ASN RSS https://amnat.org/ Latest press releases and announcements from the ASN en-us Fri, 23 Aug 2019 05:00:00 GMT 60 “Combined effects of natural enemies and competition for resources on a forest defoliator: a theoretical and empirical analysis” https://amnat.org/an/newpapers/Dec-Gallagher.html Molly E. Gallagher and Greg Dwyer (Dec 2019)Read the Article (Just Accepted) Resource competition & parasitoids drive budworm outbreaks in jack pine forests; climate change may upend the ecosystem Insect outbreaks can quickly damage or destroy thousands of acres of forests. Jack pine forests are frequently attacked by a species of very hungry caterpillar called the jack pine budworm. Jack pine budworm outbreaks occur every 6-12 years and continue for 2-4 years. Molly Gallagher and Greg Dwyer asked why these outbreaks happen, what causes them to end, and whether outbreaks might become more severe in the future as climate change progresses and the frequency of forest fires increases. To understand the factors that determine budworm survival, Molly Gallagher and Greg Dwyer constructed mathematical models that included different ecological effects and interactions. To estimate model parameters, they collected data from budworm outbreaks in jack pine forests in Wisconsin and Michigan from 2012-2015. They measured the density of budworm caterpillars in different parts of the forest over time, and recorded the size and age of trees that were under attack. They also raised caterpillars in the lab to determine how many were infected with parasitoids such as wasps or flies, which lay their eggs inside their caterpillar hosts, and eventually kill their hosts. By using their data to choose the best model, Dwyer and Gallagher showed that to best understand patterns of insect outbreaks, it is necessary to consider the effects of both parasitoid attacks and resource competition. At lower budworm densities, parasitoid attacks are more important, but when budworm density is very high, more caterpillars die due to a lack of plant resources. Simulations of a model including both of these factors result in realistic cycles of the budworm population. In future work, the researchers plan to extend their model to include the interacting effects of climate variables and fire frequency on forest health. Jack pine forests are a major component of the North American landscape, and with changing pressures from insect outbreaks and climate stressors, their future remains uncertain. Abstract Explanations for the dynamics of insect outbreaks often focus on natural enemies, on the grounds that parasitoid and pathogen attack rates are high during outbreaks. While natural enemy models can successfully reproduce outbreak cycles, experiments have repeatedly demonstrated the importance of resource quality and abundance. Experiments, however, are rarely invoked in modeling studies. Here we combine mechanistic models, observational data, and field experiments to quantify the roles of parasitoid attacks and resource competition on the jack pine budworm, Choristoneura pinus. By fitting models to a combination of observational and experimental data, we show that parasitoid attacks are the main source of larval budworm mortality at low and intermediate budworm densities, but that resource competition is the main source of mortality at high densities. Our results further show that the effects of resource competition become more severe with increasing host tree age, and that the effects of parasitoids are moderated by strong competition between parasitoids for hosts. Allowing for these effects in a model of insect outbreaks leads to realistic outbreak cycles, while a host-parasitoid model without resource competition produces an unrealistic stable equilibrium. The effects of resource competition are modulated by tree age, which in turn depends on fire regimes. Our model therefore suggests that increases in fire frequency due to climate change may interact in complex ways with budworm outbreaks. Our work shows that resource competition can be as important as natural enemies in modulating insect outbreaks, while demonstrating the usefulness of high-performance computing in experimental field ecology. More forthcoming papers &raquo; <p>Molly E. Gallagher and Greg Dwyer (Dec 2019)</p><p><i><a href="https://dx.doi.org/10.1086/705940">Read the Article</a></i> (Just Accepted) </p> <p><b>Resource competition & parasitoids drive budworm outbreaks in jack pine forests; climate change may upend the ecosystem </b></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>nsect outbreaks can quickly damage or destroy thousands of acres of forests. Jack pine forests are frequently attacked by a species of very hungry caterpillar called the jack pine budworm. Jack pine budworm outbreaks occur every 6-12 years and continue for 2-4 years. Molly Gallagher and Greg Dwyer asked why these outbreaks happen, what causes them to end, and whether outbreaks might become more severe in the future as climate change progresses and the frequency of forest fires increases. </p><p>To understand the factors that determine budworm survival, Molly Gallagher and Greg Dwyer constructed mathematical models that included different ecological effects and interactions. To estimate model parameters, they collected data from budworm outbreaks in jack pine forests in Wisconsin and Michigan from 2012-2015. They measured the density of budworm caterpillars in different parts of the forest over time, and recorded the size and age of trees that were under attack. They also raised caterpillars in the lab to determine how many were infected with parasitoids such as wasps or flies, which lay their eggs inside their caterpillar hosts, and eventually kill their hosts. </p><p>By using their data to choose the best model, Dwyer and Gallagher showed that to best understand patterns of insect outbreaks, it is necessary to consider the effects of both parasitoid attacks and resource competition. At lower budworm densities, parasitoid attacks are more important, but when budworm density is very high, more caterpillars die due to a lack of plant resources. Simulations of a model including both of these factors result in realistic cycles of the budworm population. </p><p>In future work, the researchers plan to extend their model to include the interacting effects of climate variables and fire frequency on forest health. Jack pine forests are a major component of the North American landscape, and with changing pressures from insect outbreaks and climate stressors, their future remains uncertain. </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>xplanations for the dynamics of insect outbreaks often focus on natural enemies, on the grounds that parasitoid and pathogen attack rates are high during outbreaks. While natural enemy models can successfully reproduce outbreak cycles, experiments have repeatedly demonstrated the importance of resource quality and abundance. Experiments, however, are rarely invoked in modeling studies. Here we combine mechanistic models, observational data, and field experiments to quantify the roles of parasitoid attacks and resource competition on the jack pine budworm, <i>Choristoneura pinus</i>. By fitting models to a combination of observational and experimental data, we show that parasitoid attacks are the main source of larval budworm mortality at low and intermediate budworm densities, but that resource competition is the main source of mortality at high densities. Our results further show that the effects of resource competition become more severe with increasing host tree age, and that the effects of parasitoids are moderated by strong competition between parasitoids for hosts. Allowing for these effects in a model of insect outbreaks leads to realistic outbreak cycles, while a host-parasitoid model without resource competition produces an unrealistic stable equilibrium. The effects of resource competition are modulated by tree age, which in turn depends on fire regimes. Our model therefore suggests that increases in fire frequency due to climate change may interact in complex ways with budworm outbreaks. Our work shows that resource competition can be as important as natural enemies in modulating insect outbreaks, while demonstrating the usefulness of high-performance computing in experimental field ecology. </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, 22 Aug 2019 05:00:00 GMT “A Grinnellian niche perspective on species-area relationships” https://amnat.org/an/newpapers/Dec-Soberon.html Jorge Soberon (Dec 2019)Read the Article (Just Accepted) The species-area relationship is re-interpreted using fundamental niche positions in niche space: This is a new approach Ecologists have known for a very long time that there is a positive relationship between the size of a region and the number of species it contains. The relationship is often modeled using a very simple power law, with two parameters, and much work has been done on explaining these from demographic processes. In this work I attempt an alternative explanation, one based on the distribution of fundamental niches in environmental space. When area grows, the size of available environmental space also increases. This in turn means that the fundamental niches (ranges of environmental tolerances) of more species are included in the larger environmental space. Approaching the species-area relationship in this way is novel and illuminating. It shifts the focus from very local ecological processes to broad-scale climatic and biographical processes. Probably both perspectives will be needed for a comprehensive understanding of the problem. Abstract In this work, Grinnellian niche theory (a body of theory about geographic distributions of species in terms of non-interacting niche variables) is used to demonstrate that species-area relationships emerge with both size of environmental space and size of geographic area. As environmental space increases, more species' fundamental niches are included, thus increasing the number of species capable of living in the corresponding region. This idea is made operational by proposing a size measure for multidimensional environmental space and approximating fundamental niches with minimum-volume ellipsoids. This framework allows estimating a presence-absence matrix based on the distribution of fundamental niches in environmental space, from which many biodiversity measures can be calculated, such as beta diversity. I establish that Whittaker’s equation for beta diversity is equivalent to MacArthur’s formula relating species numbers and niche breadth; this latter equation provides a mechanism for the species niche-space relationship. I illustrate the theoretical results via exploration of niches of the terrestrial mammals of North America (north of Panama). Each world region has a unique structure of its environmental space, and the position of fundamental niches in niche space is different for different clades; therefore, species-area relationships depend on the clades involved and the region of focus, mostly as a function of MacArthur’s niche beta diversity. Analyzing species-area relationships from the perspective of niche position in environmental space is novel, shifting emphasis from demographic processes to historical, geographic, and climatic factors; moreover, the Grinnellian approach is based on available data and is computationally feasible. More forthcoming papers &raquo; <p>Jorge Soberon (Dec 2019)</p><p><i><a href="https://dx.doi.org/10.1086/705898">Read the Article</a></i> (Just Accepted) </p> <p><b>The species-area relationship is re-interpreted using fundamental niche positions in niche space: This is a new approach </b></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>cologists have known for a very long time that there is a positive relationship between the size of a region and the number of species it contains. The relationship is often modeled using a very simple power law, with two parameters, and much work has been done on explaining these from demographic processes. In this work I attempt an alternative explanation, one based on the distribution of fundamental niches in environmental space. When area grows, the size of available environmental space also increases. This in turn means that the fundamental niches (ranges of environmental tolerances) of more species are included in the larger environmental space. Approaching the species-area relationship in this way is novel and illuminating. It shifts the focus from very local ecological processes to broad-scale climatic and biographical processes. Probably both perspectives will be needed for a comprehensive understanding of the 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;">I</span>n this work, Grinnellian niche theory (a body of theory about geographic distributions of species in terms of non-interacting niche variables) is used to demonstrate that species-area relationships emerge with both size of environmental space and size of geographic area. As environmental space increases, more species' fundamental niches are included, thus increasing the number of species capable of living in the corresponding region. This idea is made operational by proposing a size measure for multidimensional environmental space and approximating fundamental niches with minimum-volume ellipsoids. This framework allows estimating a presence-absence matrix based on the distribution of fundamental niches in environmental space, from which many biodiversity measures can be calculated, such as beta diversity. I establish that Whittaker’s equation for beta diversity is equivalent to MacArthur’s formula relating species numbers and niche breadth; this latter equation provides a mechanism for the species niche-space relationship. I illustrate the theoretical results via exploration of niches of the terrestrial mammals of North America (north of Panama). Each world region has a unique structure of its environmental space, and the position of fundamental niches in niche space is different for different clades; therefore, species-area relationships depend on the clades involved and the region of focus, mostly as a function of MacArthur’s niche beta diversity. Analyzing species-area relationships from the perspective of niche position in environmental space is novel, shifting emphasis from demographic processes to historical, geographic, and climatic factors; moreover, the Grinnellian approach is based on available data and is computationally feasible. </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, 22 Aug 2019 05:00:00 GMT “Larger genomes linked to slower development and loss of late-developing traits” https://amnat.org/an/newpapers/Dec-Womack.html Molly C. Womack, Marissa J. Metz, and Kim L. Hoke (Dec 2019) Read the Article (Just Accepted) Larger genomes linked to slower development and loss of late-developing traits Genome size (the amount of DNA in an animal) varies widely among animals and can affect an animal’s appearance, how they develop, and how their bodies function. For example, increases in genome size have been linked with loss of toes in salamanders. Recently, researchers from Colorado State University were able to show that frogs with larger genomes take longer to develop from a swimming tadpole into a hopping froglet and often lack a middle ear bone as adults. The authors suggest that larger genomes, slower development, and smaller body sizes at the transition from tadpole to froglet (metamorphosis) may contribute to more than 39 mysterious losses of the middle ear among frog lineages. In amphibians more broadly, genome size is hypothesized to affect the formation of structures (bones, muscle, and other tissues) that appear late in development, closer to adulthood. However, few studies have linked larger genome size with changes in late-forming structures, especially outside of salamanders, which have much larger genomes than most animals. This new finding from Womack et al., appearing in The&nbsp;American Naturalist, concludes that increases in frog genome size, although less drastic than in salamanders, may affect development of late-forming traits such as middle ear bones. These results raise the possibility that the development of structures in other animals may be affected by changes in genome size. Abstract Genome size varies widely among organisms and is known to affect vertebrate development, morphology, and physiology. In amphibians, genome size is hypothesized to contribute to loss of late-forming structures, although this hypothesis has mainly been discussed in salamanders. Here we estimated genome size for 22 anuran species and combined this novel dataset with existing genome size data for an additional 234 anuran species to determine whether larger genome size is associated with loss of a late-forming anuran sensory structure, the tympanic middle ear. We established that genome size is negatively correlated with development rate across 90 anuran species and found that genome size evolution is correlated with evolutionary loss of the middle ear bone (columella) among 241 species (224 eared and 17 earless). We further tested whether the development of the tympanic middle ear could be constrained by large cell sizes and small body sizes during key stages of tympanic middle ear development (metamorphosis). Together, our evidence suggests that larger genomes, slower development rate, and smaller body sizes at metamorphosis may contribute to the loss of the anuran tympanic middle ear. We conclude that increases in anuran genome size, although less drastic than in salamanders, may affect development of late-forming traits. More forthcoming papers &raquo; <p>Molly C. Womack, Marissa J. Metz, and Kim L. Hoke (Dec 2019) </p><p><i><a href="https://dx.doi.org/10.1086/705897">Read the Article</a></i> (Just Accepted) </p> <p><b>Larger genomes linked to slower development and loss of late-developing traits </b></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;">G</span>enome size (the amount of DNA in an animal) varies widely among animals and can affect an animal&rsquo;s appearance, how they develop, and how their bodies function. For example, increases in genome size have been linked with loss of toes in salamanders. Recently, researchers from Colorado State University were able to show that frogs with larger genomes take longer to develop from a swimming tadpole into a hopping froglet and often lack a middle ear bone as adults. The authors suggest that larger genomes, slower development, and smaller body sizes at the transition from tadpole to froglet (metamorphosis) may contribute to more than 39 mysterious losses of the middle ear among frog lineages. In amphibians more broadly, genome size is hypothesized to affect the formation of structures (bones, muscle, and other tissues) that appear late in development, closer to adulthood. However, few studies have linked larger genome size with changes in late-forming structures, especially outside of salamanders, which have much larger genomes than most animals. This new finding from Womack et al., appearing in <i>The&nbsp;American Naturalist</i>, concludes that increases in frog genome size, although less drastic than in salamanders, may affect development of late-forming traits such as middle ear bones. These results raise the possibility that the development of structures in other animals may be affected by changes in genome size.</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;">G</span>enome size varies widely among organisms and is known to affect vertebrate development, morphology, and physiology. In amphibians, genome size is hypothesized to contribute to loss of late-forming structures, although this hypothesis has mainly been discussed in salamanders. Here we estimated genome size for 22 anuran species and combined this novel dataset with existing genome size data for an additional 234 anuran species to determine whether larger genome size is associated with loss of a late-forming anuran sensory structure, the tympanic middle ear. We established that genome size is negatively correlated with development rate across 90 anuran species and found that genome size evolution is correlated with evolutionary loss of the middle ear bone (columella) among 241 species (224 eared and 17 earless). We further tested whether the development of the tympanic middle ear could be constrained by large cell sizes and small body sizes during key stages of tympanic middle ear development (metamorphosis). Together, our evidence suggests that larger genomes, slower development rate, and smaller body sizes at metamorphosis may contribute to the loss of the anuran tympanic middle ear. We conclude that increases in anuran genome size, although less drastic than in salamanders, may affect development of late-forming traits.</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> Thu, 22 Aug 2019 05:00:00 GMT “Trade-offs in cold-resistance at the northern range edge of the common woodland ant <i>Aphaenogaster picea</i> (Formicidae)” https://amnat.org/an/newpapers/Dec-Nguyen-A.html Andrew D. Nguyen, Megan Brown, Jordan Zhitnay, Sara Helms Cahan, Nicholas J. Gotelli, Amy Arnett, and Aaron M. Ellison (Dec 2019) Read the Article (Just Accepted)Abstract Geographic variation in low temperatures at poleward range margins of terrestrial species often mirrors population variation in cold resistance, suggesting that range boundaries may be set by evolutionary constraints on cold physiology. The northeastern woodland ant Aphaenogaster picea occurs up to approximately 45°N in central Maine. We combined presence-absence surveys with regression-tree analysis to characterize its northern range limit and assayed two measures of cold resistance operating on different timescales to determine whether and how marginal populations adapt to environmental extremes. The range boundary of A.&nbsp;picea was predicted primarily by temperature, but low winter temperatures did not emerge as the primary correlate of species occurrence. Low summer temperatures and high seasonal variability predicted absence above the boundary, whereas high mean annual temperature (MAT) predicted presence in southern Maine. In contrast, assays of cold resistance across multiple sites were consistent with the hypothesis of local cold adaptation at the range edge: among populations, there was a 4-minute reduction in Chill-Coma Recovery Time across a 2-degree reduction in MAT. Baseline resistance and capacity for additional plastic cold hardening shifted in opposite directions, with hardening capacity approaching zero at the coldest sites. This trade-off between baseline resistance and cold hardening capacity suggests that populations at range edges may adapt to colder temperatures through genetic assimilation of plastic responses, potentially constraining further adaptation and range expansion. More forthcoming papers &raquo; <p>Andrew D. Nguyen, Megan Brown, Jordan Zhitnay, Sara Helms Cahan, Nicholas J. Gotelli, Amy Arnett, and Aaron M. Ellison (Dec 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705939">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;">G</span>eographic variation in low temperatures at poleward range margins of terrestrial species often mirrors population variation in cold resistance, suggesting that range boundaries may be set by evolutionary constraints on cold physiology. The northeastern woodland ant <i>Aphaenogaster picea</i> occurs up to approximately 45°N in central Maine. We combined presence-absence surveys with regression-tree analysis to characterize its northern range limit and assayed two measures of cold resistance operating on different timescales to determine whether and how marginal populations adapt to environmental extremes. The range boundary of <i>A.&nbsp;picea</i> was predicted primarily by temperature, but low winter temperatures did not emerge as the primary correlate of species occurrence. Low summer temperatures and high seasonal variability predicted absence above the boundary, whereas high mean annual temperature (MAT) predicted presence in southern Maine. In contrast, assays of cold resistance across multiple sites were consistent with the hypothesis of local cold adaptation at the range edge: among populations, there was a 4-minute reduction in Chill-Coma Recovery Time across a 2-degree reduction in MAT. Baseline resistance and capacity for additional plastic cold hardening shifted in opposite directions, with hardening capacity approaching zero at the coldest sites. This trade-off between baseline resistance and cold hardening capacity suggests that populations at range edges may adapt to colder temperatures through genetic assimilation of plastic responses, potentially constraining further adaptation and 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, 22 Aug 2019 05:00:00 GMT “Scale both confounds and informs characterization of multi-species coexistence in empirical systems” https://amnat.org/an/newpapers/Dec-Clark-A.html Adam Thomas Clark, Helmut Hillebrand, and W. Stanley Harpole (Dec 2019) Read the Article (Just Accepted) Scale often confounds attempts to characterize coexistence in empirical systems – but, cross-scale analyses can help Abstract Identifying stable coexistence in empirical systems is notoriously difficult. Here, we show how spatiotemporal structure and complex system dynamics can confound two commonly used stability metrics in empirical contexts – response to perturbation, and invasion rate when rare. We use these metrics to characterize stable coexistence across a range of spatial and temporal scales for five simulated models, in which the ability of species to coexist in the long-term is known a priori, and an empirical old-field successional time-series. We term the resulting multivariate distribution of metrics a stability fingerprint. In accordance with a wide range of classic and recent studies, our results demonstrate that no combination of empirically tractable metrics or measurements is guaranteed to “correctly” characterize coexistence. However, we also find that heuristic information from the stability fingerprint can be used to broadly characterize dynamic behavior, and identify circumstances under which particular combinations of species are likely to persist. Moreover, stability fingerprints appear to be particularly well-suited for matching potential theoretical models to observed dynamics. These findings suggest that it may be prudent to shift the focus of empirical stability analysis away from quantifying single measures of stability, and towards more heuristic, multivariate characterizations of community dynamics. More forthcoming papers &raquo; <p>Adam Thomas Clark, Helmut Hillebrand, and W. Stanley Harpole (Dec 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705826">Read the Article</a></i> (Just Accepted)</p> <p><b>Scale often confounds attempts to characterize coexistence in empirical systems &ndash; but, cross-scale analyses can help </b></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>dentifying stable coexistence in empirical systems is notoriously difficult. Here, we show how spatiotemporal structure and complex system dynamics can confound two commonly used stability metrics in empirical contexts – response to perturbation, and invasion rate when rare. We use these metrics to characterize stable coexistence across a range of spatial and temporal scales for five simulated models, in which the ability of species to coexist in the long-term is known a priori, and an empirical old-field successional time-series. We term the resulting multivariate distribution of metrics a stability fingerprint. In accordance with a wide range of classic and recent studies, our results demonstrate that no combination of empirically tractable metrics or measurements is guaranteed to “correctly” characterize coexistence. However, we also find that heuristic information from the stability fingerprint can be used to broadly characterize dynamic behavior, and identify circumstances under which particular combinations of species are likely to persist. Moreover, stability fingerprints appear to be particularly well-suited for matching potential theoretical models to observed dynamics. These findings suggest that it may be prudent to shift the focus of empirical stability analysis away from quantifying single measures of stability, and towards more heuristic, multivariate characterizations of community 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> Thu, 15 Aug 2019 05:00:00 GMT “Patch size as a niche dimension: aquatic insects behaviorally partition enemy-free space across gradients of patch size” https://amnat.org/an/newpapers/Dec-Resetarits.html William J. Resetarits Jr., Matthew R. Pintar, Jason R. Bohenek, and Tyler M. Breech (Dec 2019) Read the Article (Just Accepted) Patch size as a niche dimension changes our view of patch size variation in supporting local and regional diversity One of the truisms in Nature is that habitat patches in all types of systems – terrestrial, aquatic, marine – vary in size, whether they are host plants for plant-eating insects, prairie remnants for grassland birds, coral reefs for marine fish, or ponds for aquatic insects. In all these systems, both average population size and number of species tend to increase with patch size. This relationship is partly attributable to reduced extinction rates in larger patches, higher passive colonization rates as a result of larger “targets,” and possibly increased cue intensity resulting in easier detection. When considering habitat selection, however, organisms may conceivably display active preferences for patches of different size. Thus, patch size could function as another component of patch quality, along with factors like predation risk and resource level. We have a strong, consistent pattern (increasing diversity with patch area) that may arise from a variety of processes, requiring an experimental approach to disentangle the ecological drivers. Resetarits et al. manipulated both patch quality (fish presence/absence) and patch size, and found that, in contrast to expectations of no preference or overall preference for large patches, insect species showed strong and highly variable active preferences for patch size. Most insect species avoided fish, but differentially colonized fishless patches of different size, resulting in different colonist species composition and relative abundance across the size gradient. Thus, for colonizing aquatic insects, patch size functions as a niche dimension that generates spatial segregation and reduces the potential for intense species interactions (both competition and predation) within the insect assemblage. Establishing patch size as a niche dimension changes how we view the role of patch size variation in supporting conservation of local and regional diversity, as well as the importance of preserving patch size variation as a driver of diversity. Abstract Positive correlation of species richness with area is ubiquitous in nature, but the processes driving that relationship, and those constraining typical patterns, remain elusive. Patch size variation is pervasive in natural systems, and thus it is critical to understand how variation in patch size, as well as its potential interaction with factors like predation and isolation, affect community assembly. We crossed patch quality (fish presence/absence) with patch size to examine effects of quality, size, and their interaction on colonization by aquatic insects. Overall, beetles favored small, fishless patches, but individual species sorted across patch size, while hemipterans aggregated into large, fishless patches, producing sorting between Coleoptera and Hemiptera. Both size and predation risk generated significant variation in community structure and diversity. Patch size preferences for the 14 most abundant species, and pre-eminence of species turnover in patterns of beta-diversity, reinforce patch size as a driver of regional species sorting via habitat selection. Species sorting at the immigration stage plays a critical role in community assembly. Identifying patch size as a component of perceived quality establishes patch size as a critical niche dimension, and alters our view of its role in assembly dynamics, and the maintenance of local and regional diversity. More forthcoming papers &raquo; <p>William J. Resetarits Jr., Matthew R. Pintar, Jason R. Bohenek, and Tyler M. Breech (Dec 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705809">Read the Article</a></i> (Just Accepted)</p> <p><b>Patch size as a niche dimension changes our view of patch size variation in supporting local and regional diversity </b></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 of the truisms in Nature is that habitat patches in all types of systems – terrestrial, aquatic, marine – vary in size, whether they are host plants for plant-eating insects, prairie remnants for grassland birds, coral reefs for marine fish, or ponds for aquatic insects. In all these systems, both average population size and number of species tend to increase with patch size. This relationship is partly attributable to reduced extinction rates in larger patches, higher passive colonization rates as a result of larger “targets,” and possibly increased cue intensity resulting in easier detection. When considering habitat selection, however, organisms may conceivably display active preferences for patches of different size. Thus, patch size could function as another component of patch quality, along with factors like predation risk and resource level. We have a strong, consistent pattern (increasing diversity with patch area) that may arise from a variety of processes, requiring an experimental approach to disentangle the ecological drivers. </p><p>Resetarits et al. manipulated both patch quality (fish presence/absence) and patch size, and found that, in contrast to expectations of no preference or overall preference for large patches, insect species showed strong and highly variable active preferences for patch size. Most insect species avoided fish, but differentially colonized fishless patches of different size, resulting in different colonist species composition and relative abundance across the size gradient. Thus, for colonizing aquatic insects, patch size functions as a niche dimension that generates spatial segregation and reduces the potential for intense species interactions (both competition and predation) within the insect assemblage. Establishing patch size as a niche dimension changes how we view the role of patch size variation in supporting conservation of local and regional diversity, as well as the importance of preserving patch size variation as a driver of diversity.</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>ositive correlation of species richness with area is ubiquitous in nature, but the processes driving that relationship, and those constraining typical patterns, remain elusive. Patch size variation is pervasive in natural systems, and thus it is critical to understand how variation in patch size, as well as its potential interaction with factors like predation and isolation, affect community assembly. We crossed patch quality (fish presence/absence) with patch size to examine effects of quality, size, and their interaction on colonization by aquatic insects. Overall, beetles favored small, fishless patches, but individual species sorted across patch size, while hemipterans aggregated into large, fishless patches, producing sorting between Coleoptera and Hemiptera. Both size and predation risk generated significant variation in community structure and diversity. Patch size preferences for the 14 most abundant species, and pre-eminence of species turnover in patterns of beta-diversity, reinforce patch size as a driver of regional species sorting via habitat selection. Species sorting at the immigration stage plays a critical role in community assembly. Identifying patch size as a component of perceived quality establishes patch size as a critical niche dimension, and alters our view of its role in assembly dynamics, and the maintenance of local and regional diversity. </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, 15 Aug 2019 05:00:00 GMT “Trophic position of consumers and size structure of food webs across aquatic and terrestrial ecosystems” https://amnat.org/an/newpapers/Dec-Potapov.html Anton Potapov, Ulrich Brose, Stefan Scheu, and Alexei Tiunov (Dec 2019) Read the Article (Just Accepted) Do large organisms occupy higher trophic levels? Size matters in water, but on land top predators can be of any size Thinking about a “superpredator” we would imagine a white shark, or a tiger. As humans, we intuitively expect large predators to occupy top trophic position in food webs. This is true for marine food webs, that have been long recognized as size-structured – they are based on unicellular phytoplankton, that is being eaten by zooplankton, which is further being eaten by fish and mammals. Thus, organic matter is transferred all the way from unicellular producers to large predators, such as white sharks. On the other hand, terrestrial ecosystems are dominated by multicellular vascular plants, which can be eaten by both small animals, such as leafhoppers, and large animals, such as megaherbivores. In this case, organic matter is unlikely to be transferred from small herbivores to large predators; in other words, tigers do not hunt leafhoppers, or animals that feed on leafhoppers. This straightforward idea appears from theory, but has never been tested empirically across invertebrate and vertebrate consumers and across ecosystems. A group of researchers from Germany (University of G&ouml;ttingen and German Centre for Integrative Biodiversity Research) and Russia (Institute of Ecology and Evolution) leaded by Anton Potapov compiled published data on stable isotope composition and sizes of consumers, from microscopic fauna to whales, from marine, freshwater and terrestrial ecosystems and both grazing and detrital food webs. The results show that size matters in water, but not on land – trophic position in terrestrial consumers (including those belowground) does not depend on body size. Namely, a small mite living in soil may be positioned higher in a food web than a large mammalian predator. As predators are systematically larger than their prey, results of the study suggest that small and large consumers on land (and partly in fresh water) belong to different food webs, or “size compartments”. If we want to predict responses of natural interaction networks to perturbations, we need to know that these responses will be intrinsically different in size-compartmentalized terrestrial and size-structured marine food webs. Abstract Do large organisms occupy higher trophic levels? Predators are often larger than their prey in food chains, but empirical evidence for positive body mass – trophic level scaling for entire food webs mostly comes from marine communities based on unicellular producers. Using published data on stable isotope compositions of 1093 consumer species, we explored how trophic level scales with body size, food-web type (green vs. brown) and phylogenetic group across biomes. In contrast to widespread assumptions, the relationship between body size and trophic level of consumers, from protists to large vertebrates, was not significant per se, but varied among ecosystem types and animal groups. The correlation between body size and trophic level was strong in marine, weak in freshwater and absent in terrestrial consumers, which was observed also at the scale of local food webs. Vertebrates occupied higher trophic positions than invertebrates and green trophic chains were longer than brown ones in aquatic (primarily marine) but not in terrestrial food webs. Variations in body size of top predators suggest that terrestrial and many freshwater food webs are size-compartmentalized, implying different trophic dynamics and responses to perturbations than in size-structured marine food webs. More forthcoming papers &raquo; <p>Anton Potapov, Ulrich Brose, Stefan Scheu, and Alexei Tiunov (Dec 2019) </p><p><i><a href="https://dx.doi.org/10.1086/705811">Read the Article</a></i> (Just Accepted) </p> <p><b>Do large organisms occupy higher trophic levels? Size matters in water, but on land top predators can be of any size </b></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>hinking about a &ldquo;superpredator&rdquo; we would imagine a white shark, or a tiger. As humans, we intuitively expect large predators to occupy top trophic position in food webs. This is true for marine food webs, that have been long recognized as size-structured &ndash; they are based on unicellular phytoplankton, that is being eaten by zooplankton, which is further being eaten by fish and mammals. Thus, organic matter is transferred all the way from unicellular producers to large predators, such as white sharks. On the other hand, terrestrial ecosystems are dominated by multicellular vascular plants, which can be eaten by both small animals, such as leafhoppers, and large animals, such as megaherbivores. In this case, organic matter is unlikely to be transferred from small herbivores to large predators; in other words, tigers do not hunt leafhoppers, or animals that feed on leafhoppers. This straightforward idea appears from theory, but has never been tested empirically across invertebrate and vertebrate consumers and across ecosystems.</p> <p>A group of researchers from Germany (University of G&ouml;ttingen and German Centre for Integrative Biodiversity Research) and Russia (Institute of Ecology and Evolution) leaded by Anton Potapov compiled published data on stable isotope composition and sizes of consumers, from microscopic fauna to whales, from marine, freshwater and terrestrial ecosystems and both grazing and detrital food webs. The results show that size matters in water, but not on land &ndash; trophic position in terrestrial consumers (including those belowground) does not depend on body size. Namely, a small mite living in soil may be positioned higher in a food web than a large mammalian predator. As predators are systematically larger than their prey, results of the study suggest that small and large consumers on land (and partly in fresh water) belong to different food webs, or &ldquo;size compartments&rdquo;. If we want to predict responses of natural interaction networks to perturbations, we need to know that these responses will be intrinsically different in size-compartmentalized terrestrial and size-structured marine food webs.</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;">D</span>o large organisms occupy higher trophic levels? Predators are often larger than their prey in food chains, but empirical evidence for positive body mass &ndash; trophic level scaling for entire food webs mostly comes from marine communities based on unicellular producers. Using published data on stable isotope compositions of 1093 consumer species, we explored how trophic level scales with body size, food-web type (green vs. brown) and phylogenetic group across biomes. In contrast to widespread assumptions, the relationship between body size and trophic level of consumers, from protists to large vertebrates, was not significant per se, but varied among ecosystem types and animal groups. The correlation between body size and trophic level was strong in marine, weak in freshwater and absent in terrestrial consumers, which was observed also at the scale of local food webs. Vertebrates occupied higher trophic positions than invertebrates and green trophic chains were longer than brown ones in aquatic (primarily marine) but not in terrestrial food webs. Variations in body size of top predators suggest that terrestrial and many freshwater food webs are size-compartmentalized, implying different trophic dynamics and responses to perturbations than in size-structured marine food webs.</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> Thu, 15 Aug 2019 05:00:00 GMT “Assortative mating in animals and its role for speciation” https://amnat.org/an/newpapers/Dec-Janicke-A.html Tim Janicke, Lucas Marie-Orleach, Thomas G. Aubier, Charles Perrier, and Edward H. Morrow (Dec 2019) Read the Article (Just Accepted) Meta-analysis finds no relationship between assortative mating and species richness across animals Abstract Evolutionary theory predicts that positive assortative mating – the tendency of similar individuals to mate with each other – plays a key role for speciation by generating reproductive isolation between diverging populations. However, comprehensive tests for an effect of assortative mating on species richness at the macro-evolutionary scale are lacking. We used a meta-analytic approach to test the hypothesis that the strength of assortative mating within populations is positively related to species richness across a broad range of animal taxa. Specifically, we ran a phylogenetically independent meta-analysis using an extensive database of 1447 effect sizes for the strength of assortative mating, encompassing 307 species from 130 families and 14 classes. Our results suggest that there is no relationship between the strength of assortative mating and species richness across and within major taxonomic groups and trait categories. Moreover, our analysis confirms an earlier finding that animals typically mate assortatively (global Pearson correlation coefficient: r&nbsp;=&nbsp;0.36; 95% confidence limits: 0.19−0.52) when accounting for phylogenetic non-independence. We argue that future advances will rely on a better understanding of the evolutionary causes and consequences of the observed intra- and interspecific variation in the strength of assortative mating. More forthcoming papers &raquo; <p>Tim Janicke, Lucas Marie-Orleach, Thomas G. Aubier, Charles Perrier, and Edward H. Morrow (Dec 2019) </p> <p><i><a href="https://dx.doi.org/10.1086/705825">Read the Article</a></i> (Just Accepted) </p> <p><b>Meta-analysis finds no relationship between assortative mating and species richness across animals </b></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 theory predicts that positive assortative mating – the tendency of similar individuals to mate with each other – plays a key role for speciation by generating reproductive isolation between diverging populations. However, comprehensive tests for an effect of assortative mating on species richness at the macro-evolutionary scale are lacking. We used a meta-analytic approach to test the hypothesis that the strength of assortative mating within populations is positively related to species richness across a broad range of animal taxa. Specifically, we ran a phylogenetically independent meta-analysis using an extensive database of 1447 effect sizes for the strength of assortative mating, encompassing 307 species from 130 families and 14 classes. Our results suggest that there is no relationship between the strength of assortative mating and species richness across and within major taxonomic groups and trait categories. Moreover, our analysis confirms an earlier finding that animals typically mate assortatively (global Pearson correlation coefficient: <i>r</i>&nbsp;=&nbsp;0.36; 95% confidence limits: 0.19−0.52) when accounting for phylogenetic non-independence. We argue that future advances will rely on a better understanding of the evolutionary causes and consequences of the observed intra- and interspecific variation in the strength of assortative mating. </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, 15 Aug 2019 05:00:00 GMT “Lifetime fitness in wild baboons: tradeoffs and individual heterogeneity in quality” https://amnat.org/an/newpapers/Dec-McLean-A.html Emily M. McLean, Elizabeth A. Archie, and Susan C. Alberts (Dec 2019) Read the Article (Just Accepted) Life history tradeoffs in female baboons evident after accounting for heterogeneity in individual quality Abstract Understanding the evolution of life histories requires information on how life histories vary among individuals, and how such variation predicts individual fitness. Using complete life histories for females in a well-studied population of wild baboons, we tested two non-exclusive hypotheses about the relationships among survival, reproduction, and fitness: the quality hypothesis, which predicts positive correlations between life history traits, mediated by variation in resource acquisition, and the tradeoff hypothesis, which predicts negative correlations between life history traits, mediated by tradeoffs in resource allocation. In support of the quality hypothesis, we found that females with higher rates of offspring survival were themselves better at surviving. Further, after statistically controlling for variation in female quality, we found evidence for two types of tradeoffs: females who produced surviving offspring at a slower rate had longer lifespans than those who produced surviving offspring at a faster rate, and females who produced surviving offspring at a slower rate had a higher overall proportion of offspring survive infancy than females who produced surviving offspring at a faster rate. Importantly, these tradeoffs were evident even when accounting for: (i) the influence of offspring survival on maternal birth rate, (ii) the dependence of offspring survival on maternal survival, and (iii) potential age-related changes in birth rate and/or offspring survival. Our results shed light on why tradeoffs are evident in some populations, while variation in individual quality masks tradeoffs in others. More forthcoming papers &raquo; <p>Emily M. McLean, Elizabeth A. Archie, and Susan C. Alberts (Dec 2019) </p><p><i><a href="https://dx.doi.org/10.1086/705810">Read the Article</a></i> (Just Accepted) </p> <p><b>Life history tradeoffs in female baboons evident after accounting for heterogeneity in individual quality </b></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 evolution of life histories requires information on how life histories vary among individuals, and how such variation predicts individual fitness. Using complete life histories for females in a well-studied population of wild baboons, we tested two non-exclusive hypotheses about the relationships among survival, reproduction, and fitness: the quality hypothesis, which predicts positive correlations between life history traits, mediated by variation in resource acquisition, and the tradeoff hypothesis, which predicts negative correlations between life history traits, mediated by tradeoffs in resource allocation. In support of the quality hypothesis, we found that females with higher rates of offspring survival were themselves better at surviving. Further, after statistically controlling for variation in female quality, we found evidence for two types of tradeoffs: females who produced surviving offspring at a slower rate had longer lifespans than those who produced surviving offspring at a faster rate, and females who produced surviving offspring at a slower rate had a higher overall proportion of offspring survive infancy than females who produced surviving offspring at a faster rate. Importantly, these tradeoffs were evident even when accounting for: (i) the influence of offspring survival on maternal birth rate, (ii) the dependence of offspring survival on maternal survival, and (iii) potential age-related changes in birth rate and/or offspring survival. Our results shed light on why tradeoffs are evident in some populations, while variation in individual quality masks tradeoffs in others. </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, 15 Aug 2019 05:00:00 GMT Registration for the ASN Stand-Alone Meeting 2020 https://amnat.org/announcements/ASNAsilomar.html Registration for the American Society of Naturalists Stand-Alone meeting at Asilomar opens on August 15. 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>Registration for the American Society of Naturalists Stand-Alone meeting at Asilomar opens on August 15.</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, 13 Aug 2019 05:00:00 GMT Call for Symposium Proposals for Evolution 2020 https://amnat.org/announcements/CallSympASN2018.html Proposals for a Symposium to be held at the 2020 SSE/ASN/SSB Meeting in Cleveland, OH The American Society of Naturalists invites proposals for a special symposium at the 2020 annual joint meeting of the Society for the Study of Evolution, the American Society of Naturalists, and the Society of Systematic Biologists, to be held June 19-23, 2020, in Cleveland, OH. Proposed symposium topics should support the Society’s goal to advance the conceptual unification of the biological sciences and to further knowledge in evolution, ecology, behavior, and organismal biology. Proposals should be synthetic and interdisciplinary, and address important emerging issues in evolution, ecology, or behavior. A budget of $8,000 for travel, registration, and accommodation is provided to help defray expenses. Proposals should include (1) a title; (2) a description of the symposium topic (one page); (3) a list of six speakers, including institutional affiliations, who have agreed to participate in the symposium; (4) a justification for the symposium, explaining why the topic and speakers are appropriate for a Society-sponsored symposium (up to one page). Please submit proposals by midnight Eastern Standard Time on October 1, 2019, by email (kmkay@ucsc.edu) as a single pdf attachment, under subject heading: ASN Symposium Proposal: Evolution 2020. Proposals that include women, young investigators, and individuals from underrepresented groups are especially encouraged. The Society’s selection committee will evaluate proposals based on the likelihood of attracting a substantial audience, the significance and timeliness of the topic, and on the topic’s differing substantively from recent symposia hosted by the Society. All applicants will be notified of the decision before the end of November. Kathleen M. Kay ASN Symposium Committee Chair Department of Ecology and Evolutionary Biology University of California, Santa Cruz kmkay@ucsc.edu <p><strong>Proposals for a Symposium to be held at the 2020 SSE/ASN/SSB Meeting in Cleveland, OH</strong></p> <p>The American Society of Naturalists invites proposals for a special symposium at the 2020 annual joint meeting of the Society for the Study of Evolution, the American Society of Naturalists, and the Society of Systematic Biologists, to be held June 19-23, 2020, in Cleveland, OH.</p> <p>Proposed symposium topics should support the Society&rsquo;s goal to advance the conceptual unification of the biological sciences and to further knowledge in evolution, ecology, behavior, and organismal biology. Proposals should be synthetic and interdisciplinary, and address important emerging issues in evolution, ecology, or behavior. A budget of $8,000 for travel, registration, and accommodation is provided to help defray expenses.</p> <p>Proposals should include (1) a title; (2) a description of the symposium topic (one page); (3) a list of six speakers, including institutional affiliations, who have agreed to participate in the symposium; (4) a justification for the symposium, explaining why the topic and speakers are appropriate for a Society-sponsored symposium (up to one page).</p> <p>Please submit proposals by midnight Eastern Standard Time on October 1, 2019, by email (<a href="mailto:kmkay@ucsc.edu?subject=ASN%20Symposium%20Proposal%3A%20Evolution%202020">kmkay@ucsc.edu</a>) as a single pdf attachment, under subject heading: ASN Symposium Proposal: Evolution 2020. Proposals that include women, young investigators, and individuals from underrepresented groups are especially encouraged.</p> <p>The Society&rsquo;s selection committee will evaluate proposals based on the likelihood of attracting a substantial audience, the significance and timeliness of the topic, and on the topic&rsquo;s differing substantively from recent symposia hosted by the Society. All applicants will be notified of the decision before the end of November.</p> <p><br /> Kathleen M. Kay<br /> ASN Symposium Committee Chair<br /> Department of Ecology and Evolutionary Biology<br /> University of California, Santa Cruz<br /> <a href="mailto:kmkay@ucsc.edu?subject=ASN%20Symposium%20Proposal%3A%20Evolution%202020">kmkay@ucsc.edu</a></p> Mon, 12 Aug 2019 05:00:00 GMT “Within-individual canalization contributes to age-related increases in trait repeatability: a longitudinal experiment in red knots” https://amnat.org/an/newpapers/Sep-Kok.html Eva M. A. Kok, Joseph B. Burant, Anne Dekinga, Petra Manche, Darren Saintonge, Theunis Piersma, and Kimberley J. Mathot (Oct 2019) Read the Article Longitudinal lab experiment shows how canalization contributes to age-related changes in trait repeatability Individual variation is at the core of Darwin’s theory of evolution. Yet in ecology, variation between individuals was often considered as ‘noise’ or a nuisance. However, under changing environmental conditions, variation between individuals increases resilience for a population as a whole. Therefore, understanding what processes generate variation between individuals is important. This study focuses on individual variation and, in particular, what factors promote the development of variation between individuals. Researchers from the Royal Netherlands Institute for Sea Research (NL) and the University of Alberta (CA) looked at changes in bird ‘character’ with age, and if these changes are the unavoidable consequence of ageing or whether different experiences during life cause individuals to diverge.The scientists study the behavior of red knots—migratory shorebirds—exploring their surroundings in search of food. These birds differ in how they search (exploration behavior) and in the size of their stomachs (physiology). To investigate how these differences come about, 90 birds were brought into captivity either as juvenile or as adult, and then given identical experiences over the next two years. While the birds age, exploration behavior and stomach size are measured repeatedly to tease apart the effects of age, experience, and time in captivity on the amount of variation in both traits. If the birds’ individual experiences help maintain the differences between individuals, this variation should disappear during the course of the study because in these experiments, all birds have the same experience. Although it may seem easier to change one’s behavior than one’s physiology, these birds maintain their exploratory character while their stomach size changes. The next step is to follow the birds after their release back into the wild, to examine how the changes measured in the lab translate to real life. Abstract Age-related increases in the repeatable expression of labile phenotypic traits are often assumed to arise from an increase in among-individual variance due to differences in developmental plasticity or by means of state-behavior feedbacks. However, age-related increases in repeatability could also arise from a decrease in within-individual variance as a result of stabilizing trait expression, i.e. canalization. Here we describe age-related changes in within- and among-individual variance components in two correlated traits, gizzard mass and exploration behavior, in a medium-sized shorebird, the red knot (Calidris canutus). Increased repeatability of gizzard mass came about due to an increase in among-individual variance, unrelated to differences in developmental plasticity, together with decreases in within-individual variance, consistent with canalization. We also found canalization of exploration, but no age-related increase in overall repeatability, which suggests that showing predictable expression of exploration behavior may be advantageous from a very young age onward. Contrasts between juveniles and adults in the first year after their capture provide support for the idea that environmental conditions play a key role in generating among-individual variation in both gizzard mass and exploration behavior. Our study shows that stabilization of traits occurs under constant conditions: with increased exposure to predictable cues, individuals may become more certain in their assessment of the environment allowing traits to become canalized. De foarspelbere &ucirc;ntwikkeling fan lichems- en gedrachseigenskippen: in eksperiment oer welhelberhyd fan eigenskippen by mientsen Alhoewol guon lichemseigenskippen fan jonge yndividu&euml;n hyltiten wer feroarje kinne, komme by it &acirc;lder wurden sokke eigenskippen ornaris dochs hyltiten mear f&ecirc;st te lizzen. Soks kin komme troch it feroarjen fan yndividuele plastisiteit en troch weromkeppelingen tusken it gedrach en de steat fan sa’n bist. Yndividuele ferskillen yn it f&ecirc;stlizzen fan eigenskippen fergrutsje de fariaasje tusken yndividu&euml;n. In technysk begrip om yndividuele fariaasje fan eigenskippen te kwantifisearjen is ‘repeatability’ (‘werhelberhyd’), mar it euvel is dat in taname fan dizze statistyske maat sawol komme kin troch in taname yn ‘e fariaasje tusken yndividu&euml;n en troch in &ocirc;fname fan de fariaasje binnen yndividu&euml;n; dit l&ecirc;ste neame wy ‘kanalisaasje’. Yn dit artikel beskriuwe wy hoe’t dizze twa boarnen fan fariaasje by it &acirc;lder wurden feroarje kinne by mientsen (Calidris canutus), en dat dogge wy oan ‘e h&acirc;n fan twa besibbe eigenskippen: (1) it gewicht fan de spiermage, en (2) de wize werop mientsen yn in eksperimentele romte lytse stikjes waad ferkenne (der binne f&ucirc;gels dy’t bot eksplorearje, en guon dy’t &ocirc;fwachtsje). It die bliken dat de werhelberhyd fan it magegewicht feroare troch tanimmende ferskillen tusken yndividu&euml;n en in &ocirc;fname fan de fariaasje binnen yndividu&euml;n, in kombinaasje fan plastisiteit en kanalisaasje dus. By eksploraasje-gedrach f&ucirc;nen wy by it &acirc;lder wurden oanwizings foar kanalisaasje. Dat soe betsjutte kinne dat der foardielen binne om al op jonge leeftyd in bepaalde yndividuele wize fan eksploraasje oan te h&acirc;lden. &Uacute;t in fergeliking tusken jonge en &acirc;lde f&ucirc;gels (dy’t in ferskil yn &ucirc;ntwikkeling yn it frije fjild wjerspegelje), blykte it bestean fan weromkeppelingen tusken de steat fan it lichem (magegewicht) en it gedrach (eksploraasje). &Uacute;s st&uacute;dzje lit lykwols foaral sjen dat eigenskippen, sels yn sitewaasjes dy’t net feroarje, f&ecirc;st komme te lizzen. Miskien makket it fenomeen dat f&ucirc;gels har omjouwing hyltiten better foarspelle kinne sokke kanalisaasje mooglik. More forthcoming papers &raquo; <p>Eva M. A. Kok, Joseph B. Burant, Anne Dekinga, Petra Manche, Darren Saintonge, Theunis Piersma, and Kimberley J. Mathot (Oct 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/704593">Read the Article</a></i> </p> <p><b>Longitudinal lab experiment shows how canalization contributes to age-related changes in trait repeatability </b></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;">I</span>ndividual variation is at the core of Darwin&rsquo;s theory of evolution. Yet in ecology, variation between individuals was often considered as &lsquo;noise&rsquo; or a nuisance. However, under changing environmental conditions, variation between individuals increases resilience for a population as a whole. Therefore, understanding what processes generate variation between individuals is important.</p> <p>This study focuses on individual variation and, in particular, what factors promote the development of variation between individuals. Researchers from the Royal Netherlands Institute for Sea Research (NL) and the University of Alberta (CA) looked at changes in bird &lsquo;character&rsquo; with age, and if these changes are the unavoidable consequence of ageing or whether different experiences during life cause individuals to diverge.</p><p>The scientists study the behavior of red knots&mdash;migratory shorebirds&mdash;exploring their surroundings in search of food. These birds differ in how they search (exploration behavior) and in the size of their stomachs (physiology). To investigate how these differences come about, 90 birds were brought into captivity either as juvenile or as adult, and then given identical experiences over the next two years. While the birds age, exploration behavior and stomach size are measured repeatedly to tease apart the effects of age, experience, and time in captivity on the amount of variation in both traits. If the birds&rsquo; individual experiences help maintain the differences between individuals, this variation should disappear during the course of the study because in these experiments, all birds have the same experience.</p> <p>Although it may seem easier to change one&rsquo;s behavior than one&rsquo;s physiology, these birds maintain their exploratory character while their stomach size changes. The next step is to follow the birds after their release back into the wild, to examine how the changes measured in the lab translate to real life.</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;">A</span>ge-related increases in the repeatable expression of labile phenotypic traits are often assumed to arise from an increase in among-individual variance due to differences in developmental plasticity or by means of state-behavior feedbacks. However, age-related increases in repeatability could also arise from a decrease in within-individual variance as a result of stabilizing trait expression, i.e. canalization. Here we describe age-related changes in within- and among-individual variance components in two correlated traits, gizzard mass and exploration behavior, in a medium-sized shorebird, the red knot (<i>Calidris canutus</i>). Increased repeatability of gizzard mass came about due to an increase in among-individual variance, unrelated to differences in developmental plasticity, together with decreases in within-individual variance, consistent with canalization. We also found canalization of exploration, but no age-related increase in overall repeatability, which suggests that showing predictable expression of exploration behavior may be advantageous from a very young age onward. Contrasts between juveniles and adults in the first year after their capture provide support for the idea that environmental conditions play a key role in generating among-individual variation in both gizzard mass and exploration behavior. Our study shows that stabilization of traits occurs under constant conditions: with increased exposure to predictable cues, individuals may become more certain in their assessment of the environment allowing traits to become canalized.</p> <h4>De foarspelbere &ucirc;ntwikkeling fan lichems- en gedrachseigenskippen: in eksperiment oer welhelberhyd fan eigenskippen by mientsen</h4> <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>lhoewol guon lichemseigenskippen fan jonge yndividu&euml;n hyltiten wer feroarje kinne, komme by it &acirc;lder wurden sokke eigenskippen ornaris dochs hyltiten mear f&ecirc;st te lizzen. Soks kin komme troch it feroarjen fan yndividuele plastisiteit en troch weromkeppelingen tusken it gedrach en de steat fan sa&rsquo;n bist. Yndividuele ferskillen yn it f&ecirc;stlizzen fan eigenskippen fergrutsje de fariaasje tusken yndividu&euml;n. In technysk begrip om yndividuele fariaasje fan eigenskippen te kwantifisearjen is &lsquo;repeatability&rsquo; (&lsquo;werhelberhyd&rsquo;), mar it euvel is dat in taname fan dizze statistyske maat sawol komme kin troch in taname yn &lsquo;e fariaasje tusken yndividu&euml;n en troch in &ocirc;fname fan de fariaasje <i>binnen</i> yndividu&euml;n; dit l&ecirc;ste neame wy &lsquo;kanalisaasje&rsquo;. Yn dit artikel beskriuwe wy hoe&rsquo;t dizze twa boarnen fan fariaasje by it &acirc;lder wurden feroarje kinne by mientsen (<i>Calidris canutus</i>), en dat dogge wy oan &lsquo;e h&acirc;n fan twa besibbe eigenskippen: (1) it gewicht fan de spiermage, en (2) de wize werop mientsen yn in eksperimentele romte lytse stikjes waad ferkenne (der binne f&ucirc;gels dy&rsquo;t bot eksplorearje, en guon dy&rsquo;t &ocirc;fwachtsje). It die bliken dat de werhelberhyd fan it magegewicht feroare troch tanimmende ferskillen tusken yndividu&euml;n en in &ocirc;fname fan de fariaasje binnen yndividu&euml;n, in kombinaasje fan plastisiteit en kanalisaasje dus. By eksploraasje-gedrach f&ucirc;nen wy by it &acirc;lder wurden oanwizings foar kanalisaasje. Dat soe betsjutte kinne dat der foardielen binne om al op jonge leeftyd in bepaalde yndividuele wize fan eksploraasje oan te h&acirc;lden. &Uacute;t in fergeliking tusken jonge en &acirc;lde f&ucirc;gels (dy&rsquo;t in ferskil yn &ucirc;ntwikkeling yn it frije fjild wjerspegelje), blykte it bestean fan weromkeppelingen tusken de steat fan it lichem (magegewicht) en it gedrach (eksploraasje). &Uacute;s st&uacute;dzje lit lykwols foaral sjen dat eigenskippen, sels yn sitewaasjes dy&rsquo;t net feroarje, f&ecirc;st komme te lizzen. Miskien makket it fenomeen dat f&ucirc;gels har omjouwing hyltiten better foarspelle kinne sokke kanalisaasje mooglik.</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> Wed, 07 Aug 2019 05:00:00 GMT “Meta-analysis shows that rapid phenotypic change in Angiosperms in response to environmental change is followed by stasis” https://amnat.org/an/newpapers/Dec-Gorne.html Lucas D. Gorn&eacute; and Sandra D&iacute;az (Dec 2019) Read the Article (Just Accepted) Fast but limited: that’s how phenotypic change happens for plants faced with novel environmental conditionsFast phenotypic change (at the time scales of years to a few centuries) in response to human-driven changes in the environment is known to occur in a wide range of wild plants and animals, but so far the information has been somewhat scattered. Gorn&eacute; and D&iacute;az have carried out a quantitative synthesis of the largest yet database of contemporary phenotypic change in plants. They find that plants are capable of a substantial amount of change in the first few years after environmental novelty and then remain stable. Although phenotypic plasticity may increase the initial response, the authors find an important proportion of heritable change. This pattern of abrupt change is general and independent from plant longevity and growth form, spatial scale (from few-meters-distant populations to populations on different continents) of analysis and from the type of trait (e.g. morphological, phenological). Interestingly, the authors report some unexpected patterns. First, long-lived species experience amounts and rates of change similar to short-lived ones. Second, those traits closely related to fitness display amounts and rates of change similar to morphological or physiological traits. Third, greater and faster divergence tends to occur between populations connected at the local scale, where gene flow can be intense, than between distant populations. This last, and the pattern of abrupt change, suggest that standing variability is crucial for adaptation in plants, and new adaptive variability is unlikely to arise in contemporary time-scales. Abstract The amount and rate of phenotypic change at ecological time scales varies widely, but there has not been a comprehensive quantitative synthesis of patterns and causes of such variation for plants. Present knowledge is based predominantly on animals, whose differences with plants in the origin of germ cells and the level of modularity (among others) could make it invalid for plants. We synthesized data on contemporary phenotypic responses of angiosperms to environmental change and show that if extinction does not occur, quantitative traits change quickly in the first few years following the environmental novelty and then remain stable. This general pattern is independent from lifespan, growth form, spatial scale or the type of trait. Our work shows that high amounts and rates of phenotypic change at contemporary timescales observed in plants are consistent with the pattern of stasis and bounded evolution previously observed over longer time frames. We also found evidence that may contradict some common ideas about phenotypic evolution: (1) the total amount of phenotypic change observed does not differ significantly according to growth form or lifespan, (2) greater and faster divergence tend to occur between populations connected at the local scale, where gene flow could be intense, than between distant populations, and that (3) traits closely related to fitness change as much and as fast as other traits. More forthcoming papers &raquo; <p>Lucas D. Gorn&eacute; and Sandra D&iacute;az (Dec 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705680">Read the Article</a></i> (Just Accepted)</p> <p><strong>Fast but limited: that&rsquo;s how phenotypic change happens for plants faced with novel environmental conditions</strong></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;">F</span>ast phenotypic change (at the time scales of years to a few centuries) in response to human-driven changes in the environment is known to occur in a wide range of wild plants and animals, but so far the information has been somewhat scattered. Gorn&eacute; and D&iacute;az have carried out a quantitative synthesis of the largest yet database of contemporary phenotypic change in plants. They find that plants are capable of a substantial amount of change in the first few years after environmental novelty and then remain stable. Although phenotypic plasticity may increase the initial response, the authors find an important proportion of heritable change. This pattern of abrupt change is general and independent from plant longevity and growth form, spatial scale (from few-meters-distant populations to populations on different continents) of analysis and from the type of trait (e.g. morphological, phenological). Interestingly, the authors report some unexpected patterns. First, long-lived species experience amounts and rates of change similar to short-lived ones. Second, those traits closely related to fitness display amounts and rates of change similar to morphological or physiological traits. Third, greater and faster divergence tends to occur between populations connected at the local scale, where gene flow can be intense, than between distant populations. This last, and the pattern of abrupt change, suggest that standing variability is crucial for adaptation in plants, and new adaptive variability is unlikely to arise in contemporary time-scales.</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;">T</span>he amount and rate of phenotypic change at ecological time scales varies widely, but there has not been a comprehensive quantitative synthesis of patterns and causes of such variation for plants. Present knowledge is based predominantly on animals, whose differences with plants in the origin of germ cells and the level of modularity (among others) could make it invalid for plants. We synthesized data on contemporary phenotypic responses of angiosperms to environmental change and show that if extinction does not occur, quantitative traits change quickly in the first few years following the environmental novelty and then remain stable. This general pattern is independent from lifespan, growth form, spatial scale or the type of trait. Our work shows that high amounts and rates of phenotypic change at contemporary timescales observed in plants are consistent with the pattern of stasis and bounded evolution previously observed over longer time frames. We also found evidence that may contradict some common ideas about phenotypic evolution: (1) the total amount of phenotypic change observed does not differ significantly according to growth form or lifespan, (2) greater and faster divergence tend to occur between populations connected at the local scale, where gene flow could be intense, than between distant populations, and that (3) traits closely related to fitness change as much and as fast as other traits.</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, 30 Jul 2019 05:00:00 GMT “Sex-specific among-individual covariation in locomotor activity and resting metabolic rate in <i>Drosophila melanogaster</i>” https://amnat.org/an/newpapers/Dec-Videlier.html Mathieu Videlier, Howard D. Rundle, and Vincent Careau (Dec 2019) Read the Article (Just Accepted) Sex differences in the metabolism-activity link imply males and females manage their energy budgets differently According to a new study by a research team at the University of Ottawa, there are strong differences in how male vs. female flies manage their energy expenditures. Individuals expend energy (calories) for all bodily functions, from movement to breathing to digestion and reproduction. Two important components of the energy budget are those spent on bodily maintenance and activity, because both are fundamental to surviving and reproducing. How the two components co-vary among individuals is unclear, however. In their paper appearing in The&nbsp;American Naturalist, a team led by PhD student Mathieu Videlier gathered repeated measurements of maintenance energy expenditure and activity on several hundred Drosophila melanogaster. Surprisingly, the relationship between maintenance energy expenditure and activity was fundamentally different in males vs. females. In males, there was a strong and positive correlation between these, such that the individuals that spent more energy on maintenance were also more active. In contrast, the relationship was negative in females, such that the individuals that spent more energy on maintenance were also less active. These differences in the relationship between maintenance energy expenditure and activity between the sexes imply that male and female flies manage their energy budget very differently, perhaps arising from the different life histories of the sexes. Abstract A&nbsp;key endeavor in evolutionary physiology is to identify sources of among- and within-individual variation in resting metabolic rate (RMR). Although males and females often differ in whole-organism RMR due to sexual size dimorphism, sex differences in RMR sometimes persist after conditioning on body mass, suggesting phenotypic differences between males and females in energy-expensive activities contributing to RMR. One potential difference is locomotor activity, yet its relationship with RMR is unclear and different energy budget models predict different associations. We quantified locomotor activity (walking) over 24h and RMR (overnight) on 232 males and 245 females Drosophila melanogaster that were either mated or maintained as virgins between two sets of measurements. Accounting for body mass, sex, and reproductive status, RMR and activity were significantly and moderately repeatable (RMR: R=0.33±0.06; activity: R=0.58±0.03). RMR and activity were positively correlated among (rind=0.26±0.09) but not within (re=0.05±0.06) individuals. Moreover, activity varied throughout the day and between the sexes. Partitioning our analysis by sex and activity by time of day revealed that all among-individual correlations were positive and significant in males, but non-significant or even significantly negative in females. Such differences in the RMR-activity covariance suggests fundamental differences in how the sexes manage their energy budget. More forthcoming papers &raquo; <p>Mathieu Videlier, Howard D. Rundle, and Vincent Careau (Dec 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705678">Read the Article</a></i> (Just Accepted)</p> <p><b>Sex differences in the metabolism-activity link imply males and females manage their energy budgets differently </b></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>ccording to a new study by a research team at the University of Ottawa, there are strong differences in how male vs. female flies manage their energy expenditures. Individuals expend energy (calories) for all bodily functions, from movement to breathing to digestion and reproduction. Two important components of the energy budget are those spent on bodily maintenance and activity, because both are fundamental to surviving and reproducing. How the two components co-vary among individuals is unclear, however. In their paper appearing in <i>The&nbsp;American Naturalist</i>, a team led by PhD student Mathieu Videlier gathered repeated measurements of maintenance energy expenditure and activity on several hundred <i>Drosophila melanogaster</i>. Surprisingly, the relationship between maintenance energy expenditure and activity was fundamentally different in males vs. females. In males, there was a strong and positive correlation between these, such that the individuals that spent more energy on maintenance were also more active. In contrast, the relationship was negative in females, such that the individuals that spent more energy on maintenance were also less active. These differences in the relationship between maintenance energy expenditure and activity between the sexes imply that male and female flies manage their energy budget very differently, perhaps arising from the different life histories of the sexes.</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;key endeavor in evolutionary physiology is to identify sources of among- and within-individual variation in resting metabolic rate (RMR). Although males and females often differ in whole-organism RMR due to sexual size dimorphism, sex differences in RMR sometimes persist after conditioning on body mass, suggesting phenotypic differences between males and females in energy-expensive activities contributing to RMR. One potential difference is locomotor activity, yet its relationship with RMR is unclear and different energy budget models predict different associations. We quantified locomotor activity (walking) over 24h and RMR (overnight) on 232 males and 245 females <i>Drosophila melanogaster</i> that were either mated or maintained as virgins between two sets of measurements. Accounting for body mass, sex, and reproductive status, RMR and activity were significantly and moderately repeatable (RMR: R=0.33±0.06; activity: R=0.58±0.03). RMR and activity were positively correlated among (<i>r</i><span style="font-size:70%; position:relative; bottom:-0.3em;">ind</span>=0.26±0.09) but not within (<i>r<span style="font-size:70%; position:relative; bottom:-0.3em;">e</span></i>=0.05±0.06) individuals. Moreover, activity varied throughout the day and between the sexes. Partitioning our analysis by sex and activity by time of day revealed that all among-individual correlations were positive and significant in males, but non-significant or even significantly negative in females. Such differences in the RMR-activity covariance suggests fundamental differences in how the sexes manage their energy budget. </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, 30 Jul 2019 05:00:00 GMT “Climate warming, resource availability, and the metabolic meltdown of ectotherms” https://amnat.org/an/newpapers/Dec-Huey-A.html Raymond B. Huey and Joel G. Kingsolver (Dec 2019) Read the Article (Just Accepted) Deleterious impacts of climate warming are amplified if food is reduced because food or foraging time is reduced Abstract Climate warming may lower environmental resource levels, growth, and fitness of many ectotherms. In a classic experiment, Brett and colleagues (1969, 1971) documented that growth rates of salmon depended strikingly on both temperature and food levels. Here we develop a simple bioenergetic model that explores how fixed temperatures and food jointly alter the thermal sensitivity of net energy gain. The model incorporates differing thermal sensitivities of energy intake and metabolism. In qualitative agreement with Brett’s results, it predicts that decreased food intake reduces growth rates, lowers optimal temperatures for growth, and lowers the highest temperatures sustaining growth (upper thermal limit). Consequently, ectotherms facing reduced food intake in warm environments should restrict activity to times when low body temperatures are biophysically feasible, but – in a warming world – that will force ectotherms to shorten activity times and thus further reduce food intake. This ‘metabolic meltdown’ is a consequence of declining energy intake coupled with accelerating metabolic costs at high temperatures, and with warming-imposed restrictions on activity. Next, we extend the model to explore how increasing mean environmental temperatures alter the thermal sensitivity of growth: when food intake is reduced, optimal temperatures and upper thermal limits for growth are lowered. We discuss our model’s key assumptions and caveats, and its relationship to a recent model for phytoplankton. Both models illustrate that the deleterious impacts of climate warming on ectotherms will be amplified if food intake is also reduced, either because warming reduces standing food resources or because it restricts foraging time. More forthcoming papers &raquo; <p>Raymond B. Huey and Joel G. Kingsolver (Dec 2019) </p><p><i><a href="https://dx.doi.org/10.1086/705679">Read the Article</a></i> (Just Accepted) </p> <p><b>Deleterious impacts of climate warming are amplified if food is reduced because food or foraging time is reduced </b></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>limate warming may lower environmental resource levels, growth, and fitness of many ectotherms. In a classic experiment, Brett and colleagues (1969, 1971) documented that growth rates of salmon depended strikingly on both temperature and food levels. Here we develop a simple bioenergetic model that explores how fixed temperatures and food jointly alter the thermal sensitivity of net energy gain. The model incorporates differing thermal sensitivities of energy intake and metabolism. In qualitative agreement with Brett’s results, it predicts that decreased food intake reduces growth rates, lowers optimal temperatures for growth, and lowers the highest temperatures sustaining growth (upper thermal limit). Consequently, ectotherms facing reduced food intake in warm environments should restrict activity to times when low body temperatures are biophysically feasible, but – in a warming world – that will force ectotherms to shorten activity times and thus further reduce food intake. This ‘metabolic meltdown’ is a consequence of declining energy intake coupled with accelerating metabolic costs at high temperatures, and with warming-imposed restrictions on activity. Next, we extend the model to explore how increasing mean environmental temperatures alter the thermal sensitivity of growth: when food intake is reduced, optimal temperatures and upper thermal limits for growth are lowered. We discuss our model’s key assumptions and caveats, and its relationship to a recent model for phytoplankton. Both models illustrate that the deleterious impacts of climate warming on ectotherms will be amplified if food intake is also reduced, either because warming reduces standing food resources or because it restricts foraging time. </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, 30 Jul 2019 05:00:00 GMT “Genetic diversity-area relationships across bird species” https://amnat.org/an/newpapers/Nov-Fan-A.html Haiying Fan (樊海英), Qingchen Zhang (张清臣), Juanjuan Rao (饶娟娟), Jingwen Cao (曹静文), and Xin Lu (卢欣) (Nov 2019) Read the Article (Just Accepted) The first step towards quantifying the effect of habitat loss on genetic diversity Abstract The genetic diversity-area relationship (GAR), compared to the extensively explored species-area relationship (SAR), remains poorly recognized despite the importance of understanding it for the development and application of biodiversity theory. It has been hypothesized that maintaining genetic diversity within a population is mechanistically similar to maintaining species diversity within a community, implying that GAR trajectories should mathematically behave as SAR ones. Here we test this prediction by fitting microsatellite heterozygosity and allelic richness in relation to distribution range size across bird species against eight well-known SAR models. The Monod model best described the data of resident and migratory species combined, and especially the data of resident species only, showing that with increasing range size, genetic diversity across species rapidly increased up to a certain level and then tended towards an asymptote. None of the candidate models provided an adequate fit for the data of migratory species, likely because their breeding range size mostly is large in that a GAR curve has become flat. Our work takes the first step towards formulating GARs and applying them to predicting the effect of habitat fragmentation on genetic diversity. 鸟类的遗传多样性-面积关系 理解遗传多样性-面积关系(Genetic diversity-area relationship, GAR)对于生物多样性理论的发展和应用具有重要意义。但与已被广泛探索的种-面积关系(Species-area relationship, SAR)相比,我们对GAR的认识仍然不足。根据现有假说,种群内遗传多样性的维持机制平行于群落内物种多样性的维持机制,这意味着GAR与SAR的轨迹在数学上应该相似。本文使用8个著名的SAR模型来检验这一预测,分别对不同鸟类物种的微卫星杂合度和等位基因丰富度与其繁殖分布范围的大小进行拟合。Monod模型最好地描述了居留和迁徙物种合并的数据,尤其是居留物种的数据拟合度最高。这表明,随着分布范围的增大,物种的遗传多样性迅速增加至一定水平,然后增速变缓并趋近于一条渐近线。没有一个候选模型能够充分拟合迁徙物种的数据,原因可能是它们中大多数的繁殖分布范围很大,使其GAR曲线变得平坦。我们的工作迈出了模型化GARs,并将其应用于预测栖息地片段化对遗传多样性影响的第一步。 More forthcoming papers &raquo; <p>Haiying Fan (樊海英), Qingchen Zhang (张清臣), Juanjuan Rao (饶娟娟), Jingwen Cao (曹静文), and Xin Lu (卢欣) (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705346">Read the Article</a></i> (Just Accepted)</p> <p><b>The first step towards quantifying the effect of habitat loss on genetic diversity </b></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 genetic diversity-area relationship (GAR), compared to the extensively explored species-area relationship (SAR), remains poorly recognized despite the importance of understanding it for the development and application of biodiversity theory. It has been hypothesized that maintaining genetic diversity within a population is mechanistically similar to maintaining species diversity within a community, implying that GAR trajectories should mathematically behave as SAR ones. Here we test this prediction by fitting microsatellite heterozygosity and allelic richness in relation to distribution range size across bird species against eight well-known SAR models. The Monod model best described the data of resident and migratory species combined, and especially the data of resident species only, showing that with increasing range size, genetic diversity across species rapidly increased up to a certain level and then tended towards an asymptote. None of the candidate models provided an adequate fit for the data of migratory species, likely because their breeding range size mostly is large in that a GAR curve has become flat. Our work takes the first step towards formulating GARs and applying them to predicting the effect of habitat fragmentation on genetic diversity. </p> <h4>鸟类的遗传多样性-面积关系</h4> <!-- <p>Haiying Fan (樊海英), Qingchen Zhang (张清臣), Juanjuan Rao (饶娟娟), Jingwen Cao (曹静文), and Xin Lu (卢欣)</p> --> <p>理解遗传多样性-面积关系(Genetic diversity-area relationship, GAR)对于生物多样性理论的发展和应用具有重要意义。但与已被广泛探索的种-面积关系(Species-area relationship, SAR)相比,我们对GAR的认识仍然不足。根据现有假说,种群内遗传多样性的维持机制平行于群落内物种多样性的维持机制,这意味着GAR与SAR的轨迹在数学上应该相似。本文使用8个著名的SAR模型来检验这一预测,分别对不同鸟类物种的微卫星杂合度和等位基因丰富度与其繁殖分布范围的大小进行拟合。Monod模型最好地描述了居留和迁徙物种合并的数据,尤其是居留物种的数据拟合度最高。这表明,随着分布范围的增大,物种的遗传多样性迅速增加至一定水平,然后增速变缓并趋近于一条渐近线。没有一个候选模型能够充分拟合迁徙物种的数据,原因可能是它们中大多数的繁殖分布范围很大,使其GAR曲线变得平坦。我们的工作迈出了模型化GARs,并将其应用于预测栖息地片段化对遗传多样性影响的第一步。 </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, 25 Jul 2019 05:00:00 GMT “On the consequences of the interdependence of stabilizing and equalizing mechanisms” https://amnat.org/an/newpapers/Nov-Song.html Chuliang Song, György Barabás, and Serguei Saavedra (Nov 2019) Read the Article (Just Accepted) The essence of the Darwinian view of life is that species better adapted to their environments outcompete those less well adapted. This, however, raises the question of why there are more than one species on Earth, instead of just a single “best” one. The basic answer is that it is impossible to be the best at everything simultaneously. Ground finches on the Galápagos Islands, from the genus Geospiza, all eat seeds, for instance, but each species has a different characteristic beak size. Large beaks are excellent for breaking and eating large seeds, but are useless in eating small ones. And conversely, small beaks are much better at capturing small seeds than large ones. Thus the finches avoid competition and are able to coexist, because they compete for different things. Ecologists have a way of classifying how such differences between otherwise similar species contribute to their coexistence. Differences are classified into two categories: “stabilizing” differences are those helping coexistence (such as eating different seed types), while “equalizing” differences are those that, all else equal, cause one species to be better adapted than the other (two finch species which eat the exact same seed type may differ in how well they are able to make use of those seeds – the difference in their abilities is the “fitness inequality” between them). While this classification scheme is intuitive and theoretically sound, the authors show that these two types of differences, widely considered independent and opposing forces, are actually interdependent, and are so in intricate ways. This means that one cannot use these concepts in an overly simplistic way to understand why species coexist in nature. However, by perceiving the stabilizing and equalizing contributions as net effects, rather than general ecological causes, we may get a better understanding of coexistence. Abstract We present an overlooked but important property of modern coexistence theory (MCT), along with two key new results and their consequences. The overlooked property is that stabilizing mechanisms (increasing species’ niche differences) and equalizing mechanisms (reducing species’ fitness differences) have two distinct sets of meanings within MCT: one in a 2-species, and another in a general multispecies context. We demonstrate that the 2-species framework is not a special case of the multispecies one, and therefore these two parallel frameworks must be studied independently. Our first result is that, using the 2-species framework and mechanistic consumer-resource models, stabilizing and equalizing mechanisms exhibit complex interdependence, such that changing one will simultaneously change the other. Furthermore, the nature and direction of this simultaneous change depend sensitively on model parameters. The second result states that while MCT is often seen as bridging niche and neutral modes of coexistence by building a niche-neutrality continuum, the interdependence between stabilizing and equalizing mechanisms acts to break this continuum under almost any biologically relevant circumstance. We conclude that the complex entanglement of stabilizing and equalizing terms makes their impact on coexistence difficult to understand, but by seeing them as aggregated effects (rather than underlying causes) of coexistence, we may increase our understanding of ecological dynamics. More forthcoming papers &raquo; <p>Chuliang Song, György Barabás, and Serguei Saavedra (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705347">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 essence of the Darwinian view of life is that species better adapted to their environments outcompete those less well adapted. This, however, raises the question of why there are more than one species on Earth, instead of just a single “best” one. The basic answer is that it is impossible to be the best at everything simultaneously. Ground finches on the Galápagos Islands, from the genus <i>Geospiza</i>, all eat seeds, for instance, but each species has a different characteristic beak size. Large beaks are excellent for breaking and eating large seeds, but are useless in eating small ones. And conversely, small beaks are much better at capturing small seeds than large ones. Thus the finches avoid competition and are able to coexist, because they compete for different things. Ecologists have a way of classifying how such differences between otherwise similar species contribute to their coexistence. Differences are classified into two categories: “stabilizing” differences are those helping coexistence (such as eating different seed types), while “equalizing” differences are those that, all else equal, cause one species to be better adapted than the other (two finch species which eat the exact same seed type may differ in how well they are able to make use of those seeds &ndash; the difference in their abilities is the “fitness inequality” between them). While this classification scheme is intuitive and theoretically sound, the authors show that these two types of differences, widely considered independent and opposing forces, are actually interdependent, and are so in intricate ways. This means that one cannot use these concepts in an overly simplistic way to understand why species coexist in nature. However, by perceiving the stabilizing and equalizing contributions as net effects, rather than general ecological causes, we may get a better understanding of coexistence.</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>e present an overlooked but important property of modern coexistence theory (MCT), along with two key new results and their consequences. The overlooked property is that stabilizing mechanisms (increasing species’ niche differences) and equalizing mechanisms (reducing species’ fitness differences) have two distinct sets of meanings within MCT: one in a 2-species, and another in a general multispecies context. We demonstrate that the 2-species framework is not a special case of the multispecies one, and therefore these two parallel frameworks must be studied independently. Our first result is that, using the 2-species framework and mechanistic consumer-resource models, stabilizing and equalizing mechanisms exhibit complex interdependence, such that changing one will simultaneously change the other. Furthermore, the nature and direction of this simultaneous change depend sensitively on model parameters. The second result states that while MCT is often seen as bridging niche and neutral modes of coexistence by building a niche-neutrality continuum, the interdependence between stabilizing and equalizing mechanisms acts to break this continuum under almost any biologically relevant circumstance. We conclude that the complex entanglement of stabilizing and equalizing terms makes their impact on coexistence difficult to understand, but by seeing them as aggregated effects (rather than underlying causes) of coexistence, we may increase our understanding of ecological 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> Thu, 25 Jul 2019 05:00:00 GMT “Eco-evolutionary feedbacks predict the time course of rapid life history evolution” https://amnat.org/an/newpapers/Nov-Reznick.html David N. Reznick, Ronald D. Bassar, Corey A. Handelsman, Cameron K. Ghalambor, Jeff Arendt, Tim Coulson, Tomos Potter, Emily W. Ruell, Julián Torres-Dowdall, Paul Bentzen, and Joseph Travis (Nov 2019) Read the Article (Just Accepted)Guppies, a perennial pet store favorite, have helped a UC Riverside scientist unlock a key question about evolution. Do animals evolve in response to the risk of being eaten, or to the environment that they create in the absence of predators? Turns out, it’s the latter. Riverside biology professor David Reznick explained that in the wild, guppies can migrate over waterfalls and rapids to places where most predators can’t follow them. Once they arrive in safer terrain, Reznick’s previous research shows they evolve rapidly, becoming genetically distinct from their ancestors. “We already knew that they evolved quickly, but what we didn’t yet understand was why,” Reznick said. In a paper appearing in The&nbsp;American Naturalist, Reznick and his co-authors explain the reason that the tiny fish evolve so quickly in safer waters. To answer their questions, the scientists traveled to Trinidad, guppies’ native habitat, and did an experiment. They moved guppies from areas in streams where predators were plentiful to areas where predators were mostly absent. Over the course of four years, they studied how the introduced guppies changed in comparison to ones from where they originated. “If guppies evolve because they aren’t at risk of becoming food for other fish, then evolution should be visible right away,” Reznick said. “However, if in the absence of predators, they become abundant and deplete the environment of food, then there will be a lag in detectable changes.” Guppies from all four streams were marked so they could be tracked over the course of four years. Specifically, in this paper, the scientists considered results for males, which tend to live about five months. They looked at the fishes’ age and size at maturity, which are key traits affecting population growth. They also tracked how the environment changed as the guppy populations expanded, focusing on the abundance of food such as algae and insects, as well as the presence of other non-predator fish. The finished product includes evidence from the four experimental populations in nature and from laboratory common garden studies of the grandchildren of wild caught fish, mathematical modeling, and quantitative genetic analyses of the one experimental population for which they had a pedigree. They found a two-to-three-year lag between when guppies were introduced and when males evolved, suggesting the second hypothesis was correct; guppies were first changing their new environments, and then as a result, they turned out to be changing themselves. “The speed of evolution makes it possible to study how it happens. The new news is that organisms can shape their own evolution by changing their environment,” Reznick said. One of Reznick’s current projects includes applying these concepts to questions about human evolution. “Unlike guppies and other organisms, human population density seems to increase without apparent limit, which increases our impact on our environment and on ourselves,” he said. Co-authors on this study included Ron Basser, a former PhD student at UC Riverside now assistant professor at Williams College, Joe Travis at Florida State University and Corey Handelsman, Cameron Ghalambor, Emily Ruell, and Julian Torres-Dowdall from Colorado State University, Tim Coulson and Tomos Potter of Oxford University, and Paul Bentzen of Dalhousie University. Abstract Organisms can change their environment and, in so doing, change the selection they experience and how they evolve. Population density is one potential mediator of such interactions because high population densities can impact the ecosystem and reduce resource availability. At present, such interactions are best known from theory and laboratory experiments. Here we quantify the importance of such interactions in nature by transplanting guppies from a stream where they co-occur with predators into tributaries that previously lacked both guppies and predators. If guppies evolve solely because of the immediate reduction in mortality rate, the strength of selection and rate of evolution should be greatest at the outset then decline as the population adapts to its new environment. If indirect effects caused by the increase in guppy population density in the absence of predation prevail, then there should be a lag in guppy evolution because time is required for them to modify their environment. The duration of this lag is predicted to be associated with the environmental modification caused by guppies. We observed a lag in life history evolution associated with increases in population density and altered ecology. How guppies evolved matched predictions derived from evolutionary theory that incorporates such density effects. More forthcoming papers &raquo; <p>David N. Reznick, Ronald D. Bassar, Corey A. Handelsman, Cameron K. Ghalambor, Jeff Arendt, Tim Coulson, Tomos Potter, Emily W. Ruell, Julián Torres-Dowdall, Paul Bentzen, and Joseph Travis (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705380">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;">G</span>uppies, a perennial pet store favorite, have helped a UC Riverside scientist unlock a key question about evolution. Do animals evolve in response to the risk of being eaten, or to the environment that they create in the absence of predators? Turns out, it&rsquo;s the latter.</p> <p>Riverside biology professor David Reznick explained that in the wild, guppies can migrate over waterfalls and rapids to places where most predators can&rsquo;t follow them. Once they arrive in safer terrain, Reznick&rsquo;s previous research shows they evolve rapidly, becoming genetically distinct from their ancestors. &ldquo;We already knew that they evolved quickly, but what we didn&rsquo;t yet understand was why,&rdquo; Reznick said. In a paper appearing in <i>The&nbsp;American Naturalist,</i> Reznick and his co-authors explain the reason that the tiny fish evolve so quickly in safer waters.</p> <p>To answer their questions, the scientists traveled to Trinidad, guppies&rsquo; native habitat, and did an experiment. They moved guppies from areas in streams where predators were plentiful to areas where predators were mostly absent. Over the course of four years, they studied how the introduced guppies changed in comparison to ones from where they originated. &ldquo;If guppies evolve because they aren&rsquo;t at risk of becoming food for other fish, then evolution should be visible right away,&rdquo; Reznick said. &ldquo;However, if in the absence of predators, they become abundant and deplete the environment of food, then there will be a lag in detectable changes.&rdquo;</p> <p>Guppies from all four streams were marked so they could be tracked over the course of four years. Specifically, in this paper, the scientists considered results for males, which tend to live about five months. They looked at the fishes&rsquo; age and size at maturity, which are key traits affecting population growth.</p> <p>They also tracked how the environment changed as the guppy populations expanded, focusing on the abundance of food such as algae and insects, as well as the presence of other non-predator fish. The finished product includes evidence from the four experimental populations in nature and from laboratory common garden studies of the grandchildren of wild caught fish, mathematical modeling, and quantitative genetic analyses of the one experimental population for which they had a pedigree.</p> <p>They found a two-to-three-year lag between when guppies were introduced and when males evolved, suggesting the second hypothesis was correct; guppies were first changing their new environments, and then as a result, they turned out to be changing themselves. &ldquo;The speed of evolution makes it possible to study how it happens. The new news is that organisms can shape their own evolution by changing their environment,&rdquo; Reznick said.</p> <p>One of Reznick&rsquo;s current projects includes applying these concepts to questions about human evolution. &ldquo;Unlike guppies and other organisms, human population density seems to increase without apparent limit, which increases our impact on our environment and on ourselves,&rdquo; he said.</p> <p>Co-authors on this study included Ron Basser, a former PhD student at UC Riverside now assistant professor at Williams College, Joe Travis at Florida State University and Corey Handelsman, Cameron Ghalambor, Emily Ruell, and Julian Torres-Dowdall from Colorado State University, Tim Coulson and Tomos Potter of Oxford University, and Paul Bentzen of Dalhousie University.</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;">O</span>rganisms can change their environment and, in so doing, change the selection they experience and how they evolve. Population density is one potential mediator of such interactions because high population densities can impact the ecosystem and reduce resource availability. At present, such interactions are best known from theory and laboratory experiments. Here we quantify the importance of such interactions in nature by transplanting guppies from a stream where they co-occur with predators into tributaries that previously lacked both guppies and predators. If guppies evolve solely because of the immediate reduction in mortality rate, the strength of selection and rate of evolution should be greatest at the outset then decline as the population adapts to its new environment. If indirect effects caused by the increase in guppy population density in the absence of predation prevail, then there should be a lag in guppy evolution because time is required for them to modify their environment. The duration of this lag is predicted to be associated with the environmental modification caused by guppies. We observed a lag in life history evolution associated with increases in population density and altered ecology. How guppies evolved matched predictions derived from evolutionary theory that incorporates such density effects.</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> Thu, 18 Jul 2019 05:00:00 GMT “Queen execution, diploid males, and selection for and against polyandry in the Brazilian stingless bee <i>Scaptotrigona depilis</i>” https://amnat.org/an/newpapers/Nov-Vollet-Neto-A.html Ayrton Vollet-Neto, Vera L. Imperatriz-Fonseca, and Francis L. W. Ratnieks (Nov 2019) Read the Article (Just Accepted)Abstract Female mating frequency varies. Determining the causes of this variation is an active research area. We tested the hypothesis that in stingless bees, Meliponini, single mating is due to the execution of queens that make a matched mating at the CSD (complementary sex determination) locus and have diploid male offspring. We studied the Brazilian species Scaptotrigona depilis. We made up 70 test colonies so that 50% (single matched mating), 25% (double mating), 12.5% (4-mating), or 0% (single non-matched mating) emerging brood were diploid males. Queen execution following diploid male emergence was equal and high in colonies producing 50% (77% executed) and 25% (75%) diploid males, versus equal and low in colonies producing 12.5% (7%) and 0% (0%) diploid males. These results show that queens that mate with two males with similar paternity suffer an increased chance of being executed, which selects against double mating. However, double mating with unequal paternity (e.g., 25:75), which occasionally occurs in S.&nbsp;depilis, is selectively neutral. Single mating and double mating with unequal paternity form one adaptive peak. The results show a second adaptive peak at 4-mating. However, this is inaccessible via gradual evolutionary change in a selective landscape with reduced fitness at double mating. More forthcoming papers &raquo; <p>Ayrton Vollet-Neto, Vera L. Imperatriz-Fonseca, and Francis L. W. Ratnieks (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705393">Read the Article</a></i> (Just Accepted)</p><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;">F</span>emale mating frequency varies. Determining the causes of this variation is an active research area. We tested the hypothesis that in stingless bees, Meliponini, single mating is due to the execution of queens that make a matched mating at the CSD (complementary sex determination) locus and have diploid male offspring. We studied the Brazilian species <i>Scaptotrigona depilis</i>. We made up 70 test colonies so that 50% (single matched mating), 25% (double mating), 12.5% (4-mating), or 0% (single non-matched mating) emerging brood were diploid males. Queen execution following diploid male emergence was equal and high in colonies producing 50% (77% executed) and 25% (75%) diploid males, versus equal and low in colonies producing 12.5% (7%) and 0% (0%) diploid males. These results show that queens that mate with two males with similar paternity suffer an increased chance of being executed, which selects against double mating. However, double mating with unequal paternity (e.g., 25:75), which occasionally occurs in <i>S.&nbsp;depilis</i>, is selectively neutral. Single mating and double mating with unequal paternity form one adaptive peak. The results show a second adaptive peak at 4-mating. However, this is inaccessible via gradual evolutionary change in a selective landscape with reduced fitness at double mating.</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> Wed, 17 Jul 2019 05:00:00 GMT “Head shape modulates diversification of a classic cichlid pharyngeal jaw innovation” https://amnat.org/an/newpapers/Nov-Burress.html Edward D. Burress, Milton Tan, and Peter C. Wainwright (Nov 2019) Read the Article (Just Accepted) Shape disparity and rate of evolution of a major cichlid pharyngeal jaw innovation is dependent upon head shape Key innovations are morphological, physiological, or behavioral traits that facilitate the exploitation of new resources and are often proposed to explain why some groups of organisms are diverse while others are not. However, groups that share such an innovation may also exhibit unevenly distributed ecological diversity, raising the possibility that the utility of innovations may be dependent upon other factors. In this study, Edward Burress, Milton Tan, and Peter Wainwright at the University of California-Davis test whether head shape influences diversification of cichlid pharyngeal jaws, which provide an enhanced ability to crush, chew, and grasp prey. The authors show that wide heads evolve in association with feeding upon items that require extensive processing by the pharyngeal jaws such as snails, likely to accommodate large pharyngeal jaw bones and associated musculature. However, head width is negatively correlated with pharyngeal jaw shape diversity and rates of shape evolution. Species with wide heads exhibit only a fraction of observed pharyngeal jaw shapes, whereas species with narrow heads exhibit more pharyngeal jaw shapes and exploit correspondingly more types of prey. The authors determine that head shape modulates diversification of pharyngeal jaws and subsequently the ecological diversity of cichlids. This study provides an example of how a simple aspect of morphology can have broad evolutionary and ecological implications by interacting with a major innovation. Abstract Functional innovations are often invoked to explain the uneven distribution of ecological diversity. Innovations may provide access to new adaptive zones by expanding available ecological opportunities and may serve as catalysts of adaptive radiation. However, diversity is often unevenly distributed within clades that share a key innovation, highlighting the possibility that the impact of the innovation is mediated by other traits. Pharyngognathy is a widely recognized innovation of the pharyngeal jaws that enhances the ability to process hard and tough prey in several major radiations of fishes, including marine wrasses and freshwater cichlids. We explored diversification of lower pharyngeal jaw shape, a key feature of pharyngognathy, and the extent to which it is influenced by head shape in Neotropical cichlids. While pharyngeal jaw shape was unaffected by either head length or head depth, its disparity declined dramatically with increasing head width. Head width also predicted the rate of pharyngeal jaw evolution such that higher rates were associated with narrow heads. Wide heads are associated with exploiting prey that require intense processing by pharyngeal jaws that have expanded surfaces for the attachment of enlarged muscles. However, we show that a wide head constrains access to adaptive peaks associated with several trophic roles. A constraint on the independent evolution of pharyngeal jaw and head shape may explain the uneven distribution of ecological diversity within a clade that shares a major functional innovation. More forthcoming papers &raquo; <p>Edward D. Burress, Milton Tan, and Peter C. Wainwright (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705392">Read the Article</a></i> (Just Accepted)</p> <p><b>Shape disparity and rate of evolution of a major cichlid pharyngeal jaw innovation is dependent upon head shape </b></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;">K</span>ey innovations are morphological, physiological, or behavioral traits that facilitate the exploitation of new resources and are often proposed to explain why some groups of organisms are diverse while others are not. However, groups that share such an innovation may also exhibit unevenly distributed ecological diversity, raising the possibility that the utility of innovations may be dependent upon other factors. In this study, Edward Burress, Milton Tan, and Peter Wainwright at the University of California-Davis test whether head shape influences diversification of cichlid pharyngeal jaws, which provide an enhanced ability to crush, chew, and grasp prey. The authors show that wide heads evolve in association with feeding upon items that require extensive processing by the pharyngeal jaws such as snails, likely to accommodate large pharyngeal jaw bones and associated musculature. However, head width is negatively correlated with pharyngeal jaw shape diversity and rates of shape evolution. Species with wide heads exhibit only a fraction of observed pharyngeal jaw shapes, whereas species with narrow heads exhibit more pharyngeal jaw shapes and exploit correspondingly more types of prey. The authors determine that head shape modulates diversification of pharyngeal jaws and subsequently the ecological diversity of cichlids. This study provides an example of how a simple aspect of morphology can have broad evolutionary and ecological implications by interacting with a major innovation.</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;">F</span>unctional innovations are often invoked to explain the uneven distribution of ecological diversity. Innovations may provide access to new adaptive zones by expanding available ecological opportunities and may serve as catalysts of adaptive radiation. However, diversity is often unevenly distributed within clades that share a key innovation, highlighting the possibility that the impact of the innovation is mediated by other traits. Pharyngognathy is a widely recognized innovation of the pharyngeal jaws that enhances the ability to process hard and tough prey in several major radiations of fishes, including marine wrasses and freshwater cichlids. We explored diversification of lower pharyngeal jaw shape, a key feature of pharyngognathy, and the extent to which it is influenced by head shape in Neotropical cichlids. While pharyngeal jaw shape was unaffected by either head length or head depth, its disparity declined dramatically with increasing head width. Head width also predicted the rate of pharyngeal jaw evolution such that higher rates were associated with narrow heads. Wide heads are associated with exploiting prey that require intense processing by pharyngeal jaws that have expanded surfaces for the attachment of enlarged muscles. However, we show that a wide head constrains access to adaptive peaks associated with several trophic roles. A constraint on the independent evolution of pharyngeal jaw and head shape may explain the uneven distribution of ecological diversity within a clade that shares a major functional innovation. </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, 17 Jul 2019 05:00:00 GMT “Variability in dispersal syndromes is a key driver of metapopulation dynamics in experimental microcosms” https://amnat.org/an/newpapers/Nov-Jacob.html Staffan Jacob, Alexis S. Chaine, Michèle Huet, Jean Clobert, and Delphine Legrand (Nov 2019) Read the Article (Just Accepted) A microcosm experiment shows that variability in dispersal syndromes is a key driver of metapopulation dynamics Differences among individuals within species are of major importance for evolution, but we know little about the role such intraspecific variability can play for the dynamics of connected populations facing environmental changes. Research in the past decades has especially highlighted the great variability in phenotypic and behavioral traits related to dispersal, the movements of individuals between populations. Using an experimental approach with connected microcosms of a ciliate, Staffan Jacob and colleagues at the Theoretical and Experimental Ecology Station, in the south of France, quantified the importance of this intraspecific variability in dispersal for the dynamics of connected populations. They demonstrated that differences among individuals are at least as important for metapopulation dynamics as the spatial and temporal variability of resources. An important part of this effect moreover results from variability of dispersal strategies. This study demonstrates that intraspecific variability in dispersal syndromes can be key in the functioning of metapopulations facing environmental changes. Abstract Evolutionary ecology studies have increasingly focused on the impact of intraspecific variability on population processes. However, the role such variation plays in the dynamics of spatially structured populations and how it interacts with environmental changes remains unclear. Here we experimentally quantify the relative importance of intraspecific variability in dispersal-related traits and spatiotemporal variability of environmental conditions for the dynamics of two-patch metapopulations using clonal genotypes of a ciliate in connected microcosms. We demonstrate that, in our simple two-patch microcosms, differences among genotypes are at least as important as spatiotemporal variability of resources for metapopulation dynamics. Furthermore, we show that an important proportion of this effect results from variability of dispersal syndromes. These syndromes can therefore be as important for metapopulation dynamics as spatiotemporal variability of environmental conditions. This study demonstrates that intraspecific variability in dispersal syndromes can be key in the functioning of metapopulations facing environmental changes. More forthcoming papers &raquo; <p>Staffan Jacob, Alexis S. Chaine, Michèle Huet, Jean Clobert, and Delphine Legrand (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705410">Read the Article</a></i> (Just Accepted) </p> <p><b>A microcosm experiment shows that variability in dispersal syndromes is a key driver of metapopulation dynamics </b></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;">D</span>ifferences among individuals within species are of major importance for evolution, but we know little about the role such intraspecific variability can play for the dynamics of connected populations facing environmental changes. Research in the past decades has especially highlighted the great variability in phenotypic and behavioral traits related to dispersal, the movements of individuals between populations. Using an experimental approach with connected microcosms of a ciliate, Staffan Jacob and colleagues at the Theoretical and Experimental Ecology Station, in the south of France, quantified the importance of this intraspecific variability in dispersal for the dynamics of connected populations. They demonstrated that differences among individuals are at least as important for metapopulation dynamics as the spatial and temporal variability of resources. An important part of this effect moreover results from variability of dispersal strategies. This study demonstrates that intraspecific variability in dispersal syndromes can be key in the functioning of metapopulations facing environmental changes. </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 ecology studies have increasingly focused on the impact of intraspecific variability on population processes. However, the role such variation plays in the dynamics of spatially structured populations and how it interacts with environmental changes remains unclear. Here we experimentally quantify the relative importance of intraspecific variability in dispersal-related traits and spatiotemporal variability of environmental conditions for the dynamics of two-patch metapopulations using clonal genotypes of a ciliate in connected microcosms. We demonstrate that, in our simple two-patch microcosms, differences among genotypes are at least as important as spatiotemporal variability of resources for metapopulation dynamics. Furthermore, we show that an important proportion of this effect results from variability of dispersal syndromes. These syndromes can therefore be as important for metapopulation dynamics as spatiotemporal variability of environmental conditions. This study demonstrates that intraspecific variability in dispersal syndromes can be key in the functioning of metapopulations facing environmental changes.</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> Wed, 17 Jul 2019 05:00:00 GMT “Macroevolutionary origin and adaptive function of a polymorphic female signal involved in sexual conflict” https://amnat.org/an/newpapers/Nov-Willink.html Beatriz Willink, M. Catherine Duryea, and Erik I. Svensson (Nov 2019) Read the Article (Just Accepted) Developmental color signals in female-polymorphic damselflies exploit male biases and reduce premature mating attempts Evolutionary biologists have studied male color signals for decades and asked how this variation influences male mating success. The occurrence of conspicuous color signals in females constitutes somewhat of a paradox, as in most species females are unlikely to compete for mating opportunities with males. Many species of pond damselflies in the genus Ischnura have two or three heritable female color morphs that are not present in the monomorphic males. Females belonging to one of the morphs typically resemble males in their color pattern, and are thought to be “male mimics”. Because superfluous male-mating attempts are costly to females, male mimics might benefit if their male-like appearance reduces the rate by which males approach them. The other female morph(s) are termed “heterochromatic females” and are more easily recognized as potential mates by males. Heterochromatic females may suffer greater costs from unsought mating attempts, particularly prior to female sexual maturity. Willink et al. asked if developmental color changes in heterochromatic females could protect them from male-induced harm, by reducing the number of male-mating attempts. Through field observations of one focal species (the common bluetail damselfly, Ischnura elegans), Willink et al. showed that sexually-immature heterochromatic females express a bright abdomen color patch that is also present in males and male-mimics of all ages. However, as heterochromatic females become sexually mature, their color patch is covered with darker pigment. Experimental manipulations of the color patch showed that heterochromatic females with immature coloration were approached less often by males than seemingly older females were. This experimental manipulation suggests that the bright color patch serves an adaptive anti-harassment function. Willink et al. further performed a phylogenetic comparative analysis of female color changes across the genus Ischnura. They demonstrate that this immature signal has evolved multiple times in heterochromatic females, but only in the presence of male-mimics. The combination of experimental and comparative approaches in this study therefore suggest that antagonistic inter-sexual interactions during development has driven the evolution of color signals in females. Abstract Inter-sexual signals that reveal developmental or mating status in females have evolved repeatedly in many animal lineages. Such signals have functions in sexual conflict over mating and can therefore influence sexually antagonistic coevolution. However, we know little about how female signal development modifies male mating harassment and thereby sexual conflict. Here, we combine phylogenetic comparative analyses of a color polymorphic damselfly genus (Ischnura) with behavioral experiments in one target species to investigate the evolutionary origin and current adaptive function of a developmental female-color signal. Many Ischnura species have multiple female color morphs, which include a male-colored morph (“male mimics”) and one or two female morphs that differ markedly from males (heterochrome females). In I.&nbsp;elegans, males and male-mimicking females express a blue abdominal patch throughout post-emergence life. Using phenotypic manipulations we show that the developmental expression of this signalling trait in heterochrome females reduces pre-mating harassment prior to sexual maturity. Across species, this signal evolved repeatedly, but in heterochrome females, its origin is contingent upon the signal expressed by co-occurring male-mimicking females. Our results suggest that the co-option of a male-like trait to a novel female anti-harassment function has a key role in sexual conflict driven by pre-mating interactions. More forthcoming papers &raquo; <p>Beatriz Willink, M. Catherine Duryea, and Erik I. Svensson (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705294">Read the Article</a></i> (Just Accepted) </p> <p><b>Developmental color signals in female-polymorphic damselflies exploit male biases and reduce premature mating attempts </b></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>volutionary biologists have studied male color signals for decades and asked how this variation influences male mating success. The occurrence of conspicuous color signals in females constitutes somewhat of a paradox, as in most species females are unlikely to compete for mating opportunities with males. </p><p>Many species of pond damselflies in the genus <i>Ischnura</i> have two or three heritable female color morphs that are not present in the monomorphic males. Females belonging to one of the morphs typically resemble males in their color pattern, and are thought to be “male mimics”. Because superfluous male-mating attempts are costly to females, male mimics might benefit if their male-like appearance reduces the rate by which males approach them. The other female morph(s) are termed “heterochromatic females” and are more easily recognized as potential mates by males. Heterochromatic females may suffer greater costs from unsought mating attempts, particularly prior to female sexual maturity. Willink et al. asked if developmental color changes in heterochromatic females could protect them from male-induced harm, by reducing the number of male-mating attempts. </p><p>Through field observations of one focal species (the common bluetail damselfly, <i>Ischnura elegans</i>), Willink et al. showed that sexually-immature heterochromatic females express a bright abdomen color patch that is also present in males and male-mimics of all ages. However, as heterochromatic females become sexually mature, their color patch is covered with darker pigment. Experimental manipulations of the color patch showed that heterochromatic females with immature coloration were approached less often by males than seemingly older females were. This experimental manipulation suggests that the bright color patch serves an adaptive anti-harassment function. Willink et al. further performed a phylogenetic comparative analysis of female color changes across the genus <i>Ischnura</i>. They demonstrate that this immature signal has evolved multiple times in heterochromatic females, but only in the presence of male-mimics. The combination of experimental and comparative approaches in this study therefore suggest that antagonistic inter-sexual interactions during development has driven the evolution of color signals in females.</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>nter-sexual signals that reveal developmental or mating status in females have evolved repeatedly in many animal lineages. Such signals have functions in sexual conflict over mating and can therefore influence sexually antagonistic coevolution. However, we know little about how female signal development modifies male mating harassment and thereby sexual conflict. Here, we combine phylogenetic comparative analyses of a color polymorphic damselfly genus (<i>Ischnura</i>) with behavioral experiments in one target species to investigate the evolutionary origin and current adaptive function of a developmental female-color signal. Many <i>Ischnura</i> species have multiple female color morphs, which include a male-colored morph (“male mimics”) and one or two female morphs that differ markedly from males (heterochrome females). In <i>I.&nbsp;elegans</i>, males and male-mimicking females express a blue abdominal patch throughout post-emergence life. Using phenotypic manipulations we show that the developmental expression of this signalling trait in heterochrome females reduces pre-mating harassment prior to sexual maturity. Across species, this signal evolved repeatedly, but in heterochrome females, its origin is contingent upon the signal expressed by co-occurring male-mimicking females. Our results suggest that the co-option of a male-like trait to a novel female anti-harassment function has a key role in sexual conflict driven by pre-mating 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> Tue, 16 Jul 2019 05:00:00 GMT “A meta-analysis of plant interaction networks reveals competitive hierarchies as well as facilitation and intransitivity” https://amnat.org/an/newpapers/Nov-Kinlock.html Nicole L. Kinlock (Nov 2019)Read the Article (Just Accepted) Kinlock combined network structure across plant communities and found competition and hierarchies, but some stabilizing forces The nature of interactions in plant communities poses problems with classical roots and modern controversy, many of which remain unresolved. In this paper, N.&nbsp;L. Kinlock combines network approaches with meta-analysis methods to investigate major questions in plant community ecology, including the intensity of competition and/or facilitation, the reciprocity of interactions (asymmetry), and the degree to which species in communities can be ranked in a hierarchy (transitivity). She used plant community interaction data from the literature, as well as data from her own fieldwork of an invaded woody plant community, and analyzed communities as networks of interactions. She then combined network metrics using meta-analysis, incorporating variation at the interaction level, to generalize structure across communities. On the whole, plant communities were competitive, interactions between species were not reciprocal, and communities were hierarchical (transitive), similar to what has been reported in isolated studies and narrative reviews. However, there were instances of facilitation, symmetric interactions, and intransitivity in individual networks. Also, community structure differed between networks based on study design, habitat type, plant habit (woody or herbaceous), and plant age. This paper quantifies the nature of plant interactions in a systematic and unbiased way, finding some support for classic conceptions of plant community structure, while also bringing to light previously undescribed structural characteristics. This paper is a part of Kinlock’s Ph.D. dissertation at Stony Brook University, where she is studying how plant community structure influences invasion. Abstract The extent to which competitive interactions and niche differentiation structure communities has been highly controversial. To quantify evidence for key features of plant community structure, I recharacterized published data from interaction experiments as networks of competitive and facilitative interactions. I measured the network structure of 31 woody and herbaceous communities, including the intensity, distribution, and diversity of interactions at the species-pair and community level to determine the generality of competition, winner-loser relationships, and unequal interaction allocation. I developed novel methodology using meta-analysis to incorporate interaction uncertainty into estimates of structural metrics among independent networks. Plant communities were competitive, but intraspecific interactions were sometimes more intense than interspecific interactions. On the whole, interactions were imbalanced and communities were transitive. However, facilitation, balanced interactions, and intransitivity were common in individual communities. Synthesizing network metrics using meta-analysis is an original approach with which to generalize community structure in a systematic way. More forthcoming papers &raquo; <p>Nicole L. Kinlock (Nov 2019)</p><p><i><a href="https://dx.doi.org/10.1086/705293">Read the Article</a></i> (Just Accepted) </p> <p><b>Kinlock combined network structure across plant communities and found competition and hierarchies, but some stabilizing forces </b></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 nature of interactions in plant communities poses problems with classical roots and modern controversy, many of which remain unresolved. In this paper, N.&nbsp;L. Kinlock combines network approaches with meta-analysis methods to investigate major questions in plant community ecology, including the intensity of competition and/or facilitation, the reciprocity of interactions (asymmetry), and the degree to which species in communities can be ranked in a hierarchy (transitivity). She used plant community interaction data from the literature, as well as data from her own fieldwork of an invaded woody plant community, and analyzed communities as networks of interactions. She then combined network metrics using meta-analysis, incorporating variation at the interaction level, to generalize structure across communities. </p><p>On the whole, plant communities were competitive, interactions between species were not reciprocal, and communities were hierarchical (transitive), similar to what has been reported in isolated studies and narrative reviews. However, there were instances of facilitation, symmetric interactions, and intransitivity in individual networks. Also, community structure differed between networks based on study design, habitat type, plant habit (woody or herbaceous), and plant age. This paper quantifies the nature of plant interactions in a systematic and unbiased way, finding some support for classic conceptions of plant community structure, while also bringing to light previously undescribed structural characteristics. </p><p>This paper is a part of Kinlock’s Ph.D. dissertation at Stony Brook University, where she is studying how plant community structure influences invasion.</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 extent to which competitive interactions and niche differentiation structure communities has been highly controversial. To quantify evidence for key features of plant community structure, I recharacterized published data from interaction experiments as networks of competitive and facilitative interactions. I measured the network structure of 31 woody and herbaceous communities, including the intensity, distribution, and diversity of interactions at the species-pair and community level to determine the generality of competition, winner-loser relationships, and unequal interaction allocation. I developed novel methodology using meta-analysis to incorporate interaction uncertainty into estimates of structural metrics among independent networks. Plant communities were competitive, but intraspecific interactions were sometimes more intense than interspecific interactions. On the whole, interactions were imbalanced and communities were transitive. However, facilitation, balanced interactions, and intransitivity were common in individual communities. Synthesizing network metrics using meta-analysis is an original approach with which to generalize community structure in a systematic way.</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, 16 Jul 2019 05:00:00 GMT “A minimal model for the latitudinal diversity gradient suggests a dominant role for ecological limits” https://amnat.org/an/newpapers/Nov-Etienne.html Rampal S. Etienne, Juliano Sarmento Cabral, Oskar Hagen, Florian Hartig, Allen H. Hurlbert, Lo&iuml;c Pellissier, Mikael Pontarp, and David Storch (Nov 2019) Read the Article A model for the latitudinal diversity gradient predicts that it is most affected by a gradient in ecological limits Why are there more species in the tropics than at higher latitudes? This question has been boggling the minds of biologists for decades. Is it because the formation of species in the tropics is higher, or species extinction is lower? Or is it because species have had more time to accumulate in the tropics? Or because the tropics can host more species than temperate areas? Each of these explanations is feasible, but which explanation creates the strongest gradient in species richness across latitudes? Eight researchers from many different countries got together at the Centre of Integrative Biodiversity Research in Leipzig several times over the past few years to discuss this question, and they built a mathematical model to compare the effect of all the possible explanations on the distribution of species across different latitudes. They found that the last answer, the tropics can host more species, creates the strongest patterns. They made their model available online for scientists and other interested people to explore: https://seldig.shinyapps.io/RBM-ODE/. Abstract The latitudinal diversity gradient (LDG) is one of Earth’s most iconic biodiversity patterns, and still one of the most debated. Explanations for the LDG are often categorized into three broad pathways, in which the diversity gradient is created by (1) differential diversification rates, (2) differential carrying capacities (ecological limits) or (3) differential time to accumulate species across latitude. Support for these pathways has, however, been mostly verbally expressed. Here, we present a minimal model to clarify the essential assumptions of the three pathways and explore the sensitivity of diversity dynamics to these pathways. We find that an LDG arises most easily from a gradient in ecological limits than a gradient in the time for species accumulation or diversification rate under most modeled scenarios. Differential diversification rates create a stronger LDG than ecological limits only when speciation and dispersal rates are low, but then the predicted LDG seems weaker than the observed LDG. Moreover, range dynamics may reduce an LDG created by a gradient in diversification rates or time for species accumulation, but they cannot reduce an LDG induced by differential ecological limits. We conclude that our simple model provides a null prediction for the effectiveness of the three LDG pathways, and can thus aid discussions about the causal mechanisms underlying the LDG, or motivate more complex models to confirm or falsify our findings. More forthcoming papers &raquo; <p>Rampal S. Etienne, Juliano Sarmento Cabral, Oskar Hagen, Florian Hartig, Allen H. Hurlbert, Lo&iuml;c Pellissier, Mikael Pontarp, and David Storch (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705243">Read the Article</a></i></p> <p><b>A model for the latitudinal diversity gradient predicts that it is most affected by a gradient in ecological limits </b></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>hy are there more species in the tropics than at higher latitudes? This question has been boggling the minds of biologists for decades. Is it because the formation of species in the tropics is higher, or species extinction is lower? Or is it because species have had more time to accumulate in the tropics? Or because the tropics can host more species than temperate areas? Each of these explanations is feasible, but which explanation creates the strongest gradient in species richness across latitudes? Eight researchers from many different countries got together at the Centre of Integrative Biodiversity Research in Leipzig several times over the past few years to discuss this question, and they built a mathematical model to compare the effect of all the possible explanations on the distribution of species across different latitudes. They found that the last answer, the tropics can host more species, creates the strongest patterns. They made their model available online for scientists and other interested people to explore: <a href="https://seldig.shinyapps.io/RBM-ODE/">https://seldig.shinyapps.io/RBM-ODE/</a>.</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;">T</span>he latitudinal diversity gradient (LDG) is one of Earth&rsquo;s most iconic biodiversity patterns, and still one of the most debated. Explanations for the LDG are often categorized into three broad pathways, in which the diversity gradient is created by (1) differential diversification rates, (2) differential carrying capacities (ecological limits) or (3) differential time to accumulate species across latitude. Support for these pathways has, however, been mostly verbally expressed. Here, we present a minimal model to clarify the essential assumptions of the three pathways and explore the sensitivity of diversity dynamics to these pathways. We find that an LDG arises most easily from a gradient in ecological limits than a gradient in the time for species accumulation or diversification rate under most modeled scenarios. Differential diversification rates create a stronger LDG than ecological limits only when speciation and dispersal rates are low, but then the predicted LDG seems weaker than the observed LDG. Moreover, range dynamics may reduce an LDG created by a gradient in diversification rates or time for species accumulation, but they cannot reduce an LDG induced by differential ecological limits. We conclude that our simple model provides a null prediction for the effectiveness of the three LDG pathways, and can thus aid discussions about the causal mechanisms underlying the LDG, or motivate more complex models to confirm or falsify our findings.</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, 16 Jul 2019 05:00:00 GMT Call for ASN Graduate Student Representatives https://amnat.org/announcements/NomGCtoECRep.html The American Society of Naturalists Graduate Student Council invites applications for two to three new graduate student representatives to join us this year! The new application deadline is 7/31/2019. As a member of the Graduate Student Council you have the chance to participate in the workings of the society and interact with many of the great researchers who are members of the ASN. The ASN is committed to developing a variety of initiatives to provide more valuable services to its student members. Representatives take part in several committees that include choosing ASN-sponsored workshops, helping choose winners of the annual student research grant, organizing student events at conferences, participating in various committees, and running the website for grad student ASN members at http://asngrads.com/. Each year we seek new members to join for a 3-year term. We are also open to new roles or ideas for things you think the Grad Council could do to encourage student involvement and interaction among researchers. If you are interested in joining, please email Shengpei Wang (swang74@syr.edu) with the subject line “ASN GC application” and attach a single pdf document containing your CV and a short paragraph (less than 1 page) about what you hope to contribute and why you want to join the grad council. &nbsp;Kim Gilbert&nbsp;(GC rep 2014-2015): "Serving on the ASN grad council is a fantastic opportunity to not only meet faculty, post-docs, and students from a wide range of universities, but to become more involved in a great community of researchers in ecology and evolution. You learn about how journal societies run, as well as the ins and outs of organizing conference events. You also serve as an important representative for all graduate student members of the ASN to ensure the society is doing its best to meet student&#39;s needs at conferences or through other opportunities." Emily Weiss (GC rep 2013-2014): Serving on the Grad Council really was an incredibly enriching experience for me, and I hope that many other students will apply and get to have that experience too. Rafael Maia&nbsp;(GC rep 2013-2014): "I served the council for a couple years and strongly recommend it. Great society, exciting possibilities!" Courtney Fitzpatrick&nbsp;(founding GC rep): "Grad students: excellent opportunity to get involved, meet collaborators/mentors, and learn about your scientific society!" <p>The American Society of Naturalists Graduate Student Council invites applications for two to three new graduate student representatives to join us this year! The new application deadline is 7/31/2019.</p> <p>As a member of the Graduate Student Council you have the chance to participate in the workings of the society and interact with many of the great researchers who are members of the ASN. The ASN is committed to developing a variety of initiatives to provide more valuable services to its student members.</p> <p>Representatives take part in several committees that include choosing ASN-sponsored workshops, helping choose winners of the annual student research grant, organizing student events at conferences, participating in various committees, and running the website for grad student ASN members at <a href="http://asngrads.com/">http://asngrads.com/</a>.<br /> Each year we seek new members to join for a 3-year term. We are also open to new roles or ideas for things you think the Grad Council could do to encourage student involvement and interaction among researchers.</p> <p>If you are interested in joining, please email Shengpei Wang (<a href="mailto:swang74@syr.edu">swang74@syr.edu</a>) with the subject line &ldquo;ASN GC application&rdquo; and attach a single pdf document containing your CV and a short paragraph (less than 1 page) about what you hope to contribute and why you want to join the grad council.</p> <p>&nbsp;</p><p><strong>Kim Gilbert&nbsp;</strong>(GC rep 2014-2015):<br /> &quot;Serving on the ASN grad council is a fantastic opportunity to not only meet faculty, post-docs, and students from a wide range of universities, but to become more involved in a great community of researchers in ecology and evolution. You learn about how journal societies run, as well as the ins and outs of organizing conference events. You also serve as an important representative for all graduate student members of the ASN to ensure the society is doing its best to meet student&#39;s needs at conferences or through other opportunities.&quot;</p> <p><strong>Emily Weiss (</strong>GC rep 2013-2014):<br /> Serving on the Grad Council really was an incredibly enriching experience for me, and I hope that many other students will apply and get to have that experience too.</p> <p><strong>Rafael Maia&nbsp;</strong>(GC rep 2013-2014):<br /> &quot;I served the council for a couple years and strongly recommend it. Great society, exciting possibilities!&quot;</p> <p><strong>Courtney Fitzpatrick</strong>&nbsp;(founding GC rep):<br /> &quot;Grad students: excellent opportunity to get involved, meet collaborators/mentors, and learn about your scientific society!&quot;</p> Thu, 11 Jul 2019 05:00:00 GMT “False exclusion: A case to embed predator performance in classical population models” https://amnat.org/an/newpapers/Nov-Montagnes.html David J. S. Montagnes, Xuexia Zhu, Lei Gu, Yunfei Sun, Jun Wang, Rosie Horner, and Zhou Yang (Nov 2019) Read the Article (Just Accepted) Predator-prey dynamics are driven by insufficiently-explored predator behaviors that are inherently prey-dependent Ignorance is not bliss. Global health and, ultimately, our survival rely on strategic forward planning. Today, computer-driven simulations are the “crystal balls” by which we predict the future. But computers require valid instruction. If we “falsely exclude” – ignore – essential facts and concepts, then predictions will go disastrously wrong. Recently, through a UK-Chinese collaboration, researchers have re-evaluated and quantified three very basic, but essential, biological concepts: 1) when animals are fed less they are more likely to die; 2) an animal’s efficiency to use food changes with food availability (e.g., when food is abundant animals are wasteful); and 3) reproduction only occurs when there is sufficient quantities of food. Surprisingly, these “food-dependent” behaviors have been overlooked, or at least inadequately incorporated, in many models that predict population dynamics. The first step of this research produced a theoretical, mathematical framework that embraces these concepts. Then, essential experimental evidence, provided proof of concept. Only then could the experimental data and the computer model be used to reveal that including all three of these fundamental aspects of animal biology places into question our current evaluation of population dynamics. For instance, the revised approach predicts extinction when the old ones predicted survival. Now biologists can include these food-dependent behaviors, making more informed predictions of how predators respond in nature. Abstract We argue that predator-prey dynamics, a cornerstone of ecology, can be driven by insufficiently-explored aspects of predator performance that are inherently prey-dependent: i.e., these have been falsely excluded. Classical—Lotka-Volterra-based—models tend to only consider prey-dependent ingestion rate. We highlight three other prey-dependent responses and provide empirically-derived functions to describe them. These functions introduce neglected nonlinearities and threshold behaviors into dynamic models leading to unexpected outcomes: specifically, as prey abundance increases predators: 1) become less efficient at using prey; 2) initially allocate resources towards survival and then allocate resources towards reproduction; and 3) are less likely to die. Based on experiments using model-zooplankton, we explore consequences of including these functions in the classical structure and show they alter qualitative and quantitative dynamics of an empirically-informed, generic predator-prey model. Through bifurcation analysis, our revised structure predicts: 1) predator extinctions, where the classical structure allows persistence; 2) predator survival, where the classical structure drives predators towards extinction; and 3) greater stability through smaller amplitude of cycles, relative to the classical structure. Then, by exploring parameter space, we show how these responses alter predictions of predator-prey stability and competition between predators. Based on our results, we suggest that classical assumptions about predator responses to prey abundance should be re-evaluated. More forthcoming papers &raquo; <p>David J. S. Montagnes, Xuexia Zhu, Lei Gu, Yunfei Sun, Jun Wang, Rosie Horner, and Zhou Yang (Nov 2019) </p><p><i><a href="https://dx.doi.org/10.1086/705381">Read the Article</a></i> (Just Accepted)</p> <p><b>Predator-prey dynamics are driven by insufficiently-explored predator behaviors that are inherently prey-dependent </b></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>gnorance is not bliss. Global health and, ultimately, our survival rely on strategic forward planning. Today, computer-driven simulations are the “crystal balls” by which we predict the future. But computers require valid instruction. If we “falsely exclude” – ignore – essential facts and concepts, then predictions will go disastrously wrong. Recently, through a UK-Chinese collaboration, researchers have re-evaluated and quantified three very basic, but essential, biological concepts: 1) when animals are fed less they are more likely to die; 2) an animal’s efficiency to use food changes with food availability (e.g., when food is abundant animals are wasteful); and 3) reproduction only occurs when there is sufficient quantities of food. Surprisingly, these “food-dependent” behaviors have been overlooked, or at least inadequately incorporated, in many models that predict population dynamics. The first step of this research produced a theoretical, mathematical framework that embraces these concepts. Then, essential experimental evidence, provided proof of concept. Only then could the experimental data and the computer model be used to reveal that including all three of these fundamental aspects of animal biology places into question our current evaluation of population dynamics. For instance, the revised approach predicts extinction when the old ones predicted survival. Now biologists can include these food-dependent behaviors, making more informed predictions of how predators respond in nature. </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>e argue that predator-prey dynamics, a cornerstone of ecology, can be driven by insufficiently-explored aspects of predator performance that are inherently prey-dependent: i.e., these have been falsely excluded. Classical—Lotka-Volterra-based—models tend to only consider prey-dependent ingestion rate. We highlight three other prey-dependent responses and provide empirically-derived functions to describe them. These functions introduce neglected nonlinearities and threshold behaviors into dynamic models leading to unexpected outcomes: specifically, as prey abundance increases predators: 1) become less efficient at using prey; 2) initially allocate resources towards survival and then allocate resources towards reproduction; and 3) are less likely to die. Based on experiments using model-zooplankton, we explore consequences of including these functions in the classical structure and show they alter qualitative and quantitative dynamics of an empirically-informed, generic predator-prey model. Through bifurcation analysis, our revised structure predicts: 1) predator extinctions, where the classical structure allows persistence; 2) predator survival, where the classical structure drives predators towards extinction; and 3) greater stability through smaller amplitude of cycles, relative to the classical structure. Then, by exploring parameter space, we show how these responses alter predictions of predator-prey stability and competition between predators. Based on our results, we suggest that classical assumptions about predator responses to prey abundance should be re-evaluated. </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, 10 Jul 2019 05:00:00 GMT “A spatial perspective on the phenological distribution of the spring woodland caterpillar peak” https://amnat.org/an/newpapers/Nov-Shutt.html Jack D. Shutt, Malcolm D. Burgess, and Albert B. Phillimore (Nov 2019) Read the Article (Just Accepted)In temperate regions, warmer springs cause a whole suite of ecological events to occur earlier, from trees coming into leaf to birds breeding. A cause for concern is whether species higher up the food chain are able to shift their timings forward by as much as those species below them. In deciduous forests there is a peak in moth caterpillar abundance during the spring, coinciding with the new leaves on the trees. It is well known that many bird species, including tits and flycatchers, rely heavily upon this spring food peak to raise their nestlings. However, little is known about how this caterpillar peak varies among the particular deciduous tree species involved, or geographically (e.g. by elevation or latitude), or which caterpillar species are most important in creating this food peak and whether their identity varies from one location or tree species to another. Drs.&nbsp;Shutt, Burgess, and Phillimore set about answering these questions by collecting caterpillars from 40 woodlands spread over 220&nbsp;km in Scotland. They identified 62 different caterpillar species based on DNA; however, just three species made up over half of all caterpillars collected, with the most common species (the winter moth) representing a third of the total, showing the importance of key species in the food chain. However, different tree species had different overall numbers of caterpillars, with oak and willow having the most, making these tree species of more value to the birds in spring. In addition, the timing of the peak in caterpillars was considerably later at higher elevations but didn’t change across latitude and was similar across the different tree species within a given area. These results are important as they show that poor breeding timing for the birds cannot be buffered by having a variety of tree species present. Abstract A&nbsp;classic system for studying trophic mismatch focuses on the timing of the spring caterpillar peak in relation to the breeding time and productivity of woodland passerine birds. Most work has been conducted in single-site oak woodlands and little is known about how insights generalize to other woodland types or across space. Here we present the results of a three-year study on the species composition and temporal distribution of the spring caterpillar peak on different tree taxa across 40 woodland sites spanning two degrees of latitude in Scotland. We used molecular barcoding to identify 62 caterpillar species, with winter moth (Operophtera brumata) the most abundant, comprising a third of the sample. Oak (Quercus sp.) and willow (Salix sp.) hosted significantly higher caterpillar abundances than other tree taxa, with winter moth exhibiting similar trends and invariantly proportionate across tree taxa. Caterpillar peak phenology was broadly similar between tree taxa. While latitude had little effect, increasing elevation increased the height of the caterpillar peak and retarded timing by 3.7 days/100&nbsp;m. These findings extend our understanding of how mismatch may play out spatially, with caterpillar peak date varying with elevation, and tree taxa varying in the caterpillar resource that they host. More forthcoming papers &raquo; <p>Jack D. Shutt, Malcolm D. Burgess, and Albert B. Phillimore (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705241">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 temperate regions, warmer springs cause a whole suite of ecological events to occur earlier, from trees coming into leaf to birds breeding. A cause for concern is whether species higher up the food chain are able to shift their timings forward by as much as those species below them. In deciduous forests there is a peak in moth caterpillar abundance during the spring, coinciding with the new leaves on the trees. It is well known that many bird species, including tits and flycatchers, rely heavily upon this spring food peak to raise their nestlings. However, little is known about how this caterpillar peak varies among the particular deciduous tree species involved, or geographically (e.g. by elevation or latitude), or which caterpillar species are most important in creating this food peak and whether their identity varies from one location or tree species to another. Drs.&nbsp;Shutt, Burgess, and Phillimore set about answering these questions by collecting caterpillars from 40 woodlands spread over 220&nbsp;km in Scotland. They identified 62 different caterpillar species based on DNA; however, just three species made up over half of all caterpillars collected, with the most common species (the winter moth) representing a third of the total, showing the importance of key species in the food chain. However, different tree species had different overall numbers of caterpillars, with oak and willow having the most, making these tree species of more value to the birds in spring. In addition, the timing of the peak in caterpillars was considerably later at higher elevations but didn’t change across latitude and was similar across the different tree species within a given area. These results are important as they show that poor breeding timing for the birds cannot be buffered by having a variety of tree species present.</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;classic system for studying trophic mismatch focuses on the timing of the spring caterpillar peak in relation to the breeding time and productivity of woodland passerine birds. Most work has been conducted in single-site oak woodlands and little is known about how insights generalize to other woodland types or across space. Here we present the results of a three-year study on the species composition and temporal distribution of the spring caterpillar peak on different tree taxa across 40 woodland sites spanning two degrees of latitude in Scotland. We used molecular barcoding to identify 62 caterpillar species, with winter moth (<i>Operophtera brumata</i>) the most abundant, comprising a third of the sample. Oak (<i>Quercus</i> sp.) and willow (<i>Salix</i> sp.) hosted significantly higher caterpillar abundances than other tree taxa, with winter moth exhibiting similar trends and invariantly proportionate across tree taxa. Caterpillar peak phenology was broadly similar between tree taxa. While latitude had little effect, increasing elevation increased the height of the caterpillar peak and retarded timing by 3.7 days/100&nbsp;m. These findings extend our understanding of how mismatch may play out spatially, with caterpillar peak date varying with elevation, and tree taxa varying in the caterpillar resource that they host. </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, 10 Jul 2019 05:00:00 GMT “Information about predators varies across an Amazonian rainforest as a result of sentinel species distribution” https://amnat.org/an/newpapers/Nov-Camerlenghi.html Ettore Camerlenghi, Paola Tellaroli, Matteo Griggio, and Ari E. Mart&iacute;nez (Nov 2019) Read the Article The distribution of different alarm calling species drives the patchiness of predator information in a rainforest Predation risk is considered one of the main drivers of the formation of mixed-species flocks of birds, in which different species aggregate, forage and move together in the forest. In many cases, certain species are exceptionally vigilant against predators and emit alarm calls upon detecting ambush predators. These species are considered a key element in allowing other flocking species to exploit otherwise “risky habitats”. The presence of these “sentinel species” allows other species to navigate a forested version of a landscape of fear.In the Amazon lowland rainforests of southeastern Peru, two different sentinel bird species occupy different types of habitats across tierra firme forest without overlapping. The Bluish-slate Antshrike specializes in patches of early successional stage, such as those gaps created by fallen trees. The Dusky-throated Antshrike occupies undisturbed areas of primary forest. Camerlenghi and colleagues showed that other flocking bird species (which can associate with either of these sentinel species) perceive the alarm calls given by the Bluish-slate as more reliable than those emitted by the Dusky-throated and react accordingly. Thus, not only do forest habitats inhabited by flocks differ structurally, but they may also differ in the quality of predator information provided by alarm calling species that inhabit them, with potential effects for the long-term survival of flock mates. Abstract Information about predation risk is of fundamental value in biological communities. As many prey species have shared predators, eavesdropping on other species’ alarms is a widely recognized mechanism underlying the formation of mixed-species groups. However, information transfer may vary both across and within groups because some species provide higher quality information about predators than others. We tested this phenomenon in Amazonian understory mixed-species flocks of birds in which two sentinel species, the Bluish-slate Antshrike (Thamnomanes schistogynus) and the Dusky-throated Antshrike (Thamnomanes ardesiacus) occupy different habitats and provide alarm calls that are used by eavesdropping flock mates. In a playback experiment, both associate species responded significantly more strongly to alarm calls from the same sentinel species, reflecting the greater reliability of information about predator threats that could affect survival and habitat choice. Our work provides evidence of a repeated asymmetry across space in the available information about threats. More forthcoming papers &raquo; <p>Ettore Camerlenghi, Paola Tellaroli, Matteo Griggio, and Ari E. Mart&iacute;nez (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705242">Read the Article</a></i></p> <p><b>The distribution of different alarm calling species drives the patchiness of predator information in a rainforest </b></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;">P</span>redation risk is considered one of the main drivers of the formation of mixed-species flocks of birds, in which different species aggregate, forage and move together in the forest. In many cases, certain species are exceptionally vigilant against predators and emit alarm calls upon detecting ambush predators. These species are considered a key element in allowing other flocking species to exploit otherwise &ldquo;risky habitats&rdquo;. The presence of these &ldquo;sentinel species&rdquo; allows other species to navigate a forested version of a landscape of fear.</p><p>In the Amazon lowland rainforests of southeastern Peru, two different sentinel bird species occupy different types of habitats across tierra firme forest without overlapping. The Bluish-slate Antshrike specializes in patches of early successional stage, such as those gaps created by fallen trees. The Dusky-throated Antshrike occupies undisturbed areas of primary forest. Camerlenghi and colleagues showed that other flocking bird species (which can associate with either of these sentinel species) perceive the alarm calls given by the Bluish-slate as more reliable than those emitted by the Dusky-throated and react accordingly. Thus, not only do forest habitats inhabited by flocks differ structurally, but they may also differ in the quality of predator information provided by alarm calling species that inhabit them, with potential effects for the long-term survival of flock mates.</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>nformation about predation risk is of fundamental value in biological communities. As many prey species have shared predators, eavesdropping on other species’ alarms is a widely recognized mechanism underlying the formation of mixed-species groups. However, information transfer may vary both across and within groups because some species provide higher quality information about predators than others. We tested this phenomenon in Amazonian understory mixed-species flocks of birds in which two sentinel species, the Bluish-slate Antshrike (<i>Thamnomanes schistogynus</i>) and the Dusky-throated Antshrike (<i>Thamnomanes ardesiacus</i>) occupy different habitats and provide alarm calls that are used by eavesdropping flock mates. In a playback experiment, both associate species responded significantly more strongly to alarm calls from the same sentinel species, reflecting the greater reliability of information about predator threats that could affect survival and habitat choice. Our work provides evidence of a repeated asymmetry across space in the available information about threats. </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, 10 Jul 2019 05:00:00 GMT “Understanding maladaptation by uniting ecological and evolutionary perspectives” https://amnat.org/an/newpapers/Oct-Brady-A.html Read the Article (Just Accepted) Abstract Evolutionary biologists have long trained their sights on adaptation, focusing on the power of natural selection to produce relative fitness advantages, while often ignoring changes in absolute fitness. Ecologists generally have taken a different tack, focusing on changes in abundance and ranges that reflect absolute fitness, while often ignoring relative fitness. We articulate the various causes of both forms of maladaptation and review numerous examples of their occurrence. This review indicates that maladaptation is reasonably common from both perspectives, yet often in contrasting ways. That is, maladaptation can appear strong from a relative fitness perspective and yet populations can be growing in abundance. Conversely, resident individuals can appear locally adapted (relative to non-resident individuals), and yet be declining in abundance. Understanding and interpreting these disconnects between relative and absolute maladaptation, as well as the cases of agreement, is increasingly critical in the face of accelerating human-mediated environmental change. We therefore present a framework for studying maladaptation, focusing in particular on the relationship between absolute and relative fitness, thereby drawing together evolutionary and ecological perspectives. The unification of these ecological and evolutionary perspectives has the potential to bring together previously disjunct research areas while addressing key conceptual issues and specific practical problems. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/705020">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 trained their sights on adaptation, focusing on the power of natural selection to produce relative fitness advantages, while often ignoring changes in absolute fitness. Ecologists generally have taken a different tack, focusing on changes in abundance and ranges that reflect absolute fitness, while often ignoring relative fitness. We articulate the various causes of both forms of maladaptation and review numerous examples of their occurrence. This review indicates that maladaptation is reasonably common from both perspectives, yet often in contrasting ways. That is, maladaptation can appear strong from a relative fitness perspective and yet populations can be growing in abundance. Conversely, resident individuals can appear locally adapted (relative to non-resident individuals), and yet be declining in abundance. Understanding and interpreting these disconnects between relative and absolute maladaptation, as well as the cases of agreement, is increasingly critical in the face of accelerating human-mediated environmental change. We therefore present a framework for studying maladaptation, focusing in particular on the relationship between absolute and relative fitness, thereby drawing together evolutionary and ecological perspectives. The unification of these ecological and evolutionary perspectives has the potential to bring together previously disjunct research areas while addressing key conceptual issues and specific practical problems. </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, 27 Jun 2019 05:00:00 GMT