were also reduced, which are likely to impair viability and pre-copulatory success. We discuss the potential evolutionary causes of these differences between drive and standard males. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 19 Nov 2019 06:00:00 GMT “Life history plasticity and water use trade-offs associated with drought resistance in a clade of California jewelflowers” https://amnat.org/an/newpapers/Apr-Pearse.html Ian S. Pearse, Jessica M. Aguilar, and Sharon Y. Strauss (Apr 2020) Mustards live in drought; having trait plasticity keeps their fitness high Read the Article (Just Accepted) Water limits the success and the distribution of plants in many parts of the world. The availability of water is rapidly changing the environment. Longer, more severe droughts are predicted to become the norm in places where they were once uncommon. Drought-resistant plants are those that thrive and produce high fitness in the low water conditions. Drought resistance is caused by numerous aspects of a plant’s biology, such as the timing of its life cycle, its traits that limit water loss, and its traits that allow it to persist despite water loss. Drought resistance is fundamentally a plastic trait, describing the relationship between water and plant fitness. As plants evolve, are there tradeoffs to drought resistance, such as the ability to capitalize on high water environments? And what mechanisms cause these tradeoffs? Ian Pearse and colleagues explore the evolution of drought resistance in a clade of mustards, the jewelflowers. Many jewelflower species, native to the western USA, grow in extreme, water-limited habitats, such as scree slopes, deserts, and serpentine barrens. Species that were the most drought-resistant were unable to capitalize on high water environments. These species tended to live in the most drought-prone environments. They coped with drought by having a short and fixed life span, producing seeds before the harshest summer conditions. In contrast, less drought-resistant species could extend their flowering late into the summer and achieve high fitness in high water environments. Thus, flowering phenology and annual lifespan underlie a fundamental tradeoff between fitness at high and low water in these short-lived plants. By exploring how plants produce fitness over water conditions, we will better understand how drought resistance evolves, what traits underlie it, and how plants will cope with drier environments. Abstract Water limitation is a primary driver of plant geographic distributions and individual plant fitness. Drought resistance is the ability to survive and reproduce despite limited water, and numerous studies have explored its physiological basis in plants. However, it is unclear how drought resistance and trade-offs associated with drought resistance evolve within plant clades. We quantified the relationship between water availability and fitness for 13 short-lived plant taxa in the Streptanthus clade that vary in their phenology and the availability of water in the environments where they occur. We derived two parameters from these relationships: plant fitness when water is not limiting, and the water inflection point (WIF), the watering level at which additional water is most efficiently turned into fitness. We used phylogenetic comparative methods to explore trade-offs related to drought resistance and trait plasticity, and the degree to which water relationship parameters are conserved. Taxa from drier climates produced fruits at the lowest water levels, had a lower WIF, flowered earlier, had shorter lifespans, more plastic water use efficiency (WUE), and lower fitness at non-limiting water. In contrast, later-flowering Streptanthus taxa from less xeric climates experienced high fitness at non-limiting water but had no fitness at the lowest water levels. Across the clade, we found a trade-off between drought resistance and fitness at high water, though a single ruderal species was an outlier in this relationship. Our results suggest that drought escape trades off with maximal fitness under non-limiting water, and both are tied to phenology. We also found that variation in trait plasticity determines how different plant species produce fitness over a water gradient. More forthcoming papers &raquo; <p>Ian S. Pearse, Jessica M. Aguilar, and Sharon Y. Strauss (Apr 2020) </p> <p><b>Mustards live in drought; having trait plasticity keeps their fitness high </b></p> <p><i><a href="https://dx.doi.org/10.1086/707371">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>ater limits the success and the distribution of plants in many parts of the world. The availability of water is rapidly changing the environment. Longer, more severe droughts are predicted to become the norm in places where they were once uncommon. Drought-resistant plants are those that thrive and produce high fitness in the low water conditions. Drought resistance is caused by numerous aspects of a plant’s biology, such as the timing of its life cycle, its traits that limit water loss, and its traits that allow it to persist despite water loss. Drought resistance is fundamentally a plastic trait, describing the relationship between water and plant fitness. As plants evolve, are there tradeoffs to drought resistance, such as the ability to capitalize on high water environments? And what mechanisms cause these tradeoffs? </p><p>Ian Pearse and colleagues explore the evolution of drought resistance in a clade of mustards, the jewelflowers. Many jewelflower species, native to the western USA, grow in extreme, water-limited habitats, such as scree slopes, deserts, and serpentine barrens. Species that were the most drought-resistant were unable to capitalize on high water environments. These species tended to live in the most drought-prone environments. They coped with drought by having a short and fixed life span, producing seeds before the harshest summer conditions. In contrast, less drought-resistant species could extend their flowering late into the summer and achieve high fitness in high water environments. Thus, flowering phenology and annual lifespan underlie a fundamental tradeoff between fitness at high and low water in these short-lived plants. By exploring how plants produce fitness over water conditions, we will better understand how drought resistance evolves, what traits underlie it, and how plants will cope with drier environments. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>ater limitation is a primary driver of plant geographic distributions and individual plant fitness. Drought resistance is the ability to survive and reproduce despite limited water, and numerous studies have explored its physiological basis in plants. However, it is unclear how drought resistance and trade-offs associated with drought resistance evolve within plant clades. We quantified the relationship between water availability and fitness for 13 short-lived plant taxa in the <i>Streptanthus</i> clade that vary in their phenology and the availability of water in the environments where they occur. We derived two parameters from these relationships: plant fitness when water is not limiting, and the water inflection point (WIF), the watering level at which additional water is most efficiently turned into fitness. We used phylogenetic comparative methods to explore trade-offs related to drought resistance and trait plasticity, and the degree to which water relationship parameters are conserved. Taxa from drier climates produced fruits at the lowest water levels, had a lower WIF, flowered earlier, had shorter lifespans, more plastic water use efficiency (WUE), and lower fitness at non-limiting water. In contrast, later-flowering <i>Streptanthus</i> taxa from less xeric climates experienced high fitness at non-limiting water but had no fitness at the lowest water levels. Across the clade, we found a trade-off between drought resistance and fitness at high water, though a single ruderal species was an outlier in this relationship. Our results suggest that drought escape trades off with maximal fitness under non-limiting water, and both are tied to phenology. We also found that variation in trait plasticity determines how different plant species produce fitness over a water gradient. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 19 Nov 2019 06:00:00 GMT “Pathogens and mutualists as joint drivers of host species coexistence and turnover: implications for plant competition and succession” https://amnat.org/an/newpapers/Apr-Jiang.html Jiang Jiang, Karen C. Abbott, Mara Baudena, Maarten B. Eppinga, James A. Umbanhowar, and James Bever (Apr 2020) Pathogens and mutualists as joint drivers of host species coexistence and turnover Read the Article (Just Accepted) In plant ecology, host-host interactions can be influenced by interactions with pathogens and mutualists. Recent studies have demonstrated that either a pathogen or a mutualist can generate a positive feedback and cause alternative stable states, and either may generate a negative feedback and promoting coexistence. However, the joint influence of both microbes on plant-plant interactions has rarely been studied. When pathogens and mutualists are both present, the potential for simultaneous positive and negative feedbacks can generate a wide range of possible effects on host species coexistence and turnover. This study uses a simple model to produce novel and surprising outcomes about the dynamics of plant-soil feedbacks and their consequences for host species competition and succession. The authors identify the conditions under which the joint actions of pathogens and mutualists can mediate coexistence. Interestingly, they find that a combination of positive and negative plant-microbe feedbacks could result in a coexistence state as an alternative stable state, alongside exclusion of some of the community members. The outcome may not be detectable through the typical design of experimental plant-soil feedback studies. The study provides guidance for empiricists to test these model predictions with a new type of pot experiment that independently and factorially manipulates components of plant microbiome. Such an experiment might evaluate plant fitness and competitive effects across a range of initial densities of two plant species factorially manipulated with the presence and timing of introduction of a pathogen and a mutualist. Abstract The potential for either pathogens or mutualists to alter the outcome of interactions between host species has been clearly demonstrated experimentally, but our understanding of their joint influence remains limited. Individually, pathogens and mutualists can each stabilize (via negative feedback) or destabilize (via positive feedback) host-host interactions. When pathogens and mutualist are both present, the potential for simultaneous positive and negative feedbacks can generate a wide range of possible effects on host species coexistence and turnover. Extending existing theoretical frameworks, we explore the range of dynamics generated by simultaneous interactions with pathogens and mutualists and identify the conditions for pathogen or mutualist mediation of host coexistence. We then explore the potential role of microbial mutualists and pathogens in plant species turnover during succession. We show how a combination of positive and negative plant-microbe feedbacks can generate a coexistence state that is part of a set of alternative stable states. This result implies that the outcomes of coexistence from classical plant-soil feedback experiments may be susceptible to disturbances, and that empirical investigations of microbially-mediated coexistence would benefit from consideration of interactive effects of feedbacks generated from different distinct components of the plant microbiome. More forthcoming papers &raquo; <p>Jiang Jiang, Karen C. Abbott, Mara Baudena, Maarten B. Eppinga, James A. Umbanhowar, and James Bever (Apr 2020) </p> <p><b>Pathogens and mutualists as joint drivers of host species coexistence and turnover </b></p> <p><i><a href="https://dx.doi.org/10.1086/707355">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n plant ecology, host-host interactions can be influenced by interactions with pathogens and mutualists. Recent studies have demonstrated that either a pathogen or a mutualist can generate a positive feedback and cause alternative stable states, and either may generate a negative feedback and promoting coexistence. However, the joint influence of both microbes on plant-plant interactions has rarely been studied. When pathogens and mutualists are both present, the potential for simultaneous positive and negative feedbacks can generate a wide range of possible effects on host species coexistence and turnover. This study uses a simple model to produce novel and surprising outcomes about the dynamics of plant-soil feedbacks and their consequences for host species competition and succession. The authors identify the conditions under which the joint actions of pathogens and mutualists can mediate coexistence. Interestingly, they find that a combination of positive and negative plant-microbe feedbacks could result in a coexistence state as an alternative stable state, alongside exclusion of some of the community members. The outcome may not be detectable through the typical design of experimental plant-soil feedback studies. The study provides guidance for empiricists to test these model predictions with a new type of pot experiment that independently and factorially manipulates components of plant microbiome. Such an experiment might evaluate plant fitness and competitive effects across a range of initial densities of two plant species factorially manipulated with the presence and timing of introduction of a pathogen and a mutualist. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he potential for either pathogens or mutualists to alter the outcome of interactions between host species has been clearly demonstrated experimentally, but our understanding of their joint influence remains limited. Individually, pathogens and mutualists can each stabilize (via negative feedback) or destabilize (via positive feedback) host-host interactions. When pathogens and mutualist are both present, the potential for simultaneous positive and negative feedbacks can generate a wide range of possible effects on host species coexistence and turnover. Extending existing theoretical frameworks, we explore the range of dynamics generated by simultaneous interactions with pathogens and mutualists and identify the conditions for pathogen or mutualist mediation of host coexistence. We then explore the potential role of microbial mutualists and pathogens in plant species turnover during succession. We show how a combination of positive and negative plant-microbe feedbacks can generate a coexistence state that is part of a set of alternative stable states. This result implies that the outcomes of coexistence from classical plant-soil feedback experiments may be susceptible to disturbances, and that empirical investigations of microbially-mediated coexistence would benefit from consideration of interactive effects of feedbacks generated from different distinct components of the plant microbiome. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 19 Nov 2019 06:00:00 GMT “Ecological and evolutionary stochasticity shape natural selection” https://amnat.org/an/newpapers/Apr-Start-A.html Denon Start, Arthur E. Weis, and Benjamin Gilbert (Apr 2020) Random ecological and evolutionary processes have deterministic consequences Read the Article (Just Accepted)Abstract The distribution of biodiversity depends on the combined and interactive effects of ecological and evolutionary processes. The joint contribution of these processes has focused almost exclusively on deterministic effects, even though mechanisms that increase the importance of random ecological processes are expected to also increase the importance of random evolutionary processes. Here we manipulate the sizes of old-field fragments to generate correlated sampling effects for a focal population (a gall maker) and its enemy community. Traits and communities were more variable in smaller patches. However, because of the preference of some enemies for some trait values (gall sizes), random variation in population mean trait values exacerbated differences in community composition. The random distribution of traits and interactions created predictable but highly variable patterns of natural selection. Our study highlights how stochastic processes can affect ecological and evolutionary processes structuring the strength and direction of selection locally and at larger scales. More forthcoming papers &raquo; <p>Denon Start, Arthur E. Weis, and Benjamin Gilbert (Apr 2020)</p> <p><b>Random ecological and evolutionary processes have deterministic consequences </b></p> <p><i><a href="https://dx.doi.org/10.1086/707364">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he distribution of biodiversity depends on the combined and interactive effects of ecological and evolutionary processes. The joint contribution of these processes has focused almost exclusively on deterministic effects, even though mechanisms that increase the importance of random ecological processes are expected to also increase the importance of random evolutionary processes. Here we manipulate the sizes of old-field fragments to generate correlated sampling effects for a focal population (a gall maker) and its enemy community. Traits and communities were more variable in smaller patches. However, because of the preference of some enemies for some trait values (gall sizes), random variation in population mean trait values exacerbated differences in community composition. The random distribution of traits and interactions created predictable but highly variable patterns of natural selection. Our study highlights how stochastic processes can affect ecological and evolutionary processes structuring the strength and direction of selection locally and at larger scales. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 19 Nov 2019 06:00:00 GMT “Local adaptation to biotic interactions: a meta-analysis across latitudes” https://amnat.org/an/newpapers/Mar-Hargreaves.html Anna L. Hargreaves, Rachel M. Germain, Megan Bontrager, Joshua Persi, and Amy L. Angert (March 2020) Global synthesis finds species interactions strongly affect fitness, but only broadly drive local adaptation in tropics Read the Article (Just Accepted) Adaption to local conditions drives biological diversification, but what drives local adaptation? Famous experiments have shown populations adapt to their local climates, soils, even pollution, but how often they adapt to their local communities has remained a mystery. To solve it, researchers at McGill University and the University of British Columbia synthesized more than 125 studies testing local adaptation in over 100 species. “As field biologists we’d seen firsthand how strongly interactions can affect fitness,” says Anna Hargreaves, who lead the study. “I thought for sure local adaptation to interactions was widespread and we just needed a meta-analysis to show it. But—surprise!” The authors found frequent local adaptation across studies and that negative interactions like being eaten or outcompeted strongly reduced performance. Nevertheless, local adaptation was not stronger or more common when experiments left interactions intact.So why don’t interactions drive local adaptation even though they affect fitness? Maybe, the authors suggest, interactions vary too much to exert consistent divergent selection, as individuals move around and populations grow and crash. Or maybe we’re looking in the wrong places. Interactions are often thought to be strongest in the tropics, but most data are from temperate zones. When the authors analyzed tropical data separately a stronger signal of local adaptation to interactions emerged.“It doesn’t explain why interactions don’t drive local adaptation more often in temperate ecosystems, but it is intriguing evidence that interactions might be more evolutionarily important in the tropics,” says Hargreaves. The authors say more direct tests of what drives local adaptation, especially studies of positive interactions and tropical species, are needed before we know the real scope of local adaptation to interactions. Abstract Adaptation to local conditions can increase species’ geographic distributions and rates of diversification, but which components of the environment commonly drive local adaptation—particularly the importance of biotic interactions—is unclear. Biotic interactions should drive local adaptation when they impose consistent divergent selection; if this is common we expect transplant experiments to detect more frequent and stronger local adaptation when biotic interactions are left intact. We tested this hypothesis using a meta-analysis of transplant experiments from >125 studies (mostly on plants). Overall, local adaptation was common and biotic interactions affected fitness. Nevertheless, local adaptation was neither more common nor stronger when biotic interactions were left intact, either between experimental treatments within studies (control vs. biotic interactions experimentally manipulated) or between studies that used natural vs. biotically-altered transplant environments. However, the effect of ameliorating negative interactions varied with latitude, suggesting that interactions may promote local adaptation more often in tropical vs. temperate ecosystems, though few tropical studies were available to test this. Our results suggest that biotic interactions often fail to drive local adaptation even though they strongly affect fitness, perhaps because temperate biotic environments are unpredictable at the spatiotemporal scales required for local adaptation. More forthcoming papers &raquo; <p>Anna L. Hargreaves, Rachel M. Germain, Megan Bontrager, Joshua Persi, and Amy L. Angert (March 2020) </p> <p><b>Global synthesis finds species interactions strongly affect fitness, but only broadly drive local adaptation in tropics </b></p> <p><i><a href="https://dx.doi.org/10.1086/707323">Read the Article</a></i> (Just Accepted) </p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>daption to local conditions drives biological diversification, but what drives local adaptation? Famous experiments have shown populations adapt to their local climates, soils, even pollution, but how often they adapt to their local communities has remained a mystery. To solve it, researchers at McGill University and the University of British Columbia synthesized more than 125 studies testing local adaptation in over 100 species.</p> <p>&ldquo;As field biologists we&rsquo;d seen firsthand how strongly interactions can affect fitness,&rdquo; says Anna Hargreaves, who lead the study. &ldquo;I thought for sure local adaptation to interactions was widespread and we just needed a meta-analysis to show it. But&mdash;surprise!&rdquo; The authors found frequent local adaptation across studies and that negative interactions like being eaten or outcompeted strongly reduced performance. Nevertheless, local adaptation was not stronger or more common when experiments left interactions intact.</p><p>So why don&rsquo;t interactions drive local adaptation even though they affect fitness? Maybe, the authors suggest, interactions vary too much to exert consistent divergent selection, as individuals move around and populations grow and crash. Or maybe we&rsquo;re looking in the wrong places. Interactions are often thought to be strongest in the tropics, but most data are from temperate zones. When the authors analyzed tropical data separately a stronger signal of local adaptation to interactions emerged.</p><p>“It doesn’t explain why interactions don’t drive local adaptation more often in temperate ecosystems, but it is intriguing evidence that interactions might be more evolutionarily important in the tropics,” says Hargreaves. The authors say more direct tests of what drives local adaptation, especially studies of positive interactions and tropical species, are needed before we know the real scope of local adaptation to interactions.</p> <hr /><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>daptation to local conditions can increase species’ geographic distributions and rates of diversification, but which components of the environment commonly drive local adaptation—particularly the importance of biotic interactions—is unclear. Biotic interactions should drive local adaptation when they impose consistent divergent selection; if this is common we expect transplant experiments to detect more frequent and stronger local adaptation when biotic interactions are left intact. We tested this hypothesis using a meta-analysis of transplant experiments from >125 studies (mostly on plants). Overall, local adaptation was common and biotic interactions affected fitness. Nevertheless, local adaptation was neither more common nor stronger when biotic interactions were left intact, either between experimental treatments within studies (control vs. biotic interactions experimentally manipulated) or between studies that used natural vs. biotically-altered transplant environments. However, the effect of ameliorating negative interactions varied with latitude, suggesting that interactions may promote local adaptation more often in tropical vs. temperate ecosystems, though few tropical studies were available to test this. Our results suggest that biotic interactions often fail to drive local adaptation even though they strongly affect fitness, perhaps because temperate biotic environments are unpredictable at the spatiotemporal scales required for local adaptation. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 18 Nov 2019 06:00:00 GMT “Context dependence of local adaptation to abiotic and biotic environments: a quantitative and qualitative synthesis” https://amnat.org/an/newpapers/Mar-Briscoe-Runquist.html Ryan D. Briscoe Runquist, Amanda J. Gorton, Jeremy B. Yoder, Nicholas J. Deacon, Jake J. Grossman, Shan Kothari, Marta P. Lyons, Seema N. Sheth, Peter Tiffin, and David A. Moeller (March 2020) Metasynthesis reveals context dependent local adaptation to abiotic and biotic factors but bias in experimental design Read the Article (Just Accepted) Local adaptation occurs when environmental variation across the landscape causes changes in traits that optimize fitness in alternative environments. Decades of studies have shown that local adaptation is common and occurs in response to a wide variety of environmental factors. But what types of environmental variables lead to the greatest expression of local adaptation? Is it abiotic variables (e.g. temperature) or biotic variables (e.g. competition)? Furthermore, how is the importance of these variables influenced by the ways in which scientists design and conduct experiments to test local adaptation? Briscoe Runquist and others at the University of Minnesota combined two summary approaches to address these questions. They first used a meta-analysis to summarize data from 31 papers that manipulated both abiotic and biotic factors simultaneously. They found that biotic factors have stronger effects on fitness than abiotic factors. The extent of local adaptation was context-dependent: populations expressed greater local adaptation to their abiotic environment when they also experienced their home biotic environment. They also found the fitness effects of biotic factors was greater at low than high latitudes whereas the opposite was true for abiotic factors, consistent with longstanding predictions. The researchers then used a qualitative meta-synthesis to analyze the text of articles to identify common themes and experimental biases in studies of local adaptation. Meta-syntheses are common in medical and social sciences but are new to ecology and evolution. The researchers found that the selection of abiotic and biotic variables was often biased towards extreme implementations (presence/absence, rare environments) that do not reflect the gradients often found in nature. Further, tests of local adaptation were nearly always conducted on short-lived, sessile organisms even though these are relatively uncommon in nature. Last, they identified opportunities moving forward for planning experiments that incorporate greater natural variation in abiotic and biotic environments. Abstract Understanding how spatially-variable selection shapes adaptation is an area of longstanding interest in evolutionary ecology. Recent meta-analyses have quantified the extent of local adaptation, but the relative importance of abiotic and biotic factors in driving population divergence remains poorly understood. To address this gap, we combined a quantitative meta-analysis and a qualitative meta-synthesis to (1) quantify the magnitude of local adaptation to abiotic and biotic factors and (2) characterize major themes that influence the motivation and design of experiments that seek to test for local adaptation. Using local-foreign contrasts as a metric of local adaptation (or maladaptation), we found that local adaptation was greater in the presence than absence of a biotic interactor, especially for plants. We also found that biotic environments had stronger effects on fitness than abiotic environments when ignoring whether those environments were local versus foreign. Finally, biotic effects were stronger at low latitudes and abiotic effects were stronger at high latitudes. Our qualitative analysis revealed that the lens through which local adaptation has been examined differs for abiotic and biotic factors. It also revealed biases in the design and implementation of experiments that make quantitative results challenging to interpret and provided directions for future research. More forthcoming papers &raquo; <p>Ryan D. Briscoe Runquist, Amanda J. Gorton, Jeremy B. Yoder, Nicholas J. Deacon, Jake J. Grossman, Shan Kothari, Marta P. Lyons, Seema N. Sheth, Peter Tiffin, and David A. Moeller (March 2020) </p> <p><b>Metasynthesis reveals context dependent local adaptation to abiotic and biotic factors but bias in experimental design </b></p> <p><i><a href="https://dx.doi.org/10.1086/707322">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">L</span>ocal adaptation occurs when environmental variation across the landscape causes changes in traits that optimize fitness in alternative environments. Decades of studies have shown that local adaptation is common and occurs in response to a wide variety of environmental factors. But what types of environmental variables lead to the greatest expression of local adaptation? Is it abiotic variables (e.g. temperature) or biotic variables (e.g. competition)? Furthermore, how is the importance of these variables influenced by the ways in which scientists design and conduct experiments to test local adaptation? </p><p>Briscoe Runquist and others at the University of Minnesota combined two summary approaches to address these questions. They first used a meta-analysis to summarize data from 31 papers that manipulated both abiotic and biotic factors simultaneously. They found that biotic factors have stronger effects on fitness than abiotic factors. The extent of local adaptation was context-dependent: populations expressed greater local adaptation to their abiotic environment when they also experienced their home biotic environment. They also found the fitness effects of biotic factors was greater at low than high latitudes whereas the opposite was true for abiotic factors, consistent with longstanding predictions. </p><p>The researchers then used a qualitative meta-synthesis to analyze the text of articles to identify common themes and experimental biases in studies of local adaptation. Meta-syntheses are common in medical and social sciences but are new to ecology and evolution. The researchers found that the selection of abiotic and biotic variables was often biased towards extreme implementations (presence/absence, rare environments) that do not reflect the gradients often found in nature. Further, tests of local adaptation were nearly always conducted on short-lived, sessile organisms even though these are relatively uncommon in nature. Last, they identified opportunities moving forward for planning experiments that incorporate greater natural variation in abiotic and biotic environments. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">U</span>nderstanding how spatially-variable selection shapes adaptation is an area of longstanding interest in evolutionary ecology. Recent meta-analyses have quantified the extent of local adaptation, but the relative importance of abiotic and biotic factors in driving population divergence remains poorly understood. To address this gap, we combined a quantitative meta-analysis and a qualitative meta-synthesis to (1) quantify the magnitude of local adaptation to abiotic and biotic factors and (2) characterize major themes that influence the motivation and design of experiments that seek to test for local adaptation. Using local-foreign contrasts as a metric of local adaptation (or maladaptation), we found that local adaptation was greater in the presence than absence of a biotic interactor, especially for plants. We also found that biotic environments had stronger effects on fitness than abiotic environments when ignoring whether those environments were local versus foreign. Finally, biotic effects were stronger at low latitudes and abiotic effects were stronger at high latitudes. Our qualitative analysis revealed that the lens through which local adaptation has been examined differs for abiotic and biotic factors. It also revealed biases in the design and implementation of experiments that make quantitative results challenging to interpret and provided directions for future research. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 18 Nov 2019 06:00:00 GMT Applications for the 2020 ASN Student Research Awards, due January 31 https://amnat.org/announcements/AWAStuResearch.html The ASN Student Research Awards: The ASN Student Research Awards support research by student members that advances the goals of the society: the conceptual unification of ecology, evolution, or behavior. Each award consists of a $2,000 check to the candidate. An applicant must must hold a bachelor’s degree or equivalent, must have passed to candidacy in a Ph.D. program or equivalent, and must be at least one year from completing the Ph.D. Projects in all types of research (i.e., laboratory, field, theory) are encouraged. A total of ten proposals will receive awards. Proposals will be judged on originality, strength, and significance of the questions being addressed, prospects for significant results, and the match between the proposed research and the ASN mission. If not already a member of the ASN (student membership is international, and US$20), awardees are expected to join ASN at the time of the award. Applications include four elements: 1) A two-page proposal describing the research project for which support is requested; 2) A budget with justification (one page); 3) a short curriculum vitae (two pages); 4) a statement from the Ph.D. supervisor that verifies that the applicant meets the eligibility requirements, and confirms the supervisor’s support for the proposed project (one page). Detailed Instructions: The two-page proposal should describe a specific research project for which support is requested.&nbsp; While some background and context is appropriate, the proposal should not be a general overview of the applicant’s complete dissertation.&nbsp; The proposal should have a title at the top of the first page.&nbsp; The proposal should be single-spaced, have 1-inch (2.5cm) margins all around, and be written in an 11- or 12-point standard font on 8.5 x 11 inch pages.&nbsp; A list of references should follow, but is not included in the 2-page limit. The budget and budget justification should clearly support the specific proposed project. If total costs of the project exceed $2000, some indication of how the applicant intends to find support for remaining costs should be given. The CV should meet the same formatting requirements as the project description. All materials should be compiled into one PDF.&nbsp; The .pdf filename should be in the format Lastname_Firstname_SRA (example:&nbsp; Wright_Sewall_SRA.pdf). Send your application via e-mail to Dr. Kenneth Whitney at whitneyk@unm.edu with “ASN Student Research Award [last name]” in the subject line. Deadline for submission of all materials is January 31, 2020. Judging. Applications will be reviewed by a committee of six persons: three faculty-level researchers and three graduate students. Senior-level appointments are made by the President-Elect. Members each serve for three years; the longest-serving committee member serves as chair in her/his final year on the committee. Graduate student appointments are made from the Graduate Council, in consultation with the President-Elect. &nbsp; <p><strong>The ASN Student Research Awards:</strong></p> <p>The ASN Student Research Awards support research by student members that advances the goals of the society: the conceptual unification of ecology, evolution, or behavior. Each award consists of a $2,000 check to the candidate. An applicant must must hold a bachelor&rsquo;s degree or equivalent, must have passed to candidacy in a Ph.D. program or equivalent, and must be at least one year from completing the Ph.D. Projects in all types of research (i.e., laboratory, field, theory) are encouraged. A total of ten proposals will receive awards. Proposals will be judged on originality, strength, and significance of the questions being addressed, prospects for significant results, and the match between the proposed research and the ASN mission. If not already a member of the ASN (student membership is international, and US$20), awardees are expected to join ASN at the time of the award.</p> <p>Applications include four elements: 1) A two-page proposal describing the research project for which support is requested; 2) A budget with justification (one page); 3) a short curriculum vitae (two pages); 4) a statement from the Ph.D. supervisor that verifies that the applicant meets the eligibility requirements, and confirms the supervisor&rsquo;s support for the proposed project (one page).</p> <p>Detailed Instructions:</p> <ol> <li>The two-page proposal should describe a specific research project for which support is requested.&nbsp; While some background and context is appropriate, the proposal should not be a general overview of the applicant&rsquo;s complete dissertation.&nbsp; The proposal should have a title at the top of the first page.&nbsp; The proposal should be single-spaced, have 1-inch (2.5cm) margins all around, and be written in an 11- or 12-point standard font on 8.5 x 11 inch pages.&nbsp; A list of references should follow, but is not included in the 2-page limit.</li> <li>The budget and budget justification should clearly support the specific proposed project. If total costs of the project exceed $2000, some indication of how the applicant intends to find support for remaining costs should be given.</li> <li>The CV should meet the same formatting requirements as the project description.</li> <li>All materials should be compiled into one PDF.&nbsp; The .pdf filename should be in the format Lastname_Firstname_SRA (example:&nbsp; Wright_Sewall_SRA.pdf).</li> <li>Send your application via e-mail to Dr. Kenneth Whitney at <a href="mailto:whitneyk@unm.edu?subject=ASN%20Student%20Research%20Award">whitneyk@unm.edu</a> with &ldquo;ASN Student Research Award [last name]&rdquo; in the subject line.</li> <li><strong>Deadline for submission of all materials is January 31, 2020.</strong></li> </ol> <p><strong>Judging. </strong></p> <p>Applications will be reviewed by a committee of six persons: three faculty-level researchers and three graduate students. Senior-level appointments are made by the President-Elect. Members each serve for three years; the longest-serving committee member serves as chair in her/his final year on the committee. Graduate student appointments are made from the Graduate Council, in consultation with the President-Elect.</p> <p>&nbsp;</p> Wed, 13 Nov 2019 06:00:00 GMT “Evolution transforms pushed waves into pulled waves” https://amnat.org/an/newpapers/Mar-Erm.html Philip Erm and Ben L. Phillips (March 2020) Invasion waves can turn from pushed to pulled due to selection for low-density adapted individuals on invasion fronts Read the Article (Just Accepted) Can the evolution of an invasive species fundamentally reshape an entire biological invasion? Like a ripple expanding across the surface of a pond, plant and animal invasions have long been treated by ecologists as travelling waves of catastrophe that flow over entire landscapes. These waves are not all alike, however; they can either be “pushed” waves, so called because migrants from the well-populated core of the invasion spill over onto the invasion front and push it forward, or “pulled” waves, likewise named because isolated pioneers at the very edge of the invasion pull it forward in the absence of competitors. In this way the shape of an invasion wave will depend almost entirely on how successfully an invader can reproduce at low population densities – rely on others for cooperation or reproduction and your invasion will be pushed; thrive when freed from the pressures of competition and your invasion well be pulled. But what if the selective pressures inherent in invasions meant that an invader’s ability to cope with low densities could itself change over time? Could a pushed wave transform into a pulled wave as invaders evolve? Philip Erm from the University of Cambridge and Ben L. Phillips from the University of Melbourne explored this very question by developing simulation models in which an invading species’ ability to reproduce at low densities was free to evolve as their population spread. They found that intense selection on the sparsely populated invasion front meant that invaders rapidly acquired the ability to cope with low densities. This caused invasions to transform from pushed waves to pulled waves, a result that not only changed the speed of the invasions, but also altered the genetic diversity of the populations left in their wake. Abstract Understanding the dynamics of biological invasions is crucial for managing numerous phenomena, from invasive species to tumors. While the Allee effect (where individuals in low-density populations suffer lowered fitness) is known to influence both the ecological and evolutionary dynamics of an invasion, the possibility that an invader's susceptibility to the Allee effect might itself evolve has received little attention. Since invasion fronts are regions of perpetually low population density, selection should be expected to favour vanguard invaders that are resistant to Allee effects. This may not only cause invasions to accelerate over time, but, by mitigating the Allee effects experienced by the vanguard, also make the invasion transition from a pushed wave, propelled by dispersal from behind the invasion front, to a pulled wave, driven instead by the invasion vanguard. To examine this possibility, we construct an individual-based model in which a trait that governs resistance to the Allee effect is allowed to evolve during an invasion. We find that vanguard invaders evolve resistance to the Allee effect, causing invasions to accelerate. This results in invasions transforming from pushed waves to pulled waves, an outcome with consequences for invasion speed, population genetic structure, and other emergent behaviors. These findings underscore the importance of accounting for evolution in invasion forecasts, and suggest that evolution has the capacity to fundamentally alter invasion dynamics. More forthcoming papers &raquo; <p>Philip Erm and Ben L. Phillips (March 2020) </p> <p><b>Invasion waves can turn from pushed to pulled due to selection for low-density adapted individuals on invasion fronts </b></p> <p><i><a href="https://dx.doi.org/10.1086/707324">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>an the evolution of an invasive species fundamentally reshape an entire biological invasion? Like a ripple expanding across the surface of a pond, plant and animal invasions have long been treated by ecologists as travelling waves of catastrophe that flow over entire landscapes. These waves are not all alike, however; they can either be “pushed” waves, so called because migrants from the well-populated core of the invasion spill over onto the invasion front and push it forward, or “pulled” waves, likewise named because isolated pioneers at the very edge of the invasion pull it forward in the absence of competitors. In this way the shape of an invasion wave will depend almost entirely on how successfully an invader can reproduce at low population densities – rely on others for cooperation or reproduction and your invasion will be pushed; thrive when freed from the pressures of competition and your invasion well be pulled. But what if the selective pressures inherent in invasions meant that an invader’s ability to cope with low densities could itself change over time? Could a pushed wave transform into a pulled wave as invaders evolve? </p><p>Philip Erm from the University of Cambridge and Ben L. Phillips from the University of Melbourne explored this very question by developing simulation models in which an invading species’ ability to reproduce at low densities was free to evolve as their population spread. They found that intense selection on the sparsely populated invasion front meant that invaders rapidly acquired the ability to cope with low densities. This caused invasions to transform from pushed waves to pulled waves, a result that not only changed the speed of the invasions, but also altered the genetic diversity of the populations left in their wake. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">U</span>nderstanding the dynamics of biological invasions is crucial for managing numerous phenomena, from invasive species to tumors. While the Allee effect (where individuals in low-density populations suffer lowered fitness) is known to influence both the ecological and evolutionary dynamics of an invasion, the possibility that an invader's susceptibility to the Allee effect might itself evolve has received little attention. Since invasion fronts are regions of perpetually low population density, selection should be expected to favour vanguard invaders that are resistant to Allee effects. This may not only cause invasions to accelerate over time, but, by mitigating the Allee effects experienced by the vanguard, also make the invasion transition from a pushed wave, propelled by dispersal from behind the invasion front, to a pulled wave, driven instead by the invasion vanguard. To examine this possibility, we construct an individual-based model in which a trait that governs resistance to the Allee effect is allowed to evolve during an invasion. We find that vanguard invaders evolve resistance to the Allee effect, causing invasions to accelerate. This results in invasions transforming from pushed waves to pulled waves, an outcome with consequences for invasion speed, population genetic structure, and other emergent behaviors. These findings underscore the importance of accounting for evolution in invasion forecasts, and suggest that evolution has the capacity to fundamentally alter invasion dynamics. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 12 Nov 2019 06:00:00 GMT “Disturbances can promote and hinder coexistence of competitors in on-going partner choice mutualisms” https://amnat.org/an/newpapers/Mar-Bachelot.html Benedicte Bachelot and Charlotte T. Lee (March 2020) Disturbances can promote and hinder coexistence of competitors in on-going partner choice mutualisms Read the Article (Just Accepted) Most animals and plants rely on positive (mutualistic) associations with microorganisms to meet their dietary needs. Such positive associations are key for plant and animal survival. Yet they can be fragile and environmental disturbances may disrupt them, potentially leading to the death of the partners. Understanding how disturbances influence these mutualistic associations is a very important task in the face of global changes. A team composed of a theoretical ecologist at Duke University and quantitative community ecologist at Rice University used a mathematical model to simulate positive interactions among a plant and two mutualistic fungi under different disturbance scenarios. During the simulations, the plant was able to maximize its fitness over a long period of time by changing how much it interacted with each fungus. The study showed that depending on the disturbance characteristics (strength, timing, etc…), survival of the two fungi could be either compromised or promoted. This finding emphasizes the need to understand how the environment influences mutualistic interactions. Since ecosystems are under constant threat from anthropogenic and natural disturbances, further research about the effect of disturbances is needed. Abstract Ecosystems are under threat from anthropogenic and natural disturbances, yet little is known about how these disturbances alter mutualistic interactions. Many mutualistic interactions are highly context-dependent and dynamic due to “on-going” partner choice, impeding our understanding of how disturbances might influence mutualistic systems. Previously we showed that, in the absence of additional known mechanisms of competitive coexistence, mutualistic fungi can coexist in a system where the plant community associates dynamically with two empirically-defined arbuscular mycorrhizal fungal types: a cheap kind that provides low nutrient benefits and an expensive type that provides high nutrient benefits. We built on this framework to ask how disturbances of different types, frequencies, amplitudes, and predictabilities alter on-going partner choice and thereby influence the coexistence of mutualists. We found that the effects of disturbances depend on the type, amplitude, and predictability of disturbances, and to a lesser extent on their frequency. Disturbance can disrupt mutualist coexistence by enabling hosts more efficiently to exclude partners that behave as parasites. Disturbance can also promote coexistence by altering the strength and direction of consumer-resource interactions. Predicting the effects of disturbance on the mutualist community therefore requires us to understand better the consumer-resource relationships under various environmental conditions. We show how, through such context-dependent effects, disturbance and on-going partner choice can together generate relative nonlinearity and investment in future benefit, introducing fluctuation-dependent mechanisms of competitive coexistence. Our findings support a broadening of the conceptual framework regarding disturbances and competition to include fluctuation-dependent mechanisms alongside the spatiotemporal Intermediate Disturbance Hypothesis. More forthcoming papers &raquo; <p>Benedicte Bachelot and Charlotte T. Lee (March 2020) </p> <p><b>Disturbances can promote and hinder coexistence of competitors in on-going partner choice mutualisms </b></p> <p><i><a href="https://dx.doi.org/10.1086/707258">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>ost animals and plants rely on positive (mutualistic) associations with microorganisms to meet their dietary needs. Such positive associations are key for plant and animal survival. Yet they can be fragile and environmental disturbances may disrupt them, potentially leading to the death of the partners. Understanding how disturbances influence these mutualistic associations is a very important task in the face of global changes. </p><p>A team composed of a theoretical ecologist at Duke University and quantitative community ecologist at Rice University used a mathematical model to simulate positive interactions among a plant and two mutualistic fungi under different disturbance scenarios. During the simulations, the plant was able to maximize its fitness over a long period of time by changing how much it interacted with each fungus. </p><p>The study showed that depending on the disturbance characteristics (strength, timing, etc…), survival of the two fungi could be either compromised or promoted. This finding emphasizes the need to understand how the environment influences mutualistic interactions. Since ecosystems are under constant threat from anthropogenic and natural disturbances, further research about the effect of disturbances is needed.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>cosystems are under threat from anthropogenic and natural disturbances, yet little is known about how these disturbances alter mutualistic interactions. Many mutualistic interactions are highly context-dependent and dynamic due to “on-going” partner choice, impeding our understanding of how disturbances might influence mutualistic systems. Previously we showed that, in the absence of additional known mechanisms of competitive coexistence, mutualistic fungi can coexist in a system where the plant community associates dynamically with two empirically-defined arbuscular mycorrhizal fungal types: a cheap kind that provides low nutrient benefits and an expensive type that provides high nutrient benefits. We built on this framework to ask how disturbances of different types, frequencies, amplitudes, and predictabilities alter on-going partner choice and thereby influence the coexistence of mutualists. We found that the effects of disturbances depend on the type, amplitude, and predictability of disturbances, and to a lesser extent on their frequency. Disturbance can disrupt mutualist coexistence by enabling hosts more efficiently to exclude partners that behave as parasites. Disturbance can also promote coexistence by altering the strength and direction of consumer-resource interactions. Predicting the effects of disturbance on the mutualist community therefore requires us to understand better the consumer-resource relationships under various environmental conditions. We show how, through such context-dependent effects, disturbance and on-going partner choice can together generate relative nonlinearity and investment in future benefit, introducing fluctuation-dependent mechanisms of competitive coexistence. Our findings support a broadening of the conceptual framework regarding disturbances and competition to include fluctuation-dependent mechanisms alongside the spatiotemporal Intermediate Disturbance Hypothesis. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 11 Nov 2019 06:00:00 GMT “The evolution of egg trading in simultaneous hermaphrodites” https://amnat.org/an/newpapers/Mar-Pena.html Jorge Peña, Georg Nöldeke, and Oscar Puebla (March 2020) Researchers study the evolutionary dynamics of egg trading in simultaneous hermaphrodites by means of a mathematical model Read the Article (Just Accepted) The sex life of simultaneous hermaphrodites is complicated by a difficult but necessary choice: who plays the female role and who plays the male role? The male role is tempting as sperm is energetically cheaper to produce than eggs, but things won&#39;t go far if no partner plays the more energetically costly female role. Some simultaneously hermaphroditic worms and fishes have found a solution to this problem by trading eggs, that is by mating in each sex role sequentially with the same partner. Yet egg trading is a form of cooperation, and as such it is open to cheating—in this case mating in the male role and parting ways. Being too picky can also be a bad idea if partners are difficult to find: in this case mating with a cheater might be better than rejecting it and risking not mating at all. These subtleties make it unclear how egg trading can evolve and be maintained, a question that has frustrated biologists since the eighties. To tackle this question, an interdisciplinary group of researchers from the Institute for Advanced Study in Toulouse (France), the University of Basel (Switzerland), and the GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany) built and analyzed a game-theoretic model that captures the most relevant features of this mating system. Their results indicate that egg trading can theoretically evolve and be maintained, but only if eggs are relatively costly to produce, partners are neither too easy nor not too difficult to find, and cheaters can be detected beforehand with some probability and punished by not mating with them. This restrictive set of conditions is consistent with the observation that just a handful of simultaneously hermaphroditic species do trade eggs. For the vast majority of simultaneous hermaphrodites, sex and trade are separate businesses. Abstract Egg trading, whereby simultaneous hermaphrodites exchange each other’s eggs for fertilization, constitutes one of the few rigorously documented and most widely cited examples of direct reciprocity among unrelated individuals. Yet how egg trading may initially invade a population of non-trading simultaneous hermaphrodites is still unresolved. Here, we address this question with an analytical model that considers mate encounter rates and costs of egg production in a population that may include traders (who provide eggs for fertilization only if their partners also have eggs to reciprocate), providers (who provide eggs regardless of whether their partners have eggs to reciprocate), and withholders (“cheaters” who only mate in the male role and just use their eggs to elicit egg release from traders). Our results indicate that a combination of intermediate mate encounter rates, sufficiently high costs of egg production, and a sufficiently high probability that traders detect withholders (in which case eggs are not provided) is conducive to the evolution of egg trading. Under these conditions traders can invade—and resist invasion from—providers and withholders alike. The prediction that egg trading evolves only under these specific conditions is consistent with the rare occurrence of this mating system among simultaneous hermaphrodites. More forthcoming papers &raquo; <p>Jorge Peña, Georg Nöldeke, and Oscar Puebla (March 2020) </p> <p><b>Researchers study the evolutionary dynamics of egg trading in simultaneous hermaphrodites by means of a mathematical model </b></p> <p><i><a href="https://dx.doi.org/10.1086/707016">Read the Article</a></i> (Just Accepted) </p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">T</span>he sex life of simultaneous hermaphrodites is complicated by a difficult but necessary choice: who plays the female role and who plays the male role? The male role is tempting as sperm is energetically cheaper to produce than eggs, but things won&#39;t go far if no partner plays the more energetically costly female role. Some simultaneously hermaphroditic worms and fishes have found a solution to this problem by trading eggs, that is by mating in each sex role sequentially with the same partner. Yet egg trading is a form of cooperation, and as such it is open to cheating&mdash;in this case mating in the male role and parting ways. Being too picky can also be a bad idea if partners are difficult to find: in this case mating with a cheater might be better than rejecting it and risking not mating at all. These subtleties make it unclear how egg trading can evolve and be maintained, a question that has frustrated biologists since the eighties.</p> <p>To tackle this question, an interdisciplinary group of researchers from the Institute for Advanced Study in Toulouse (France), the University of Basel (Switzerland), and the GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany) built and analyzed a game-theoretic model that captures the most relevant features of this mating system. Their results indicate that egg trading can theoretically evolve and be maintained, but only if eggs are relatively costly to produce, partners are neither too easy nor not too difficult to find, and cheaters can be detected beforehand with some probability and punished by not mating with them. This restrictive set of conditions is consistent with the observation that just a handful of simultaneously hermaphroditic species do trade eggs. For the vast majority of simultaneous hermaphrodites, sex and trade are separate businesses.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">E</span>gg trading, whereby simultaneous hermaphrodites exchange each other&rsquo;s eggs for fertilization, constitutes one of the few rigorously documented and most widely cited examples of direct reciprocity among unrelated individuals. Yet how egg trading may initially invade a population of non-trading simultaneous hermaphrodites is still unresolved. Here, we address this question with an analytical model that considers mate encounter rates and costs of egg production in a population that may include traders (who provide eggs for fertilization only if their partners also have eggs to reciprocate), providers (who provide eggs regardless of whether their partners have eggs to reciprocate), and withholders (&ldquo;cheaters&rdquo; who only mate in the male role and just use their eggs to elicit egg release from traders). Our results indicate that a combination of intermediate mate encounter rates, sufficiently high costs of egg production, and a sufficiently high probability that traders detect withholders (in which case eggs are not provided) is conducive to the evolution of egg trading. Under these conditions traders can invade&mdash;and resist invasion from&mdash;providers and withholders alike. The prediction that egg trading evolves only under these specific conditions is consistent with the rare occurrence of this mating system among simultaneous hermaphrodites.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 08 Nov 2019 06:00:00 GMT “Gene flow limits adaptation along steep environmental gradients” https://amnat.org/an/newpapers/Mar-Bachmann-A.html Judith C. Bachmann, Alexandra Jansen van Rensburg, Maria Cortazar-Chinarro, Anssi Laurila, and Josh Van Buskirk (March 2020) Genetic adaptation in frogs is limited on steep climate gradients by dispersal connecting pops in very distinct habitats Read the Article (Just Accepted) Abstract When environmental variation is spatially continuous, dispersing individuals move among nearby sites with similar habitat conditions. But as an environmental gradient becomes steeper, gene flow may connect more divergent habitats, and this is predicted to reduce the slope of the adaptive cline that evolves. We compared quantitative genetic divergence of Rana temporaria frog populations along a 2000&nbsp;m elevational gradient in eastern Switzerland (new experimental results) with divergence along a 1550&nbsp;km latitudinal gradient in Fennoscandia (previously published results). Both studies found significant countergradient variation in larval development rate (i.e., animals from cold climates developed more rapidly). The cline was weaker with elevation than with latitude. Animals collected on both gradients were genotyped at ~2000 SNP markers, revealing that dispersal distance was 30% farther on the latitudinal gradient but 3.9 times greater with respect to environmental conditions on the elevational gradient. A meta-analysis on 19 experimental studies of anuran populations spanning temperature gradients revealed that countergradient variation in larval development, while significant overall, was weaker when measured on steeper gradients. These findings support the prediction that adaptive population divergence is less pronounced, and maladaptation more pervasive, on steep environmental gradients. More forthcoming papers &raquo; <p>Judith C. Bachmann, Alexandra Jansen van Rensburg, Maria Cortazar-Chinarro, Anssi Laurila, and Josh Van Buskirk (March 2020) </p> <p><b>Genetic adaptation in frogs is limited on steep climate gradients by dispersal connecting pops in very distinct habitats </b></p> <p><i><a href="https://dx.doi.org/10.1086/707209">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hen environmental variation is spatially continuous, dispersing individuals move among nearby sites with similar habitat conditions. But as an environmental gradient becomes steeper, gene flow may connect more divergent habitats, and this is predicted to reduce the slope of the adaptive cline that evolves. We compared quantitative genetic divergence of <i>Rana temporaria</i> frog populations along a 2000&nbsp;m elevational gradient in eastern Switzerland (new experimental results) with divergence along a 1550&nbsp;km latitudinal gradient in Fennoscandia (previously published results). Both studies found significant countergradient variation in larval development rate (i.e., animals from cold climates developed more rapidly). The cline was weaker with elevation than with latitude. Animals collected on both gradients were genotyped at ~2000 SNP markers, revealing that dispersal distance was 30% farther on the latitudinal gradient but 3.9 times greater with respect to environmental conditions on the elevational gradient. A meta-analysis on 19 experimental studies of anuran populations spanning temperature gradients revealed that countergradient variation in larval development, while significant overall, was weaker when measured on steeper gradients. These findings support the prediction that adaptive population divergence is less pronounced, and maladaptation more pervasive, on steep environmental gradients. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 07 Nov 2019 06:00:00 GMT “Does evolutionary history correlate with contemporary extinction risk by influencing range size dynamics?” https://amnat.org/an/newpapers/Mar-Tanentzap.html Andrew J. Tanentzap, Javier Igea, Matthew G. Johnston, and Matthew J. Larcombe (March 2020) Range dynamics can explain why evolutionary age and diversification rate predict contemporary extinction in plants Read the Article (Just Accepted) In a new note in The American Naturalist, Tanentzap et al. provide one of the most in-depth analyses of why patterns of extinction risk vary across the Tree of Life. It would have been hard to miss this headline: “1 million species at risk of extinction” according to the 2019 Global Assessment of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. But why these species and not millions of others on Earth? Common reasons that species become extinct are habitat loss, overexploitation, and the introduction of novel predators. In their paper, Tanentzap et al. present new evidence that the amount of time that a taxon has existed – also known as its age – may also help predict its risk of contemporary extinction. Age is important because, among other reasons, it influences the physical and ecological space that taxa can occupy. For example, older taxa that evolved longer ago may become maladapted as their environments change. These changes can limit the number of habitats that taxa occupy and increase their extinction risk by making their geographic range and population size small and fragmented. Detecting an association between taxon age and extinction may make it easier to determine the risks faced by species and inform future conservation. However, evidence for an association between taxon age and extinction risk has varied and few studies have considered why. Tanentzap et al. test how and why taxon age influences extinction risk across the plant kingdom. Using data from nearly 9,000 species, they found groups of species faced greater extinction risk when they evolved species more quickly. As range size is often smaller in recently evolved species, it can explain this correlation. They then tried to model how range size influenced these patterns by focusing on two large, well-sampled groups. In conifers, older species had smaller potential range sizes, which correlated with higher extinction risk. In palms, age was neither directly nor indirectly correlated with extinction. Despite the different patterns, the general message is that range size can explain why taxon age correlates with extinction risk. As range size can vary in taxa of the same age, because of different geographic histories, it can explain why other studies have found both young and old taxa face greater extinction. Ultimately, these results further emphasize the importance of large ranges for biodiversity conservation. Abstract Extinction threatens many species, yet is predicted by few factors across the plant Tree of Life (ToL). Taxon age is one factor that may associate with extinction if occupancy of geographic and adaptive zones varies with time, but evidence for such an association has been equivocal. Age-dependent occupancy can also influence diversification rates and thus extinction risk where new taxa have small range and population sizes. To test how age, diversification, and range size were correlated with extinction, we analyzed 639 well-sampled genera representing 8,937 species from across the plant ToL. We found a greater proportion of species were threatened by contemporary extinction in younger and faster-diversifying genera. When we directly tested how range size mediated this pattern in two large, well-sampled groups, our results varied. In conifers, potential range size was smaller in older species and was correlated with higher extinction risk. Age on its own had no direct effect on extinction when accounting for its influence on range size. In palm species, age was neither directly nor indirectly correlated with extinction risk. Our results suggest range size dynamics may explain differing patterns of extinction risk across the ToL with consequences for biodiversity conservation. More forthcoming papers &raquo; <p>Andrew J. Tanentzap, Javier Igea, Matthew G. Johnston, and Matthew J. Larcombe (March 2020) </p> <p><b>Range dynamics can explain why evolutionary age and diversification rate predict contemporary extinction in plants </b></p> <p><i><a href="https://dx.doi.org/10.1086/707207">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n a new note in <i>The American Naturalist</i>, Tanentzap et al. provide one of the most in-depth analyses of why patterns of extinction risk vary across the Tree of Life. It would have been hard to miss this headline: “1 million species at risk of extinction” according to the 2019 Global Assessment of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. But why these species and not millions of others on Earth? Common reasons that species become extinct are habitat loss, overexploitation, and the introduction of novel predators. </p><p>In their paper, Tanentzap et al. present new evidence that the amount of time that a taxon has existed – also known as its age – may also help predict its risk of contemporary extinction. Age is important because, among other reasons, it influences the physical and ecological space that taxa can occupy. For example, older taxa that evolved longer ago may become maladapted as their environments change. These changes can limit the number of habitats that taxa occupy and increase their extinction risk by making their geographic range and population size small and fragmented. Detecting an association between taxon age and extinction may make it easier to determine the risks faced by species and inform future conservation. However, evidence for an association between taxon age and extinction risk has varied and few studies have considered why. </p><p>Tanentzap et al. test how and why taxon age influences extinction risk across the plant kingdom. Using data from nearly 9,000 species, they found groups of species faced greater extinction risk when they evolved species more quickly. As range size is often smaller in recently evolved species, it can explain this correlation. They then tried to model how range size influenced these patterns by focusing on two large, well-sampled groups. In conifers, older species had smaller potential range sizes, which correlated with higher extinction risk. In palms, age was neither directly nor indirectly correlated with extinction. Despite the different patterns, the general message is that range size can explain why taxon age correlates with extinction risk. As range size can vary in taxa of the same age, because of different geographic histories, it can explain why other studies have found both young and old taxa face greater extinction. Ultimately, these results further emphasize the importance of large ranges for biodiversity conservation.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>xtinction threatens many species, yet is predicted by few factors across the plant Tree of Life (ToL). Taxon age is one factor that may associate with extinction if occupancy of geographic and adaptive zones varies with time, but evidence for such an association has been equivocal. Age-dependent occupancy can also influence diversification rates and thus extinction risk where new taxa have small range and population sizes. To test how age, diversification, and range size were correlated with extinction, we analyzed 639 well-sampled genera representing 8,937 species from across the plant ToL. We found a greater proportion of species were threatened by contemporary extinction in younger and faster-diversifying genera. When we directly tested how range size mediated this pattern in two large, well-sampled groups, our results varied. In conifers, potential range size was smaller in older species and was correlated with higher extinction risk. Age on its own had no direct effect on extinction when accounting for its influence on range size. In palm species, age was neither directly nor indirectly correlated with extinction risk. Our results suggest range size dynamics may explain differing patterns of extinction risk across the ToL with consequences for biodiversity conservation. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 07 Nov 2019 06:00:00 GMT “Developmental constraints do not influence long-term phenotypic evolution of marsupial forelimbs as revealed by interspecific disparity and integration patterns” https://amnat.org/an/newpapers/Mar-Martin-Serra.html Alberto Mart&iacute;n-Serra and Roger B. J. Benson (March 2020) Phenotypic disparity and integration patterns of marsupial limbs cast doubts on the role of developmental constraints Read the Article (Just Accepted)The developmental constraints of organisms may constrain their ability to evolve new morphologies. Marsupials have low ecological variation and diversity compared to placental mammals, and one influential hypothesis explains this by invoking constraints imposed by their unusual reproductive strategy. In particular, the variability of marsupial arms (forelimbs) might be limited because of their early development and use during the newborn’s arduous crawl to the mother’s pouch. This hypothesis makes several predictions about variation among marsupial species that are analyzed in this study from a macroevolutionary perspective by Alberto Martín-Serra and Roger Benson, using 3D digital models of the limb skeletons of many marsupials. If this hypothesis is correct, then the morphological disparity of marsupial forelimbs should be lower than for their hindlimbs, co-evolutionary integration between fore- and hindlimb should be weaker than within the forelimb, and both patterns should be more conspicuous for diprotodontians (i.e., koalas, wombats, wallabies, kangaroos, and their relatives) because they perform the hardest crawl as newborns. However, the new analyses provide no support for any of these predictions. This indicates that the constrained developmental patterns of marsupial forelimbs have not strongly influenced their long-term evolution history. Therefore, we may have to look for alternative explanations for the differences in ecological and taxonomical diversity between marsupials and placentals, such as geographical distribution and ecological opportunities. Finally, in a broad sense, this work reveals that developmental constraints may be less important than expected when natural selection can act over long timescales. Abstract Marsupials show a smaller range of forelimb ecomorphologies than placental mammals, and it is hypothesized that this results from macroevolutionary constraints imposed by the specialised reproductive biology of marsupials. Specifically, the accelerated development of the marsupial forelimb allows neonates to crawl to the mother’s pouch, but may constrain adult morphology. This hypothesis makes three main predictions: (i) that marsupial forelimbs should show less interspecific disparity than their hindlimbs; (ii) that morphological integration within the marsupial forelimb is stronger than integration between limbs; and (iii) that these patterns should be strongest in diprotodontians, which undergo the most rigorous crawls as neonates. We use a three-dimensional geometric morphometric dataset of limb bones for 51 marsupial species to tests these predictions. We find that (i) marsupial forelimbs and hindlimbs show similar disparities, (ii) no clear differences in integration exist either within or between limbs, and (iii) the same patterns occur in diprotodontians as in other marsupials, even correcting for lineage age. Therefore, there is currently little evidence that the developmental biology of marsupials has constrained their macroevolutionary patterns. Possibly, functional selection can overcome the effects of developmental constraint on macroevolutionary timescales. Our findings suggest that the role of developmental constraints in explaining the limited phenotypic variability of marsupials (compared with placentals) should be reconsidered. More forthcoming papers &raquo; <p>Alberto Mart&iacute;n-Serra and Roger B. J. Benson (March 2020)</p> <p><b>Phenotypic disparity and integration patterns of marsupial limbs cast doubts on the role of developmental constraints</b></p> <p><i><a href="https://dx.doi.org/10.1086/707194">Read the Article</a></i> (Just Accepted)</p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he developmental constraints of organisms may constrain their ability to evolve new morphologies. Marsupials have low ecological variation and diversity compared to placental mammals, and one influential hypothesis explains this by invoking constraints imposed by their unusual reproductive strategy. In particular, the variability of marsupial arms (forelimbs) might be limited because of their early development and use during the newborn’s arduous crawl to the mother’s pouch. This hypothesis makes several predictions about variation among marsupial species that are analyzed in this study from a macroevolutionary perspective by Alberto Martín-Serra and Roger Benson, using 3D digital models of the limb skeletons of many marsupials. If this hypothesis is correct, then the morphological disparity of marsupial forelimbs should be lower than for their hindlimbs, co-evolutionary integration between fore- and hindlimb should be weaker than within the forelimb, and both patterns should be more conspicuous for diprotodontians (i.e., koalas, wombats, wallabies, kangaroos, and their relatives) because they perform the hardest crawl as newborns. However, the new analyses provide no support for any of these predictions. This indicates that the constrained developmental patterns of marsupial forelimbs have not strongly influenced their long-term evolution history. Therefore, we may have to look for alternative explanations for the differences in ecological and taxonomical diversity between marsupials and placentals, such as geographical distribution and ecological opportunities. Finally, in a broad sense, this work reveals that developmental constraints may be less important than expected when natural selection can act over long timescales. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>arsupials show a smaller range of forelimb ecomorphologies than placental mammals, and it is hypothesized that this results from macroevolutionary constraints imposed by the specialised reproductive biology of marsupials. Specifically, the accelerated development of the marsupial forelimb allows neonates to crawl to the mother’s pouch, but may constrain adult morphology. This hypothesis makes three main predictions: (i) that marsupial forelimbs should show less interspecific disparity than their hindlimbs; (ii) that morphological integration within the marsupial forelimb is stronger than integration between limbs; and (iii) that these patterns should be strongest in diprotodontians, which undergo the most rigorous crawls as neonates. We use a three-dimensional geometric morphometric dataset of limb bones for 51 marsupial species to tests these predictions. We find that (i) marsupial forelimbs and hindlimbs show similar disparities, (ii) no clear differences in integration exist either within or between limbs, and (iii) the same patterns occur in diprotodontians as in other marsupials, even correcting for lineage age. Therefore, there is currently little evidence that the developmental biology of marsupials has constrained their macroevolutionary patterns. Possibly, functional selection can overcome the effects of developmental constraint on macroevolutionary timescales. Our findings suggest that the role of developmental constraints in explaining the limited phenotypic variability of marsupials (compared with placentals) should be reconsidered. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 06 Nov 2019 06:00:00 GMT “Tolerance of novel toxins through generalized mechanisms: simulating gradual host shifts of butterflies” https://amnat.org/an/newpapers/Mar-Sikkink.html Kristin L. Sikkink, Reilly Hostager, Megan E. Kobiela, Nathan Fremling, Katherine Johnston, Amod Zambre, and Emilie C. Snell-Rood (March 2020) Generalized stress responses, like anti-oxidant defenses, confer tolerance of novel toxins, facilitating host shifts Read the Article (Just Accepted) Animals encounter novel toxins as they incorporate new foods into their diets, shift into different habitats, or come into contact with humans. How do organisms deal with completely new chemicals – why do some individuals survive new toxins while others perish? And how does this influence which species will get a leg-hold in a new environment, leading to subsequent evolutionary change? Many well-studied adaptations to toxins are very specific to certain chemical structures. In recent work, Kristin Sikkink and colleagues at the University of Minnesota considered how general adaptations to stress may predispose organisms to cope with novel toxins. In many species, the expression of genes in response to one stress, like heat or a poison, can result in beneficial responses to a variety of stressors. In this study, the researchers introduced novel plant toxins into artificial diets fed on by cabbage white butterflies. Family groups that coped well with one toxin type also did well on other toxin types, consistent with the idea of a general ability to deal with new stressors. These families also had higher expression of genes involved in antioxidant stress pathways, such as glutathione-s-transferase and tyrosine hydroxylase. There were very few trade-offs with the ability to deal with new toxins, although there were hints of costs associated with melanin expression, consistent with the role of this pigment in antioxidant defenses.“These results offer clues about how organisms can colonize new environments with novel toxins,” says lead investigator Emilie Snell-Rood. “Higher expression of these generalized stress responses may represent a pre-adaptation.” This research may lead to better predictions of which species or populations will thrive or perish in response to novel toxins, whether pollutants, pesticides, or chemical defenses in an arms race with a plant. Abstract Organisms encounter a wide range of toxic compounds in their environments, from chemicals that serve anti-consumption or anti-competition functions, to pollutants and pesticides. Although we understand many detoxification mechanisms that allow organisms to consume toxins typical of their diet, we know little about why organisms vary in their ability to tolerate entirely novel toxins. We tested whether variation in generalized stress responses, such as antioxidant pathways, may underlie variation in reactions to novel toxins, and, if so, their associated costs. We used an artificial diet to present cabbage white butterfly caterpillars (Pieris rapae) with plant material containing toxins not experienced in their evolutionary history. Families that maintained high performance (e.g. high survival, fast development time, large body size) on diets containing one novel, toxic plant also performed well when exposed to two other novel toxic plants, consistent with a generalized response. Variation in constitutive (but not induced) expression of genes involved in oxidative stress responses was positively related to performance on the novel diets. While we did not detect reproductive trade-offs of this generalized response, there was a tendency to have less melanin investment in the wings, consistent of the role of melanin in oxidative stress responses. Taken together, our results support the hypothesis that variation in generalized stress responses, such as genes involved in oxidative stress responses, may explain the variation in tolerance to entirely novel toxins and may facilitate colonization of novel hosts and environments. More forthcoming papers &raquo; <p>Kristin L. Sikkink, Reilly Hostager, Megan E. Kobiela, Nathan Fremling, Katherine Johnston, Amod Zambre, and Emilie C. Snell-Rood (March 2020) </p> <p><b>Generalized stress responses, like anti-oxidant defenses, confer tolerance of novel toxins, facilitating host shifts </b></p> <p><i><a href="https://dx.doi.org/10.1086/707195">Read the Article</a></i> (Just Accepted) </p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>nimals encounter novel toxins as they incorporate new foods into their diets, shift into different habitats, or come into contact with humans. How do organisms deal with completely new chemicals &ndash; why do some individuals survive new toxins while others perish? And how does this influence which species will get a leg-hold in a new environment, leading to subsequent evolutionary change? Many well-studied adaptations to toxins are very specific to certain chemical structures. In recent work, Kristin Sikkink and colleagues at the University of Minnesota considered how general adaptations to stress may predispose organisms to cope with novel toxins. In many species, the expression of genes in response to one stress, like heat or a poison, can result in beneficial responses to a variety of stressors.</p> <p>In this study, the researchers introduced novel plant toxins into artificial diets fed on by cabbage white butterflies. Family groups that coped well with one toxin type also did well on other toxin types, consistent with the idea of a general ability to deal with new stressors. These families also had higher expression of genes involved in antioxidant stress pathways, such as glutathione-s-transferase and tyrosine hydroxylase. There were very few trade-offs with the ability to deal with new toxins, although there were hints of costs associated with melanin expression, consistent with the role of this pigment in antioxidant defenses.</p><p>“These results offer clues about how organisms can colonize new environments with novel toxins,” says lead investigator Emilie Snell-Rood. “Higher expression of these generalized stress responses may represent a pre-adaptation.” This research may lead to better predictions of which species or populations will thrive or perish in response to novel toxins, whether pollutants, pesticides, or chemical defenses in an arms race with a plant. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">O</span>rganisms encounter a wide range of toxic compounds in their environments, from chemicals that serve anti-consumption or anti-competition functions, to pollutants and pesticides. Although we understand many detoxification mechanisms that allow organisms to consume toxins typical of their diet, we know little about why organisms vary in their ability to tolerate entirely novel toxins. We tested whether variation in generalized stress responses, such as antioxidant pathways, may underlie variation in reactions to novel toxins, and, if so, their associated costs. We used an artificial diet to present cabbage white butterfly caterpillars (<i>Pieris rapae</i>) with plant material containing toxins not experienced in their evolutionary history. Families that maintained high performance (e.g. high survival, fast development time, large body size) on diets containing one novel, toxic plant also performed well when exposed to two other novel toxic plants, consistent with a generalized response. Variation in constitutive (but not induced) expression of genes involved in oxidative stress responses was positively related to performance on the novel diets. While we did not detect reproductive trade-offs of this generalized response, there was a tendency to have less melanin investment in the wings, consistent of the role of melanin in oxidative stress responses. Taken together, our results support the hypothesis that variation in generalized stress responses, such as genes involved in oxidative stress responses, may explain the variation in tolerance to entirely novel toxins and may facilitate colonization of novel hosts and environments. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 06 Nov 2019 06:00:00 GMT “The population genetics of evolutionary rescue in diploids: X chromosomal vs. autosomal rescue” https://amnat.org/an/newpapers/Mar-Unckless.html Robert L. Unckless and H. Allen Orr (Mar 2020) Evolutionary rescue alters the dynamics of adaptation on the autosomes vs. sex chromosomes Read the Article (Just Accepted) Extinction is eventually inevitable for all species. However, when challenged by environmental changes (pesticides, climate change, new parasites, etc.), populations may be able to prevent extinction by adapting to these new conditions. This is essentially a race – the population must adapt before it goes extinct. Evolutionary rescue describes those cases in which adaptation wins the race and a population survives. Unckless and Orr explore the likelihood that evolutionary rescue occurs because of mutations on the sex chromosomes versus non-sex chromosomes. They find that the X chromosome is more likely to contribute to evolutionary rescue, all else being equal, than non-sex chromosomes under more conditions than when populations are not threatened by extinction. Unckless and Orr use both mathematical models and computer simulations to explore this problem. Abstract Most population genetic theory assumes that populations adapt to an environmental change without a change in population size. However, environmental changes might be so severe that populations decline in size and, without adaptation, go extinct. This “evolutionary rescue” scenario differs from traditional models of adaptation in that rescue involves a race between adaptation and extinction. While most previous work usually focused on models of evolutionary rescue in haploids, here we consider diploids. In many species, diploidy introduces a novel feature into adaptation: adaptive evolution might occur either on sex chromosomes or on autosomes. Previous studies of non-rescue adaptation revealed that the relative rates of adaptation on the X chromosome vs. autosomes depend on the dominance of beneficial mutations, reflecting differences in effective population size and the efficacy of selection. Here, we extend these results to evolutionary rescue and find that, given equal-sized chromosomes, there is greater parameter space in which the X is more likely to contribute to adaptation than the autosomes relative to standard non-rescue models. We also discuss how subtle effects of dominance can increase the chance of evolutionary rescue in diploids when absolute heterozygote fitness is close to one. These effects do not arise in standard non-rescue models. More forthcoming papers &raquo; <p>Robert L. Unckless and H. Allen Orr (Mar 2020) </p> <p><b>Evolutionary rescue alters the dynamics of adaptation on the autosomes vs. sex chromosomes </b></p> <p><i><a href="https://dx.doi.org/10.1086/707139">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>xtinction is eventually inevitable for all species. However, when challenged by environmental changes (pesticides, climate change, new parasites, etc.), populations may be able to prevent extinction by adapting to these new conditions. This is essentially a race – the population must adapt before it goes extinct. Evolutionary rescue describes those cases in which adaptation wins the race and a population survives. Unckless and Orr explore the likelihood that evolutionary rescue occurs because of mutations on the sex chromosomes versus non-sex chromosomes. They find that the X chromosome is more likely to contribute to evolutionary rescue, all else being equal, than non-sex chromosomes under more conditions than when populations are not threatened by extinction. Unckless and Orr use both mathematical models and computer simulations to explore this problem. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>ost population genetic theory assumes that populations adapt to an environmental change without a change in population size. However, environmental changes might be so severe that populations decline in size and, without adaptation, go extinct. This “evolutionary rescue” scenario differs from traditional models of adaptation in that rescue involves a race between adaptation and extinction. While most previous work usually focused on models of evolutionary rescue in haploids, here we consider diploids. In many species, diploidy introduces a novel feature into adaptation: adaptive evolution might occur either on sex chromosomes or on autosomes. Previous studies of non-rescue adaptation revealed that the relative rates of adaptation on the X chromosome vs. autosomes depend on the dominance of beneficial mutations, reflecting differences in effective population size and the efficacy of selection. Here, we extend these results to evolutionary rescue and find that, given equal-sized chromosomes, there is greater parameter space in which the X is more likely to contribute to adaptation than the autosomes relative to standard non-rescue models. We also discuss how subtle effects of dominance can increase the chance of evolutionary rescue in diploids when absolute heterozygote fitness is close to one. These effects do not arise in standard non-rescue models. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 05 Nov 2019 06:00:00 GMT “Stochasticity and infectious-disease dynamics: Density and weather effects on a fungal insect pathogen” https://amnat.org/an/newpapers/Mar-Kyle-A.html Colin H. Kyle, Jiawei Liu, Molly E. Gallagher, Vanja Dukic, and Greg Dwyer (Mar 2020) Models plus data reveal strong effects of weather and density on the spread of a disease that controls the gypsy moth Read the Article (Just Accepted) Abstract In deterministic models of epidemics, there is a host abundance threshold, above which the introduction of a few infected individuals leads to a severe epidemic. Studies of weather driven animal pathogens often assume that abundance thresholds will be overwhelmed by weather driven stochasticity, but tests of this assumption are lacking. We collected observational and experimental data for a fungal pathogen, Entomophaga maimaiga, that infects the gypsy moth, Lymantria dispar. We used an advanced statistical-computing algorithm to fit mechanistic models to our data, such that different models made different assumptions about the effects of host density and weather on E.&nbsp;maimaiga epizootics (epidemics in animals). We then used AIC analysis to choose the best model. In the best model, epizootics are driven by a combination of weather and host density, and the model does an excellent job of explaining the data, whereas models that allow only for weather effects, or only density-dependence effects, do a poor job of explaining the data. Density-dependent transmission in our best model produces a host-density threshold, but this threshold is strongly blurred by the stochastic effects of weather. Our work shows that host-abundance thresholds may be important even if weather strongly affects transmission, suggesting that epidemiological models that allow for weather have an important role to play in understanding animal pathogens. The success of our model means that it could be useful for managing the gypsy moth, an important pest of hardwood forests in North America. More forthcoming papers &raquo; <p>Colin H. Kyle, Jiawei Liu, Molly E. Gallagher, Vanja Dukic, and Greg Dwyer (Mar 2020) </p> <p><b>Models plus data reveal strong effects of weather and density on the spread of a disease that controls the gypsy moth </b></p> <p><i><a href="https://dx.doi.org/10.1086/707138">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n deterministic models of epidemics, there is a host abundance threshold, above which the introduction of a few infected individuals leads to a severe epidemic. Studies of weather driven animal pathogens often assume that abundance thresholds will be overwhelmed by weather driven stochasticity, but tests of this assumption are lacking. We collected observational and experimental data for a fungal pathogen, <i>Entomophaga maimaiga</i>, that infects the gypsy moth, <i>Lymantria dispar</i>. We used an advanced statistical-computing algorithm to fit mechanistic models to our data, such that different models made different assumptions about the effects of host density and weather on <i>E.&nbsp;maimaiga</i> epizootics (epidemics in animals). We then used AIC analysis to choose the best model. In the best model, epizootics are driven by a combination of weather and host density, and the model does an excellent job of explaining the data, whereas models that allow only for weather effects, or only density-dependence effects, do a poor job of explaining the data. Density-dependent transmission in our best model produces a host-density threshold, but this threshold is strongly blurred by the stochastic effects of weather. Our work shows that host-abundance thresholds may be important even if weather strongly affects transmission, suggesting that epidemiological models that allow for weather have an important role to play in understanding animal pathogens. The success of our model means that it could be useful for managing the gypsy moth, an important pest of hardwood forests in North America. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 05 Nov 2019 06:00:00 GMT “Nonlinear effects of intraspecific competition alter landscape-wide scaling up of ecosystem function” https://amnat.org/an/newpapers/Mar-Little.html Chelsea Jean Little, Emanuel A. Fronhofer, and Florian Altermatt (March 2020) Macroinvertebrates process leaf litter in streams in nonlinear relation to their population density Read the Article (Just Accepted) Scientists have always been interested in understanding populations and processes at large scales. How many of this kind of animal are there in the world? How much plant growth is produced globally each year? What’s the biomass of trees in this state or province? In an era of global change, interest in predicting these kinds of measures is growing, because it’s apparent that nature contributes a lot to human wellbeing. But getting answers to these questions is not always easy. In this research, Little et al. asked how much leaf litter was processed by invertebrates in entire stream catchments. Leaves and other dead material from trees are an important resource input to freshwater ecosystems, which don’t produce as much of their own plant material as you can find in a forest. That dead material is often processed by invertebrates (but also microbes and sometimes even fish), which incorporates it into the freshwater food web. In a lab experiment, Little et al. showed that the rate at which invertebrates consume leaf litter depends on the density of invertebrates: the more neighbors they have, the less they eat. This turned out to be very important in predicting how much leaf litter might be processed in whole stream catchments. Because the relationship was nonlinear, simply extrapolating the leaf processing rate of the average density of invertebrates would not produce an accurate prediction. Instead, the authors used geostatistical modeling to estimate the distribution of invertebrates in the stream catchments based on field survey data, and then to map the predicted the variation in leaf litter processing in space through the catchments. Little et al. worked in ten streams in eastern Switzerland which were roughly matched for stream length and catchment size. The nonlinear density dependence of leaf consumption, in combination with differences in invertebrate distributions between the catchments, led to a 40-fold difference in how much leaf litter was predicted to be processed between the lowest- and highest-processing rate streams. This is potentially important because it determines how much terrestrial material is available to the aquatic food web. It also suggests that depending on the stream catchment, some dead terrestrial material may be exported downstream and end up in a lake to decompose, rather than being processed in the stream. Abstract A&nbsp;major focus of ecology is to understand and predict ecosystem function across scales. Many ecosystem functions are only measured at local scales, while their effects occur at a landscape level. Here, we investigate how landscape-scale predictions of ecosystem function depend on intraspecific competition, a fine-scale process, by manipulating intraspecific density of shredding macroinvertebrates and examining effects on leaf litter decomposition, a key function in freshwater ecosystems. For two species, we found that per-capita leaf processing rates declined with increasing density following power functions with negative exponents, likely due to interference competition. To demonstrate consequences of this nonlinearity, we scaled up estimates of leaf litter processing from shredder abundance surveys in 10 replicated headwater streams. In accordance with Jensen’s inequality, applying density-dependent consumption rates reduced estimates of catchment-scale leaf consumption by an order of magnitude relative to density-independent rates. Density-dependent consumption estimates aligned closely with metabolic requirements in catchments with large, but not small, shredder populations. Importantly, shredder abundance was not limited by leaf litter availability and catchment-level leaf litter supply was much higher than estimated consumption. Thus leaf litter processing was not limited by resource supply. Our work highlights the need for scaling-up which accounts for intraspecific interactions. More forthcoming papers &raquo; <p>Chelsea Jean Little, Emanuel A. Fronhofer, and Florian Altermatt (March 2020) </p> <p><b>Macroinvertebrates process leaf litter in streams in nonlinear relation to their population density </b></p> <p><i><a href="https://dx.doi.org/10.1086/707018">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>cientists have always been interested in understanding populations and processes at large scales. How many of this kind of animal are there in the world? How much plant growth is produced globally each year? What’s the biomass of trees in this state or province? In an era of global change, interest in predicting these kinds of measures is growing, because it’s apparent that nature contributes a lot to human wellbeing. </p><p>But getting answers to these questions is not always easy. In this research, Little et al. asked how much leaf litter was processed by invertebrates in entire stream catchments. Leaves and other dead material from trees are an important resource input to freshwater ecosystems, which don’t produce as much of their own plant material as you can find in a forest. That dead material is often processed by invertebrates (but also microbes and sometimes even fish), which incorporates it into the freshwater food web. </p><p>In a lab experiment, Little et al. showed that the rate at which invertebrates consume leaf litter depends on the density of invertebrates: the more neighbors they have, the less they eat. This turned out to be very important in predicting how much leaf litter might be processed in whole stream catchments. Because the relationship was nonlinear, simply extrapolating the leaf processing rate of the average density of invertebrates would not produce an accurate prediction. Instead, the authors used geostatistical modeling to estimate the distribution of invertebrates in the stream catchments based on field survey data, and then to map the predicted the variation in leaf litter processing in space through the catchments. </p><p>Little et al. worked in ten streams in eastern Switzerland which were roughly matched for stream length and catchment size. The nonlinear density dependence of leaf consumption, in combination with differences in invertebrate distributions between the catchments, led to a 40-fold difference in how much leaf litter was predicted to be processed between the lowest- and highest-processing rate streams. This is potentially important because it determines how much terrestrial material is available to the aquatic food web. It also suggests that depending on the stream catchment, some dead terrestrial material may be exported downstream and end up in a lake to decompose, rather than being processed in the stream.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>&nbsp;major focus of ecology is to understand and predict ecosystem function across scales. Many ecosystem functions are only measured at local scales, while their effects occur at a landscape level. Here, we investigate how landscape-scale predictions of ecosystem function depend on intraspecific competition, a fine-scale process, by manipulating intraspecific density of shredding macroinvertebrates and examining effects on leaf litter decomposition, a key function in freshwater ecosystems. For two species, we found that per-capita leaf processing rates declined with increasing density following power functions with negative exponents, likely due to interference competition. To demonstrate consequences of this nonlinearity, we scaled up estimates of leaf litter processing from shredder abundance surveys in 10 replicated headwater streams. In accordance with Jensen’s inequality, applying density-dependent consumption rates reduced estimates of catchment-scale leaf consumption by an order of magnitude relative to density-independent rates. Density-dependent consumption estimates aligned closely with metabolic requirements in catchments with large, but not small, shredder populations. Importantly, shredder abundance was not limited by leaf litter availability and catchment-level leaf litter supply was much higher than estimated consumption. Thus leaf litter processing was not limited by resource supply. Our work highlights the need for scaling-up which accounts for intraspecific interactions. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 04 Nov 2019 06:00:00 GMT “Stochastic dynamics of three competing clones: Conditions and times for invasion, coexistence, and fixation” https://amnat.org/an/newpapers/Mar-Billiard.html Sylvain Billiard and Charline Smadi (March 2020) Intransitive competitive interactions can explain the complex dynamics of clonal species during adaptation Read the Article (Just Accepted) Competition drives evolution and pushes species coexistence. Though the fundamental mechanisms are simple, the dynamics of competing clones are surprisingly diverse in bacteria, yeasts, or viruses. This is the case even without sexual reproduction and in very simple, stable, controlled environments: clones can replace each other, can coexist for long stretches of time, and can have cyclical or linear dynamics. Existing population models provide only a partial understanding of this diversity, because they lack generality in either competition, time scales, or the importance of chance. Owing to a collaboration between a mathematician and an evolutionary ecologist, it has been made possible to encompass competition intransitivity, mutation, and chance in a single ecological and evolutionary model. Using such a simple model, it is possible to describe most dynamics observed in clonal populations. Approximations of the stochastic process also allow accurate predictions to be made about the likelihood and the duration of the different possible outcomes. Unexpected outcomes were also detected: even if a succession of favorable mutations have arisen, they can be unexpectedly wiped out, and adaptation can be accelerated n some cases when multiple strains interfere. The authors’ model shows that, for a better understanding and prediction of the dynamics of clone evolution, ecological and evolutionary theoretical frameworks must be merged together. The development of stochastic models could reconcile these two frameworks, which are too often isolated from each other. Such a synthesis would certainly be extremely fruitful, as clonal populations with many different competing species or strains are ubiquitous (for instance, tumoral cancers, microbial communities, or viruses within a host). Abstract In large clonal populations, several clones generally compete which results in complex evolutionary and ecological dynamics: experiments show successive selective sweeps of favorable mutations as well as long-term coexistence of multiple clonal strains. The mechanisms underlying either coexistence or fixation of several competing strains have rarely been studied altogether. Conditions for coexistence have mostly been studied by population and community ecology, while rates of invasion and fixation have mostly been studied by population genetics. In order to provide a global understanding of the complexity of the dynamics observed in large clonal populations, we develop a stochastic model where three clones compete. Competitive interactions can be intransitive and we suppose that strains enter the population via mutations or rare immigrations. We first describe all possible final states of the population, including stable coexistence of two or three strains, or the fixation of a single strain. Second, we give estimate of the invasion and fixation times of a favorable mutant (or immigrant) entering the population in a single copy. We show that invasion and fixation can be slower or faster when considering complex competitive interactions. Third, we explore the parameter space assuming prior distributions of reproduction, death and competitive rates and we estimate the likelihood of the possible dynamics. We show that when mutations can affect competitive interactions, even slightly, stable coexistence is likely. We discuss our results in the context of the evolutionary dynamics of large clonal populations. More forthcoming papers &raquo; <p>Sylvain Billiard and Charline Smadi (March 2020) </p> <p><b>Intransitive competitive interactions can explain the complex dynamics of clonal species during adaptation </b></p> <p><i><a href="https://dx.doi.org/10.1086/707017">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>ompetition drives evolution and pushes species coexistence. Though the fundamental mechanisms are simple, the dynamics of competing clones are surprisingly diverse in bacteria, yeasts, or viruses. This is the case even without sexual reproduction and in very simple, stable, controlled environments: clones can replace each other, can coexist for long stretches of time, and can have cyclical or linear dynamics. Existing population models provide only a partial understanding of this diversity, because they lack generality in either competition, time scales, or the importance of chance. </p><p>Owing to a collaboration between a mathematician and an evolutionary ecologist, it has been made possible to encompass competition intransitivity, mutation, and chance in a single ecological and evolutionary model. Using such a simple model, it is possible to describe most dynamics observed in clonal populations. Approximations of the stochastic process also allow accurate predictions to be made about the likelihood and the duration of the different possible outcomes. Unexpected outcomes were also detected: even if a succession of favorable mutations have arisen, they can be unexpectedly wiped out, and adaptation can be accelerated n some cases when multiple strains interfere. </p><p>The authors’ model shows that, for a better understanding and prediction of the dynamics of clone evolution, ecological and evolutionary theoretical frameworks must be merged together. The development of stochastic models could reconcile these two frameworks, which are too often isolated from each other. Such a synthesis would certainly be extremely fruitful, as clonal populations with many different competing species or strains are ubiquitous (for instance, tumoral cancers, microbial communities, or viruses within a host). </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n large clonal populations, several clones generally compete which results in complex evolutionary and ecological dynamics: experiments show successive selective sweeps of favorable mutations as well as long-term coexistence of multiple clonal strains. The mechanisms underlying either coexistence or fixation of several competing strains have rarely been studied altogether. Conditions for coexistence have mostly been studied by population and community ecology, while rates of invasion and fixation have mostly been studied by population genetics. In order to provide a global understanding of the complexity of the dynamics observed in large clonal populations, we develop a stochastic model where three clones compete. Competitive interactions can be intransitive and we suppose that strains enter the population via mutations or rare immigrations. We first describe all possible final states of the population, including stable coexistence of two or three strains, or the fixation of a single strain. Second, we give estimate of the invasion and fixation times of a favorable mutant (or immigrant) entering the population in a single copy. We show that invasion and fixation can be slower or faster when considering complex competitive interactions. Third, we explore the parameter space assuming prior distributions of reproduction, death and competitive rates and we estimate the likelihood of the possible dynamics. We show that when mutations can affect competitive interactions, even slightly, stable coexistence is likely. We discuss our results in the context of the evolutionary dynamics of large clonal populations. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 04 Nov 2019 06:00:00 GMT “A general model for seed and seedling respiratory metabolism” https://amnat.org/an/newpapers/Mar-Huang-A.html Heng Huang, Jinzhi Ran, Xiaowei Li, Zhiqiang Wang, Renfei Chen, Fan Wu, Miao Ye, Fei Jia, Karl J. Niklas, and Jianming Deng (Mar 2020) A general model for seed and seedling respiratory metabolism Read the Article (Just Accepted) Abstract The ontogeny of seed plants usually involves a dormant dehydrated state and the breaking of dormancy and germination, which distinguishes it from that of most organisms. Seed germination and seedling establishment are critical ontogenetic stages in the plant life cycle and both are fueled by respiratory metabolism. However, the scaling of metabolic rate with respect to individual traits remains poorly understood. Here, we tested metabolic scaling theory during seed germination and early establishment growth using a recently developed model and empirical data collected from 41 species. The results show that (i) the mass-specific respiration rate (Rm) was weakly correlated with body mass, mass-specific N, and C content, (ii) Rm conformed to a single Michaelis-Menten curve as a function of tissue water content, and (iii) the central parameters in the model were highly correlated with DNA content and critical enzyme activities. The model offers new insights and a more integrative scaling theory that quantifies the combined effects of tissue water content and body mass on respiratory metabolism during early plant ontogeny. More forthcoming papers &raquo; <p>Heng Huang, Jinzhi Ran, Xiaowei Li, Zhiqiang Wang, Renfei Chen, Fan Wu, Miao Ye, Fei Jia, Karl J. Niklas, and Jianming Deng (Mar 2020) </p> <p><b>A general model for seed and seedling respiratory metabolism </b></p> <p><i><a href="https://dx.doi.org/10.1086/707072">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he ontogeny of seed plants usually involves a dormant dehydrated state and the breaking of dormancy and germination, which distinguishes it from that of most organisms. Seed germination and seedling establishment are critical ontogenetic stages in the plant life cycle and both are fueled by respiratory metabolism. However, the scaling of metabolic rate with respect to individual traits remains poorly understood. Here, we tested metabolic scaling theory during seed germination and early establishment growth using a recently developed model and empirical data collected from 41 species. The results show that (i) the mass-specific respiration rate (Rm) was weakly correlated with body mass, mass-specific N, and C content, (ii) Rm conformed to a single Michaelis-Menten curve as a function of tissue water content, and (iii) the central parameters in the model were highly correlated with DNA content and critical enzyme activities. The model offers new insights and a more integrative scaling theory that quantifies the combined effects of tissue water content and body mass on respiratory metabolism during early plant ontogeny. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 04 Nov 2019 06:00:00 GMT “Demography-dispersal trait correlations modify the eco-evolutionary dynamics of range expansion” https://amnat.org/an/newpapers/Feb-Ochocki.html Brad M. Ochocki, Julia B. Saltz, and Tom E. X. Miller (Feb 2020) Read the Article (Just Accepted)Many species are expanding their ranges into novel territory. Understanding and predicting the speed of range expansion are long-standing goals with important practical applications for the spread of introduced species and migration by native species in response to climate change. Genetic variation in movement and reproductive potential – the traits thought to control the rate of expansion – sets the stage for rapid evolution, which can affect expansion speed. But what happens when there genetic covariation between these traits? Brad Ochocki and colleagues measured the genetic covariance between dispersal and reproduction in the seed beetle Callosobruchus maculatus, a laboratory model organism for the study of spatial population dynamics. They found that beetles that dispersed very far had reduced reproductive output, and vice versa. This genetic correlation acted as an evolutionary constraint, dampening the extent to which rapid evolution can accelerate range expansion. The authors then used mathematical models to generalize beyond the beetle system to show that, under some conditions, genetically based trade-offs can even cause an evolutionary slowdown of range expansion, since strong dispersers at the leading range edge have poor reproductive performance. The results suggest that rapid evolution should be incorporated into forecasts for range expansion, but that genetic correlations between key expansion traits can generate more diverse eco-evolutionary outcomes than expected under classic models with independently evolving traits. Abstract Spreading populations are subject to evolutionary processes acting on dispersal and reproduction that can increase invasion speed and variability. It is typically assumed that dispersal and demography traits evolve independently, but abundant evidence points to correlations between them that may be positive or negative and genetic, maternal, or environmental. We sought to understand how demography-dispersal correlations modify the eco-evolutionary dynamics of range expansion. We first explored this question with the beetle Callosobruchus maculatus, a laboratory model in which evolutionary acceleration of invasion has been demonstrated. We then built a simulation model to explore the role of trait correlations in this system and more generally. We found that positive correlations amplify the positive influence of evolution on speed and variability, while negative correlations (such as we found empirically) constrain that influence. Strong negative genetic correlations can even cause evolution to decelerate invasion. Genetic and non-genetic (maternal and environmental) correlations had similar effects on some measures of invasion but different effects on others. Model results enabled us to retrospectively explain invasion dynamics and trait evolution in C.&nbsp;maculatus, and may similarly aid the interpretation of other field and laboratory studies. Non-independence of demography and dispersal is an important consideration for understanding and predicting outcomes of range expansion. More forthcoming papers &raquo; <p>Brad M. Ochocki, Julia B. Saltz, and Tom E. X. Miller (Feb 2020)</p> <p><i><a href="https://dx.doi.org/10.1086/706904">Read the Article</a></i> (Just Accepted)</p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>any species are expanding their ranges into novel territory. Understanding and predicting the speed of range expansion are long-standing goals with important practical applications for the spread of introduced species and migration by native species in response to climate change. Genetic variation in movement and reproductive potential – the traits thought to control the rate of expansion – sets the stage for rapid evolution, which can affect expansion speed. But what happens when there genetic covariation between these traits? </p><p> Brad Ochocki and colleagues measured the genetic covariance between dispersal and reproduction in the seed beetle <i>Callosobruchus maculatus</i>, a laboratory model organism for the study of spatial population dynamics. They found that beetles that dispersed very far had reduced reproductive output, and vice versa. This genetic correlation acted as an evolutionary constraint, dampening the extent to which rapid evolution can accelerate range expansion. The authors then used mathematical models to generalize beyond the beetle system to show that, under some conditions, genetically based trade-offs can even cause an evolutionary slowdown of range expansion, since strong dispersers at the leading range edge have poor reproductive performance. The results suggest that rapid evolution should be incorporated into forecasts for range expansion, but that genetic correlations between key expansion traits can generate more diverse eco-evolutionary outcomes than expected under classic models with independently evolving traits. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>preading populations are subject to evolutionary processes acting on dispersal and reproduction that can increase invasion speed and variability. It is typically assumed that dispersal and demography traits evolve independently, but abundant evidence points to correlations between them that may be positive or negative and genetic, maternal, or environmental. We sought to understand how demography-dispersal correlations modify the eco-evolutionary dynamics of range expansion. We first explored this question with the beetle <i>Callosobruchus maculatus</i>, a laboratory model in which evolutionary acceleration of invasion has been demonstrated. We then built a simulation model to explore the role of trait correlations in this system and more generally. We found that positive correlations amplify the positive influence of evolution on speed and variability, while negative correlations (such as we found empirically) constrain that influence. Strong negative genetic correlations can even cause evolution to decelerate invasion. Genetic and non-genetic (maternal and environmental) correlations had similar effects on some measures of invasion but different effects on others. Model results enabled us to retrospectively explain invasion dynamics and trait evolution in <i>C.&nbsp;maculatus</i>, and may similarly aid the interpretation of other field and laboratory studies. Non-independence of demography and dispersal is an important consideration for understanding and predicting outcomes of range expansion. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 24 Oct 2019 05:00:00 GMT “Detecting mosaic patterns in macroevolutionary disparity” https://amnat.org/an/newpapers/Feb-Parins-Fukuchi.html Caroline Parins-Fukuchi (Feb 2020) Read the Article (Just Accepted) Abstract Evolutionary biologists have long sought to understand the full complexity in pattern and process that shapes organismal diversity. Although phylogenetic comparative methods are often used to reconstruct complex evolutionary dynamics, they are typically limited to a single phenotypic trait. Extensions that accommodate multiple traits lack the ability to partition multidimensional datasets into a set of mosaic suites of evolutionarily linked characters. I introduce a comparative framework that identifies heterogeneity in evolutionary patterns across large datasets of continuous traits. Using a model of continuous trait evolution based on the differential accumulation of disparity across lineages in a phylogeny, the approach algorithmically partitions traits into a set of character suites that best explains the data, where each suite displays a distinct pattern in phylogenetic morphological disparity. When applied to empirical data, the approach revealed a mosaic pattern predicted by developmental biology. The evolutionary distinctiveness of individual suites can be investigated in more detail, either by fitting conventional comparative models or by directly studying the phylogenetic patterns in disparity recovered during the analysis. This framework can supplement existing comparative approaches by inferring the complex, integrated patterns that shape evolution across the body plan from disparate developmental, morphometric, and environmental sources of phenotypic data. More forthcoming papers &raquo; <p>Caroline Parins-Fukuchi (Feb 2020) </p> <p><i><a href="https://dx.doi.org/10.1086/706903">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>volutionary biologists have long sought to understand the full complexity in pattern and process that shapes organismal diversity. Although phylogenetic comparative methods are often used to reconstruct complex evolutionary dynamics, they are typically limited to a single phenotypic trait. Extensions that accommodate multiple traits lack the ability to partition multidimensional datasets into a set of mosaic suites of evolutionarily linked characters. I introduce a comparative framework that identifies heterogeneity in evolutionary patterns across large datasets of continuous traits. Using a model of continuous trait evolution based on the differential accumulation of disparity across lineages in a phylogeny, the approach algorithmically partitions traits into a set of character suites that best explains the data, where each suite displays a distinct pattern in phylogenetic morphological disparity. When applied to empirical data, the approach revealed a mosaic pattern predicted by developmental biology. The evolutionary distinctiveness of individual suites can be investigated in more detail, either by fitting conventional comparative models or by directly studying the phylogenetic patterns in disparity recovered during the analysis. This framework can supplement existing comparative approaches by inferring the complex, integrated patterns that shape evolution across the body plan from disparate developmental, morphometric, and environmental sources of phenotypic data. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 24 Oct 2019 05:00:00 GMT “Transitions between the terrestrial and epiphytic habit drove the evolution of seed-aerodynamic traits in orchids” https://amnat.org/an/newpapers/Feb-Fan.html Xu-Li Fan, Guillaume Chomicki, Kai Hao, Qiang Liu, Ying-Ze Xiong, Susanne S. Renner, Jiang-Yun Gao, and Shuang-Quan Huang (Feb 2020) Orchidaceae have repeatedly evolved large seed air spaces, and this correlates with being terrestrial, not epiphytic Read the Article (Just Accepted) The height at which seeds are released is a critical parameter determining the efficiency of seed dispersal by wind. Does this apply to the minute seeds of orchids? We addressed this question with phylogenetically-controlled analyses of 20 seed traits in 121 terrestrial and epiphytic species (from 63 genera), spanning the orchid family. Close-up images of all studied seeds are included with our paper. It turns out that seed air space is closely correlated with the terrestrial or epiphytic habit, which each evolved several times, including returns from the epiphytic to the terrestrial habit. This suggests that aerodynamic traits are under strong selection to increase dispersal ability even in orchid seeds. Abstract Orchids are globally distributed, a feature often attributed to their tiny dust-like seeds. They were ancestrally terrestrial, but in the Eocene expanded into tree canopies, with some lineages later returning to the ground, providing an evolutionarily replicated system. Because seeds are released closer to the ground in terrestrial species than in epiphytic ones, seed traits in terrestrials may have been under selective pressure to increase seed dispersal efficiency. In this study, we test the expectations that (i) seed air space –a trait known to increase seed floatation time in the air– is larger in terrestrial lineages and (ii) has increased following secondary returns to a terrestrial habit. We quantified and scored 20 seed traits in 121 species and carried out phylogenetically-informed analyses. Results strongly support both expectations, suggesting that aerodynamics traits even in dust seeds are under selection to increase dispersal ability, following shifts in average release heights correlated with changes in habit. More forthcoming papers &raquo; <p>Xu-Li Fan, Guillaume Chomicki, Kai Hao, Qiang Liu, Ying-Ze Xiong, Susanne S. Renner, Jiang-Yun Gao, and Shuang-Quan Huang (Feb 2020) </p> <p><b>Orchidaceae have repeatedly evolved large seed air spaces, and this correlates with being terrestrial, not epiphytic </b></p> <p><i><a href="https://dx.doi.org/10.1086/706905">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he height at which seeds are released is a critical parameter determining the efficiency of seed dispersal by wind. Does this apply to the minute seeds of orchids? We addressed this question with phylogenetically-controlled analyses of 20 seed traits in 121 terrestrial and epiphytic species (from 63 genera), spanning the orchid family. Close-up images of all studied seeds are included with our paper. It turns out that seed air space is closely correlated with the terrestrial or epiphytic habit, which each evolved several times, including returns from the epiphytic to the terrestrial habit. This suggests that aerodynamic traits are under strong selection to increase dispersal ability even in orchid seeds. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">O</span>rchids are globally distributed, a feature often attributed to their tiny dust-like seeds. They were ancestrally terrestrial, but in the Eocene expanded into tree canopies, with some lineages later returning to the ground, providing an evolutionarily replicated system. Because seeds are released closer to the ground in terrestrial species than in epiphytic ones, seed traits in terrestrials may have been under selective pressure to increase seed dispersal efficiency. In this study, we test the expectations that (i) seed air space –a trait known to increase seed floatation time in the air– is larger in terrestrial lineages and (ii) has increased following secondary returns to a terrestrial habit. We quantified and scored 20 seed traits in 121 species and carried out phylogenetically-informed analyses. Results strongly support both expectations, suggesting that aerodynamics traits even in dust seeds are under selection to increase dispersal ability, following shifts in average release heights correlated with changes in habit. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 24 Oct 2019 05:00:00 GMT “Comparative analyses of phenotypic sequences using phylogenetic trees” https://amnat.org/an/newpapers/Feb-Caetano.html Daniel S. Caetano and Jeremy M. Beaulieu (Feb 2020) Phylogenetic comparative analysis of cricket songs show strong autocorrelation of rates among sequence positions Read the Article (Just Accepted) Cricket calls are a very common background soundtrack of evening hikes. In field crickets (genus Gryllus), the males relentlessly rub their wings producing the signature chirp sound. The temporal pattern of chirps, or the timing of sounds that comprise the overall cricket melody, varies among different species and is often used by taxonomists to identify and describe species. In this study, Drs. Daniel Caetano and Jeremy Beaulieu at the University of Arkansas combined a robust phylogeny depicting relationships among Gryllus crickets with a novel statistical approach to characterize the evolutionary dynamics of a cricket’s melody. For instance, does the variation among cricket melodies emerge as a consequence of independent evolution of species-specific chirps? Or has the variation among cricket songs evolved by changing neighboring blocks of linked chirps? The authors found strong evidence for correlated changes among neighboring regions of the songs observed within Gryllus. In other words, the diversity of cricket melodies was likely produced by coordinated evolutionary changes within specific chirp blocks. Another important finding was that the silence intervals between each block of chirps were differentiated as the most evolutionary labile attribute of the melodies. Taken together, these results confirm previous work which suggested that cricket melodies generally evolve through the expansion and contraction of both neighboring chirp and silence blocks. Abstract Phenotypic sequences are a type of multivariate trait organized structurally, such as teeth distributed along the dental arch, or temporally, such as the stages of an ontogenetic series. Unlike other multivariate traits, the elements of a phenotypic sequence are distributed along an ordered set, which allows for distinct evolutionary patterns between neighboring and distant positions. In fact, sequence traits share many characteristics with molecular sequences, although important distinctions pose challenges to current comparative methods. We implement an approach to estimate rates of trait evolution that explicitly incorporates the sequence organization of traits. We apply models to study the temporal pattern evolution of cricket calling songs. We test whether neighboring positions along a phenotypic sequence have correlated rates of evolution or if rate variation is independent of sequence position. Our results show that cricket song evolution is strongly autocorrelated and models perform well when used with sequence phenotypes even under small sample sizes. Our approach is flexible and can be applied to any multivariate trait with discrete units organized in a sequence-like structure. More forthcoming papers &raquo; <p>Daniel S. Caetano and Jeremy M. Beaulieu (Feb 2020) </p> <p><b>Phylogenetic comparative analysis of cricket songs show strong autocorrelation of rates among sequence positions </b></p> <p><i><a href="https://dx.doi.org/10.1086/706912">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>ricket calls are a very common background soundtrack of evening hikes. In field crickets (genus <i>Gryllus</i>), the males relentlessly rub their wings producing the signature chirp sound. The temporal pattern of chirps, or the timing of sounds that comprise the overall cricket melody, varies among different species and is often used by taxonomists to identify and describe species. In this study, Drs. Daniel Caetano and Jeremy Beaulieu at the University of Arkansas combined a robust phylogeny depicting relationships among <i>Gryllus</i> crickets with a novel statistical approach to characterize the evolutionary dynamics of a cricket’s melody. For instance, does the variation among cricket melodies emerge as a consequence of independent evolution of species-specific chirps? Or has the variation among cricket songs evolved by changing neighboring blocks of linked chirps? The authors found strong evidence for correlated changes among neighboring regions of the songs observed within <i>Gryllus</i>. In other words, the diversity of cricket melodies was likely produced by coordinated evolutionary changes within specific chirp blocks. Another important finding was that the silence intervals between each block of chirps were differentiated as the most evolutionary labile attribute of the melodies. Taken together, these results confirm previous work which suggested that cricket melodies generally evolve through the expansion and contraction of both neighboring chirp and silence blocks. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>henotypic sequences are a type of multivariate trait organized structurally, such as teeth distributed along the dental arch, or temporally, such as the stages of an ontogenetic series. Unlike other multivariate traits, the elements of a phenotypic sequence are distributed along an ordered set, which allows for distinct evolutionary patterns between neighboring and distant positions. In fact, sequence traits share many characteristics with molecular sequences, although important distinctions pose challenges to current comparative methods. We implement an approach to estimate rates of trait evolution that explicitly incorporates the sequence organization of traits. We apply models to study the temporal pattern evolution of cricket calling songs. We test whether neighboring positions along a phenotypic sequence have correlated rates of evolution or if rate variation is independent of sequence position. Our results show that cricket song evolution is strongly autocorrelated and models perform well when used with sequence phenotypes even under small sample sizes. Our approach is flexible and can be applied to any multivariate trait with discrete units organized in a sequence-like structure. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 24 Oct 2019 05:00:00 GMT “Wasp waist and flight: convergent evolution in wasps reveals a link between wings and body shapes” https://amnat.org/an/newpapers/Feb-Perrard.html Adrien Perrard (Feb 2020) Coevolution of wings and body shapes suggests that some wasps were selected to fly fast and others to turn quickly Read the Article (Just Accepted) About 400 million years ago, insects took to the sky before any other known animal. Today, we observe a tremendous diversity of insects, including many species with astonishing flight performances, but insect flight remains ill-understood. Since the morphology of an organism affects its performance, we need to understand better how the body parts related to flight in insects evolve to identify the components underlying these flight performances. For example, do the different body parts involved in flight evolve in concert, because of common selective pressure? If so, do they compensate each other to keep flight performances around a single optimum? To answer these questions, Dr. Adrien Perrard studied how the shapes of wings, thorax and abdomen change relative to each other in vespid wasps. In these wasps, the most striking morphological variation is the elongation of the ‘petiole’, the segment connecting the equivalent of thorax and abdomen in wasps. Some species display a short petiole with a bullet-like silhouette likely minimizing drag forces, hence improving flight speed. Other species have a very elongated petiole, which would increase the efficiency of abdominal movements for flight stability. According to recent phylogenies, such a variation in petiole morphology occurred multiple times in the evolutionary history of wasps. But wings and thorax are also related to flight performances. Variation in wings or thorax shapes reflecting the petiole variation would be unlikely by chance. However, they would be expected if a change in petiole had an influence on flight performance, which in turn modified natural selection on the other two body parts. Therefore, the author tested whether wasps with a similar petiole also developed similar wings and thorax morphologies during their evolution, and whether these morphologies could be related to flight performances. The results show a clear link between the morphology of the wings and that of the abdomen. Wasps with different body-types tend to have wing shapes more similar than expected by chance. In addition, those morphologies were related to similar flight performances, both wings and petiole promoting either speed or maneuverability. Surprisingly, the shape of the thorax was not related to wing shapes: the overall shape of the thorax may not be as important for flight as that of the wings or the petiole. These results shed some light on the evolutionary mechanisms which drove the morphological diversity of these wasps. Previously, there was no clear explanation for the observed petiole shape elongation in these insects. However, wasps with different body types seem to have experienced different selective pressures regarding their flight performances, to optimize either their maximal speed or their maneuverability. So the diversity of selective regimes on flight-related structures may have contributed to the evolution of the diversity in body shapes in these wasps. In addition, these results strongly suggest that the evolution of wing shape was influenced by the shape of the body wings have to lift, and they stress the importance of abdomen in insect flight. Abstract Insect flight is made possible by different morphological structures: wings produce the lift, the thorax drives the wings’ movements and the abdomen serves as a secondary control device. As such, the covariation of these structures could reflect functional constraints related to flight performances. This study examines evolutionary convergences in wasp body shapes to provide the first evidence for morphological integration among insect wings, thorax and abdomen. Shapes of the fore- and hindwings, thorax and petiole (connecting abdomen and thorax) of 22 Vespidae species were analyzed using computerized tomography and geometric morphometrics. Results show a clear relationship between petiole and wings or thorax shapes, but not between wings and thorax. Wasps with elongated bodies have pointed wings, both features thought to improve flight maneuverability. In contrast, stouter species have rounded wings, which may allow for higher flight speeds. These integration patterns suggest that multiple selective regimes on flight performance, some of them biased towards maneuverability or maximal speed, drove the morphological diversity in Vespidae. The results also suggest that wing shapes evolved under constraints related to the body type they have to lift. The abdomen morphology is thus another factor to take into account to understand the flight performance of insects. More forthcoming papers &raquo; <p>Adrien Perrard (Feb 2020) </p> <p><b>Coevolution of wings and body shapes suggests that some wasps were selected to fly fast and others to turn quickly </b></p> <p><i><a href="https://dx.doi.org/10.1086/706914">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>bout 400 million years ago, insects took to the sky before any other known animal. Today, we observe a tremendous diversity of insects, including many species with astonishing flight performances, but insect flight remains ill-understood. Since the morphology of an organism affects its performance, we need to understand better how the body parts related to flight in insects evolve to identify the components underlying these flight performances. For example, do the different body parts involved in flight evolve in concert, because of common selective pressure? If so, do they compensate each other to keep flight performances around a single optimum? To answer these questions, Dr. Adrien Perrard studied how the shapes of wings, thorax and abdomen change relative to each other in vespid wasps. </p><p>In these wasps, the most striking morphological variation is the elongation of the ‘petiole’, the segment connecting the equivalent of thorax and abdomen in wasps. Some species display a short petiole with a bullet-like silhouette likely minimizing drag forces, hence improving flight speed. Other species have a very elongated petiole, which would increase the efficiency of abdominal movements for flight stability. According to recent phylogenies, such a variation in petiole morphology occurred multiple times in the evolutionary history of wasps. But wings and thorax are also related to flight performances. Variation in wings or thorax shapes reflecting the petiole variation would be unlikely by chance. However, they would be expected if a change in petiole had an influence on flight performance, which in turn modified natural selection on the other two body parts. Therefore, the author tested whether wasps with a similar petiole also developed similar wings and thorax morphologies during their evolution, and whether these morphologies could be related to flight performances. </p><p>The results show a clear link between the morphology of the wings and that of the abdomen. Wasps with different body-types tend to have wing shapes more similar than expected by chance. In addition, those morphologies were related to similar flight performances, both wings and petiole promoting either speed or maneuverability. Surprisingly, the shape of the thorax was not related to wing shapes: the overall shape of the thorax may not be as important for flight as that of the wings or the petiole. </p><p>These results shed some light on the evolutionary mechanisms which drove the morphological diversity of these wasps. Previously, there was no clear explanation for the observed petiole shape elongation in these insects. However, wasps with different body types seem to have experienced different selective pressures regarding their flight performances, to optimize either their maximal speed or their maneuverability. So the diversity of selective regimes on flight-related structures may have contributed to the evolution of the diversity in body shapes in these wasps. In addition, these results strongly suggest that the evolution of wing shape was influenced by the shape of the body wings have to lift, and they stress the importance of abdomen in insect flight.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>nsect flight is made possible by different morphological structures: wings produce the lift, the thorax drives the wings’ movements and the abdomen serves as a secondary control device. As such, the covariation of these structures could reflect functional constraints related to flight performances. This study examines evolutionary convergences in wasp body shapes to provide the first evidence for morphological integration among insect wings, thorax and abdomen. Shapes of the fore- and hindwings, thorax and petiole (connecting abdomen and thorax) of 22 Vespidae species were analyzed using computerized tomography and geometric morphometrics. Results show a clear relationship between petiole and wings or thorax shapes, but not between wings and thorax. Wasps with elongated bodies have pointed wings, both features thought to improve flight maneuverability. In contrast, stouter species have rounded wings, which may allow for higher flight speeds. These integration patterns suggest that multiple selective regimes on flight performance, some of them biased towards maneuverability or maximal speed, drove the morphological diversity in Vespidae. The results also suggest that wing shapes evolved under constraints related to the body type they have to lift. The abdomen morphology is thus another factor to take into account to understand the flight performance of insects. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 24 Oct 2019 05:00:00 GMT “Spatial scales of population synchrony in predator-prey systems” https://amnat.org/an/newpapers/Feb-Jarillo.html Javier Jarillo, Bernt-Erik Sæther, Steinar Engen, and Francisco Javier Cao García (Feb 2020) Predator population has larger spatial scale of synchrony than the prey and the environmental noise Read the Article (Just Accepted) Predators often have changes in population size correlated over larger distances than their prey species, and therefore face a higher risk of regional extinction. Environmental conditions in an ecosystem are not constant; they fluctuate around their mean value, but they are usually similar in locations close to each other. These environmental fluctuations change the population growth of the different species, influencing their population size. However, there is a tendency for environmental fluctuations to have a particularly strong effect at the lower levels of the food web, and then for these effects to propagate bottom-up in the trophic chain. A recent study concluded that bottom-up propagation of the environmental fluctuations in a predator-prey ecosystem leads to higher spatial scale of population synchrony for the predator than for the prey. This is likely to imply a larger size of the regional extinctions for the predator. The study also supported the conclusion that harvesting also affects the spatial scale of population synchrony of the unharvested species. This implies that human perturbations of ecosystems through exploitation or modifying dispersal processes can affect food web structures and trophic interactions over large geographical areas. Norwegian (CBD, NTNU) and Spanish (UCM) researchers conducted this study supported by the Norwegian SUSTAIN and Abel projects and by the Spanish Ministry of Science. Abstract Many species show synchronous fluctuations in population size over large geographical areas, which are likely to increase their regional extinction risk. Here we examine how the degree of spatial synchrony in population dynamics is affected by trophic interactions using a two-species predator-prey model with spatially correlated environmental noise. We show that the predator has a larger spatial scale of population synchrony than the prey, if the population fluctuations of both species are mainly determined by the direct effect of stochastic environmental variations in the prey. This result implies that, in bottom-up regulated ecosystems, the spatial scale of synchrony of the predator population increases beyond the scale of the spatial autocorrelation in the environmental noise and in the prey fluctuations. Harvesting the prey increases the spatial scale of population synchrony of the predator, while harvesting the predator reduces the spatial scale of the population fluctuations of its prey. Hence, the development of sustainable harvesting strategies should consider the impact also on unharvested species at other trophic levels; and the human perturbations of ecosystems, through exploitation or through an effect on dispersal processes, which can affect food web structures and trophic interactions over large geographical areas. Escalas espaciales de sincronía poblacional en sistemas depredador-presa Muchas especies presentan fluctuaciones sincronizadas en su tamaño poblacional en grandes áreas geográficas, lo que probablemente aumenta su riesgo de extinción regional. Aquí examinamos cómo el grado de sincronía espacial en la dinámica poblacional se ve afectado por las interacciones tróficas utilizando un modelo depredador-presa con ruido ambiental espacialmente correlacionado. Mostramos que el depredador tiene una mayor escala espacial de sincronía poblacional que la presa, si las fluctuaciones poblacionales de ambas especies están determinadas principalmente por el efecto directo de las variaciones ambientales estocásticas en la presa. Esto implica que, en ecosistemas regulados de abajo hacia arriba (“bottom-up”), la escala espacial de sincronía de la población del depredador supera a las escalas de autocorrelación espacial del ruido ambiental y de las fluctuaciones de la presa. La extracción de presas del ecosistema aumenta la escala espacial de sincronía poblacional del depredador, mientras que la extracción de depredadores reduce la escala espacial de las fluctuaciones poblacionales de su presa. Por lo tanto, el desarrollo de estrategias de explotación sostenible debería considerar el impacto en las especies no explotadas de otros niveles tróficos; y las perturbaciones humanas sobre los ecosistemas, a través de la explotación o de cambios provocados en los procesos de dispersión, que pueden afectar a las estructuras de las cadenas alimenticias y a las interacciones tróficas en grandes áreas geográficas. More forthcoming papers &raquo; <p>Javier Jarillo, Bernt-Erik Sæther, Steinar Engen, and Francisco Javier Cao García (Feb 2020) </p> <p><b>Predator population has larger spatial scale of synchrony than the prey and the environmental noise </b></p> <p><i><a href="https://dx.doi.org/10.1086/706913">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>redators often have changes in population size correlated over larger distances than their prey species, and therefore face a higher risk of regional extinction. Environmental conditions in an ecosystem are not constant; they fluctuate around their mean value, but they are usually similar in locations close to each other. These environmental fluctuations change the population growth of the different species, influencing their population size. However, there is a tendency for environmental fluctuations to have a particularly strong effect at the lower levels of the food web, and then for these effects to propagate bottom-up in the trophic chain. </p><p>A recent study concluded that bottom-up propagation of the environmental fluctuations in a predator-prey ecosystem leads to higher spatial scale of population synchrony for the predator than for the prey. This is likely to imply a larger size of the regional extinctions for the predator. </p><p>The study also supported the conclusion that harvesting also affects the spatial scale of population synchrony of the unharvested species. This implies that human perturbations of ecosystems through exploitation or modifying dispersal processes can affect food web structures and trophic interactions over large geographical areas. Norwegian (CBD, NTNU) and Spanish (UCM) researchers conducted this study supported by the Norwegian SUSTAIN and Abel projects and by the Spanish Ministry of Science. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>any species show synchronous fluctuations in population size over large geographical areas, which are likely to increase their regional extinction risk. Here we examine how the degree of spatial synchrony in population dynamics is affected by trophic interactions using a two-species predator-prey model with spatially correlated environmental noise. We show that the predator has a larger spatial scale of population synchrony than the prey, if the population fluctuations of both species are mainly determined by the direct effect of stochastic environmental variations in the prey. This result implies that, in bottom-up regulated ecosystems, the spatial scale of synchrony of the predator population increases beyond the scale of the spatial autocorrelation in the environmental noise and in the prey fluctuations. Harvesting the prey increases the spatial scale of population synchrony of the predator, while harvesting the predator reduces the spatial scale of the population fluctuations of its prey. Hence, the development of sustainable harvesting strategies should consider the impact also on unharvested species at other trophic levels; and the human perturbations of ecosystems, through exploitation or through an effect on dispersal processes, which can affect food web structures and trophic interactions over large geographical areas. </p> <h4>Escalas espaciales de sincronía poblacional en sistemas depredador-presa</h4> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>uchas especies presentan fluctuaciones sincronizadas en su tamaño poblacional en grandes áreas geográficas, lo que probablemente aumenta su riesgo de extinción regional. Aquí examinamos cómo el grado de sincronía espacial en la dinámica poblacional se ve afectado por las interacciones tróficas utilizando un modelo depredador-presa con ruido ambiental espacialmente correlacionado. Mostramos que el depredador tiene una mayor escala espacial de sincronía poblacional que la presa, si las fluctuaciones poblacionales de ambas especies están determinadas principalmente por el efecto directo de las variaciones ambientales estocásticas en la presa. Esto implica que, en ecosistemas regulados de abajo hacia arriba (“bottom-up”), la escala espacial de sincronía de la población del depredador supera a las escalas de autocorrelación espacial del ruido ambiental y de las fluctuaciones de la presa. La extracción de presas del ecosistema aumenta la escala espacial de sincronía poblacional del depredador, mientras que la extracción de depredadores reduce la escala espacial de las fluctuaciones poblacionales de su presa. Por lo tanto, el desarrollo de estrategias de explotación sostenible debería considerar el impacto en las especies no explotadas de otros niveles tróficos; y las perturbaciones humanas sobre los ecosistemas, a través de la explotación o de cambios provocados en los procesos de dispersión, que pueden afectar a las estructuras de las cadenas alimenticias y a las interacciones tróficas en grandes áreas geográficas. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 24 Oct 2019 05:00:00 GMT Registration for the ASN Stand-Alone Meeting 2020 https://amnat.org/announcements/ASNAsilomar.html DEADLINE October 31 for Registration for the American Society of Naturalists Stand-Alone meeting at Asilomar Participants will need to submit their presentation title and a short abstract (~200-250 words) at the time of registration. Registration for the meeting will be available through Eventbrite at (payable with a credit card or Paypal) https://www.eventbrite.com/e/american-naturalist-2020-registration-68547733115?aff=ASNMembership &nbsp; Housing at Asilomar needs to be reserved separately at https://book.passkey.com/e/49957223 (updated) &nbsp; Registration costs for members are greatly discounted. Anybody can become an ASN member at anytime here: https://amnat.org/membership/beamember.html. The cost of membership is less than the additional cost of registration for non-members. &nbsp; The American Society of Naturalists invites graduate students, postdocs, faculty and other professionals from ecology, evolution, behavior, genetics, physiology, and associated fields to a stand alone meeting at the Asilomar Conference Grounds on January 3-7, 2020. This meeting will celebrate the unique ability of ASN to unify broad conceptual themes across biology by integrating theory with data and by using new technological tools to address long-standing questions. In short, this conference will showcase what it means to be a naturalist and researcher in the 21st century. &nbsp; This conference is unique because it involves a small number of participants (200 people) interacting closely over meals, scientific talks, and casual conversations in a beautiful natural setting on the shore of the Monterey Peninsula. The scientific program will consist of posters, 15-minute talks, and 5-minute lightning talks, in addition to three symposia in the afternoons. Lightning talks will also include five minutes for questions, so are helpful for getting feedback and starting a conversation. Evening activities will include a presidential debate, a natural history trivia contest, and interactions around a bonfire. More information is available at www.amnat2020.com. &nbsp; If you have any questions, concerns, or suggestions, please email Casey terHorst (casey.terhorst@csun.edu). &nbsp; &nbsp; &nbsp;Planning for stand-alone meetings requires a two-year lead time.&nbsp; We had feedback from some attendees at the 2018 meeting that they would like the meeting to move around the country more.&nbsp; Unfortunately, the lead time was too short to change venues for the the 2020 meeting. We are actively looking NOW for organizers and venues in other parts of the country for the 2022 meetings. Please make suggestions! To recap: we need a venue that can accommodate 220 people, with approx. 7 smaller meeting rooms, one large room that can accommodate all present, joint eating facilities, and that ideally is located in a nice natural setting, in a place that is pleasant outside in January and not prohibitively expensive. These are harder criteria to meet than one might imagine. Anyone with suggestions for either organizer or venue, please contact&nbsp; Michael Whitlock (whitlock@zoology.ubc.ca) <p><strong>DEADLINE October 31 </strong>for Registration for the American Society of Naturalists Stand-Alone meeting at Asilomar</p> <p>Participants will need to submit their presentation title and a short abstract (~200-250 words) at the time of registration. Registration for the meeting will be available through Eventbrite at (payable with a credit card or Paypal)<br /> <a href="https://www.eventbrite.com/e/american-naturalist-2020-registration-68547733115?aff=ASNMembership">https://www.eventbrite.com/e/american-naturalist-2020-registration-68547733115?aff=ASNMembership</a><br /> &nbsp;<br /> Housing at Asilomar needs to be reserved separately at</p> <p><span style="font-size:12.0pt"><span style="font-family:&quot;Times New Roman&quot;,serif"><a href="https://book.passkey.com/e/49957223" style="color:blue; text-decoration:underline">https://book.passkey.com/e/49957223</a></span></span><br /> (updated)<br /> &nbsp;<br /> Registration costs for members are greatly discounted. Anybody can become an ASN member at anytime here: https://amnat.org/membership/beamember.html. The cost of membership is less than the additional cost of registration for non-members.<br /> &nbsp;<br /> The American Society of Naturalists invites graduate students, postdocs, faculty and other professionals from ecology, evolution, behavior, genetics, physiology, and associated fields to a stand alone meeting at the Asilomar Conference Grounds on January 3-7, 2020. This meeting will celebrate the unique ability of ASN to unify broad conceptual themes across biology by integrating theory with data and by using new technological tools to address long-standing questions. In short, this conference will showcase what it means to be a naturalist and researcher in the 21st century.<br /> &nbsp;<br /> This conference is unique because it involves a small number of participants (200 people) interacting closely over meals, scientific talks, and casual conversations in a beautiful natural setting on the shore of the Monterey Peninsula. The scientific program will consist of posters, 15-minute talks, and 5-minute lightning talks, in addition to three symposia in the afternoons. Lightning talks will also include five minutes for questions, so are helpful for getting feedback and starting a conversation. Evening activities will include a presidential debate, a natural history trivia contest, and interactions around a bonfire. More information is available at <a href="http://www.amnat2020.com">www.amnat2020.com</a>.<br /> &nbsp;<br /> If you have any questions, concerns, or suggestions, please email Casey terHorst (<a href="mailto:casey.terhorst@csun.edu">casey.terhorst@csun.edu</a>).</p> <p>&nbsp;</p> <p>&nbsp;</p> <p>&nbsp;</p><p>Planning for stand-alone meetings requires a two-year lead time.&nbsp; We had feedback from some attendees at the 2018 meeting that they would like the meeting to move around the country more.&nbsp; Unfortunately, the lead time was too short to change venues for the the 2020 meeting.</p> <p>We are actively looking NOW for organizers and venues in other parts of the country for the 2022 meetings. Please make suggestions!</p> <p>To recap: we need a venue that can accommodate 220 people, with approx. 7 smaller meeting rooms, one large room that can accommodate all present, joint eating facilities, and that ideally is located in a nice natural setting, in a place that is pleasant outside in January and not prohibitively expensive. These are harder criteria to meet than one might imagine.</p> <p>Anyone with suggestions for either organizer or venue, please contact&nbsp; Michael Whitlock (<a href="mailto:whitlock@zoology.ubc.ca?subject=Stand-Alone%20Meeting%20Location">whitlock@zoology.ubc.ca</a>)</p> Tue, 22 Oct 2019 05:00:00 GMT Nominations for the Sewall Wright Award https://amnat.org/announcements/NomWright.html The American Society of Naturalists invites nominations for the 2020 Sewall Wright Award. The Sewall Wright Award was established in 1991 for a senior but highly active investigator who is making fundamental contributions to the Society’s goals in promoting the conceptual unification of the natural biological sciences. The winner of the 2020 Sewall Wright Award President will be announced by the President during the annual meeting prior to the Presidential address.&nbsp; The recipient will be invited to write a paper for publication in a special section of the journal and will receive an honorarium of $1000. The recipient need not be a member of the Society. The ASN strongly encourages its members to submit nominations of deserving people, preferentially scientists in their prime period as active and influential researcher rather than nearing retirement, who have been successful at conceptually unifying the biological sciences in some way. Ideally, all areas of ecology, evolution, behavioral ecology, and genetics are represented among the nominees. Nominations will be held over for two years. The names of former recipients can be found here: https://www.amnat.org/awards.html#Wright For the 2020 Sewall Wright Award, the prize committee encourages nominations from the membership. A nomination should consist of a letter with a brief description of why the nominee is deserving of the award. Please send all nominations by December 15, 2019, via e-mail to Monica Geber (mag9@cornell.edu). Please indicate “Sewall Wright Award” in the subject line and let the filename of the nomination letter indicate the name of the nominee. <p>The American Society of Naturalists invites nominations for the 2020 Sewall Wright Award. The Sewall Wright Award was established in 1991 for a senior but highly active investigator who is making fundamental contributions to the Society&rsquo;s goals in promoting the conceptual unification of the natural biological sciences. The winner of the 2020 Sewall Wright Award President will be announced by the President during the annual meeting prior to the Presidential address.&nbsp; The recipient will be invited to write a paper for publication in a special section of the journal and will receive an honorarium of $1000. The recipient need not be a member of the Society.</p> <p>The ASN strongly encourages its members to submit nominations of deserving people, preferentially scientists in their prime period as active and influential researcher rather than nearing retirement, who have been successful at conceptually unifying the biological sciences in some way. Ideally, all areas of ecology, evolution, behavioral ecology, and genetics are represented among the nominees. Nominations will be held over for two years.</p> <p>The names of former recipients can be found here:<br /> <a href="https://www.amnat.org/awards.html#Wright">https://www.amnat.org/awards.html#Wright</a></p> <p>For the 2020 Sewall Wright Award, the prize committee encourages nominations from the membership. A nomination should consist of a letter with a brief description of why the nominee is deserving of the award. Please send all nominations by December 15, 2019, via e-mail to Monica Geber (<a href="mailto:mag9@cornell.edu">mag9@cornell.edu</a>). Please indicate &ldquo;Sewall Wright Award&rdquo; in the subject line and let the filename of the nomination letter indicate the name of the nominee.</p> Sun, 20 Oct 2019 05:00:00 GMT Call for Nominations for ASN President and Vice President https://amnat.org/announcements/NomASNOfficersANN.html Members of the American Society of Naturalists are encouraged to submit nominations for the Executive Committee (EC). Elections will be held in 2020 for President and Vice President. The President serves on the EC from 2021-2025, acting as President in 2022 The Vice President serves on the EC from 2021-2023, acting as VP in 2022. The VP organizes a symposium to be presented at the meetings in 2022 and edits the symposium papers for publication in The American Naturalist. Names of nominees for specific offices should be submitted by January 15, 2020, to Megan Frederickson (m.frederickson@utoronto.ca) Please indicate “ASN Nomination” in the subject line. As you contemplate nominations, you may want to check the current (https://www.amnat.org/about/governance/execcomm.html) and past officers (https://www.amnat.org/about/history/past-ec.html) for reference. &nbsp;The PRESIDENT leads the ASN Executive Council and selects the membership of the award and officer nomination committees. The President selects the President’s Award for the “best” paper in The American Naturalist in the past year, gives the ASN Presidential Address and presents the Society’s awards at the annual meeting, and represents the ASN in multiple other ways through the year. The President serves on the Executive Council for five years, including one year as President-Elect and three years as a Past-President. The VICE PRESIDENT organizes the Vice-President’s Symposium for the annual meeting and edits the special supplement to The American Naturalist that contains the papers derived from the VP Symposium. The Vice-President is also the Society’s liaison for the organizers of the annual meeting. The Vice-President serves as a member of the Executive Council for three years, two as a regular member and one as ex officio member. <p>Members of the American Society of Naturalists are encouraged to submit nominations for the Executive Committee (EC). Elections will be held in 2020 for President and Vice President.</p> <ul> <li>The President serves on the EC from 2021-2025, acting as President in 2022</li> <li>The Vice President serves on the EC from 2021-2023, acting as VP in 2022. The VP organizes a symposium to be presented at the meetings in 2022 and edits the symposium papers for publication in <em>The American Naturalist</em>.</li> </ul> <p><strong>Names of nominees for specific offices should be submitted by January 15, 2020, to Megan Frederickson (<a href="mailto:m.frederickson@utoronto.ca?subject=ASN%20Nomination">m.frederickson@utoronto.ca</a>)</strong></p> <p>Please indicate &ldquo;ASN Nomination&rdquo; in the subject line.</p> <p>As you contemplate nominations, you may want to check the current (<a href="https://www.amnat.org/about/governance/execcomm.html">https://www.amnat.org/about/governance/execcomm.html</a>) and past officers (<a href="https://www.amnat.org/about/history/past-ec.html)">https://www.amnat.org/about/history/past-ec.html)</a> for reference.</p> <p>&nbsp;</p><p>The <strong>PRESIDENT </strong>leads the ASN Executive Council and selects the membership of the award and officer nomination committees. The President selects the President&rsquo;s Award for the &ldquo;best&rdquo; paper in <em>The American Naturalist </em>in the past year, gives the ASN Presidential Address and presents the Society&rsquo;s awards at the annual meeting, and represents the ASN in multiple other ways through the year. The President serves on the Executive Council for five years, including one year as President-Elect and three years as a Past-President.</p> <p>The <strong>VICE PRESIDENT </strong>organizes the Vice-President&rsquo;s Symposium for the annual meeting and edits the special supplement to <em>The American Naturalist </em>that contains the papers derived from the VP Symposium. The Vice-President is also the Society&rsquo;s liaison for the organizers of the annual meeting. The Vice-President serves as a member of the Executive Council for three years, two as a regular member and one as ex officio member.</p> Fri, 18 Oct 2019 05:00:00 GMT “An effective mutualism? The role of theoretical studies in ecology and evolution” https://amnat.org/an/newpapers/VP-Servedio.html Maria R. Servedio (Feb 2020) What is the role of, and challenges faced by, theoretical studies in ecology and evolution? Read the Article (Just Accepted) In an introductory article to the 2018 Vice-Presidential Symposium collection Maria Servedio briefly reviews how common theory is, how it is perceived by empiricists, and how assumptions made in theoretical studies can pose a challenge to the acceptance of theory. She includes a survey that shows how often citations of theoretical studies in non-theoretical studies are perceived by the theoretical authors as specific and appropriate, as just general to topic, or as incorrect. Although communication of theory to non-theoreticians leaves something to be desired, Servedio includes some recommendations for how the situation might be improved. The article also previews the variety of theoretical papers that comprise the contributions to the Vice-Presidential Symposium collection, including articles by Erol Akçay (on evolution of the game in game theory), Emma Goldberg and Jasmine Foo (on memory in trait macroevolution), Sarah Otto and Alirio Rosales (on the role of narrative in theoretical studies), Paula Vasconcelos and Claus Rueffler (on the evolution of resource specialization), Stephan Peischl and Kimberly Gilbert (on range expansion), Jason Sardell and Mark Kirkpatrick (on sex differences in recombination), and Hanna Kokko (on facultative sex). Abstract Theoretical models often have fundamentally different goals than do empirical studies of the same topic. Models can test the logic of existing hypotheses, explore the plausibility of new hypotheses, provide expectations that can be tested with data, and address aspects of topics that are currently inaccessible empirically. Theoretical models are common in ecology and evolution, and are generally well-cited, but I show that many citations appearing in non-theoretical studies are general to topic and a substantial proportion are incorrect. One potential cause of this pattern is that some functions of models are rather abstract, leading to miscommunication between theoreticians and empiricists. Such misunderstandings are often triggered by simplifying, logistical assumptions that modelers make. The 2018 Vice Presidential Symposium of the American Society of Naturalists included a variety of mathematical models in ecology and evolution from across several topics. Common threads that appear in the use of the models are identified, highlighting the power of a theoretical approach and the role of the assumptions that such models make. More forthcoming papers &raquo; <p>Maria R. Servedio (Feb 2020) </p> <p><b>What is the role of, and challenges faced by, theoretical studies in ecology and evolution? </b></p> <p><i><a href="https://dx.doi.org/10.1086/706814">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n an introductory article to the 2018 Vice-Presidential Symposium collection Maria Servedio briefly reviews how common theory is, how it is perceived by empiricists, and how assumptions made in theoretical studies can pose a challenge to the acceptance of theory. She includes a survey that shows how often citations of theoretical studies in non-theoretical studies are perceived by the theoretical authors as specific and appropriate, as just general to topic, or as incorrect. Although communication of theory to non-theoreticians leaves something to be desired, Servedio includes some recommendations for how the situation might be improved. </p><p>The article also previews the variety of theoretical papers that comprise the contributions to the Vice-Presidential Symposium collection, including articles by Erol Akçay (on evolution of the game in game theory), Emma Goldberg and Jasmine Foo (on memory in trait macroevolution), Sarah Otto and Alirio Rosales (on the role of narrative in theoretical studies), Paula Vasconcelos and Claus Rueffler (on the evolution of resource specialization), Stephan Peischl and Kimberly Gilbert (on range expansion), Jason Sardell and Mark Kirkpatrick (on sex differences in recombination), and Hanna Kokko (on facultative sex). </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>heoretical models often have fundamentally different goals than do empirical studies of the same topic. Models can test the logic of existing hypotheses, explore the plausibility of new hypotheses, provide expectations that can be tested with data, and address aspects of topics that are currently inaccessible empirically. Theoretical models are common in ecology and evolution, and are generally well-cited, but I show that many citations appearing in non-theoretical studies are general to topic and a substantial proportion are incorrect. One potential cause of this pattern is that some functions of models are rather abstract, leading to miscommunication between theoreticians and empiricists. Such misunderstandings are often triggered by simplifying, logistical assumptions that modelers make. The 2018 Vice Presidential Symposium of the American Society of Naturalists included a variety of mathematical models in ecology and evolution from across several topics. Common threads that appear in the use of the models are identified, highlighting the power of a theoretical approach and the role of the assumptions that such models make. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 17 Oct 2019 05:00:00 GMT Nominations for the Joint Council IDEA Award https://amnat.org/announcements/NomIDEAaward.html The American Society of Naturalists, the Society for the Study of Evolution, and the Society of Systematic Biologists announce the call for nominations for the 1st annual ASN/SSE/SSB Inclusiveness, Diversity, Equity, and Access (IDEA) Award. The IDEA Award will be given to a person at any career stage who has strengthened the ecology and evolutionary biology community by promoting inclusiveness and diversity in our fields. The award can also be presented to a group. The recipient will receive a plaque at the annual meeting of ASN/SSB/SSE and a $1000 honorarium. ***Eligibility Note: No contemporary officer, editor, member of diversity committee, or meeting organizer of the three societies is eligible for the award.*** Nomination packages should include: 1)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A single letter including biographical information (name, title, organization) of the person or group being nominated, along with a short description (300 words or less) of the activities supporting the nomination.&nbsp; The letter must also include a section on the nature of impact the person or group has had on inclusivity, diversity, and equity in the field. &nbsp; 2)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A brief biosketch or list of activities (maximum 3 pages) for the person/group nominated. 3)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Self-nominations are welcome and should be accompanied by a letter of support for the nomination from someone familiar with the activities of the nominee. Nominations should be submitted by January 15, 2020 by going to the award nomination form: http://bit.ly/evoidea <p>The American Society of Naturalists, the Society for the Study of Evolution, and the Society of Systematic Biologists announce the call for nominations for the 1st annual ASN/SSE/SSB Inclusiveness, Diversity, Equity, and Access (IDEA) Award. The IDEA Award will be given to a person at any career stage who has strengthened the ecology and evolutionary biology community by promoting inclusiveness and diversity in our fields. The award can also be presented to a group. The recipient will receive a plaque at the annual meeting of ASN/SSB/SSE and a $1000 honorarium.</p> <p>***Eligibility Note: No contemporary officer, editor, member of diversity committee, or meeting organizer of the three societies is eligible for the award.***</p> <p><strong>Nomination packages should include:</strong></p> <p>1)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A single letter including biographical information (name, title, organization) of the person or group being nominated, along with a short description (300 words or less) of the activities supporting the nomination.&nbsp; The letter must also include a section on the nature of impact the person or group has had on inclusivity, diversity, and equity in the field. &nbsp;</p> <p>2)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; A brief biosketch or list of activities (maximum 3 pages) for the person/group nominated.</p> <p>3)&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Self-nominations are welcome and should be accompanied by a letter of support for the nomination from someone familiar with the activities of the nominee.</p> <p>Nominations should be submitted by January 15, 2020 by going to the award nomination form: <a href="http://bit.ly/evoidea">http://bit.ly/evoidea</a></p> Thu, 17 Oct 2019 05:00:00 GMT Applications for the 2020 ASN Jasper Loftus-Hills Young Investigator’s Awards https://amnat.org/announcements/NomYIAforms.html The Jasper Loftus-Hill Young Investigator’s Award of the American Society of Naturalists honors outstanding promise and accomplishments of young investigators who conduct integrative work in the fields of Ecology, Evolutionary Biology, Behavioral Ecology, and Genetics. Applicants working in any of these fields are encouraged to apply. The award honors outstanding promise and accomplishments of young investigators (3 years post-Ph.D., or in the final year of their Ph.D) who conduct integrative work in ecology, evolution, behavioral ecology, and genetics (see * below) . The award was established in 1984 to recognize exceptional work by investigators who received their doctorates in the three years preceding the application deadline, or who are in their final year of graduate school. The award commemorates Jasper Loftus-Hills (1946-1974), an Australian biologist of exceptional promise who died tragically during the course of fieldwork three years after receiving his degree. Winners of this award will present a research paper in the Young Investigator’s Symposium at the ASN annual meeting and receive a $500 prize, a travel allowance of $700, cost of registration for the meetings, and a supplement of $500 in case of intercontinental travel. Four awards are made annually. Recipients need not be members of the Society. In order to apply for this award, applicants should go to this link to the Google form, where they will be asked to answer a few questions and upload their application (see ** below). The application should consist of one pdf, with the following (in this exact order): - CV (no page limit) - Research statement (3 page limit, including figures) - 3 reprints Additionally, two letters by individuals familiar with the applicant’s work should be uploaded by referees to the following link to a Google form.&nbsp;(see ** below).&nbsp; Applicants are responsible for ensuring their letter writers submit their letters before the deadline (this can be done before submitting an application), as applications will not be considered complete without these two letters. &nbsp; * The standard timeframe covers anyone who graduated in 2017, 2018, or 2019 or who plans to defend in 2020. Time since PhD degree can be extended by 1 year for each child born or adopted during this period if the applicant was a primary care giver. Other forms of exceptional care giving responsibility (e.g. partner, spouse, aged parent, etc.) will be considered on a case-by-case basis. **Applicants and letter writers will be required to sign into an account registered with Google (does not have to be a gmail address) to upload their applications and letters, respectively. If you or your letter writers do not have a google account, please send materials directly to Renee Duckworth. &nbsp;Jasper Loftus-Hills (1946-1974) was an Australian biologist of exceptional promise who lost his life doing fieldwork recording frog calls in Texas, three years after receiving his degree from the University of Melbourne. An obituary appeared in Copeia in 1974 (Alexander, Richard D. "Jasper Loftus-Hills." Copeia 1974:812-13). The Golden Coqu&iacute; (in the photo above) was discovered on Puerto Rico by George E. Drewry, Kirkland L. Jones, Julia R. Clark, and Jasper J. Loftus-Hills. They had planned to name the species for its color, but when Loftus-Hills was killed in 1974, his colleagues chose instead to name it in his honor: A further description of Jasper Loftus-Hills appeared in Copeia 2015 (103:467-475), which is a retrospective on his mentor, Murray John Littlejohn (doi:&nbsp;http://dx.doi.org/10.1643/OT-15-274) The most gifted graduate student Murray ever worked with (in his own estimation) was Jasper Loftus-Hills, whose Ph.D. thesis “Auditory function and acoustic communication in anuran amphibians” was completed in 1971. Jasper followed in Murray’s footsteps to Austin and then went on to Cornell University and the University of Michigan. He was tragically killed by a hit-and-run driver while doing night fieldwork on Gastrophryne in Texas in 1974. The 1992 Gastrophryne paper coauthored by Jasper and Murray is a lucid analysis of the state of the art in character displacement and reinforcement, two terms burdened with a long history of confusion. (Loftus-Hills, J. J., and M. J. Littlejohn.&nbsp;1992.&nbsp;Reinforcement and reproductive character displacement inGastrophryne carolinensis&nbsp;and&nbsp;G. olivacea&nbsp;(Anura: Microhylidae): a re-evaluation.&nbsp;Evolution 46:896–906.) &nbsp; <p>The Jasper Loftus-Hill Young Investigator&rsquo;s Award of the American Society of Naturalists honors outstanding promise and accomplishments of young investigators who conduct integrative work in the fields of Ecology, Evolutionary Biology, Behavioral Ecology, and Genetics. Applicants working in any of these fields are encouraged to apply.</p> <p>The award honors outstanding promise and accomplishments of young investigators (3 years post-Ph.D., or in the final year of their Ph.D) who conduct integrative work in ecology, evolution, behavioral ecology, and genetics <strong><a href="#time">(see * below</a></strong>) . The award was established in 1984 to recognize exceptional work by investigators who received their doctorates in the three years preceding the application deadline, or who are in their final year of graduate school. The award commemorates Jasper Loftus-Hills (1946-1974), an Australian biologist of exceptional promise who died tragically during the course of fieldwork three years after receiving his degree.</p> <p>Winners of this award will present a research paper in the Young Investigator&rsquo;s Symposium at the ASN annual meeting and receive a $500 prize, a travel allowance of $700, cost of registration for the meetings, and a supplement of $500 in case of intercontinental travel. Four awards are made annually. Recipients need not be members of the Society.</p> <p>In order to apply for this award, applicants should go to this<span style="font-size: 11pt;"><span style="font-family: &quot;Calibri&quot;,sans-serif;"> <a href="https://forms.gle/QyC99nAJb7HE42KS8" style="color: blue; text-decoration: underline;">link</a> to the Google form, </span></span>where they will be asked to answer a few questions and upload their application <span style="font-size: 11pt;"><span style="font-family: &quot;Calibri&quot;,sans-serif;"><a href="#time">(<strong>see ** below</strong>)</a></span></span>. The application should consist of one pdf, with the following (in this exact order):<br /> - CV (no page limit)<br /> - Research statement (3 page limit, including figures)<br /> - 3 reprints</p> <p>Additionally, two letters by individuals familiar with the applicant&rsquo;s work should be uploaded by referees <span style="font-size: 11pt;"><span style="font-family: &quot;Calibri&quot;,sans-serif;">to the following <a href="https://forms.gle/DcSjx34MasjwPGZe7" style="color: blue; text-decoration: underline;">link</a> to a Google form.&nbsp;<a href="#time">(<strong>see ** below</strong>)</a>.&nbsp; </span></span>Applicants are responsible for ensuring their letter writers submit their letters before the deadline (this can be done before submitting an application), as applications will not be considered complete without these two letters.</p> <p>&nbsp;</p> <p id="time">* The standard timeframe covers anyone who graduated in 2017, 2018, or 2019 or who plans to defend in 2020. <strong>Time since PhD degree</strong> can be extended by 1 year for each child born or adopted during this period if the applicant was a primary care giver. Other forms of exceptional care giving responsibility (e.g. partner, spouse, aged parent, etc.) will be considered on a case-by-case basis.</p> <p>**<strong>Applicants and letter writers will be required to sign into an account registered with Google</strong> (does not have to be a gmail address) to upload their applications and letters, respectively. If you or your letter writers do not have a google account, please send materials directly to <a href="mailto:rad3@email.arizona.edu?subject=Young%20Investigator%20application">Renee Duckworth</a>.</p> <p>&nbsp;</p><p>Jasper Loftus-Hills (1946-1974) was an Australian biologist of exceptional promise who lost his life doing fieldwork recording frog calls in Texas, three years after receiving his degree from the University of Melbourne. <a href="/dam/jcr:50a091cd-227f-4bff-9f60-687a6679b1d8/JLH%20obituary.pdf">An obituary appeared in <i>Copeia</i></a> in 1974 (Alexander, Richard D. &quot;Jasper Loftus-Hills.&quot; <em>Copeia</em> 1974:812-13).</p> <p>The Golden Coqu&iacute; (in the photo above) was discovered on Puerto Rico by George E. Drewry, Kirkland L. Jones, Julia R. Clark, and Jasper J. Loftus-Hills. They had planned to name the species for its color, but when Loftus-Hills was killed in 1974, his colleagues chose instead to name it in his honor:</p> <p>A further description of Jasper Loftus-Hills appeared in <i>Copeia</i> 2015 (103:467-475), which is a retrospective on his mentor, Murray John Littlejohn (doi:&nbsp;<a href="http://dx.doi.org/10.1643/OT-15-274">http://dx.doi.org/10.1643/OT-15-274</a>)</p> <blockquote>The most gifted graduate student Murray ever worked with (in his own estimation) was Jasper Loftus-Hills, whose Ph.D. thesis &ldquo;Auditory function and acoustic communication in anuran amphibians&rdquo; was completed in 1971. Jasper followed in Murray&rsquo;s footsteps to Austin and then went on to Cornell University and the University of Michigan. He was tragically killed by a hit-and-run driver while doing night fieldwork on Gastrophryne in Texas in 1974. The 1992 Gastrophryne paper coauthored by Jasper and Murray is a lucid analysis of the state of the art in character displacement and reinforcement, two terms burdened with a long history of confusion.<br /> (<span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">Loftus-Hills, J. J., and M. J. Littlejohn.&nbsp;</span><span class="NLM_year" style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">1992</span><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">.&nbsp;</span><span class="NLM_article-title" style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">Reinforcement and reproductive character displacement in<i>Gastrophryne carolinensis</i>&nbsp;and&nbsp;<i>G. olivacea</i>&nbsp;(Anura: Microhylidae): a re-evaluation</span><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">.&nbsp;</span><span class="citation_source-journal" style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px; font-style: italic;">Evolution </span><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">46:</span><span class="NLM_fpage" style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">896</span><span style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">&ndash;</span><span class="NLM_lpage" style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px;">906</span><span class="citation_source-journal" style="color: rgb(0, 0, 0); font-family: Verdana, Arial, Helvetica, sans-serif; font-size: 12.51px; font-style: italic;">.</span>)</blockquote> <p>&nbsp;</p> Thu, 17 Oct 2019 05:00:00 GMT “Deconstructing evolutionary game theory: coevolution of social behaviors with their evolutionary setting” https://amnat.org/an/newpapers/VP-Akcay-A.html Erol Akçay (Feb 2020) Read the Article (Just Accepted) Abstract Evolution of social behaviors is one of the most fascinating and active fields of evolutionary biology. During the past half century, social evolution theory developed into a mature field with powerful tools to understand the dynamics of social traits such as cooperation under a wide range of conditions. In this paper, I argue that the next stage in the development of social evolution theory should consider the evolution of the setting in which social behaviors evolve. To that end, I propose a conceptual map of the components that make up the evolutionary setting of social behaviors, review existing work that considers the evolution of each component, and discuss potential future directions. The theoretical work reviewed here illustrates how unexpected dynamics can happen when the setting of social evolution itself is evolving, such as cooperation sometimes being self-limiting. I argue that a theory of how the setting of social evolution itself evolves will lead to a deeper understanding of when cooperation and other social behaviors evolve and diversify. More forthcoming papers &raquo; <p>Erol Akçay (Feb 2020) </p> <p><i><a href="https://dx.doi.org/10.1086/706811">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>volution of social behaviors is one of the most fascinating and active fields of evolutionary biology. During the past half century, social evolution theory developed into a mature field with powerful tools to understand the dynamics of social traits such as cooperation under a wide range of conditions. In this paper, I argue that the next stage in the development of social evolution theory should consider the evolution of the setting in which social behaviors evolve. To that end, I propose a conceptual map of the components that make up the evolutionary setting of social behaviors, review existing work that considers the evolution of each component, and discuss potential future directions. The theoretical work reviewed here illustrates how unexpected dynamics can happen when the setting of social evolution itself is evolving, such as cooperation sometimes being self-limiting. I argue that a theory of how the setting of social evolution itself evolves will lead to a deeper understanding of when cooperation and other social behaviors evolve and diversify. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Oct 2019 05:00:00 GMT “When synchrony makes the best of both worlds even better: how well do we really understand facultative sex?” https://amnat.org/an/newpapers/VP-Kokko.html Hanna Kokko (Feb 2020) Read the Article (Just Accepted) One can often hear evolutionary biologists describe sexual reproduction as one of the major puzzles in evolutionary theory, sometimes with the addition that facultative sex is an even bigger problem. The problem is that creating offspring sexually is surprisingly inefficient (compared with asexual reproduction), but whenever we are tempted to claim we have understood why sex is on balance selected for, we should also deal with an extra complication: the genetic benefits and economic (demographic) costs scale nonlinearly and do not increase at the same rate when the frequency of sex increases. Very rare sex – for example, once every 100 or 1000 generations – appears, for many models, to be almost as good as obligate sex at producing the adaptive benefit, but it avoids paying the cost in most generations. This is why facultative sex is sometimes stated to offer the best of both worlds, and the consequent puzzle is why not all life is organized that way. This paper does not claim to have found the ultimate solution. Instead, it highlights that existing theories sometimes make simplifications that make the problem mathematically more tractable, but ignore real-life complications that may really matter. One is that facultative sex occurs in synchrony, which links theories of sex with those of bet-hedging. This paper shows why synchrony makes facultative sex even better: if sex is rare, synchrony alleviates mate-finding problems, and if sex has – due to some ecological change – become costlier than before, synchrony helps finding a better rate of sex much more quickly. Abstract Biological diversity abounds in potential study topics. Studies of model systems have their advantages, but reliance on a few well understood cases may create false impressions of what biological phenomena are the ‘norm’. Here I focus on facultative sex, which is often hailed as offering the best of both worlds, in that rare sex offers benefits almost equal to obligate sex, and avoids paying most of the demographic costs. How well do we understand when and why this form of sexual reproduction is expected to prevail? I show several gaps in the theoretical literature, and by contrasting asynchronous with synchronous sex, I highlight the need to link sex theories to the theoretical underpinnings of bet-hedging on the one hand and to mate limitation considerations on the other. Condition-dependent sex, and links between sex with dispersal or dormancy, appear understudied. Simplifications on the one hand are justifiable as a simple assumption structure enhances analytical tractability, but on the other hand, much remains to be done to incorporate key features of real sex to the main theoretical edifice. More forthcoming papers &raquo; <p>Hanna Kokko (Feb 2020) </p><p><i><a href="https://dx.doi.org/10.1086/706812">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">O</span>ne can often hear evolutionary biologists describe sexual reproduction as one of the major puzzles in evolutionary theory, sometimes with the addition that facultative sex is an even bigger problem. The problem is that creating offspring sexually is surprisingly inefficient (compared with asexual reproduction), but whenever we are tempted to claim we have understood why sex is on balance selected for, we should also deal with an extra complication: the genetic benefits and economic (demographic) costs scale nonlinearly and do not increase at the same rate when the frequency of sex increases. Very rare sex – for example, once every 100 or 1000 generations – appears, for many models, to be almost as good as obligate sex at producing the adaptive benefit, but it avoids paying the cost in most generations. This is why facultative sex is sometimes stated to offer the best of both worlds, and the consequent puzzle is why not all life is organized that way. This paper does not claim to have found the ultimate solution. Instead, it highlights that existing theories sometimes make simplifications that make the problem mathematically more tractable, but ignore real-life complications that may really matter. One is that facultative sex occurs in synchrony, which links theories of sex with those of bet-hedging. This paper shows why synchrony makes facultative sex even better: if sex is rare, synchrony alleviates mate-finding problems, and if sex has – due to some ecological change – become costlier than before, synchrony helps finding a better rate of sex much more quickly.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">B</span>iological diversity abounds in potential study topics. Studies of model systems have their advantages, but reliance on a few well understood cases may create false impressions of what biological phenomena are the ‘norm’. Here I focus on facultative sex, which is often hailed as offering the best of both worlds, in that rare sex offers benefits almost equal to obligate sex, and avoids paying most of the demographic costs. How well do we understand when and why this form of sexual reproduction is expected to prevail? I show several gaps in the theoretical literature, and by contrasting asynchronous with synchronous sex, I highlight the need to link sex theories to the theoretical underpinnings of bet-hedging on the one hand and to mate limitation considerations on the other. Condition-dependent sex, and links between sex with dispersal or dormancy, appear understudied. Simplifications on the one hand are justifiable as a simple assumption structure enhances analytical tractability, but on the other hand, much remains to be done to incorporate key features of real sex to the main theoretical edifice. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Oct 2019 05:00:00 GMT “How does co-evolution of consumer traits affect resource specialization?” https://amnat.org/an/newpapers/VP-Vasconcelos.html Paula Vasconcelos and Claus Rueffler (Feb 2020) How does joint evolution of consumer traits affect resource specialization? Hint: it’s more complicated than you think! Read the Article (Just Accepted) When should we expect the evolution of different resource specialists instead of a single generalists? To simplify the analysis, mathematical models addressing this question are usually based on the assumption of a single evolving consumer trait (think beak size in birds), which led to a pleasingly simple prediction: the evolution of resource specialists is favored by strong trade-offs (where resource generalists perform relatively poorly compared to specialists) while weak trade-offs (where resource generalists perform relatively well) favor the evolution of generalists. However, the assumption of a single evolving consumer trait is not realistic since organisms are complex and the interaction between consumers and their resources is affected by many jointly evolving traits. PhD student Paula Vasconcelos and her supervisor Claus Rueffler from Uppsala University set out to investigate how evolutionary predictions are altered if two or three consumer traits were allowed to jointly evolve. They find that the simple dichotomy suggested by models based on a single evolving trait does not hold true in this more general setting. Instead, weak trade-offs can lead to either one or two specialists, as well as to a single generalist. The reason for these deviating results is that jointly evolving traits can interact in complicated ways in their effect on resource consumption. The results serve as a warning that simplifying assumptions—in this case, that the degree of resource specialization depends on a single trait—must be made carefully, and the results of models that use them should be qualified if the effects of violating these assumptions is unknown. This study touches on another important question in biology: does complexity, as measured in number of jointly evolving traits, facilitates diversification? Surprisingly, the results show that complexity is in fact not a good predictor of diversifying potential as the conditions leading to two specialists are not necessarily more likely to be fulfilled when increasing the number of jointly evolving traits. Abstract Consumers regularly experience trade-offs in their ability to find, handle and digest different resources. Evolutionary ecologists recognized the significance of this observation for the evolution and maintenance of biological diversity long ago and continue to elaborate on the conditions under which to expect one or several specialists, generalists or combinations thereof. Existing theory based on a single evolving trait predicts that specialization requires strong trade-offs such that generalists perform relatively poorly, while weak trade-offs favor a single generalist. Here, we show that this simple dichotomy does not hold true under joint evolution of two or more foraging traits. In this case, the boundary between trade-offs resulting in resource specialists and resource generalists is shifted toward weaker trade-off curvatures. In particular, weak trade-offs can result in evolutionary branching leading to the evolution of two coexisting resource specialists while the evolution of a single resource generalist requires particularly weak trade-offs. These findings are explained by performance benefits due to epistatic trait interactions enjoyed by phenotypes that are specialized in more than one trait for the same resource. More forthcoming papers &raquo; <p>Paula Vasconcelos and Claus Rueffler (Feb 2020) </p> <p><b>How does joint evolution of consumer traits affect resource specialization? Hint: it’s more complicated than you think!</b> </p> <p><i><a href="https://dx.doi.org/10.1086/706813">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hen should we expect the evolution of different resource specialists instead of a single generalists? To simplify the analysis, mathematical models addressing this question are usually based on the assumption of a single evolving consumer trait (think beak size in birds), which led to a pleasingly simple prediction: the evolution of resource specialists is favored by strong trade-offs (where resource generalists perform relatively poorly compared to specialists) while weak trade-offs (where resource generalists perform relatively well) favor the evolution of generalists. However, the assumption of a single evolving consumer trait is not realistic since organisms are complex and the interaction between consumers and their resources is affected by many jointly evolving traits. </p><p>PhD student Paula Vasconcelos and her supervisor Claus Rueffler from Uppsala University set out to investigate how evolutionary predictions are altered if two or three consumer traits were allowed to jointly evolve. They find that the simple dichotomy suggested by models based on a single evolving trait does not hold true in this more general setting. Instead, weak trade-offs can lead to either one or two specialists, as well as to a single generalist. The reason for these deviating results is that jointly evolving traits can interact in complicated ways in their effect on resource consumption. The results serve as a warning that simplifying assumptions—in this case, that the degree of resource specialization depends on a single trait—must be made carefully, and the results of models that use them should be qualified if the effects of violating these assumptions is unknown. </p><p>This study touches on another important question in biology: does complexity, as measured in number of jointly evolving traits, facilitates diversification? Surprisingly, the results show that complexity is in fact not a good predictor of diversifying potential as the conditions leading to two specialists are not necessarily more likely to be fulfilled when increasing the number of jointly evolving traits.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>onsumers regularly experience trade-offs in their ability to find, handle and digest different resources. Evolutionary ecologists recognized the significance of this observation for the evolution and maintenance of biological diversity long ago and continue to elaborate on the conditions under which to expect one or several specialists, generalists or combinations thereof. Existing theory based on a single evolving trait predicts that specialization requires strong trade-offs such that generalists perform relatively poorly, while weak trade-offs favor a single generalist. Here, we show that this simple dichotomy does not hold true under joint evolution of two or more foraging traits. In this case, the boundary between trade-offs resulting in resource specialists and resource generalists is shifted toward weaker trade-off curvatures. In particular, weak trade-offs can result in evolutionary branching leading to the evolution of two coexisting resource specialists while the evolution of a single resource generalist requires particularly weak trade-offs. These findings are explained by performance benefits due to epistatic trait interactions enjoyed by phenotypes that are specialized in more than one trait for the same resource. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Oct 2019 05:00:00 GMT “Evolution of dispersal can rescue populations from expansion load” https://amnat.org/an/newpapers/VP-Peischl-A.html Stephan Peischl and Kimberly J. Gilbert (Feb 2020) Read the Article (Just Accepted)Abstract Understanding the causes and consequences of range expansions or range shifts has a long history in evolutionary biology. Recent theoretical, experimental, and empirical work has identified two particularly interesting phenomena in the context of species range expansions: (i) gene surfing and the relaxation of natural selection, and (ii) spatial sorting. The former can lead to an accumulation of deleterious mutations at range edges, causing an expansion load and slowing down expansion. The latter can create gradients in dispersal-related traits along the expansion axis and cause an acceleration of expansion. We present a theoretical framework that treats spatial sorting and gene surfing as spatial versions of natural selection and genetic drift, respectively. This model allows us to analytically study how gene surfing and spatial sorting interact and derive the probability of fixation of pleiotropic mutations at the expansion front. We use our results to predict the co-evolution of mean fitness and dispersal rates, taking into account the effects of random genetic drift, natural selection, and spatial sorting, as well as correlations between fitness- and dispersal-related traits. We identify a “rescue effect” of spatial sorting, where the evolution of higher dispersal rates at the leading edge rescues the population from incurring expansion load. More forthcoming papers &raquo; <p>Stephan Peischl and Kimberly J. Gilbert (Feb 2020)</p> <p><i><a href="https://dx.doi.org/10.1086/705993">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">U</span>nderstanding the causes and consequences of range expansions or range shifts has a long history in evolutionary biology. Recent theoretical, experimental, and empirical work has identified two particularly interesting phenomena in the context of species range expansions: (i) gene surfing and the relaxation of natural selection, and (ii) spatial sorting. The former can lead to an accumulation of deleterious mutations at range edges, causing an expansion load and slowing down expansion. The latter can create gradients in dispersal-related traits along the expansion axis and cause an acceleration of expansion. We present a theoretical framework that treats spatial sorting and gene surfing as spatial versions of natural selection and genetic drift, respectively. This model allows us to analytically study how gene surfing and spatial sorting interact and derive the probability of fixation of pleiotropic mutations at the expansion front. We use our results to predict the co-evolution of mean fitness and dispersal rates, taking into account the effects of random genetic drift, natural selection, and spatial sorting, as well as correlations between fitness- and dispersal-related traits. We identify a &ldquo;rescue effect&rdquo; of spatial sorting, where the evolution of higher dispersal rates at the leading edge rescues the population from incurring expansion load. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 16 Oct 2019 05:00:00 GMT Listen to Diverse Scientists Tell Their Stories--Story Collider 2019 https://amnat.org/announcements/ANNCollider.html This was a moving, edifying, and entertaining evening. As Samuel Scarpino said on Twitter: "The @storycollider x @Evol_mtg crossover was by far the best conference event I&#39;ve attended.&nbsp; It was inspiring, humbling, and emotional.&nbsp; I can&#39;t recommend listening to these scientists tell their stories enough." Aparna Agarwal https://soundcloud.com/sse-communications/aparna-agarwal-story-collider-evolution-2019 Patty Brennan https://soundcloud.com/sse-communications/patty-brennan-story-collider-evolution-2019 Ambika Kamath https://soundcloud.com/sse-communications/ambika-kamath-story-collider-evolution-2019 C. Brendan Ogbunu https://soundcloud.com/sse-communications/c-brandon-ogbunu-story-collider-evolution-2019 Scott Taylor https://soundcloud.com/sse-communications/scott-taylor-story-collider-evolution-2019 Stories are powerful. Whether hilarious or heartbreaking, subversive or soothing, it matters who takes the stage and what stories are told. On June 23, 2019, The Story Collider hosted a live show at the Evolution Meetings in Providence. This event is co-organized by the Diversity Committees of the ASN, SSB, and SSE with the goal of highlighting the diverse voices of evolutionary biology!The Story Collider producers and event organizers worked with the volunteers who offered stories: about almost anything—an important experiment, a rough day in the field, misadventure, love, loss, and more; but it must be about you. Our format does not include slides or props.It’s about lived experiences. Exotic locations and exciting action never hurt, but what we care about is how you’ve grown as a result of the events in your life. If you’re selected for the show, experienced Story Collider producers will work with you for more than a month to help you prepare. <p>This was a moving, edifying, and entertaining evening. As Samuel Scarpino said on Twitter: &quot;The @storycollider x @Evol_mtg crossover was by far the best conference event I&#39;ve attended.&nbsp; It was inspiring, humbling, and emotional.&nbsp; I can&#39;t recommend listening to these scientists tell their stories enough.&quot;</p> <ul> <li>Aparna Agarwal <a href="https://soundcloud.com/sse-communications/aparna-agarwal-story-collider-evolution-2019">https://soundcloud.com/sse-communications/aparna-agarwal-story-collider-evolution-2019</a></li> <li>Patty Brennan <a href="https://soundcloud.com/sse-communications/patty-brennan-story-collider-evolution-2019">https://soundcloud.com/sse-communications/patty-brennan-story-collider-evolution-2019</a></li> <li>Ambika Kamath <a href="https://soundcloud.com/sse-communications/ambika-kamath-story-collider-evolution-2019">https://soundcloud.com/sse-communications/ambika-kamath-story-collider-evolution-2019</a></li> <li>C. Brendan Ogbunu <a href="https://soundcloud.com/sse-communications/c-brandon-ogbunu-story-collider-evolution-2019">https://soundcloud.com/sse-communications/c-brandon-ogbunu-story-collider-evolution-2019</a></li> <li>Scott Taylor <a href="https://soundcloud.com/sse-communications/scott-taylor-story-collider-evolution-2019">https://soundcloud.com/sse-communications/scott-taylor-story-collider-evolution-2019</a></li> </ul><p>Stories are powerful. Whether hilarious or heartbreaking, subversive or soothing, it matters who takes the stage and what stories are told. On June 23, 2019, The Story Collider hosted a live show at the Evolution Meetings in Providence. This event is co-organized by the Diversity Committees of the ASN, SSB, and SSE with the goal of highlighting the diverse voices of evolutionary biology!</p><p>The Story Collider producers and event organizers worked with the volunteers who offered stories: about almost anything&mdash;an important experiment, a rough day in the field, misadventure, love, loss, and more; but it must be about you. Our format does not include slides or props.It&rsquo;s about lived experiences. Exotic locations and exciting action never hurt, but what we care about is how you&rsquo;ve grown as a result of the events in your life. If you&rsquo;re selected for the show, experienced Story Collider producers will work with you for more than a month to help you prepare.</p> Tue, 15 Oct 2019 05:00:00 GMT Nominations for the Edward O. Wilson Naturalist Award https://amnat.org/announcements/NomEOWilson.html The Edward O. Wilson Naturalist Award is given to an active investigator in mid-career (within 25 years of completion of the PhD) who has made significant contributions to the knowledge of a particular ecosystem or group of organisms.&nbsp;Time since PhD degree can be extended in light of parental leave. Other forms of exceptional caregiving responsibility [e.g., partner, spouse, aged parent, etc]. or extenuating circumstances will be considered on a case-by-case basis. Individuals whose research and writing illuminate principles of evolutionary biology and an enhanced aesthetic appreciation of natural history will merit special consideration. The recipient need not be a member of the Society. The award will consist of an especially appropriate work of art and a prize of $2,000. The ASN strongly encourages its members to submit nominations of deserving people. The names of former recipients can be found here&nbsp;https://www.amnat.org/awards.html#Wilson Nominations will be held over for two years. The application packet should in the form of a single PDF consisting of a letter of nominations, curriculum vitae of the candidate including a publication list, and three key publications to be send electronically by January 15, 2020, to Joe Travis (travis@bio.fsu.edu). Please indicate "E. O. Wilson Award" in the subject line.&nbsp; <p>The Edward O. Wilson Naturalist Award is given to an active investigator in mid-career (within 25 years of completion of the PhD) who has made significant contributions to the knowledge of a particular ecosystem or group of organisms.&nbsp;Time since PhD degree can be extended in light of parental leave. Other forms of exceptional caregiving responsibility [e.g., partner, spouse, aged parent, etc]. or extenuating circumstances will be considered on a case-by-case basis.</p> <p>Individuals whose research and writing illuminate principles of evolutionary biology and an enhanced aesthetic appreciation of natural history will merit special consideration. <em>The recipient need not be a member of the Society</em>. The award will consist of an especially appropriate work of art and a prize of $2,000.</p> <p>The ASN strongly encourages its members to submit nominations of deserving people. The names of former recipients can be found here&nbsp;<a href="https://www.amnat.org/awards.html#Wilson">https://www.amnat.org/awards.html#Wilson</a></p> <p>Nominations will be held over for two years.</p> <p>The application packet should in the form of a single PDF consisting of a letter of nominations, curriculum vitae of the candidate including a publication list, and three key publications to be send electronically by January 15, 2020, to Joe Travis (<a href="mailto:travis@bio.fsu.edu">travis@bio.fsu.edu</a>). Please indicate &quot;E. O. Wilson Award&quot; in the subject line.&nbsp;</p> Tue, 15 Oct 2019 05:00:00 GMT “Theory in service of narratives in evolution and ecology” https://amnat.org/an/newpapers/VP-Otto.html Sarah P. Otto and Alirio Rosales (Feb 2020) Read the Article (Just Accepted)Abstract Considering the role of theory in ecology and evolution, we argue that scientific theorizing involves an interplay between narratives and models in which narratives play a key creative and organizing role. Specifically, as scientists, we reason through the use of narratives that explain biological phenomena by envisaging, or mentally simulating, causal paths leading from a plausible initial state to an outcome of interest. Within these narratives, parts may appear clear, while others puzzling. It is at these tenuous junctions – junctions where reasoning is made challenging by conflicting possible outcomes – that we often build mathematical models to support and extend, or reject and revise, our narratives. Accordingly, models, both analytical and computational, are framed by and interpreted within a narrative. We illustrate these points using case studies from population genetics. This perspective on scientific theorizing helps to clarify the nature of theoretical debates, which often arise from the narratives in which math is embedded, not from the math itself. Finally, this perspective helps place appropriate creative weight on the importance of developing, revising, and challenging narratives in the scientific enterprise. More forthcoming papers &raquo; <p>Sarah P. Otto and Alirio Rosales (Feb 2020) </p> <p><i><a href="https://dx.doi.org/10.1086/705991">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>onsidering the role of theory in ecology and evolution, we argue that scientific theorizing involves an interplay between narratives and models in which narratives play a key creative and organizing role. Specifically, as scientists, we reason through the use of narratives that explain biological phenomena by envisaging, or mentally simulating, causal paths leading from a plausible initial state to an outcome of interest. Within these narratives, parts may appear clear, while others puzzling. It is at these tenuous junctions – junctions where reasoning is made challenging by conflicting possible outcomes – that we often build mathematical models to support and extend, or reject and revise, our narratives. Accordingly, models, both analytical and computational, are framed by and interpreted within a narrative. We illustrate these points using case studies from population genetics. This perspective on scientific theorizing helps to clarify the nature of theoretical debates, which often arise from the narratives in which math is embedded, not from the math itself. Finally, this perspective helps place appropriate creative weight on the importance of developing, revising, and challenging narratives in the scientific enterprise. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 10 Oct 2019 05:00:00 GMT “Sex differences in the recombination landscape” https://amnat.org/an/newpapers/VP-Sardell.html Jason M. Sardell and Mark Kirkpatrick (Feb 2020) Read the Article (Just Accepted)Abstract Sex differences in overall recombination rates are well known, but little theoretical or empirical attention has been given to how and why sexes differ in their recombination landscapes: the patterns of recombination along chromosomes. In the first scientific review of this phenomenon, we find that recombination is biased towards telomeres in males and more uniformly distributed in females in most vertebrates and many other eukaryotes. Notable exceptions to this pattern exist, however. Fine scale recombination patterns also frequently differ between males and females. The molecular mechanisms responsible for sex-differences remain unclear, but chromatin landscapes play a role. Why these sex differences evolve also is unclear. Hypotheses suggest that they may result from sexually antagonistic selection acting on coding genes and their regulatory elements, meiotic drive in females, selection during the haploid phase of the life cycle, selection against aneuploidy, or mechanistic constraints. No single hypothesis, however, can adequately explain the evolution of sex differences in all cases. Sex-specific recombination landscapes have important consequences for population differentiation and sex chromosome evolution. More forthcoming papers &raquo; <p>Jason M. Sardell and Mark Kirkpatrick (Feb 2020)</p> <p><i><a href="https://dx.doi.org/10.1086/704943">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>ex differences in overall recombination rates are well known, but little theoretical or empirical attention has been given to how and why sexes differ in their recombination landscapes: the patterns of recombination along chromosomes. In the first scientific review of this phenomenon, we find that recombination is biased towards telomeres in males and more uniformly distributed in females in most vertebrates and many other eukaryotes. Notable exceptions to this pattern exist, however. Fine scale recombination patterns also frequently differ between males and females. The molecular mechanisms responsible for sex-differences remain unclear, but chromatin landscapes play a role. Why these sex differences evolve also is unclear. Hypotheses suggest that they may result from sexually antagonistic selection acting on coding genes and their regulatory elements, meiotic drive in females, selection during the haploid phase of the life cycle, selection against aneuploidy, or mechanistic constraints. No single hypothesis, however, can adequately explain the evolution of sex differences in all cases. Sex-specific recombination landscapes have important consequences for population differentiation and sex chromosome evolution. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 10 Oct 2019 05:00:00 GMT “Memory in trait macroevolution” https://amnat.org/an/newpapers/VP-Goldberg.html Emma E. Goldberg and Jasmine Foo (Feb 2020) Read the Article (Just Accepted)Abstract The history of a trait within a lineage may influence its future evolutionary trajectory, but macroevolutionary theory of this process is not well developed. For example, consider the simplified binary trait of living in cave versus surface habitat. The longer a species has been cave-dwelling, the more may accumulated loss of vision, pigmentation, and defense restrict future adaptation if the species encounters the surface environment. However, the Markov model of discrete trait evolution that is widely adopted in phylogenetics does not allow the rate of cave-to-surface transition to decrease with longer duration as a cave-dweller. Here, we describe three models of evolution that remove this ‘memory-less’ constraint, using a renewal process to generalize beyond the typical Poisson process of discrete trait macroevolution. We then show how the two-state renewal process can be used for inference, and we investigate the potential of phylogenetic comparative data to reveal different influences of trait duration, or ‘memory’ in trait evolution. We hope that such approaches may open new avenues for modeling trait evolution and for broad comparative tests of hypotheses that some traits become entrenched. More forthcoming papers &raquo; <p>Emma E. Goldberg and Jasmine Foo (Feb 2020) </p> <p><i><a href="https://dx.doi.org/10.1086/705992">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he history of a trait within a lineage may influence its future evolutionary trajectory, but macroevolutionary theory of this process is not well developed. For example, consider the simplified binary trait of living in cave versus surface habitat. The longer a species has been cave-dwelling, the more may accumulated loss of vision, pigmentation, and defense restrict future adaptation if the species encounters the surface environment. However, the Markov model of discrete trait evolution that is widely adopted in phylogenetics does not allow the rate of cave-to-surface transition to decrease with longer duration as a cave-dweller. Here, we describe three models of evolution that remove this &lsquo;memory-less&rsquo; constraint, using a renewal process to generalize beyond the typical Poisson process of discrete trait macroevolution. We then show how the two-state renewal process can be used for inference, and we investigate the potential of phylogenetic comparative data to reveal different influences of trait duration, or &lsquo;memory&rsquo; in trait evolution. We hope that such approaches may open new avenues for modeling trait evolution and for broad comparative tests of hypotheses that some traits become entrenched. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 10 Oct 2019 05:00:00 GMT “Social games and genic selection drives mammalian mating system evolution and speciation” https://amnat.org/an/newpapers/Feb-Sinervo.html Barry Sinervo, Alexis S. Chaine, and Donald Miles (Feb 2020) Genes drive mating system evolution in models and rodents Read the Article (Just Accepted) Whether animals partner with just one mate or with many, or even if individuals in a population differ in their mating patterns, has largely been explained by control over territorial resources. In an upcoming issue of The&nbsp;American Naturalist, researchers from the US and France have proposed a new explanation: genes for three alternative behaviors of aggression, sneaking, and the combination of cooperation and care that underlie both mating and social behavior can drive the evolution of mating patterns. The research team used mathematical models to describe mating system evolution based on genes for male-male competition (vs. cooperation), choice of neighborhoods, and paternal care premised on shared genes between interacting individuals. Using published data on rodent mating behavior, they then tested whether the predictions generated by their genetic model captured patterns in mating system while ignoring resource distribution. Rodents exhibit behaviors that the researchers modeled, including alternative mating tactics, genetic recognition, and paternal care, which are often linked to specific genes identified in molecular studies. Both distribution of mating systems and reconstruction of the evolutionary history of rodent mating systems among 288 species across all families match predictions of the model. Interestingly, cooperation and care behaviors associated with a monogamous mating strategy moves species from a mixed-mating system containing alternative strategies towards either monogamous or polygynous species and accelerates speciation. Monogamy in rodents (~20%) is far more common than previously believed. Taken together, these findings open a new possibility for what drives mating patterns: genes that underlie cooperative and care behavior linked to how you interact with offspring and neighbors and drive a rock-paper-scissors (RPS) dynamic among alternative behavioral types. The model generalizes the RPS game from mating dynamics to speciation across vertebrate classes and other organisms. Abstract Mating system theory based on economics of resource defense has been applied to describe social system diversity across taxa. Such models are generally successful, but fail to account for stable mating systems across different environments or shifts in mating system without a change in ecological conditions. We propose an alternative approach to resource defense theory based on frequency dependent competition among genetically determined alternative behavioral strategies characterizing many social systems (polygyny, monogamy, sneak). We modeled payoffs for competition, neighborhood choice, and paternal care to determine evolutionary transitions among mating systems. Our model predicts 4 stable outcomes driven by the balance between cooperative and agonistic behaviors: promiscuity (2 or 3 strategies), polygyny, and monogamy. Phylogenetic analysis of 288 rodent species support assumptions of our model and is consistent with patterns of evolutionarily stable states and mating system transitions. Support for model assumptions include monogamy and polygyny evolve from promiscuity and paternal care and monogamy are coadapted in rodents. As predicted by our model, monogamy and polygyny occur in sister taxa among rodents more often than chance. Transitions to monogamy also favor higher speciation rates in subsequent lineages, relative to polygynous sister lineages. Taken together, our results suggest that genetically based neighborhood choice behavior and paternal care can drive transitions in mating system evolution. While our genic mating system theory could complement resource based theory, it can explain mating system transitions regardless of resource distribution and provides alternative explanations such as evolutionary inertia when resource ecology and mating systems do not match. More forthcoming papers &raquo; <p>Barry Sinervo, Alexis S. Chaine, and Donald Miles (Feb 2020) </p> <p><b>Genes drive mating system evolution in models and rodents </b></p> <p><i><a href="https://dx.doi.org/10.1086/706810">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hether animals partner with just one mate or with many, or even if individuals in a population differ in their mating patterns, has largely been explained by control over territorial resources. In an upcoming issue of <i>The&nbsp;American Naturalist</i>, researchers from the US and France have proposed a new explanation: genes for three alternative behaviors of aggression, sneaking, and the combination of cooperation and care that underlie both mating and social behavior can drive the evolution of mating patterns. The research team used mathematical models to describe mating system evolution based on genes for male-male competition (vs. cooperation), choice of neighborhoods, and paternal care premised on shared genes between interacting individuals. Using published data on rodent mating behavior, they then tested whether the predictions generated by their genetic model captured patterns in mating system while ignoring resource distribution. Rodents exhibit behaviors that the researchers modeled, including alternative mating tactics, genetic recognition, and paternal care, which are often linked to specific genes identified in molecular studies. Both distribution of mating systems and reconstruction of the evolutionary history of rodent mating systems among 288 species across all families match predictions of the model. Interestingly, cooperation and care behaviors associated with a monogamous mating strategy moves species from a mixed-mating system containing alternative strategies towards either monogamous or polygynous species and accelerates speciation. Monogamy in rodents (~20%) is far more common than previously believed. Taken together, these findings open a new possibility for what drives mating patterns: genes that underlie cooperative and care behavior linked to how you interact with offspring and neighbors and drive a rock-paper-scissors (RPS) dynamic among alternative behavioral types. The model generalizes the RPS game from mating dynamics to speciation across vertebrate classes and other organisms.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>ating system theory based on economics of resource defense has been applied to describe social system diversity across taxa. Such models are generally successful, but fail to account for stable mating systems across different environments or shifts in mating system without a change in ecological conditions. We propose an alternative approach to resource defense theory based on frequency dependent competition among genetically determined alternative behavioral strategies characterizing many social systems (polygyny, monogamy, sneak). We modeled payoffs for competition, neighborhood choice, and paternal care to determine evolutionary transitions among mating systems. Our model predicts 4 stable outcomes driven by the balance between cooperative and agonistic behaviors: promiscuity (2 or 3 strategies), polygyny, and monogamy. Phylogenetic analysis of 288 rodent species support assumptions of our model and is consistent with patterns of evolutionarily stable states and mating system transitions. Support for model assumptions include monogamy and polygyny evolve from promiscuity and paternal care and monogamy are coadapted in rodents. As predicted by our model, monogamy and polygyny occur in sister taxa among rodents more often than chance. Transitions to monogamy also favor higher speciation rates in subsequent lineages, relative to polygynous sister lineages. Taken together, our results suggest that genetically based neighborhood choice behavior and paternal care can drive transitions in mating system evolution. While our genic mating system theory could complement resource based theory, it can explain mating system transitions regardless of resource distribution and provides alternative explanations such as evolutionary inertia when resource ecology and mating systems do not match. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 10 Oct 2019 05:00:00 GMT “Shared patterns of genome-wide differentiation are more strongly predicted by geography than by ecology” https://amnat.org/an/newpapers/Feb-Rennison-A.html Diana J. Rennison, Kira E. Delmore, Kieran Samuk, Gregory L. Owens, and Sara E. Miller (Feb 2020) Geographic proximity of populations strongly predicts magnitude of parallel genomic differentiation Read the Article (Just Accepted) Abstract Closely related populations often display similar patterns of genomic differentiation, yet it remains an open question which ecological and evolutionary forces generate these patterns. The leading hypothesis is that this similarity in divergence is driven by parallel natural selection. However, several recent studies have suggested that these patterns may instead be a product of the depletion of genetic variation that occurs as result of background selection (i.e. linked negative selection). To date, there have been few direct tests of these competing hypotheses. To determine the relative contributions of background selection and parallel selection to patterns of repeated differentiation, we examined 24 independently derived populations of freshwater stickleback occupying a variety of niches and estimated genomic patterns of differentiation in each relative to their common marine ancestor. Patterns of genetic differentiation were strongly correlated across pairs of freshwater populations adapting to the same ecological niche, supporting a role for parallel natural selection. In contrast to other recent work, our study comparing populations adapting to the same niche produced no evidence signifying that similar patterns of genomic differentiation are generated by background selection. We also found that overall patterns of genetic differentiation were considerably more similar for populations found in closer geographic proximity. In fact, the effect of geography on the repeatability of differentiation was greater than that of parallel selection. Our results suggest that shared selective landscapes and ancestral variation are the key drivers of repeated patterns of differentiation in systems that have recently colonized novel environments. More forthcoming papers &raquo; <p>Diana J. Rennison, Kira E. Delmore, Kieran Samuk, Gregory L. Owens, and Sara E. Miller (Feb 2020) </p> <p><b>Geographic proximity of populations strongly predicts magnitude of parallel genomic differentiation </b></p> <p><i><a href="https://dx.doi.org/10.1086/706476">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>losely related populations often display similar patterns of genomic differentiation, yet it remains an open question which ecological and evolutionary forces generate these patterns. The leading hypothesis is that this similarity in divergence is driven by parallel natural selection. However, several recent studies have suggested that these patterns may instead be a product of the depletion of genetic variation that occurs as result of background selection (i.e. linked negative selection). To date, there have been few direct tests of these competing hypotheses. To determine the relative contributions of background selection and parallel selection to patterns of repeated differentiation, we examined 24 independently derived populations of freshwater stickleback occupying a variety of niches and estimated genomic patterns of differentiation in each relative to their common marine ancestor. Patterns of genetic differentiation were strongly correlated across pairs of freshwater populations adapting to the same ecological niche, supporting a role for parallel natural selection. In contrast to other recent work, our study comparing populations adapting to the same niche produced no evidence signifying that similar patterns of genomic differentiation are generated by background selection. We also found that overall patterns of genetic differentiation were considerably more similar for populations found in closer geographic proximity. In fact, the effect of geography on the repeatability of differentiation was greater than that of parallel selection. Our results suggest that shared selective landscapes and ancestral variation are the key drivers of repeated patterns of differentiation in systems that have recently colonized novel environments. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 08 Oct 2019 05:00:00 GMT “Integrating fitness components reveals that survival costs outweigh other benefits and costs of group living in two closely related species” https://amnat.org/an/newpapers/Feb-Brouwer.html Lyanne Brouwer, Andrew Cockburn, and Martijn van de Pol (Feb 2020) Integrating fitness components reveals the importance of survival in shaping the costs and benefits of group living Read the Article (Just Accepted) Studies on group living animals have shown that living in groups maybe beneficial, for example because it increases foraging success, provides protection against predators, or even increases reproduction because group members assist in raising each other’s offspring. However, group living can also be costly because group members compete for food, space, or mating opportunities. Despite the enormous attention on the costs and benefits of group living, a limitation is that most studies have focused on a single cost or benefit—for example, the cost on survival or the benefit for reproduction. This means that it is unclear what the overall costs and benefits of group living are. In this study, Brouwer and collaborators investigate how six different fitness components vary with group size and subsequently integrate these to determine the overall costs and benefits of group living in two closely related fairy-wrens, family-living songbirds from Australia. They find that despite the differences between the species, the overall costs and benefits of group living are very similar, suggesting that the same behavioral mechanisms are important. For both species, the costs for additional group members on survival are most important for integrated fitness and this is amplified through carry-over effects of group size between years (i.e. large groups suffer survival costs, and are likely to do so the next year as well). In both species, integrated fitness of most group members was highest in small groups (size 2-3), and larger group sizes reduced fitness. How group size affects integrated fitness varied among different types of individuals, suggesting that group members potentially have a conflict of interest over optimal group size. This study provides a quantitative framework for future studies that aim to understand what demographic and behavioral mechanisms favor the evolution of cooperation or cause intra-group conflict. Abstract Group living can be beneficial when individuals reproduce or survive better in the presence of others, but simultaneously there might be costs due to competition for resources. Positive and negative effects on various fitness components might thus counteract each other, so integration is essential to determine their overall effect. Here, we investigated how an integrated fitness measure (reproductive values; RV) based on six fitness components varied with group size among group members in cooperatively-breeding red-winged and superb fairy-wrens (Malurus elegans and M.&nbsp;cyaneus). Despite life history differences between the species, patterns of RVs were similar, suggesting that the same behavioral mechanisms are important. Group living reduced RVs for dominant males, but for other group members this was only true in large groups. Decomposition analyses showed that our integrated fitness proxy was most strongly affected by group size effects on survival, which was amplified through carry-over effects between years. Our study shows that integrative consideration of fitness components and subsequent decomposition analysis provide much needed insights into the key behavioral mechanisms shaping the costs and benefits of group living. Such attribution is crucial if we are to synthesize the relative importance of the myriad group size costs and benefits currently reported in the literature. More forthcoming papers &raquo; <p>Lyanne Brouwer, Andrew Cockburn, and Martijn van de Pol (Feb 2020) </p> <p><b>Integrating fitness components reveals the importance of survival in shaping the costs and benefits of group living </b></p> <p><i><a href="https://dx.doi.org/10.1086/706475">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>tudies on group living animals have shown that living in groups maybe beneficial, for example because it increases foraging success, provides protection against predators, or even increases reproduction because group members assist in raising each other’s offspring. However, group living can also be costly because group members compete for food, space, or mating opportunities. Despite the enormous attention on the costs and benefits of group living, a limitation is that most studies have focused on a single cost or benefit&mdash;for example, the cost on survival or the benefit for reproduction. This means that it is unclear what the overall costs and benefits of group living are. In this study, Brouwer and collaborators investigate how six different fitness components vary with group size and subsequently integrate these to determine the overall costs and benefits of group living in two closely related fairy-wrens, family-living songbirds from Australia. </p><p>They find that despite the differences between the species, the overall costs and benefits of group living are very similar, suggesting that the same behavioral mechanisms are important. For both species, the costs for additional group members on survival are most important for integrated fitness and this is amplified through carry-over effects of group size between years (i.e. large groups suffer survival costs, and are likely to do so the next year as well). In both species, integrated fitness of most group members was highest in small groups (size 2-3), and larger group sizes reduced fitness. How group size affects integrated fitness varied among different types of individuals, suggesting that group members potentially have a conflict of interest over optimal group size. This study provides a quantitative framework for future studies that aim to understand what demographic and behavioral mechanisms favor the evolution of cooperation or cause intra-group conflict.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">G</span>roup living can be beneficial when individuals reproduce or survive better in the presence of others, but simultaneously there might be costs due to competition for resources. Positive and negative effects on various fitness components might thus counteract each other, so integration is essential to determine their overall effect. Here, we investigated how an integrated fitness measure (reproductive values; RV) based on six fitness components varied with group size among group members in cooperatively-breeding red-winged and superb fairy-wrens (<i>Malurus elegans</i> and <i>M.&nbsp;cyaneus</i>). Despite life history differences between the species, patterns of RVs were similar, suggesting that the same behavioral mechanisms are important. Group living reduced RVs for dominant males, but for other group members this was only true in large groups. Decomposition analyses showed that our integrated fitness proxy was most strongly affected by group size effects on survival, which was amplified through carry-over effects between years. Our study shows that integrative consideration of fitness components and subsequent decomposition analysis provide much needed insights into the key behavioral mechanisms shaping the costs and benefits of group living. Such attribution is crucial if we are to synthesize the relative importance of the myriad group size costs and benefits currently reported in the literature. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 08 Oct 2019 05:00:00 GMT “Community assembly and climate mismatch in Late-Quaternary eastern North American pollen assemblages” https://amnat.org/an/newpapers/Feb-Knight.html Clarke Knight, Jessica L. Blois, Benjamin Blonder, Marc Macias-Fauria, Alejandro Ordonez, and Jens-Christian Svenning (Feb 2020) Plot twist! Over 21 ka, climate-assemblage mismatch increased during fast climate shifts and in high-latitude/tree-dominated areas Read the Article (Just Accepted)What can the last 21 millennia in North America tell us about our future? Modern community ecology, which focuses on the here and now, is often disconnected from historical perspectives. However, important ecological processes – like vegetation response to climate change – manifest over a range of timespans, from decades to centuries, and millennia to deep-time. If the empirical richness of historical data could be more routinely applied to modern ecological concepts, ecologists could help forecast vegetation survival and persistence under future climate scenarios, as well as provide temporal context for modern concerns in community ecology. “We know that rapid environmental change defines our current world,” said lead author Clarke Knight, a PhD candidate at UC Berkeley in environmental science, “but by leveraging paleo data we can better understand past analogues that are applicable to modern situations.”Knight teamed up with researchers from UC Merced, the University of Oxford, and Aarhus University to look at vegetation change in North America over the last 21,000 years using a large, publicly-available fossil pollen dataset. They investigated how well plant communities kept pace with climatic changes and if certain community qualities (like the amount of trees) could predict the level of matching with the past climate. They found, for example, that tree-dominated, high-latitude communities were often out of step with climate. Such findings help constrain predictions for community response to future climate change. And, more broadly, by working at the edges of modern and paleo sciences, researchers can utilize history and advance the science of&nbsp;ecology. Abstract Plant community response to climate change ranges from synchronous tracking to strong mismatch. Explaining this variation in climate change response is critical for accurate global change modeling. Here we quantify how closely assemblages track changes in climate (match/mismatch) and how broadly climate niches are spread within assemblages (narrow/broad ecological tolerance, or ‘filtering’) using data for the last 21 ka for 531 eastern North American fossil pollen assemblages. Although climate matching has been strong over the last 21 millennia, mismatch increased in 30% of assemblages during the rapid climate shifts between 14.5 to 10 ka BP. Assemblage matching rebounded towards the present day in 10-20% of assemblages. Climate-assemblage mismatch was greater in tree-dominated and high-latitude assemblages, consistent with persisting populations, slower dispersal rates, and glacial retreat. In contrast, climate matching was greater for assemblages comprising taxa with higher median seed mass. Over half of the assemblages were climatically filtered at any given time, with peak filtering occurring at 8.5 ka BP for nearly 80% of assemblages. Thus, vegetation assemblages have highly variable rates of climate mismatch and filtering over millennial scales. These climate responses can be partially predicted by species’ traits and life histories. These findings help constrain predictions for plant community response to contemporary climate change. More forthcoming papers &raquo; <p>Clarke Knight, Jessica L. Blois, Benjamin Blonder, Marc Macias-Fauria, Alejandro Ordonez, and Jens-Christian Svenning (Feb 2020)</p> <p><b>Plot twist! Over 21 ka, climate-assemblage mismatch increased during fast climate shifts and in high-latitude/tree-dominated areas </b></p> <p><i><a href="https://dx.doi.org/10.1086/706340">Read the Article</a></i> (Just Accepted)</p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">W</span>hat can the last 21 millennia in North America tell us about our future? Modern community ecology, which focuses on the here and now, is often disconnected from historical perspectives. However, important ecological processes &ndash; like vegetation response to climate change &ndash; manifest over a range of timespans, from decades to centuries, and millennia to deep-time. If the empirical richness of historical data could be more routinely applied to modern ecological concepts, ecologists could help forecast vegetation survival and persistence under future climate scenarios, as well as provide temporal context for modern concerns in community ecology. &ldquo;We know that rapid environmental change defines our current world,&rdquo; said lead author Clarke Knight, a PhD candidate at UC Berkeley in environmental science, &ldquo;but by leveraging paleo data we can better understand past analogues that are applicable to modern situations.&rdquo;</p><p>Knight teamed up with researchers from UC Merced, the University of Oxford, and Aarhus University to look at vegetation change in North America over the last 21,000 years using a large, publicly-available fossil pollen dataset. They investigated how well plant communities kept pace with climatic changes and if certain community qualities (like the amount of trees) could predict the level of matching with the past climate. They found, for example, that tree-dominated, high-latitude communities were often out of step with climate. Such findings help constrain predictions for community response to future climate change. And, more broadly, by working at the edges of modern and paleo sciences, researchers can utilize history and advance the science of&nbsp;ecology.</p> <hr /><h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">P</span>lant community response to climate change ranges from synchronous tracking to strong mismatch. Explaining this variation in climate change response is critical for accurate global change modeling. Here we quantify how closely assemblages track changes in climate (match/mismatch) and how broadly climate niches are spread within assemblages (narrow/broad ecological tolerance, or &lsquo;filtering&rsquo;) using data for the last 21 ka for 531 eastern North American fossil pollen assemblages. Although climate matching has been strong over the last 21 millennia, mismatch increased in 30% of assemblages during the rapid climate shifts between 14.5 to 10 ka BP. Assemblage matching rebounded towards the present day in 10-20% of assemblages. Climate-assemblage mismatch was greater in tree-dominated and high-latitude assemblages, consistent with persisting populations, slower dispersal rates, and glacial retreat. In contrast, climate matching was greater for assemblages comprising taxa with higher median seed mass. Over half of the assemblages were climatically filtered at any given time, with peak filtering occurring at 8.5 ka BP for nearly 80% of assemblages. Thus, vegetation assemblages have highly variable rates of climate mismatch and filtering over millennial scales. These climate responses can be partially predicted by species&rsquo; traits and life histories. These findings help constrain predictions for plant community response to contemporary climate change.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 08 Oct 2019 05:00:00 GMT “Beyond Brownian motion and the Ornstein-Uhlenbeck process: Stochastic diffusion models for the evolution of quantitative characters” https://amnat.org/an/newpapers/Feb-Blomberg.html Simone P. Blomberg, Suren I. Rathnayake, and Cheyenne M. Moreau (Feb 2020) New evolutionary models for continuous traits, with an R package! Diffusion models get a closer evolutionary examination Read the Article (Just Accepted) Consider the way population geneticists model the evolution of gene frequencies over time, or the way quantitative genetic models are used for the understanding of trait evolution in response to natural selection. The evolutionary history of organisms does not enter into the mathematical equations describing the evolution of genes or traits. The models are “ahistorical” and hence are termed “microevolutionary” models: models that describe the evolution of traits (or genes) over short time scales. In contrast, a key principle of “macroevolutionary” models is that history matters. We cannot truly comprehend the evolution of traits without an understanding of the context of trait evolution gained by comparing multiple species over “deep time” using the so-called “comparative method.” Biologists who are interested in the evolution of quantitative traits (such as body mass, limb length, etc.) often wish to understand the tempo and mode of trait evolution over “deep time.” They ask questions such as, “Do some organisms evolve faster than others?”, “Has there been a shift in the mean value of a trait at some point in an organism’s evolutionary history?”, “How strong is natural selection in determining trait values?”, and “How are multiple traits related to each other and to the environment?” One way that biologists attempt to answer these questions is to fit mathematical models to trait data which describe the way evolution unfolds over time and along an evolutionary tree. Such models are called “diffusions,” as they model the path of a trait through evolutionary time as if it were a particle diffusing through a medium, being affected by both deterministic and stochastic forces. Most current diffusion models of evolution are designed for traits that follow the Normal distribution: the bell-shaped curve. In a new paper in The&nbsp;American Naturalist, a team from the University of Queensland in Australia, led by Dr. Simone Blomberg, describe two new models of trait evolution that do not require the traits to be described by a bell curve. These new models allow the study of quantitative traits that are not easily examined using current methods, such as lifespan or sex ratio. Using methods first developed for use in physics and quantitative finance, the team also demonstrate how to derive new, different models of evolution, how to understand their properties, and how to fit them to trait data on an evolutionary tree. They provide software tools to do this, using modern computer-intensive statistical techniques. The UQ team hope their new paper in The&nbsp;American Naturalist will inspire biologists to become more adventurous in modelling trait data over “deep time” and throw off the shackles of the Normal distribution! Abstract Gaussian processes such as Brownian motion and the Ornstein-Uhlenbeck process have been popular models for the evolution of quantitative traits and are widely used in phylogenetic comparative methods. However, they have drawbacks which limit their utility. Here we describe new, non-Gaussian stochastic differential equation (diffusion) models of quantitative trait evolution. We present general methods for deriving new diffusion models, and develop new software for fitting non-Gaussian evolutionary models to trait data. The theory of stochastic processes provides a mathematical framework for understanding the properties of current and future phylogenetic comparative methods. Attention to the mathematical details of models of trait evolution and diversification may help avoid some pitfalls when using stochastic processes to model macroevolution. More forthcoming papers &raquo; <p>Simone P. Blomberg, Suren I. Rathnayake, and Cheyenne M. Moreau (Feb 2020) </p> <p><b>New evolutionary models for continuous traits, with an R package! Diffusion models get a closer evolutionary examination </b></p> <p><i><a href="https://dx.doi.org/10.1086/706339">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>onsider the way population geneticists model the evolution of gene frequencies over time, or the way quantitative genetic models are used for the understanding of trait evolution in response to natural selection. The evolutionary history of organisms does not enter into the mathematical equations describing the evolution of genes or traits. The models are “ahistorical” and hence are termed “microevolutionary” models: models that describe the evolution of traits (or genes) over short time scales. In contrast, a key principle of “macroevolutionary” models is that history matters. We cannot truly comprehend the evolution of traits without an understanding of the context of trait evolution gained by comparing multiple species over “deep time” using the so-called “comparative method.” </p><p>Biologists who are interested in the evolution of quantitative traits (such as body mass, limb length, etc.) often wish to understand the tempo and mode of trait evolution over “deep time.” They ask questions such as, “Do some organisms evolve faster than others?”, “Has there been a shift in the mean value of a trait at some point in an organism’s evolutionary history?”, “How strong is natural selection in determining trait values?”, and “How are multiple traits related to each other and to the environment?” One way that biologists attempt to answer these questions is to fit mathematical models to trait data which describe the way evolution unfolds over time and along an evolutionary tree. Such models are called “diffusions,” as they model the path of a trait through evolutionary time as if it were a particle diffusing through a medium, being affected by both deterministic and stochastic forces. </p><p>Most current diffusion models of evolution are designed for traits that follow the Normal distribution: the bell-shaped curve. In a new paper in <i>The&nbsp;American Naturalist</i>, a team from the University of Queensland in Australia, led by Dr. Simone Blomberg, describe two new models of trait evolution that do not require the traits to be described by a bell curve. These new models allow the study of quantitative traits that are not easily examined using current methods, such as lifespan or sex ratio. Using methods first developed for use in physics and quantitative finance, the team also demonstrate how to derive new, different models of evolution, how to understand their properties, and how to fit them to trait data on an evolutionary tree. They provide software tools to do this, using modern computer-intensive statistical techniques. </p><p>The UQ team hope their new paper in <i>The&nbsp;American Naturalist</i> will inspire biologists to become more adventurous in modelling trait data over “deep time” and throw off the shackles of the Normal distribution! </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">G</span>aussian processes such as Brownian motion and the Ornstein-Uhlenbeck process have been popular models for the evolution of quantitative traits and are widely used in phylogenetic comparative methods. However, they have drawbacks which limit their utility. Here we describe new, non-Gaussian stochastic differential equation (diffusion) models of quantitative trait evolution. We present general methods for deriving new diffusion models, and develop new software for fitting non-Gaussian evolutionary models to trait data. The theory of stochastic processes provides a mathematical framework for understanding the properties of current and future phylogenetic comparative methods. Attention to the mathematical details of models of trait evolution and diversification may help avoid some pitfalls when using stochastic processes to model macroevolution. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 08 Oct 2019 05:00:00 GMT “The evolution of immigration strategies facilitates niche expansion by divergent adaptation in a structured metapopulation model” https://amnat.org/an/newpapers/Jan-Kisdi.html &Eacute;va Kisdi, Helene C. Weigang, and Mats Gyllenberg (Jan 2020) The evolution of immigration strategies facilitates niche expansion by divergent adaptation in a metapopulation model Read the ArticleVia Darwinian evolution, organisms adapt to the habitats where they live. Yet once adapted to a particular set of environmental conditions, it is pretty hard to broaden this "niche" of environments where the organism thrives, because adapting to a new environment usually comes at the cost of diminishing success in the old habitat. Since most individuals survive and reproduce in the old habitat, sacrificing reproduction in this habitat is too high a price for improving the chances of the few who wither in the new habitat. As a result, no change occurs and the niche is conserved. Many animals are able to choose actively where they live. Habitat choice appears to aggravate niche conservatism; as individuals choose favorable environments to which they are already adapted, they will not be exposed to new habitats. When not exposed to new habitats, there is no need to adapt to them. Live where you succeed, then there is no need to change how you live. This vicious circle can however be broken. The model of Kisdi et al. highlights the range of habitats that are marginally favorable, i.e., favorable if empty but unfavorable if crowded. In these habitats, a delicate balance evolves, where the local population size is just on the edge between making the habitat favorable or unfavorable. Once two strains of the organism are present (representing a minimum of genetic variability), this delicate balance is upset. No matter how little is the initial difference between the strains, each marginal habitat will be preferentially used by the strain that is better adapted there. With the two strains using different habitats, they start to adapt to different environmental conditions, which drives their habitat preferences further apart. As a result, the niche expands. Abstract Local adaptation and habitat choice are two key factors that control the distribution and diversification of species. Here we model habitat choice mechanistically as the outcome of dispersal with non-random immigration. We consider a structured metapopulation with a continuous distribution of patch types, and determine the evolutionarily stable immigration strategy as the function linking patch type to the probability of settling in the patch upon encounter. We uncover a novel mechanism whereby coexisting strains that only slightly differ in their local adaptation trait can evolve substantially different immigration strategies. In turn, different habitat use selects for divergent adaptations in the two strains. We propose that the joint evolution of immigration and local adaptation can facilitate diversification, and discuss our results in the light of niche conservatism versus niche expansion. More forthcoming papers &raquo; <p>&Eacute;va Kisdi, Helene C. Weigang, and Mats Gyllenberg (Jan 2020)</p> <p><b>The evolution of immigration strategies facilitates niche expansion by divergent adaptation in a metapopulation model </b></p> <p><i><a href="https://dx.doi.org/10.1086/706258">Read the Article</a></i></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">V</span>ia Darwinian evolution, organisms adapt to the habitats where they live. Yet once adapted to a particular set of environmental conditions, it is pretty hard to broaden this "niche" of environments where the organism thrives, because adapting to a new environment usually comes at the cost of diminishing success in the old habitat. Since most individuals survive and reproduce in the old habitat, sacrificing reproduction in this habitat is too high a price for improving the chances of the few who wither in the new habitat. As a result, no change occurs and the niche is conserved. </p><p>Many animals are able to choose actively where they live. Habitat choice appears to aggravate niche conservatism; as individuals choose favorable environments to which they are already adapted, they will not be exposed to new habitats. When not exposed to new habitats, there is no need to adapt to them. Live where you succeed, then there is no need to change how you live. </p><p>This vicious circle can however be broken. The model of Kisdi et al. highlights the range of habitats that are marginally favorable, i.e., favorable if empty but unfavorable if crowded. In these habitats, a delicate balance evolves, where the local population size is just on the edge between making the habitat favorable or unfavorable. Once two strains of the organism are present (representing a minimum of genetic variability), this delicate balance is upset. No matter how little is the initial difference between the strains, each marginal habitat will be preferentially used by the strain that is better adapted there. With the two strains using different habitats, they start to adapt to different environmental conditions, which drives their habitat preferences further apart. As a result, the niche expands. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">L</span>ocal adaptation and habitat choice are two key factors that control the distribution and diversification of species. Here we model habitat choice mechanistically as the outcome of dispersal with non-random immigration. We consider a structured metapopulation with a continuous distribution of patch types, and determine the evolutionarily stable immigration strategy as the function linking patch type to the probability of settling in the patch upon encounter. We uncover a novel mechanism whereby coexisting strains that only slightly differ in their local adaptation trait can evolve substantially different immigration strategies. In turn, different habitat use selects for divergent adaptations in the two strains. We propose that the joint evolution of immigration and local adaptation can facilitate diversification, and discuss our results in the light of niche conservatism versus niche expansion. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 08 Oct 2019 05:00:00 GMT “Gliding dragons and flying squirrels: diversifying versus stabilizing selection on morphology following the evolution of an innovation” https://amnat.org/an/newpapers/Feb-Ord.html Terry J. Ord, Joan Garcia-Porta, Marina Querejeta, and David C. Collar (Feb 2020) UNSW researchers show gliding animals are an evolutionary surprise because their innovation did not lead to a proliferation of new adaptive forms Read the Article (Just Accepted) A&nbsp;study of gliding animals has challenged the idea that evolutionary innovations – adaptations that bring new abilities and advantages – spur the origin of other new body types and other characteristics in descendent species. The research, undertaken by evolutionary biologists at UNSW Sydney and universities in the US and Spain, examined the key innovation of gliding in two types of gliding animals: ‘flying’ dragons (family Agamidae) and ‘flying’ squirrels (family Sciuridae), both common to forests in Southeast Asia. The study confirms previous assumptions that gliding animals originated from arboreal ancestors and likely arose as a means of escaping predators some 25-30 million years ago. Lead author Dr. Terry Ord, an evolutionary ecologist with UNSW’s Evolution & Ecology Research Centre, says another advantage that gliding brought was the ability to exploit a new three dimensional environment and explore more of the forest than just one tree. “From an evolutionary biologist’s perspective, these types of innovation that open up new opportunities are assumed to drive even more adapted diversification,” Dr. Ord says. “Suddenly there’s all these new microhabitats available offering up new resources and you have new species moving into those particular microhabitats where you would expect them to adapt even more.” The evolution of flight in birds, insects and bats is an example where the changes brought about by ‘taking to the wing’ caused an explosion in diversity. Millions of species of insects, tens of thousands of birds and more than a thousand species of bats developed greatly different shapes, sizes, behaviors and habitats since their ancestors first evolved to fly. But in the case of the gliding animals like the dragons and squirrels, the advantage of gliding has not led to a proliferation of changes to body shapes, sizes and functions. In fact, for the dragons the key innovation of gliding appears to have done the opposite. “In the case of the dragon lizards, gliding appears to be a constraint on subsequent adaptation because of the aerodynamics of having to glide,” Dr. Ord says. “Basically the heavier you are, the more difficult it is to glide. So there is a constraint on general body size and shape – meaning a halt to the evolution of longer limbs and bigger heads, for example, that would normally reflect adaptation to particular microhabitats. But instead, the dragons have to glide, and that means limiting their body sizes to stay small and aerodynamic – which has what we call stabilizing selection on their bodies.” Interestingly, some species of flying dragons actually did go on to evolve larger bodies, at the expense of their gliding abilities. To offset their poor gliding, they had to develop new behaviors such as flattening their bodies against the tree trunk to blend in with the bark, Dr. Ord says. “So they’re almost regressing from that gliding lifestyle. But in this case, the reason why they’re changing their body size is to overcome competition with other lizards.” There were no such bodily constraints with squirrels, due to key differences in the gliding membranes. Whereas the ribs of the dragon lizards evolved to extend laterally as the ‘wings’ of the animals, the squirrels’ gliding membrane developed as a flap of skin joining their wrists to their ankles. “So squirrels just evolve longer limbs which means the size of the membrane increases proportionally to the longer limbs, enabling somewhat bigger bodied animals to glide without sacrificing too much ability,” says Dr. Ord. But despite squirrel body sizes not being as constrained, the body sizes and characteristics of gliding squirrels are no more diverse than non-gliding squirrels. “So again the expectation of a key innovation driving the evolution of greater diversity was thwarted in the case of gliding squirrels.” Dr. Ord says his research has implications for our understanding of the way key innovations and competition come into play in evolution. “Evolutionary innovations are evocative because they’re often amazing curiosities. And perhaps this has led us to infer they’re also key in opening the door to even more adaptation. But it seems that interactions with other organisms – competition for resources – is a far more powerful force for generating adaptive diversity,” he says. Looking ahead, Dr. Ord will be following up with research into the dragon lizards to find out how they use another evolutionary innovation, their dewlaps – the colorful flap of skin that hangs beneath their jaws – to communicate. Abstract Evolutionary innovations and ecological competition are factors often cited as drivers of adaptive diversification. Yet many innovations result in stabilizing rather than diversifying selection on morphology, and morphological disparity among co-existing species can reflect competitive exclusion (species sorting) rather than sympatric adaptive divergence (character displacement). We studied the innovation of gliding in dragons (Agamidae) and squirrels (Sciuridae) and its effect on subsequent body size diversification. We found gliding either had no impact (squirrels) or resulted in strong stabilizing selection on body size (dragons). Despite this constraining effect in dragons, sympatric gliders exhibit greater size disparity compared to allopatric gliders, a pattern consistent with, though not exclusively explained by, ecological competition changing the adaptive landscape of body size evolution to induce character displacement. These results show that innovations do not necessarily instigate further differentiation among species as so often assumed, and suggest competition can be a powerful force generating morphological divergence among co-existing species, even in the face of strong stabilizing selection. More forthcoming papers &raquo; <p>Terry J. Ord, Joan Garcia-Porta, Marina Querejeta, and David C. Collar (Feb 2020) </p> <p><b>UNSW researchers show gliding animals are an evolutionary surprise because their innovation did not lead to a proliferation of new adaptive forms </b></p><p><i><a href="https://dx.doi.org/10.1086/706305">Read the Article</a></i> (Just Accepted) </p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>&nbsp;study of gliding animals has challenged the idea that evolutionary innovations &ndash; adaptations that bring new abilities and advantages &ndash; spur the origin of other new body types and other characteristics in descendent species. The research, undertaken by evolutionary biologists at UNSW Sydney and universities in the US and Spain, examined the key innovation of gliding in two types of gliding animals: &lsquo;flying&rsquo; dragons (family Agamidae) and &lsquo;flying&rsquo; squirrels (family Sciuridae), both common to forests in Southeast Asia. The study confirms previous assumptions that gliding animals originated from arboreal ancestors and likely arose as a means of escaping predators some 25-30 million years ago.</p> <p>Lead author Dr. Terry Ord, an evolutionary ecologist with UNSW&rsquo;s Evolution &amp; Ecology Research Centre, says another advantage that gliding brought was the ability to exploit a new three dimensional environment and explore more of the forest than just one tree. &ldquo;From an evolutionary biologist&rsquo;s perspective, these types of innovation that open up new opportunities are assumed to drive even more adapted diversification,&rdquo; Dr. Ord says. &ldquo;Suddenly there&rsquo;s all these new microhabitats available offering up new resources and you have new species moving into those particular microhabitats where you would expect them to adapt even more.&rdquo;</p> <p>The evolution of flight in birds, insects and bats is an example where the changes brought about by &lsquo;taking to the wing&rsquo; caused an explosion in diversity. Millions of species of insects, tens of thousands of birds and more than a thousand species of bats developed greatly different shapes, sizes, behaviors and habitats since their ancestors first evolved to fly. But in the case of the gliding animals like the dragons and squirrels, the advantage of gliding has not led to a proliferation of changes to body shapes, sizes and functions. In fact, for the dragons the key innovation of gliding appears to have done the opposite. &ldquo;In the case of the dragon lizards, gliding appears to be a constraint on subsequent adaptation because of the aerodynamics of having to glide,&rdquo; Dr. Ord says. &ldquo;Basically the heavier you are, the more difficult it is to glide. So there is a constraint on general body size and shape &ndash; meaning a halt to the evolution of longer limbs and bigger heads, for example, that would normally reflect adaptation to particular microhabitats. But instead, the dragons have to glide, and that means limiting their body sizes to stay small and aerodynamic &ndash; which has what we call stabilizing selection on their bodies.&rdquo;</p> <p>Interestingly, some species of flying dragons actually did go on to evolve larger bodies, at the expense of their gliding abilities. To offset their poor gliding, they had to develop new behaviors such as flattening their bodies against the tree trunk to blend in with the bark, Dr. Ord says. &ldquo;So they&rsquo;re almost regressing from that gliding lifestyle. But in this case, the reason why they&rsquo;re changing their body size is to overcome competition with other lizards.&rdquo; There were no such bodily constraints with squirrels, due to key differences in the gliding membranes. Whereas the ribs of the dragon lizards evolved to extend laterally as the &lsquo;wings&rsquo; of the animals, the squirrels&rsquo; gliding membrane developed as a flap of skin joining their wrists to their ankles. &ldquo;So squirrels just evolve longer limbs which means the size of the membrane increases proportionally to the longer limbs, enabling somewhat bigger bodied animals to glide without sacrificing too much ability,&rdquo; says Dr. Ord. But despite squirrel body sizes not being as constrained, the body sizes and characteristics of gliding squirrels are no more diverse than non-gliding squirrels. &ldquo;So again the expectation of a key innovation driving the evolution of greater diversity was thwarted in the case of gliding squirrels.&rdquo;</p> <p>Dr. Ord says his research has implications for our understanding of the way key innovations and competition come into play in evolution. &ldquo;Evolutionary innovations are evocative because they&rsquo;re often amazing curiosities. And perhaps this has led us to infer they&rsquo;re also key in opening the door to even more adaptation. But it seems that interactions with other organisms &ndash; competition for resources &ndash; is a far more powerful force for generating adaptive diversity,&rdquo; he says. Looking ahead, Dr. Ord will be following up with research into the dragon lizards to find out how they use another evolutionary innovation, their dewlaps &ndash; the colorful flap of skin that hangs beneath their jaws &ndash; to communicate.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">E</span>volutionary innovations and ecological competition are factors often cited as drivers of adaptive diversification. Yet many innovations result in stabilizing rather than diversifying selection on morphology, and morphological disparity among co-existing species can reflect competitive exclusion (species sorting) rather than sympatric adaptive divergence (character displacement). We studied the innovation of gliding in dragons (Agamidae) and squirrels (Sciuridae) and its effect on subsequent body size diversification. We found gliding either had no impact (squirrels) or resulted in strong stabilizing selection on body size (dragons). Despite this constraining effect in dragons, sympatric gliders exhibit greater size disparity compared to allopatric gliders, a pattern consistent with, though not exclusively explained by, ecological competition changing the adaptive landscape of body size evolution to induce character displacement. These results show that innovations do not necessarily instigate further differentiation among species as so often assumed, and suggest competition can be a powerful force generating morphological divergence among co-existing species, even in the face of strong stabilizing selection.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 23 Sep 2019 05:00:00 GMT