ASN RSS https://amnat.org/ Latest press releases and announcements from the ASN en-us Fri, 18 Sep 2020 05:00:00 GMT 60 “Did mammals bring the first mistletoes into the tree-tops?” https://amnat.org/an/newpapers/Dec-Watson-A.html David M. Watson (Dec 2020) Mistletoes are the quintessential bird-dispersed plants, but ancient mammals may have first brought them to the treetops Read the Article (Just Accepted) Abstract As the only woody parasitic plants that infect host canopies, the growth habit of mistletoes represents a key innovation. How this aerially-parasitic habit originated is unknown—mistletoe macrofossils are relatively recent, from long after they adapted to canopy life and evolved showy bird-pollinated flowers, sticky bird-dispersed seeds and woody haustoria diverting water and nutrients from host branches. Since the transition to aerial parasitism predates the origin of their contemporary avian seed dispersers by 20–30 million years, this begs the question—who were the original mistletoe dispersers? By integrating fully resolved phylogenies of mistletoes and aligning the timing of historic events, I identify two ancient mammals as likely candidates for ‘planting’ the Viscaceae and Loranthaceae in the canopy. Just as modern mouse lemurs and galagos disperse Viscaceous mistletoe externally (grooming the sticky seeds from their fur), Cretaceous primates (such as Purgatorius) may have transported seeds of root-parasitic understory shrubs up into the canopy of Laurasian forests. In the Eocene, ancestors of the today’s mistletoe-dispersing marsupials Dromiciops likely fed on the nutritious fruit of root-parasitic Loranthaceous shrubs, depositing them atop western Gondwanan forest crowns. Having colonized the canopy, subsequent mistletoe evolution and diversification coincided with the rise of nectar and fruit-dependent birds. More forthcoming papers &raquo; <p>David M. Watson (Dec 2020) </p> <p><b>Mistletoes are the quintessential bird-dispersed plants, but ancient mammals may have first brought them to the treetops </b></p> <p><i><a href="https://dx.doi.org/10.1086/711396">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;">A</span>s the only woody parasitic plants that infect host canopies, the growth habit of mistletoes represents a key innovation. How this aerially-parasitic habit originated is unknown—mistletoe macrofossils are relatively recent, from long after they adapted to canopy life and evolved showy bird-pollinated flowers, sticky bird-dispersed seeds and woody haustoria diverting water and nutrients from host branches. Since the transition to aerial parasitism predates the origin of their contemporary avian seed dispersers by 20–30 million years, this begs the question—who were the original mistletoe dispersers? By integrating fully resolved phylogenies of mistletoes and aligning the timing of historic events, I identify two ancient mammals as likely candidates for ‘planting’ the Viscaceae and Loranthaceae in the canopy. Just as modern mouse lemurs and galagos disperse Viscaceous mistletoe externally (grooming the sticky seeds from their fur), Cretaceous primates (such as <i>Purgatorius</i>) may have transported seeds of root-parasitic understory shrubs up into the canopy of Laurasian forests. In the Eocene, ancestors of the today’s mistletoe-dispersing marsupials <i>Dromiciops</i> likely fed on the nutritious fruit of root-parasitic Loranthaceous shrubs, depositing them atop western Gondwanan forest crowns. Having colonized the canopy, subsequent mistletoe evolution and diversification coincided with the rise of nectar and fruit-dependent birds. </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> Fri, 18 Sep 2020 05:00:00 GMT “Daily nest predation rates decrease with body size in passerine birds” https://amnat.org/an/newpapers/Dec-Unzeta-A.html Mar Unzeta, Thomas E. Martin, and Daniel Sol (Dec 2020) Lower daily nest predation in larger passerine birds reduces total predation compensating their extended development Read the Article (Just Accepted) Abstract Body size evolution is generally framed by the benefits of being large, while costs are largely overlooked. An important putative cost of being large is the need to extend development periods, which should increase exposure to predation and potentially select against larger size. In birds, this selection pressure can be important because predation is the main source of offspring mortality and predators should more readily detect the larger nests associated with larger body sizes. Here, we show for diverse passerine birds across the world that, counter to expectations, larger species suffer lower daily nest predation rates than smaller species. This pattern is consistent despite latitudinal variation in predation and does not seem to reflect a tendency of larger species to use more protected nests or less exposed nest locations. Evidence instead suggests that larger species attack a wider array of predator sizes, which could reduce predation rates at nests of large-bodied species. Regardless of the mechanism, the lower daily nest predation rates of larger species yield slightly lower predation rates over the entire development period compared to smaller species. These results highlight the importance of behavior as a mechanism to alter selection pressures, and have implications for body size evolution. More forthcoming papers &raquo; <p>Mar Unzeta, Thomas E. Martin, and Daniel Sol (Dec 2020) </p> <p><b>Lower daily nest predation in larger passerine birds reduces total predation compensating their extended development </b></p> <p><i><a href="https://dx.doi.org/10.1086/711413">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;">B</span>ody size evolution is generally framed by the benefits of being large, while costs are largely overlooked. An important putative cost of being large is the need to extend development periods, which should increase exposure to predation and potentially select against larger size. In birds, this selection pressure can be important because predation is the main source of offspring mortality and predators should more readily detect the larger nests associated with larger body sizes. Here, we show for diverse passerine birds across the world that, counter to expectations, larger species suffer lower daily nest predation rates than smaller species. This pattern is consistent despite latitudinal variation in predation and does not seem to reflect a tendency of larger species to use more protected nests or less exposed nest locations. Evidence instead suggests that larger species attack a wider array of predator sizes, which could reduce predation rates at nests of large-bodied species. Regardless of the mechanism, the lower daily nest predation rates of larger species yield slightly lower predation rates over the entire development period compared to smaller species. These results highlight the importance of behavior as a mechanism to alter selection pressures, and have implications for body size evolution. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 18 Sep 2020 05:00:00 GMT “Evolved phenological cueing strategies show variable responses to climate change” https://amnat.org/an/newpapers/Jan-Edwards.html Collin B. Edwards and Louie H. Yang (Jan 2021) A model simulating the evolution of phenological cueing strategies with climate data shows variable phenological shifts Read the Article (Just Accepted) As the climate changes, plants and animals are shifting the timing of their activities (“phenology”): many butterflies are now active earlier in the spring, for example, and many plants now flower weeks earlier than they used to. However, these changes are not always consistent: different species may shift their phenology very differently. In a study appearing in The&nbsp;American Naturalist, Dr. Collin Edwards (graduate student at Cornell University, now a postdoctoral researcher at Tufts University) and Dr. Louie Yang (associate professor at University of California, Davis) demonstrate how the evolution of cue use could produce these variable responses to climate change. They present a simulation study in which organisms can evolve to start their life activity (e.g. a plant can germinate or an insect can emerge) based on a combination of three environmental cues – the local temperature, the local precipitation, and the day of the year (photoperiod). By simulating populations of these organisms using real climate data from 78 locations across North America and Hawaii, the authors demonstrate two mechanisms that could lead to the variability seen in real species. First, they found that simulated species evolved to respond to different environmental cues in the different climates across North America, and the best strategy depended on how reliably different combinations of cues predicted favorable weather in the future. For example, simulated populations in Farmington, Maine generally relied on precipitation as a cue, while simulation populations in Davis, California did not. Surprisingly, they also find that for any given climate, there are often multiple strategies that are equally viable but rely on very different cues. For example, some populations simulated in the Davis climate relied almost entirely on temperature as a cue, while others relied almost entirely on day of year. When populations differed in strategy – either because they evolved in different climates or because they evolved different strategies in the same climate – they responded differently to simulated climate change, just as real species are responding differently. This study reveals a novel mechanism driving the evolution of phenological strategies, and suggests that as the climate continues to change, we should expect to see increasing variation between species in the timing of activities like germination, hatching, flowering, and mating. Abstract Several studies have documented a global pattern of phenological advancement that is consistent with ongoing climate change. However, the magnitude of these phenological shifts is highly variable across taxa and locations. This variability of phenological responses has been difficult to explain mechanistically. To examine how the evolution of multi-trait cueing strategies could produce variable responses to climate change, we constructed a model in which organisms evolve strategies that integrate multiple environmental cues to inform anticipatory phenological decisions. We simulated the evolution of phenological cueing strategies in multiple environments, using historic climate data from 78 locations in North America and Hawaii to capture features of climatic correlation structures in the real world. Organisms in our model evolved diverse strategies that were spatially autocorrelated across locations on a continental scale, showing that similar strategies tend to evolve in similar climates. Within locations, organisms often evolved a wide range of strategies that showed similar response phenotypes and fitness outcomes under historical conditions. However, these strategies responded differently to novel climatic conditions, with variable fitness consequences. Our model shows how the evolution of phenological cueing strategies can explain observed variation in phenological shifts and unexpected responses to climate change. More forthcoming papers &raquo; <p>Collin B. Edwards and Louie H. Yang (Jan 2021) </p> <p><b>A model simulating the evolution of phenological cueing strategies with climate data shows variable phenological shifts </b></p> <p><i><a href="https://dx.doi.org/10.1086/711650">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>s the climate changes, plants and animals are shifting the timing of their activities (“phenology”): many butterflies are now active earlier in the spring, for example, and many plants now flower weeks earlier than they used to. However, these changes are not always consistent: different species may shift their phenology very differently. In a study appearing in <i>The&nbsp;American Naturalist</i>, Dr. Collin Edwards (graduate student at Cornell University, now a postdoctoral researcher at Tufts University) and Dr. Louie Yang (associate professor at University of California, Davis) demonstrate how the evolution of cue use could produce these variable responses to climate change. They present a simulation study in which organisms can evolve to start their life activity (e.g. a plant can germinate or an insect can emerge) based on a combination of three environmental cues – the local temperature, the local precipitation, and the day of the year (photoperiod). By simulating populations of these organisms using real climate data from 78 locations across North America and Hawaii, the authors demonstrate two mechanisms that could lead to the variability seen in real species. First, they found that simulated species evolved to respond to different environmental cues in the different climates across North America, and the best strategy depended on how reliably different combinations of cues predicted favorable weather in the future. For example, simulated populations in Farmington, Maine generally relied on precipitation as a cue, while simulation populations in Davis, California did not. Surprisingly, they also find that for any given climate, there are often multiple strategies that are equally viable but rely on very different cues. For example, some populations simulated in the Davis climate relied almost entirely on temperature as a cue, while others relied almost entirely on day of year. When populations differed in strategy – either because they evolved in different climates or because they evolved different strategies in the same climate – they responded differently to simulated climate change, just as real species are responding differently. This study reveals a novel mechanism driving the evolution of phenological strategies, and suggests that as the climate continues to change, we should expect to see increasing variation between species in the timing of activities like germination, hatching, flowering, and mating. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>everal studies have documented a global pattern of phenological advancement that is consistent with ongoing climate change. However, the magnitude of these phenological shifts is highly variable across taxa and locations. This variability of phenological responses has been difficult to explain mechanistically. To examine how the evolution of multi-trait cueing strategies could produce variable responses to climate change, we constructed a model in which organisms evolve strategies that integrate multiple environmental cues to inform anticipatory phenological decisions. We simulated the evolution of phenological cueing strategies in multiple environments, using historic climate data from 78 locations in North America and Hawaii to capture features of climatic correlation structures in the real world. Organisms in our model evolved diverse strategies that were spatially autocorrelated across locations on a continental scale, showing that similar strategies tend to evolve in similar climates. Within locations, organisms often evolved a wide range of strategies that showed similar response phenotypes and fitness outcomes under historical conditions. However, these strategies responded differently to novel climatic conditions, with variable fitness consequences. Our model shows how the evolution of phenological cueing strategies can explain observed variation in phenological shifts and unexpected responses to climate change. </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> Fri, 18 Sep 2020 05:00:00 GMT “Simultaneous wing molt as a catalyst for the evolution of flightlessness in birds” https://amnat.org/an/newpapers/Dec-Terrill.html Ryan S. Terrill (Dec 2020) Why do some birds lose flight more readily than others? This research finds a link with rare form of wing feather molt Read the Article (Just Accepted) Even the most complex and essential traits of animals can be lost under the right conditions. Eyesight, limbs, and flight have been lost repeatedly when the benefit no longer outweighs the cost of maintaining such capabilities. Yet some groups of animals seem to lose traits more readily than others. Why does trait loss differ among groups of animals even under seemingly identical ecological conditions? The answer may lie in features that predispose animals to lose such traits. We’ve long known that certain habitats favor the loss of flight in birds. Flight is intertwined with birds’ lives, but many species of birds have lost flight, especially on islands and in aquatic environments. Even though loss of flight has evolved many times in birds, it seems to happen more often in some groups of birds than others, especially ducks, geese, grebes, and rails. This study builds off an observation that these birds all share a common feather replacement (molt) strategy that involves simultaneous loss of all flight feathers, resulting in a temporary flightless period. This temporary flightless period may force these birds to forage and escape predators without flying, thereby predisposing them to permanent flightlessness when conditions favor. If simultaneous wing molt does indeed predispose birds to loss of flight, then we should expect elevated rates in loss of flight in birds with this wing molt strategy. This study finds consistent support for this prediction across many possible evolutionary trees of birds. These results illustrate how some traits may preclude or catalyze the loss of other traits, as well as how molt strategies in birds may have long-term and profound consequences on their evolutionary trajectories. Abstract Complex features such as vision, limbs, and flight have been lost by many groups of animals. Some groups of birds are more prone to loss of flight than others, but few studies have investigated possible reasons for this variation. I tested the hypothesis that a rare strategy of flight feather replacement is involved in rate variation in the evolution of flightlessness in birds. This strategy involves a simultaneous molt of the flight feathers of the wing, resulting in a temporary flightless condition during molt. I hypothesized that adaptations for this flightless period may serve as preadaptations for permanent flightlessness under conditions that favor permanent loss of flight. I found an elevated rate of loss of flight in lineages with simultaneous wing molt, when compared to loss of flight in lineages without simultaneous wing molt. This may indicate that birds with simultaneous molt are more prepared to adjust quickly to open niches that do not require flight, such as terrestrial niches on island habitats. These results illustrate how molt strategies can influence the long-term evolutionary trajectories of birds, and provides insight into how phenotypic precursors may act as a mechanism of rate variation in the loss of complex traits. More forthcoming papers &raquo; <p>Ryan S. Terrill (Dec 2020) </p> <p><b>Why do some birds lose flight more readily than others? This research finds a link with rare form of wing feather molt </b></p> <p><i><a href="https://dx.doi.org/10.1086/711416">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>ven the most complex and essential traits of animals can be lost under the right conditions. Eyesight, limbs, and flight have been lost repeatedly when the benefit no longer outweighs the cost of maintaining such capabilities. Yet some groups of animals seem to lose traits more readily than others. Why does trait loss differ among groups of animals even under seemingly identical ecological conditions? The answer may lie in features that predispose animals to lose such traits. </p><p>We’ve long known that certain habitats favor the loss of flight in birds. Flight is intertwined with birds’ lives, but many species of birds have lost flight, especially on islands and in aquatic environments. Even though loss of flight has evolved many times in birds, it seems to happen more often in some groups of birds than others, especially ducks, geese, grebes, and rails. This study builds off an observation that these birds all share a common feather replacement (molt) strategy that involves simultaneous loss of all flight feathers, resulting in a temporary flightless period. This temporary flightless period may force these birds to forage and escape predators without flying, thereby predisposing them to permanent flightlessness when conditions favor. If simultaneous wing molt does indeed predispose birds to loss of flight, then we should expect elevated rates in loss of flight in birds with this wing molt strategy. This study finds consistent support for this prediction across many possible evolutionary trees of birds. These results illustrate how some traits may preclude or catalyze the loss of other traits, as well as how molt strategies in birds may have long-term and profound consequences on their evolutionary trajectories. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>omplex features such as vision, limbs, and flight have been lost by many groups of animals. Some groups of birds are more prone to loss of flight than others, but few studies have investigated possible reasons for this variation. I tested the hypothesis that a rare strategy of flight feather replacement is involved in rate variation in the evolution of flightlessness in birds. This strategy involves a simultaneous molt of the flight feathers of the wing, resulting in a temporary flightless condition during molt. I hypothesized that adaptations for this flightless period may serve as preadaptations for permanent flightlessness under conditions that favor permanent loss of flight. I found an elevated rate of loss of flight in lineages with simultaneous wing molt, when compared to loss of flight in lineages without simultaneous wing molt. This may indicate that birds with simultaneous molt are more prepared to adjust quickly to open niches that do not require flight, such as terrestrial niches on island habitats. These results illustrate how molt strategies can influence the long-term evolutionary trajectories of birds, and provides insight into how phenotypic precursors may act as a mechanism of rate variation in the loss of complex traits. </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> Fri, 04 Sep 2020 05:00:00 GMT “Fluctuating dynamics of mate availability promote the evolution of flexible choosiness in both sexes” https://amnat.org/an/newpapers/Dec-Chevalier.html Louise Chevalier, Jacques Labonne, Matthias Galipaud, and François-Xavier Dechaume-Moncharmont (Dec 2020) Fluctuations in the mating market trigger the evolution of flexible and quality-dependent choosiness in males as in females Read the Article (Just Accepted) Observations of reproductive behaviors in sexually reproducing organisms indicate that many species can be “choosy”: they tend to be selective for their partners quality. Mate choice has costs and potential benefits that are likely to vary depending on individual characteristics (e.g. sex, quality), and on social context (number of potential partners). Classically, scientific literature predicts that the limiting sex (in term of gametes) – females – should be choosy, whereas the common sex – males – less so or not at all, or in very peculiar situations. Indeed, as a result of anisogamy (unbalance between gametes number and/or size between sexes), female’s reproductive rate is lower than males, making ready to mate males more numerous than ready to mate females and thus generating stronger mating competition among males. But who is really ready to mate, with which partner with regard to quality, and for how long? This is what can be described as the mating market, and it is everything but stable. Who can afford to be choosy in these conditions: males, females , or both? Individuals of high and low quality alike? The authors of this new study assumed that all these individual choices affect the dynamics of pairings constantly, and allowed all individuals, whatever their quality or sex, to permanently readjust their choosiness, based on the balance between costs and benefits. As a result, they predict that choosiness should indeed evolve in many situations, even in the face of seemingly unfavorable situations: for instance, they show that some of the males could be choosy even when females are rare, and that the best choosiness strategy should be flexible. In a nutshell, using a single unified approach – a dynamic game theory model – they endeavored to provide a better picture of all the variation in choosiness than can be observed in natural populations, in a wide span of mating systems. Abstract The evolution of choosiness has a strong effect on sexual selection, as it promotes variance in mating success among individuals. The context in which choosiness is expressed, and therefore the associated gain and cost, is highly variable. An overlooked mechanism by current models is the rapid fluctuations in the availability and quality of partners, which generates a dynamic mating market, to which each individual must optimally respond. We argue that the rapid fluctuations of the mating market are central to the evolution of optimal choosiness. Using a dynamic game approach, we investigate this hypothesis for various mating systems (characterized by different adult sex ratio and latency period combinations), allowing feedback between the choosiness and partner availability throughout a breeding season, while taking into account the fine variation in individual quality. Our results indicate that, quality dependent and flexible choosiness evolve usually in both sexes for various mating systems, and that a significant amount of variance in choosiness is observed, especially in males, even when courtship is costly. Accounting for the fluctuating dynamics of the mating market, therefore, allows envisioning a much wider range of choosiness variation in natural populations and may explain a number of recent empirical results regarding choosiness in the less common sex or its variance within sexes. More forthcoming papers &raquo; <p>Louise Chevalier, Jacques Labonne, Matthias Galipaud, and François-Xavier Dechaume-Moncharmont (Dec 2020) </p> <p><b>Fluctuations in the mating market trigger the evolution of flexible and quality-dependent choosiness in males as in females </b></p> <p><i><a href="https://dx.doi.org/10.1086/711417">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">O</span>bservations of reproductive behaviors in sexually reproducing organisms indicate that many species can be “choosy”: they tend to be selective for their partners quality. Mate choice has costs and potential benefits that are likely to vary depending on individual characteristics (e.g. sex, quality), and on social context (number of potential partners). </p><p>Classically, scientific literature predicts that the limiting sex (in term of gametes) – females – should be choosy, whereas the common sex – males – less so or not at all, or in very peculiar situations. Indeed, as a result of anisogamy (unbalance between gametes number and/or size between sexes), female’s reproductive rate is lower than males, making ready to mate males more numerous than ready to mate females and thus generating stronger mating competition among males. But who is really ready to mate, with which partner with regard to quality, and for how long? This is what can be described as the mating market, and it is everything but stable. Who can afford to be choosy in these conditions: males, females , or both? Individuals of high and low quality alike? </p><p>The authors of this new study assumed that all these individual choices affect the dynamics of pairings constantly, and allowed all individuals, whatever their quality or sex, to permanently readjust their choosiness, based on the balance between costs and benefits. As a result, they predict that choosiness should indeed evolve in many situations, even in the face of seemingly unfavorable situations: for instance, they show that some of the males could be choosy even when females are rare, and that the best choosiness strategy should be flexible. </p><p>In a nutshell, using a single unified approach – a dynamic game theory model – they endeavored to provide a better picture of all the variation in choosiness than can be observed in natural populations, in a wide span of mating systems. </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 evolution of choosiness has a strong effect on sexual selection, as it promotes variance in mating success among individuals. The context in which choosiness is expressed, and therefore the associated gain and cost, is highly variable. An overlooked mechanism by current models is the rapid fluctuations in the availability and quality of partners, which generates a dynamic mating market, to which each individual must optimally respond. We argue that the rapid fluctuations of the mating market are central to the evolution of optimal choosiness. Using a dynamic game approach, we investigate this hypothesis for various mating systems (characterized by different adult sex ratio and latency period combinations), allowing feedback between the choosiness and partner availability throughout a breeding season, while taking into account the fine variation in individual quality. Our results indicate that, quality dependent and flexible choosiness evolve usually in both sexes for various mating systems, and that a significant amount of variance in choosiness is observed, especially in males, even when courtship is costly. Accounting for the fluctuating dynamics of the mating market, therefore, allows envisioning a much wider range of choosiness variation in natural populations and may explain a number of recent empirical results regarding choosiness in the less common sex or its variance within sexes. </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> Fri, 04 Sep 2020 05:00:00 GMT “Australian rodents reveal conserved Cranial Evolutionary Allometry across 10 million years of murid evolution” https://amnat.org/an/newpapers/Dec-Marcy.html Ariel E. Marcy, Thomas Guillerme, Emma Sherratt, Kevin C. Rowe, Matthew J. Phillips, and Vera Weisbecker (Dec 2020) A size-shape pattern going back ~10 million years in Aus rodents: give me the mouse size, I’ll give you the skull shape! Read the Article (Just Accepted) Rodents (mice and rats) are the only land-based placental mammals in Australia, which could have given them an opportunity to evolve unique body shapes compared to relatives on other continents. To investigate this, Dr. Ariel E. Marcy and colleagues 3D-scanned skulls for 38 species with a range of diets, habitats, and body sizes (6 grams to 1 kilogram). Despite their ecological diversity, Australian rodents all scaled their skull shapes along the same size-shape gradient. In other words, the shape of any skull in the study can be closely predicted by the rodent’s body size. This is also true for invasive species, like the house mouse, which has been separated from native rodents by over 10 million years of evolution. As Australian rodents scale along their size-shape gradient, they follow a newly proposed shape pattern rule for mammals: larger “rat-like” species have longer snouts and smaller braincases compared to smaller “mouse-like” species. The authors suggest that Australian rodents follow this rule (called CREA) to keep the skull proportions they need for gnawing. If this is the case, then stabilizing selection on this adaptation likely limits the diversity of skull shapes in rodents in Australia and elsewhere in the world. This strict size-shape gradient makes rodents an ideal case to explore what causes the “CREA” shape pattern and how these causes compare to other groups of mammals with greater shape diversity. Australian rodents could help us approach one of the oldest evolutionary questions: why are some animal groups more diverse than others? Abstract Among vertebrates, placental mammals are particularly variable in the covariance between cranial shape and body size (allometry), with rodents a major exception. Australian murid rodents allow an assessment of the cause of this anomaly because they radiated on an ecologically diverse continent notably lacking other terrestrial placentals. Here we use 3D geometric morphometrics to quantify species-level and evolutionary allometries in 38 species (317 crania) from all Australian murid genera. We ask if ecological opportunity resulted in greater allometric diversity compared to other rodents, or if conserved allometry suggests intrinsic constraints and/or stabilizing selection. We also assess whether cranial shape variation follows the proposed “rule of craniofacial evolutionary allometry” (CREA), whereby larger species have relatively longer snouts and smaller braincases. To ensure we could differentiate parallel versus non-parallel species-level allometric slopes, we compared the slopes of rarefied samples across all clades. We found exceedingly conserved allometry and CREA-like patterns across the 10 million year split between Mus and Australian murids. This could support both intrinsic constraints and stabilizing selection hypotheses for conserved allometry. Large-bodied frugivores evolved faster than other species along the allometric trajectory, which could suggest stabilizing selection on the shape of the masticatory apparatus as body size changes. More forthcoming papers &raquo; <p>Ariel E. Marcy, Thomas Guillerme, Emma Sherratt, Kevin C. Rowe, Matthew J. Phillips, and Vera Weisbecker (Dec 2020) </p> <p><b>A size-shape pattern going back ~10 million years in Aus rodents: give me the mouse size, I’ll give you the skull shape! </b></p> <p><i><a href="https://dx.doi.org/10.1086/711398">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;">R</span>odents (mice and rats) are the only land-based placental mammals in Australia, which could have given them an opportunity to evolve unique body shapes compared to relatives on other continents. To investigate this, Dr. Ariel E. Marcy and colleagues 3D-scanned skulls for 38 species with a range of diets, habitats, and body sizes (6 grams to 1 kilogram). Despite their ecological diversity, Australian rodents all scaled their skull shapes along the same size-shape gradient. In other words, the shape of any skull in the study can be closely predicted by the rodent’s body size. This is also true for invasive species, like the house mouse, which has been separated from native rodents by over 10 million years of evolution. </p><p>As Australian rodents scale along their size-shape gradient, they follow a newly proposed shape pattern rule for mammals: larger “rat-like” species have longer snouts and smaller braincases compared to smaller “mouse-like” species. The authors suggest that Australian rodents follow this rule (called CREA) to keep the skull proportions they need for gnawing. If this is the case, then stabilizing selection on this adaptation likely limits the diversity of skull shapes in rodents in Australia and elsewhere in the world. This strict size-shape gradient makes rodents an ideal case to explore what causes the “CREA” shape pattern and how these causes compare to other groups of mammals with greater shape diversity. Australian rodents could help us approach one of the oldest evolutionary questions: why are some animal groups more diverse than others? </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>mong vertebrates, placental mammals are particularly variable in the covariance between cranial shape and body size (allometry), with rodents a major exception. Australian murid rodents allow an assessment of the cause of this anomaly because they radiated on an ecologically diverse continent notably lacking other terrestrial placentals. Here we use 3D geometric morphometrics to quantify species-level and evolutionary allometries in 38 species (317 crania) from all Australian murid genera. We ask if ecological opportunity resulted in greater allometric diversity compared to other rodents, or if conserved allometry suggests intrinsic constraints and/or stabilizing selection. We also assess whether cranial shape variation follows the proposed “rule of craniofacial evolutionary allometry” (CREA), whereby larger species have relatively longer snouts and smaller braincases. To ensure we could differentiate parallel versus non-parallel species-level allometric slopes, we compared the slopes of rarefied samples across all clades. We found exceedingly conserved allometry and CREA-like patterns across the 10 million year split between <i>Mus</i> and Australian murids. This could support both intrinsic constraints and stabilizing selection hypotheses for conserved allometry. Large-bodied frugivores evolved faster than other species along the allometric trajectory, which could suggest stabilizing selection on the shape of the masticatory apparatus as body size changes. </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, 02 Sep 2020 05:00:00 GMT “The enemy within: how does a bacterium inhibit the foraging aptitude and risk management behavior of Allenby’s gerbils?” https://amnat.org/an/newpapers/Dec-Makin.html Douglas F. Makin, Burt P. Kotler, Joel S. Brown, Mario Garrido, and Jorge F. S. Menezes (Dec 2020) The behaviorally mediated indirect effects that endoparasites have on their host may be as large as the direct effects Read the Article (Just Accepted) Allenby’s gerbils are commonly infected with the Mycoplasma haemomuris-like bacteria which has been demonstrated empirically to carry relatively low direct physiological costs (i.e. mild nutrient deficiencies). However, are there indirect ecological consequences of infection that affect the ability of gerbils to forage optimally and manage predation risk within their environment? We tested two alternatives: 1) does a nutrient deficiency lead to infected gerbils increasing their foraging effort and taking more risks while foraging to make up for any energetic shortfalls? 2) Alternatively, does infection lead to lethargy, whereby sick gerbils are compromised in their ability to harvest food efficiently and avoid predators? To address these questions, we compared the risk management strategies and foraging behavior of infected and non-infected gerbils. Infected gerbils were compared at two levels, those acutely infected (i.e. peak infection loads) and those with chronic infections (i.e. low infection loads). Our findings indicated that infected gerbils incurred dramatically higher foraging costs, including less efficient foraging, diminished effectiveness of vigilance and increased predation rates. Surprisingly, chronically infected gerbils experienced higher ecological costs than acutely infected gerbils. This suggests that the debilitating effects of infection occur gradually, with a progressive decline in the quality of time allocated to activities. Overall, our findings highlight how small direct physiological costs can give rise to large indirect ecological costs. Moreover, similar to predators which have both direct lethal effects and indirect effects on prey (i.e. perceived predation risk), endoparasites affect hosts not only by killing them (direct costs), but also through altering their interactions with predators, resources and landscape features (i.e. indirect costs). Abstract Microbes inhabiting multi-cellular organisms have complex, often subtle effects on their hosts. Gerbillus andersoni allenbyi are commonly infected with the Mycoplasma haemomuris-like bacteria, which may cause mild nutrient (choline, arginine) deficiencies. However, are there more serious ecological consequences of infection such as effects on foraging aptitudes and risk management? We tested alternatives: 1) nutrient compensation hypothesis, does nutrient deficiency induce infected gerbils to make up for the shortfall by foraging more and taking greater risks? or 2) lethargy hypothesis, do sick gerbils forage less, and are they compromised in their ability to detect predators or risky microhabitats? We compared the foraging and risk management behavior of infected and non-infected gerbils. We experimentally infected gerbils with the bacteria, which allowed us to compare between non-infected, acutely infected (peak infection loads), and chronically infected (low infection loads) individuals. Our findings supported the lethargy hypothesis over the nutrient compensation hypothesis. Infected individuals incurred dramatically elevated foraging costs, including less efficient foraging, diminished “quality” of time spent vigilant, and increased owl predation. Interestingly, gerbils that were chronically infected (lower bacteria load) experienced larger ecological costs than acutely infected individuals (i.e. peak infection loads). This suggests that the debilitating effects of infection occur gradually, with a progressive decline in the quality of time gerbils allocated to foraging and managing risk. These increased long-term costs of infection demonstrate how small direct physiological costs of infection can lead to large indirect ecological costs. The indirect ecological costs of this parasite appear much greater than the direct physiological costs.   More forthcoming papers &raquo; <p>Douglas F. Makin, Burt P. Kotler, Joel S. Brown, Mario Garrido, and Jorge F. S. Menezes (Dec 2020) </p> <p><b>The behaviorally mediated indirect effects that endoparasites have on their host may be as large as the direct effects </b></p> <p><i><a href="https://dx.doi.org/10.1086/711397">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>llenby’s gerbils are commonly infected with the <i>Mycoplasma haemomuris</i>-like bacteria which has been demonstrated empirically to carry relatively low direct physiological costs (i.e. mild nutrient deficiencies). However, are there indirect ecological consequences of infection that affect the ability of gerbils to forage optimally and manage predation risk within their environment? We tested two alternatives: 1) does a nutrient deficiency lead to infected gerbils increasing their foraging effort and taking more risks while foraging to make up for any energetic shortfalls? 2) Alternatively, does infection lead to lethargy, whereby sick gerbils are compromised in their ability to harvest food efficiently and avoid predators? To address these questions, we compared the risk management strategies and foraging behavior of infected and non-infected gerbils. Infected gerbils were compared at two levels, those acutely infected (i.e. peak infection loads) and those with chronic infections (i.e. low infection loads). Our findings indicated that infected gerbils incurred dramatically higher foraging costs, including less efficient foraging, diminished effectiveness of vigilance and increased predation rates. Surprisingly, chronically infected gerbils experienced higher ecological costs than acutely infected gerbils. This suggests that the debilitating effects of infection occur gradually, with a progressive decline in the quality of time allocated to activities. Overall, our findings highlight how small direct physiological costs can give rise to large indirect ecological costs. Moreover, similar to predators which have both direct lethal effects and indirect effects on prey (i.e. perceived predation risk), endoparasites affect hosts not only by killing them (direct costs), but also through altering their interactions with predators, resources and landscape features (i.e. indirect costs). </p> <hr /><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>icrobes inhabiting multi-cellular organisms have complex, often subtle effects on their hosts. <i>Gerbillus andersoni allenbyi</i> are commonly infected with the <i>Mycoplasma haemomuris</i>-like bacteria, which may cause mild nutrient (choline, arginine) deficiencies. However, are there more serious ecological consequences of infection such as effects on foraging aptitudes and risk management? We tested alternatives: 1) <i>nutrient compensation hypothesis</i>, does nutrient deficiency induce infected gerbils to make up for the shortfall by foraging more and taking greater risks? or 2) <i>lethargy hypothesis</i>, do sick gerbils forage less, and are they compromised in their ability to detect predators or risky microhabitats? We compared the foraging and risk management behavior of infected and non-infected gerbils. We experimentally infected gerbils with the bacteria, which allowed us to compare between non-infected, acutely infected (peak infection loads), and chronically infected (low infection loads) individuals. Our findings supported the lethargy hypothesis over the nutrient compensation hypothesis. Infected individuals incurred dramatically elevated foraging costs, including less efficient foraging, diminished “quality” of time spent vigilant, and increased owl predation. Interestingly, gerbils that were chronically infected (lower bacteria load) experienced larger ecological costs than acutely infected individuals (i.e. peak infection loads). This suggests that the debilitating effects of infection occur gradually, with a progressive decline in the quality of time gerbils allocated to foraging and managing risk. These increased long-term costs of infection demonstrate how small direct physiological costs of infection can lead to large indirect ecological costs. The indirect ecological costs of this parasite appear much greater than the direct physiological costs.   </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, 02 Sep 2020 05:00:00 GMT “Adaptation and latitudinal gradients in species interactions: nest predation in birds” https://amnat.org/an/newpapers/Dec-Freeman.html Benjamin G. Freeman, Micah N. Scholer, Mannfred M. A. Boehm, Julian Heavyside, and Dolph Schluter (Dec 2020) Nest predation in birds is thought to be highest in the tropics—but new research shows this is not true, likely because of adaptation Read the Article (Just Accepted) The first bird nest Ben Freeman found in the tropics was a tidy cup tucked near the base of a grass clump, two Bluish Flowerpiercer eggs nestled inside. But the next day, the eggs were gone, consumed by a predator. Ben’s introduction to tropical breeding bird biology mirrored the consensus in the scientific literature that tropical birds face high levels of nest predation, illustrating the more general idea that interactions between species are fast and furious in the tropics. A decade later, Ben, now a postdoc at the University of British Columbia, teamed up with graduate students Micah Scholer, Mannfred Boehm, Julian Heavyside, and supervisor Dolph Schluter to revisit this dogma with data. Surprisingly, they found that daily rates of nest predation for landbirds are essentially the same across latitudes from Canada to Chile. What accounts for the discrepancy between previous studies and their new analysis? The authors propose that differential adaptation by tropical and temperate birds explains their unexpected result. When they control for a key life history trait-nesting period length, which is longer in the tropics- they find that tropical birds suffer higher rates of daily nest predation than temperate birds. This implies that if all birds had similar life history traits, then nest predation rates would indeed by greatest in the tropics. But tropical and temperate birds have diverged in their life history traits, in part driven by adaptation to differences in predation regimes. The overall conclusion? If birds across all latitudes were the same, then nest predation rates would be higher in the tropics. But species can adapt to the negative interactions they experience, and these adaptations in turn influence interaction rates. The authors argue that evolution plays a key role in geographic gradients in interactions. Abstract Are biotic interactions stronger in the tropics? Here we investigate nest predation in birds, a canonical example of a strong tropical biotic interaction. Counter to expectations, daily rates of nest predation vary minimally with latitude. However, life history traits that influence nest predation have diverged between latitudes. For example, tropical species have evolved a longer average nesting period, which is associated with reduced rates of nest attendance by parents. Daily nest mortality declines with nesting period duration within regions, but tropical species have a higher intercept. Consequently, for the same nesting period length, tropical species experience higher daily nest predation rates than temperate species. The implication of this analysis is that the evolved difference between latitudes in nesting period length produces a flatter latitudinal gradient in daily nest predation than would otherwise be predicted. We propose that adaptation may frequently dampen geographic patterns in interaction rates. More forthcoming papers &raquo; <p>Benjamin G. Freeman, Micah N. Scholer, Mannfred M. A. Boehm, Julian Heavyside, and Dolph Schluter (Dec 2020) </p> <p><b>Nest predation in birds is thought to be highest in the tropics&mdash;but new research shows this is not true, likely because of adaptation </b></p> <p><i><a href="https://dx.doi.org/10.1086/711415">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 first bird nest Ben Freeman found in the tropics was a tidy cup tucked near the base of a grass clump, two Bluish Flowerpiercer eggs nestled inside. But the next day, the eggs were gone, consumed by a predator. Ben’s introduction to tropical breeding bird biology mirrored the consensus in the scientific literature that tropical birds face high levels of nest predation, illustrating the more general idea that interactions between species are fast and furious in the tropics. </p><p>A decade later, Ben, now a postdoc at the University of British Columbia, teamed up with graduate students Micah Scholer, Mannfred Boehm, Julian Heavyside, and supervisor Dolph Schluter to revisit this dogma with data. Surprisingly, they found that daily rates of nest predation for landbirds are essentially the same across latitudes from Canada to Chile. What accounts for the discrepancy between previous studies and their new analysis? </p><p>The authors propose that differential adaptation by tropical and temperate birds explains their unexpected result. When they control for a key life history trait-nesting period length, which is longer in the tropics- they find that tropical birds suffer higher rates of daily nest predation than temperate birds. This implies that if all birds had similar life history traits, then nest predation rates would indeed by greatest in the tropics. But tropical and temperate birds have diverged in their life history traits, in part driven by adaptation to differences in predation regimes. </p><p>The overall conclusion? If birds across all latitudes were the same, then nest predation rates would be higher in the tropics. But species can adapt to the negative interactions they experience, and these adaptations in turn influence interaction rates. The authors argue that evolution plays a key role in geographic gradients in interactions. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>re biotic interactions stronger in the tropics? Here we investigate nest predation in birds, a canonical example of a strong tropical biotic interaction. Counter to expectations, daily rates of nest predation vary minimally with latitude. However, life history traits that influence nest predation have diverged between latitudes. For example, tropical species have evolved a longer average nesting period, which is associated with reduced rates of nest attendance by parents. Daily nest mortality declines with nesting period duration within regions, but tropical species have a higher intercept. Consequently, for the same nesting period length, tropical species experience higher daily nest predation rates than temperate species. The implication of this analysis is that the evolved difference between latitudes in nesting period length produces a flatter latitudinal gradient in daily nest predation than would otherwise be predicted. We propose that adaptation may frequently dampen geographic patterns in interaction rates. </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, 02 Sep 2020 05:00:00 GMT “Oxidative stress experienced during early development influences the offspring phenotype” https://amnat.org/an/newpapers/Dec-Romero-Haro.html Ana Angela Romero-Haro and Carlos Alonso-Alvarez (Dec 2020) Transgenerational effects of sustaining low antioxidant (glutathione) levels during early life Read the Article (Just Accepted) Oxidative stress is an imbalance between the level of reactive oxygen species produced by metabolism and the state of the antioxidant machinery controlling them. The imbalance leads to oxidative damage with potentially long-lasting consequences. However, the impact of oxidative stress in the next generations is poorly understood. Most studies analyzing these transgenerational effects have used compounds only indirectly related to oxidative stress, such as pollutants or radiation. Here, researchers from the University of Exeter (UK) and Museo Nacional de Ciencias Naturales (Spain) experimentally decrease the levels of a vital cellular antioxidant, glutathione, during the early development of zebra finches (Taeniopygia guttata) and study its impact on the next generation. Glutathione is synthesized from dietary amino acids, and undernourishment, a common situation in wild birds during early life, affects their levels. Previously, researchers demonstrated that low glutathione levels during development induced oxidative stress and changes in body mass and coloration in adulthood. When the same birds bred, their newborn chicks were moved among nests to distinguish between pre- and post-natal parental effects (i.e., those induced by the biological or, instead, foster parents). Female chicks from biological mothers that experienced early-life oxidative stress don’t attain a high body mass under favorable nest conditions (i.e. reduced brood sizes), suggesting a constraining effect on the maternal capacity to transfer resources to eggs. Moreover, nestlings grow shorter legs when raised by both foster parents from the early oxidative stress treatment. Hence, the treatment also affects the parental capacity to provide resources to chicks. The results demonstrate that early-life oxidative stress is able to alter the offspring phenotype, which might have an impact on evolutionary life-history trade-offs. Providing enough dietary resources to descendants to avoid oxidative stress could compromise parental survival, but simultaneously improve parental fitness through the phenotype of the second generation. Abstract Oxidative stress (OS) experienced early in life can affect an individual’s phenotype. However, its consequences for the next generation remain largely unexplored. We manipulated the OS level endured by zebra finches (Taeniopygia guttata) during their development by transitorily inhibiting the synthesis of the key antioxidant glutathione (‘early-high-OS’). The offspring of these birds and control parents were cross-fostered at hatching to enlarge or reduce its brood size. Independently of parents’ early-life OS levels, the chicks raised in enlarged broods showed lower erythrocyte glutathione levels, revealing glutathione sensitivity to environmental conditions. Control (“early-low-OS”) biological mothers produced females, not males, that attained a higher body mass when raised in a benign environment (i.e. the reduced brood). In contrast, biological mothers exposed to early-life OS produced heavier males, not females, when allocated in reduced broods. Early-life OS also affected the parental rearing capacity because 12d-old nestlings raised by a foster pair with both early-high-OS members grew shorter legs (tarsus) than chicks from other groups. The results indicate that environmental conditions during development can affect early glutathione levels, which may, in turn, influence the next generation through both pre- and postnatal parental effects. The results also demonstrate that early-life OS can constrain the offspring phenotype. More forthcoming papers &raquo; <p>Ana Angela Romero-Haro and Carlos Alonso-Alvarez (Dec 2020) </p> <p><b>Transgenerational effects of sustaining low antioxidant (glutathione) levels during early life </b></p> <p><i><a href="https://dx.doi.org/10.1086/711399">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">O</span>xidative stress is an imbalance between the level of reactive oxygen species produced by metabolism and the state of the antioxidant machinery controlling them. The imbalance leads to oxidative damage with potentially long-lasting consequences. However, the impact of oxidative stress in the next generations is poorly understood. Most studies analyzing these transgenerational effects have used compounds only indirectly related to oxidative stress, such as pollutants or radiation. Here, researchers from the University of Exeter (UK) and Museo Nacional de Ciencias Naturales (Spain) experimentally decrease the levels of a vital cellular antioxidant, glutathione, during the early development of zebra finches (<i>Taeniopygia guttata</i>) and study its impact on the next generation. Glutathione is synthesized from dietary amino acids, and undernourishment, a common situation in wild birds during early life, affects their levels. Previously, researchers demonstrated that low glutathione levels during development induced oxidative stress and changes in body mass and coloration in adulthood. When the same birds bred, their newborn chicks were moved among nests to distinguish between pre- and post-natal parental effects (i.e., those induced by the biological or, instead, foster parents). Female chicks from biological mothers that experienced early-life oxidative stress don’t attain a high body mass under favorable nest conditions (i.e. reduced brood sizes), suggesting a constraining effect on the maternal capacity to transfer resources to eggs. Moreover, nestlings grow shorter legs when raised by both foster parents from the early oxidative stress treatment. Hence, the treatment also affects the parental capacity to provide resources to chicks. The results demonstrate that early-life oxidative stress is able to alter the offspring phenotype, which might have an impact on evolutionary life-history trade-offs. Providing enough dietary resources to descendants to avoid oxidative stress could compromise parental survival, but simultaneously improve parental fitness through the phenotype of the second generation. </p> <hr /><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">O</span>xidative stress (OS) experienced early in life can affect an individual’s phenotype. However, its consequences for the next generation remain largely unexplored. We manipulated the OS level endured by zebra finches (<i>Taeniopygia guttata</i>) during their development by transitorily inhibiting the synthesis of the key antioxidant glutathione (‘early-high-OS’). The offspring of these birds and control parents were cross-fostered at hatching to enlarge or reduce its brood size. Independently of parents’ early-life OS levels, the chicks raised in enlarged broods showed lower erythrocyte glutathione levels, revealing glutathione sensitivity to environmental conditions. Control (“early-low-OS”) biological mothers produced females, not males, that attained a higher body mass when raised in a benign environment (i.e. the reduced brood). In contrast, biological mothers exposed to early-life OS produced heavier males, not females, when allocated in reduced broods. Early-life OS also affected the parental rearing capacity because 12d-old nestlings raised by a foster pair with both early-high-OS members grew shorter legs (tarsus) than chicks from other groups. The results indicate that environmental conditions during development can affect early glutathione levels, which may, in turn, influence the next generation through both pre- and postnatal parental effects. The results also demonstrate that early-life OS can constrain the offspring phenotype. </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, 02 Sep 2020 05:00:00 GMT “Positive feedback between behavioral and hormonal dynamics leads to differentiation of life-history tactics” https://amnat.org/an/newpapers/Dec-Horita.html Junnosuke Horita, Yoh Iwasa, and Yuuya Tachiki (Dec 2020) Positive feedback loop between competition and hormone synthesis induces the alternative life-history tactics Read the Article (Just Accepted) Life is not complex. We are complex. Life is simple, and the simple thing is the right thing. —Oscar WildeIn life, we sometimes find ourselves at a crossroads and are perplexed at the choice of paths before us. Wild animals must also make decisions in their lives. For example, some species of salmon have to choose whether to stay in their natal river (called the resident tactic) or undergo a feeding migration to the ocean (called the migrant tactic). Because this life decision largely influences the chances of future success, how individuals choose their way is an important issue. Jun-nosuke Horita (Kyushu Univ.) et al. tackle this problem using a mathematical model. The key factor is individuals’ hormonal state, which triggers the development of the phenotypes required. Even in humankind, which likes to fancy that it makes decisions in a logical way, physiological state affects decision-making. Horita et al. demonstrate the emergence of discrete patterns of hormonal states arising from a continuous distribution, which would work as an initiation of dimorphisms. They considered the life-history choice of masu salmon, in which maturation in the stream (the resident tactic) is induced by 11-ketoteststerone (11-KT), a kind of androgen. It has been known that 11-KT also affects the individual’s behavior. An individual with a high hormone level moves actively and tends to win competition for resources in a territory. Interestingly, the outcome of such competition, in turn, affects the hormone synthesis: 11-KT is synthesized in the winner of competition. Horita et al. address the possibility that fighting and hormone synthesis form a positive feedback loop, the so-called winner-loser effect. They constructed a mathematical model that describes the events in a fish school in which individuals grow and fight each other for food resources. Their simple model of a dynamical system for size and hormonal state reveals that individuals are finally separated into the two groups (whether they migrate or stay) according to hormonal status, even if individuals are indistinguishable from the viewpoint of size. This work emphasizes the importance of considering behavior and physiology simultaneously thinking about life-history choices. Abstract Competitive interaction among individuals of a single population may result in the differentiation to two or more distinct life history tactics. For example, although they exhibit unimodal size distribution, male juveniles of salmonids differentiate into those going down to the ocean for growth and returning after several years to the natal stream for reproduction (migratory tactic) and those staying in the stream and reproducing for multiple years (resident tactic). In this study, we developed a simple mathematical model for the positive feedback between hormonal and behavioral dynamics, with the expectation of establishing multiple discrete clusters of hormone levels leading to differentiation of life-history tactics. The assumptions were that probability of winning in fighting depends both on the body size and hormone level of the two contestants. An individual with a higher hormone level would be more likely to win the competition, which further enhanced hormone production, forming a positive feedback loop between hormone level and fighting ability. If the positive feedback was strong but not excessive, discrete clusters of hormone level emerged from a continuous distribution. In contrast, no clear clustering structure appeared in the distribution of hormone levels if the winning probability in fighting was controlled by the body size. 闘争とホルモン産生との正のフィードバックが代替生活史戦術をつくりだす 同一種の個体で異なる生活史戦術を採用する「代替生活史戦術」は、個体間の競争的相互作用によって形成されるのかもしれない。サケ科魚類のサクラマスは、雄幼魚のサイズ分布は一山であっても、海に降って成長を目指し数年後に母川に戻って繁殖する個体(降海型)と、河川にとどまって複数回繁殖する個体(残留型)に分かれる。本研究ではサクラマスの闘争行動とホルモン産生との正のフィードバックを表す数理モデルを構築した。闘争の勝利確率が、2個体の体サイズとホルモンレベルの両方に依存すると仮定した。ホルモンレベルの高い個体が闘争に勝ちやすいと、そのことでさらにホルモンレベルが上がるという正のフィードバックが作られる。これが適度に強い状況では、ホルモンレベルの離散的なクラスターが形成された。対照的に、闘争の勝利確率が体サイズによって決まる場合には、ホルモンレベルにははっきりしたクラスター構造は現れなかった。 More forthcoming papers &raquo; <p>Junnosuke Horita, Yoh Iwasa, and Yuuya Tachiki (Dec 2020) </p> <p><b>Positive feedback loop between competition and hormone synthesis induces the alternative life-history tactics </b></p> <p><i><a href="https://dx.doi.org/10.1086/711414">Read the Article</a></i> (Just Accepted) </p><blockquote>Life is not complex. We are complex. Life is simple, and the simple thing is the right thing. <br/>&mdash;Oscar Wilde</blockquote><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 life, we sometimes find ourselves at a crossroads and are perplexed at the choice of paths before us. Wild animals must also make decisions in their lives. For example, some species of salmon have to choose whether to stay in their natal river (called the resident tactic) or undergo a feeding migration to the ocean (called the migrant tactic). Because this life decision largely influences the chances of future success, how individuals choose their way is an important issue. Jun-nosuke Horita (Kyushu Univ.) et al. tackle this problem using a mathematical model. The key factor is individuals&rsquo; hormonal state, which triggers the development of the phenotypes required. Even in humankind, which likes to fancy that it makes decisions in a logical way, physiological state affects decision-making.</p> <p>Horita et al. demonstrate the emergence of discrete patterns of hormonal states arising from a continuous distribution, which would work as an initiation of dimorphisms. They considered the life-history choice of <i>masu</i> salmon, in which maturation in the stream (the resident tactic) is induced by 11-ketoteststerone (11-KT), a kind of androgen. It has been known that 11-KT also affects the individual&rsquo;s behavior. An individual with a high hormone level moves actively and tends to win competition for resources in a territory. Interestingly, the outcome of such competition, in turn, affects the hormone synthesis: 11-KT is synthesized in the winner of competition. Horita et al. address the possibility that fighting and hormone synthesis form a positive feedback loop, the so-called winner-loser effect. They constructed a mathematical model that describes the events in a fish school in which individuals grow and fight each other for food resources. Their simple model of a dynamical system for size and hormonal state reveals that individuals are finally separated into the two groups (whether they migrate or stay) according to hormonal status, even if individuals are indistinguishable from the viewpoint of size. This work emphasizes the importance of considering behavior and physiology simultaneously thinking about life-history choices.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>ompetitive interaction among individuals of a single population may result in the differentiation to two or more distinct life history tactics. For example, although they exhibit unimodal size distribution, male juveniles of salmonids differentiate into those going down to the ocean for growth and returning after several years to the natal stream for reproduction (migratory tactic) and those staying in the stream and reproducing for multiple years (resident tactic). In this study, we developed a simple mathematical model for the positive feedback between hormonal and behavioral dynamics, with the expectation of establishing multiple discrete clusters of hormone levels leading to differentiation of life-history tactics. The assumptions were that probability of winning in fighting depends both on the body size and hormone level of the two contestants. An individual with a higher hormone level would be more likely to win the competition, which further enhanced hormone production, forming a positive feedback loop between hormone level and fighting ability. If the positive feedback was strong but not excessive, discrete clusters of hormone level emerged from a continuous distribution. In contrast, no clear clustering structure appeared in the distribution of hormone levels if the winning probability in fighting was controlled by the body size.</p> <h4>闘争とホルモン産生との正のフィードバックが代替生活史戦術をつくりだす</h4> <p>同一種の個体で異なる生活史戦術を採用する「代替生活史戦術」は、個体間の競争的相互作用によって形成されるのかもしれない。サケ科魚類のサクラマスは、雄幼魚のサイズ分布は一山であっても、海に降って成長を目指し数年後に母川に戻って繁殖する個体(降海型)と、河川にとどまって複数回繁殖する個体(残留型)に分かれる。本研究ではサクラマスの闘争行動とホルモン産生との正のフィードバックを表す数理モデルを構築した。闘争の勝利確率が、2個体の体サイズとホルモンレベルの両方に依存すると仮定した。ホルモンレベルの高い個体が闘争に勝ちやすいと、そのことでさらにホルモンレベルが上がるという正のフィードバックが作られる。これが適度に強い状況では、ホルモンレベルの離散的なクラスターが形成された。対照的に、闘争の勝利確率が体サイズによって決まる場合には、ホルモンレベルにははっきりしたクラスター構造は現れなかった。</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, 02 Sep 2020 05:00:00 GMT Editorial Policy and Checklist for Archiving Data and Code https://amnat.org/announcements/DataChecklist.html As a condition of publication, all data needed to recreate the results of a paper must be publicly accessible in usable format. We encourage authors to make their data and code available to reviewers upon first submission, and we require it for revisions and resubmissions. Dryad publishes a list of best practices (https://datadryad.org/stash/best_practices) The American Naturalist provides a checklist for authors preparing their data. (Word version of the Am Nat checklist) See also the Instructions for Authors for more detail Archiving Data (Required) Complete data deposition in a public data archive is a condition for publication in The American Naturalist (embargoes on data deposits are allowed). This is required only when a paper is resubmitted with revisions but can be included at the time of initial submission, if you wish. We recommend the Dryad repository for both data and code. There are no charges for Dryad during peer review. The American Society of Naturalists covers all the costs for publishing data in Dryad if a paper is accepted. At the resubmission stage, data must be made available in a data repository to be checked by an editor before final acceptance. The data (and other repository files) are also made available to reviewers at this stage. If a paper is found to lack a complete and well-documented archive, the authors will be contacted. After publication, if the data archive is found to be insufficient to recreate the results of the study, the journal retains the right to publish an Editorial Expression of Concern noting the lack of complete data or to retract the paper. Please deposit gene sequence data and original phylogenetic trees to GenBank or TreeBASE, respectively. All accession numbers and DOIs for GenBank, TreeBASE, and Dryad must be included in accepted manuscripts before they go to Production. Archiving Code for Analysis and Modelling (Required) As part of our commitment to scientific reproducibility, The American Naturalist strongly encourages authors to provide any data analysis code (e.g., R or Python scripts or notebooks) used to generate statistical results, figures, and models. These may be provided as a single script or a separate script for each figure, table, or coherent set of analyses. This code should be included in a recommended repository or as a digital supplement to the submitted paper. The data repository should also contain all data files needed to run the code. This allows reviewers, editors, and readers, to check the statistical analysis if they so choose. All code should be clearly annotated to explain to a reader what each step in the code is intended to do and how it maps onto the contents of the manuscript (e.g., identifying figures by number). Include version numbers of all packages accessed by the code and the version of software (e.g., R or Python) used in the analysis. Citing Published Data (Required) When you use a data set, be sure to cite it in your article using the DataCite DOI and be sure the citation occurs in the Literature Cited section of your article as well as in the text. The data citation in the Literature Cited should include the name of the database, a record locator or descriptor, an access date, the URL, and the DOI if available. Reporting and Archiving Sequence Data (Required) DNA should be sequenced on both strands. The sequences of all PCR primers used should be clearly stated either in the text or in cited references. Variation inferred from cloned allelic sequences should consider polymerase error and in vitro recombination. All new nucleotide sequence data must be submitted to Genbank or EMBL. Laboratory and Field Protocols (Optional) The American Naturalist strongly encourages authors of empirical papers to deposit detailed laboratory and field protocols at protocols.io. Your protocol will be hidden from the public (except editors and reviewers with the DOI), until you select Publish on the protocols.io website. Upon publication, any protocols.io entries in the published paper will automatically become public. Write a step-by-step protocol with photographs, or links to videos, where relevant. When using commercial products, you should include the vendor and catalogue number. All details that you might record to train a new lab member on how to implement a given protocol, should be documented. This helps others replicate your methods, but also can serve as a resource for your own lab members and collaborators in the future. &nbsp; <p><strong>As a condition of publication, all data needed to recreate the results of a paper must be publicly accessible in usable format. We encourage authors to make their data and code available to reviewers upon first submission, and we require it for revisions and resubmissions. </strong></p> <ul> <li>Dryad publishes a list of best practices (<a href="https://datadryad.org/stash/best_practices">https://datadryad.org/stash/best_practices</a>)</li> <li><em>The American Naturalist </em>provides a <a href="/dam/jcr:41d9f549-859f-4fab-9e2a-e74421bd42d1/DATAchecklist.pdf">checklist for authors preparing their data.</a></li> <li>(<a href="/dam/jcr:93239a06-0272-443f-800c-bf3c421aea50/DATAchecklist.docx">Word version of the Am Nat checklist</a>)</li> <li>See also the <a href="https://www.journals.uchicago.edu/journals/an/instruct">Instructions for Authors</a> for more detail</li> </ul> <p><em><strong>Archiving Data (Required)</strong></em><br /> Complete data deposition in a public data archive is a condition for publication in <em>The American Naturalist</em> (embargoes on data deposits are allowed). This is required only when a paper is resubmitted with revisions but can be included at the time of initial submission, if you wish. We recommend the Dryad repository for both data and code. <strong>There are no charges for Dryad during peer review. The American Society of Naturalists covers all the costs for publishing data in Dryad if a paper is accepted. </strong></p> <p>At the resubmission stage, data must be made available in a data repository to be checked by an editor before final acceptance. The data (and other repository files) are also made available to reviewers at this stage. If a paper is found to lack a complete and well-documented archive, the authors will be contacted. After publication, if the data archive is found to be insufficient to recreate the results of the study, the journal retains the right to publish an Editorial Expression of Concern noting the lack of complete data or to retract the paper.</p> <p>Please deposit gene sequence data and original phylogenetic trees to GenBank or TreeBASE, respectively.</p> <p>All accession numbers and DOIs for GenBank, TreeBASE, and Dryad must be included in accepted manuscripts before they go to Production.</p> <p><em><strong>Archiving Code for Analysis and Modelling (Required)</strong></em><br /> As part of our commitment to scientific reproducibility, <em>The American Naturalist</em> strongly encourages authors to provide any data analysis code (e.g., R or Python scripts or notebooks) used to generate statistical results, figures, and models. These may be provided as a single script or a separate script for each figure, table, or coherent set of analyses. This code should be included in a recommended repository or as a digital supplement to the submitted paper. The data repository should also contain all data files needed to run the code. This allows reviewers, editors, and readers, to check the statistical analysis if they so choose. All code should be clearly annotated to explain to a reader what each step in the code is intended to do and how it maps onto the contents of the manuscript (e.g., identifying figures by number). Include version numbers of all packages accessed by the code and the version of software (e.g., R or Python) used in the analysis.</p> <p><em><strong>Citing Published Data (Required)</strong></em><br /> When you use a data set, be sure to cite it in your article using the DataCite DOI and be sure the citation occurs in the Literature Cited section of your article as well as in the text. The data citation in the Literature Cited should include the name of the database, a record locator or descriptor, an access date, the URL, and the DOI if available.</p> <p><em><strong>Reporting and Archiving Sequence Data (Required)</strong></em><br /> DNA should be sequenced on both strands. The sequences of all PCR primers used should be clearly stated either in the text or in cited references. Variation inferred from cloned allelic sequences should consider polymerase error and in vitro recombination. All new nucleotide sequence data must be submitted to Genbank or EMBL.</p> <p><em><strong>Laboratory and Field Protocols (Optional) </strong></em><br /> <em>The American Naturalist</em> strongly encourages authors of empirical papers to deposit detailed laboratory and field protocols at protocols.io. Your protocol will be hidden from the public (except editors and reviewers with the DOI), until you select Publish on the protocols.io website. Upon publication, any protocols.io entries in the published paper will automatically become public. Write a step-by-step protocol with photographs, or links to videos, where relevant. When using commercial products, you should include the vendor and catalogue number. All details that you might record to train a new lab member on how to implement a given protocol, should be documented. This helps others replicate your methods, but also can serve as a resource for your own lab members and collaborators in the future.</p> <p>&nbsp;</p> Wed, 02 Sep 2020 05:00:00 GMT “Comparing the indirect effects between exploiters in predator-prey and host-pathogen systems” https://amnat.org/an/newpapers/Dec-Cortez-A.html Michael H. Cortez and Meghan A. Duffy (Dec 2020) Read the Article (Just Accepted) Abstract In multi-predator and multi-pathogen systems, exploiters interact indirectly via shared victim species. Interspecific prey competition and the degree of predator specialization are known to in uence whether predators have competitive, i.e., (&minus;,&minus;), or noncompetitive, i.e., (&minus;,+) or (+,+), indirect interactions. Much less is known about the population-level in- direct interactions between pathogens that infect the same populations of host species. In this study, we use two-predator-two-prey and two-host-two-pathogen models to compare the indirect effects between predators with the indirect effects between pathogens. We focus on how the indirect interactions between pathogens are affected by the competitive abilities of susceptible and infected hosts, whether the pathogens are specialists or generalists, and the transmission pathway (direct versus environmental transmission). In many cases, indirect effects between pathogens and predators follow similar patterns, e.g., more positive indirect effects with increased interspecific competition between victim species. However, the indirect effects between pathogens can qualitatively differ, e.g., more negative indirect effects with increased interspecific host competition. These contrasting patterns show that an important mechanistic difference between predatory and parasitic interactions (specifically, whether interactions are immediately lethal) can have important population-level effects on the indirect interactions between exploiters. More forthcoming papers &raquo; <p>Michael H. Cortez and Meghan A. Duffy (Dec 2020) </p> <p><i><a href="https://dx.doi.org/10.1086/711345">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n multi-predator and multi-pathogen systems, exploiters interact indirectly via shared victim species. Interspecific prey competition and the degree of predator specialization are known to in uence whether predators have competitive, i.e., (&minus;,&minus;), or noncompetitive, i.e., (&minus;,+) or (+,+), indirect interactions. Much less is known about the population-level in- direct interactions between pathogens that infect the same populations of host species. In this study, we use two-predator-two-prey and two-host-two-pathogen models to compare the indirect effects between predators with the indirect effects between pathogens. We focus on how the indirect interactions between pathogens are affected by the competitive abilities of susceptible and infected hosts, whether the pathogens are specialists or generalists, and the transmission pathway (direct versus environmental transmission). In many cases, indirect effects between pathogens and predators follow similar patterns, e.g., more positive indirect effects with increased interspecific competition between victim species. However, the indirect effects between pathogens can qualitatively differ, e.g., more negative indirect effects with increased interspecific host competition. These contrasting patterns show that an important mechanistic difference between predatory and parasitic interactions (specifically, whether interactions are immediately lethal) can have important population-level effects on the indirect interactions between exploiters. </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, 02 Sep 2020 05:00:00 GMT “Miniaturization, genome size, and biological size in a diverse clade of salamanders” https://amnat.org/an/newpapers/Nov-Decena-Segarra.html Louis Paul Decena-Segarra, Lilijana Bizjak-Mali, Ale&scaron; Kladnik, Stanley K. Sessions, and Sean M. Rovito (Nov 2020) Miniature salamanders have reduced genome sizes compared to larger species Read the ArticleThe smallest salamanders in the world are found in Mexico; they are under 3.5 cm (about 1.5 in) long and have heads smaller than a pencil eraser. Not only do they have to fit their eyes, brains, and other organs into a very small space, but they also face challenges posed by large genome size (the total amount of DNA per cell). All salamanders have very big genomes (four to almost 40 times as big as the human genome), meaning these salamanders have to make all of their sensory organs (made up of big cells) fit into the small space available in their heads. As part of a collaboration between scientists at the Advanced Genomics Unit in Mexico, the University of Ljubljana, Slovenia, and Hartwick College, USA, Paul Decena (a masters student from Mexico) and his collaborators measured the genome size of Mexican salamanders and tested the prediction that smaller salamanders would have smaller genomes to avoid problems associated with making tiny organs out of big cells. They also quantify “biological size”, which measures how big the physical size of organisms is relative to their genome (and cell) size. They find support for a relationship between genome size and cell size and report the smallest salamander genome recorded to date (about three times as big as the human genome). They also show that some tiny salamanders are biologically “bigger” than others and that some salamanders that are not physically miniature have such large genomes that they are biologically “smaller” than miniature species. These results help us understand how body size impacts genome size (or perhaps the reverse) and open the door to sequencing complete salamander genomes by finding some small enough to be sequenced using available methods. Algunas salamandras miniatura son más “grandes” de lo que pensábamos Las salamandras más pequeñas del mundo se encuentran en México, miden menos de 3.5 cm (1.5 in) de longitud y sus cabezas son más pequeñas que un borrador de un lápiz. Además de tener que acomodar sus ojos, cerebro y órganos en espacios muy pequeños, también tienen que lidiar con retos impuestos por sus grandes tamaños del genoma (la cantidad de ADN por célula). Todas las salamandras tienen genomas gigantes (cuatro a 40 veces más grandes que el genoma humano), por lo que estás salamandras tienen que hacer que sus órganos sensoriales (formados por células grandes) quepan en el espacio disponible en sus cabezas. Como parte de una colaboración entre científicos de la Unidad de Genómica Avanzada en México, La Universidad de Ljubljana, Slovenia, y el Hatwick College, USA, Paul Decena (estudiante de maestría en México) y sus colaboradores midieron el tamaño del genoma de salamandras Mexicanas, y probaron la predicción de que las salamandras más pequeñas tienen genomas reducidos para evitar algunos de los problemas asociados con hacer organos pequeños con células grandes. También cuantificaron el “tamaño biológico”, que mide qué tan grande es un organismo en relación al tamaño del genoma y de sus células. También encontraron soporte para una relación entre el tamaño del genoma y el tamaño de la célula, y reportan el tamaño del genoma más pequeño encontrado en una salamandra hasta la fecha (casi tres veces más grande que el genoma humano). También encontraron que algunas salamandras son biológicamente “más grandes” que otras y que algunas salamandras que no son miniatura por sus medidas físicas tienen genomas tan grandes que en realidad son “más pequeñas” que las salamandras miniatura. Estos resultados pueden ayudarnos a entender como el tamaño del cuerpo impacta en el tamaño del genoma (o visceversa) y abre la puerta para secuenciar los genomas completos de algunas salamandras con genomas relativamente pequeños con los métodos disponibles actualmente. Abstract Genome size (C-value) can affect organismal traits across levels of biological organization, from tissue complexity to metabolism. Neotropical salamanders show wide variation in genome and body sizes, including several clades with miniature species. Because miniaturization imposes strong constraints on morphology and development, and genome size is strongly correlated with cell size, we hypothesize that body size has played an important role in the evolution of genome size in bolitoglossine salamanders. If this hypothesis is correct, then genome size and body size should be correlated in this group. Using Feulgen Image Analysis Densitometry (FIAD), we estimated genome sizes for 60 species of neotropical salamanders. We also estimated the “biological size” of species by comparing genome size and physical body sizes in a phylogenetic context. We found a significant correlation between C-value and physical body size using optimal regression with an Ornstein-Uhlenbeck model, and report the smallest salamander genome found to date. Our index of biological size showed that some salamanders with large physical body size have smaller biological body size than some miniature species, and that several clades showed patterns of increased or decreased biological size compared to their physical size. Our results suggest a causal relationship between physical body size and genome size and show the importance of considering the impact of both on the biological size of organisms. Indeed, biological size may be a more appropriate measure than physical size when considering phenotypic consequences of genome size evolution in many groups. More forthcoming papers &raquo; <p>Louis Paul Decena-Segarra, Lilijana Bizjak-Mali, Ale&scaron; Kladnik, Stanley K. Sessions, and Sean M. Rovito (Nov 2020)</p> <p><b>Miniature salamanders have reduced genome sizes compared to larger species </b></p> <p><i><a href="https://dx.doi.org/10.1086/711019">Read the Article</a></i></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he smallest salamanders in the world are found in Mexico; they are under 3.5 cm (about 1.5 in) long and have heads smaller than a pencil eraser. Not only do they have to fit their eyes, brains, and other organs into a very small space, but they also face challenges posed by large genome size (the total amount of DNA per cell). All salamanders have very big genomes (four to almost 40 times as big as the human genome), meaning these salamanders have to make all of their sensory organs (made up of big cells) fit into the small space available in their heads. As part of a collaboration between scientists at the Advanced Genomics Unit in Mexico, the University of Ljubljana, Slovenia, and Hartwick College, USA, Paul Decena (a masters student from Mexico) and his collaborators measured the genome size of Mexican salamanders and tested the prediction that smaller salamanders would have smaller genomes to avoid problems associated with making tiny organs out of big cells. They also quantify “biological size”, which measures how big the physical size of organisms is relative to their genome (and cell) size. They find support for a relationship between genome size and cell size and report the smallest salamander genome recorded to date (about three times as big as the human genome). They also show that some tiny salamanders are biologically “bigger” than others and that some salamanders that are not physically miniature have such large genomes that they are biologically “smaller” than miniature species. These results help us understand how body size impacts genome size (or perhaps the reverse) and open the door to sequencing complete salamander genomes by finding some small enough to be sequenced using available methods. </p><h4>Algunas salamandras miniatura son más “grandes” de lo que pensábamos</h4> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">L</span>as salamandras más pequeñas del mundo se encuentran en México, miden menos de 3.5 cm (1.5 in) de longitud y sus cabezas son más pequeñas que un borrador de un lápiz. Además de tener que acomodar sus ojos, cerebro y órganos en espacios muy pequeños, también tienen que lidiar con retos impuestos por sus grandes tamaños del genoma (la cantidad de ADN por célula). Todas las salamandras tienen genomas gigantes (cuatro a 40 veces más grandes que el genoma humano), por lo que estás salamandras tienen que hacer que sus órganos sensoriales (formados por células grandes) quepan en el espacio disponible en sus cabezas. Como parte de una colaboración entre científicos de la Unidad de Genómica Avanzada en México, La Universidad de Ljubljana, Slovenia, y el Hatwick College, USA, Paul Decena (estudiante de maestría en México) y sus colaboradores midieron el tamaño del genoma de salamandras Mexicanas, y probaron la predicción de que las salamandras más pequeñas tienen genomas reducidos para evitar algunos de los problemas asociados con hacer organos pequeños con células grandes. También cuantificaron el “tamaño biológico”, que mide qué tan grande es un organismo en relación al tamaño del genoma y de sus células. También encontraron soporte para una relación entre el tamaño del genoma y el tamaño de la célula, y reportan el tamaño del genoma más pequeño encontrado en una salamandra hasta la fecha (casi tres veces más grande que el genoma humano). También encontraron que algunas salamandras son biológicamente “más grandes” que otras y que algunas salamandras que no son miniatura por sus medidas físicas tienen genomas tan grandes que en realidad son “más pequeñas” que las salamandras miniatura. Estos resultados pueden ayudarnos a entender como el tamaño del cuerpo impacta en el tamaño del genoma (o visceversa) y abre la puerta para secuenciar los genomas completos de algunas salamandras con genomas relativamente pequeños con los métodos disponibles actualmente. </p> <hr /><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">G</span>enome size (C-value) can affect organismal traits across levels of biological organization, from tissue complexity to metabolism. Neotropical salamanders show wide variation in genome and body sizes, including several clades with miniature species. Because miniaturization imposes strong constraints on morphology and development, and genome size is strongly correlated with cell size, we hypothesize that body size has played an important role in the evolution of genome size in bolitoglossine salamanders. If this hypothesis is correct, then genome size and body size should be correlated in this group. Using Feulgen Image Analysis Densitometry (FIAD), we estimated genome sizes for 60 species of neotropical salamanders. We also estimated the “biological size” of species by comparing genome size and physical body sizes in a phylogenetic context. We found a significant correlation between C-value and physical body size using optimal regression with an Ornstein-Uhlenbeck model, and report the smallest salamander genome found to date. Our index of biological size showed that some salamanders with large physical body size have smaller biological body size than some miniature species, and that several clades showed patterns of increased or decreased biological size compared to their physical size. Our results suggest a causal relationship between physical body size and genome size and show the importance of considering the impact of both on the biological size of organisms. Indeed, biological size may be a more appropriate measure than physical size when considering phenotypic consequences of genome size evolution in many groups. </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> Fri, 28 Aug 2020 05:00:00 GMT “The size, symmetry, and color saturation of a male guppy’s ornaments forecast his resistance to parasites” https://amnat.org/an/newpapers/Nov-Stephenson.html Jessica F. Stephenson, Martin Stevens, Jolyon Troscianko, and Jukka Jokela (Nov 2020) Male guppy ornaments indicate parasite resistance before infection, but males may ‘fake’ quality with dynamic traits! Read the Article (Just Accepted) Females across animal species are very good at recognizing disease in their mates – these males typically have duller, smaller color patches, for example. Mating instead with males with brighter, larger color patches means that the female is less likely to become infected during sex, and perhaps that her offspring may be more resistant to parasites thanks to their dad’s genes. However, parasites are usually clumped among their hosts, so that the vast majority of males in a population will not be infected. Can females still use a male’s color patches to assess his resistance to parasites, even if he’s not currently infected? Jessica Stephenson and colleagues set out to test this question in small tropical freshwater fish – guppies. They took photographs of several males to analyze their color patterns before infecting them with a common parasite. They made repeated counts of each male’s parasite load as the parasites reproduced and died, depending on their host’s resistance. Interestingly, males with larger areas of orange and more symmetrical black coloration were more resistant, but males with more saturated orange spots were less resistant to the subsequent infection. The authors attribute this to the fact that orange saturation can change rapidly in response to changes in male condition, whereas orange area and black symmetry do not change during sexual maturity: perhaps this makes orange saturation easier to ‘fake’? Female guppies typically prefer more symmetrical color patterns, and larger, more saturated orange patches. When given the choice they prioritize orange area over saturation, suggesting they can spot the fakers and prefer to mate with more resistant males, even in the absence of infection. This finding broadens our understanding of how parasites impact sexual selection in their hosts, and how sexual selection is involved in host-parasite coevolution. Abstract Sexually selected ornaments range from highly dynamic traits to those that are fixed during development and relatively static throughout sexual maturity. Ornaments along this continuum differ in the information they provide about the qualities of potential mates, such as their parasite resistance. Dynamic ornaments enable real-time assessment of the bearer’s condition: they can reflect an individual’s current infection status, or resistance to recent infections. Static ornaments, however, are not affected by recent infection but may instead indicate an individual’s genetically determined resistance, even in the absence of infection. Given the typically aggregated distribution of parasites among hosts, infection is unlikely to affect the ornaments of the vast majority of individuals in a population: static ornaments may therefore be the more reliable indicators of parasite resistance. To test this hypothesis, we quantified the ornaments of male guppies, Poecilia reticulata, before experimentally infecting them with Gyrodactylus turnbulli. Males with more left-right symmetrical black coloration and those with larger areas of orange coloration, both static ornaments, were more resistant. However, males with more saturated orange coloration, a dynamic ornament, were less resistant. Female guppies often prefer symmetrical males with larger orange ornaments, suggesting parasite-mediated natural and sexual selection act in concert on these traits. More forthcoming papers &raquo; <p>Jessica F. Stephenson, Martin Stevens, Jolyon Troscianko, and Jukka Jokela (Nov 2020) </p> <p><b>Male guppy ornaments indicate parasite resistance <i>before</i> infection, but males may ‘fake’ quality with dynamic traits! </b></p> <p><i><a href="https://dx.doi.org/10.1086/711033">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;">F</span>emales across animal species are very good at recognizing disease in their mates &ndash; these males typically have duller, smaller color patches, for example. Mating instead with males with brighter, larger color patches means that the female is less likely to become infected during sex, and perhaps that her offspring may be more resistant to parasites thanks to their dad&rsquo;s genes. However, parasites are usually clumped among their hosts, so that the vast majority of males in a population will not be infected. Can females still use a male&rsquo;s color patches to assess his resistance to parasites, even if he&rsquo;s not currently infected? Jessica Stephenson and colleagues set out to test this question in small tropical freshwater fish &ndash; guppies. They took photographs of several males to analyze their color patterns <i>before</i> infecting them with a common parasite. They made repeated counts of each male&rsquo;s parasite load as the parasites reproduced and died, depending on their host&rsquo;s resistance. Interestingly, males with larger areas of orange and more symmetrical black coloration were more resistant, but males with more saturated orange spots were less resistant to the subsequent infection. The authors attribute this to the fact that orange saturation can change rapidly in response to changes in male condition, whereas orange area and black symmetry do not change during sexual maturity: perhaps this makes orange saturation easier to &lsquo;fake&rsquo;? Female guppies typically prefer more symmetrical color patterns, and larger, more saturated orange patches. When given the choice they prioritize orange area over saturation, suggesting they can spot the fakers and prefer to mate with more resistant males, even in the absence of infection. This finding broadens our understanding of how parasites impact sexual selection in their hosts, and how sexual selection is involved in host-parasite coevolution.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>exually selected ornaments range from highly dynamic traits to those that are fixed during development and relatively static throughout sexual maturity. Ornaments along this continuum differ in the information they provide about the qualities of potential mates, such as their parasite resistance. Dynamic ornaments enable real-time assessment of the bearer&rsquo;s condition: they can reflect an individual&rsquo;s current infection status, or resistance to recent infections. Static ornaments, however, are not affected by recent infection but may instead indicate an individual&rsquo;s genetically determined resistance, even in the absence of infection. Given the typically aggregated distribution of parasites among hosts, infection is unlikely to affect the ornaments of the vast majority of individuals in a population: static ornaments may therefore be the more reliable indicators of parasite resistance. To test this hypothesis, we quantified the ornaments of male guppies, <i>Poecilia reticulata</i>, before experimentally infecting them with <i>Gyrodactylus turnbulli</i>. Males with more left-right symmetrical black coloration and those with larger areas of orange coloration, both static ornaments, were more resistant. However, males with more saturated orange coloration, a dynamic ornament, were less resistant. Female guppies often prefer symmetrical males with larger orange ornaments, suggesting parasite-mediated natural and sexual selection act in concert on these traits.</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> Fri, 21 Aug 2020 05:00:00 GMT “Understanding the social dynamics of breeding phenology: indirect genetic effects and assortative mating in a long distance migrant” https://amnat.org/an/newpapers/Nov-Moiron.html Maria Moiron, Yimen G. Araya-Ajoy, C&eacute;line Teplitsky, Sandra Bouwhuis, and Anne Charmantier (Nov 2020) Breeding timing is influenced by indirect partner effects and assortative mating for migratory phenotype of pair members Read the Article (Just Accepted)The date at which the first egg of a clutch is laid is a trait expressed exclusively by female birds. Yet males and females interact and, as a result, males might also influence when their partners will start laying eggs. For instance, males of various species provide food as part of courtship feeding events that reinforce the pair bond, and more or better food may lead to earlier laying. From an evolutionary point of view, it is not only important to investigate whether male effects on female traits exist, but also whether they are underpinned by a genetic component, because, if so, they may facilitate or constrain evolutionary responses to selection. Researchers from the Centre d’&Eacute;cologie Fonctionnelle et &Eacute;volutive (France), Institute of Avian Research (Germany), and Norwegian University of Science and Technology (Norway) investigated male effects on female egg laying date using data from a population of individually marked common terns studied during their breeding seasons in Germany for over 30 years. Common terns are migratory seabirds and the ones breeding in Germany spend their winters in West Africa, arrive at the breeding colony in April-May, and start breeding in May-June. The team found that males influence female laying date, and this effect has a genetic component. Further analyses revealed that male arrival date was a trait underlying the observed male effect, and that it may largely be explained by assortative mating for arrival date: males that consistently arrive early mate with females that consistently arrive early and birds that arrive early also lay early. Moiron and colleagues therefore argue that it is not only important to study partner effects, but to also uncover the potential causal pathways and confounding effects underlying them. &nbsp; El inicio de la reproducci&oacute;n en las hembras de charr&aacute;n com&uacute;n est&aacute; influenciado por los machos y el apareamiento selectivo acorde al fenotipo migratorio La fecha del primer huevo de una nidada es un rasgo expresado exclusivamente por las hembras. Sin embargo, machos y hembras interact&uacute;an y, como resultado, los machos tambi&eacute;n pueden influir en el inicio de la puesta de huevos. Por ejemplo, los machos de varias especies proporcionan alimentos durante el cortejo. Este cortejo sirve para reforzar el v&iacute;nculo de pareja, y a la vez, al proporcionar m&aacute;s o mejor comida, puede repercutir en una puesta m&aacute;s temprana. Desde un punto de vista evolutivo, no solo es importante investigar si existe un efecto del macho en los rasgos de la hembra, sino tambi&eacute;n si estos tienen un componente gen&eacute;tico, ya que, de ser as&iacute;, pueden facilitar o restringir las respuestas evolutivas a la selecci&oacute;n. Investigadores del Centre d’&Eacute;cologie Fonctionnelle et &Eacute;volutive (Francia), el Institute of Avian Research (Alemania) y la Norwegian University of Science and Technology (Noruega) han estudiado los efectos que el macho puede inducir en la fecha de puesta de huevos de la hembra utilizando datos de una poblaci&oacute;n de charranes comunes marcados individualmente, y que han sido estudiados durante sus temporadas de cr&iacute;a en Alemania durante m&aacute;s de 30 a&ntilde;os. Los charranes comunes son aves marinas migratorias y los que se reproducen en Alemania pasan sus inviernos en &Aacute;frica occidental, llegan a la colonia reproductora en abril-mayo y comienzan a reproducirse en mayo-junio. El equipo de investigadores descubri&oacute; que los machos influyen en la fecha de puesta de las hembras, y que este efecto tiene un componente gen&eacute;tico. An&aacute;lisis adicionales revelaron que la fecha de llegada de la migraci&oacute;n del macho era un rasgo subyacente al efecto del macho observado, y que puede explicarse en gran medida por el apareamiento selectivo acorde con la fecha de llegada de migraci&oacute;n. Moiron y sus colaboradores, por lo tanto, argumentan que no solo es importante estudiar los efectos de pareja en la puesta de huevos, sino tambi&eacute;n descubrir las posibles v&iacute;as causales y la existencia de sesgos subyacentes. Abstract Phenological traits, such as the timing of reproduction, are often influenced by social interactions between paired individuals. Such partner effects may occur when pair members affect each other’s pre-breeding environment. Partner effects can be environmentally and/or genetically determined, and quantifying direct and indirect genetic effects is important for understanding the evolutionary dynamics of phenological traits. Here, using 26 years of data from a pedigreed population of a migratory seabird, the common tern (Sterna hirundo), we investigate male and female effects on female laying date. We find that female laying date harbors both genetic and environmental variation, and is additionally influenced by the environmental, and, to a lower extent, genetic, component of its mate. We demonstrate this partner effect to be largely explained by male arrival date. Interestingly, analyses of mating patterns with respect to arrival date show mating to be strongly assortative and, using simulations, we show that assortative mating leads to overestimation of partner effects. Our study provides evidence for partner effects on breeding phenology in a long distance migrant, while uncovering the potential causal pathways underlying the observed effects and raising awareness for confounding effects due to assortative mating or other common environmental effects. More forthcoming papers &raquo; <p>Maria Moiron, Yimen G. Araya-Ajoy, C&eacute;line Teplitsky, Sandra Bouwhuis, and Anne Charmantier (Nov 2020)</p> <p><b>Breeding timing is influenced by indirect partner effects and assortative mating for migratory phenotype of pair members </b></p> <p><i><a href="https://doi.org/10.1086/711045">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 date at which the first egg of a clutch is laid is a trait expressed exclusively by female birds. Yet males and females interact and, as a result, males might also influence when their partners will start laying eggs. For instance, males of various species provide food as part of courtship feeding events that reinforce the pair bond, and more or better food may lead to earlier laying.</p> <p>From an evolutionary point of view, it is not only important to investigate whether male effects on female traits exist, but also whether they are underpinned by a genetic component, because, if so, they may facilitate or constrain evolutionary responses to selection.</p> <p>Researchers from the Centre d&rsquo;&Eacute;cologie Fonctionnelle et &Eacute;volutive (France), Institute of Avian Research (Germany), and Norwegian University of Science and Technology (Norway) investigated male effects on female egg laying date using data from a population of individually marked common terns studied during their breeding seasons in Germany for over 30 years. Common terns are migratory seabirds and the ones breeding in Germany spend their winters in West Africa, arrive at the breeding colony in April-May, and start breeding in May-June.</p> <p>The team found that males influence female laying date, and this effect has a genetic component. Further analyses revealed that male arrival date was a trait underlying the observed male effect, and that it may largely be explained by assortative mating for arrival date: males that consistently arrive early mate with females that consistently arrive early and birds that arrive early also lay early. Moiron and colleagues therefore argue that it is not only important to study partner effects, but to also uncover the potential causal pathways and confounding effects underlying them.</p> <p>&nbsp;</p> <h4>El inicio de la reproducci&oacute;n en las hembras de charr&aacute;n com&uacute;n est&aacute; influenciado por los machos y el apareamiento selectivo acorde al fenotipo migratorio</h4> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">L</span>a fecha del primer huevo de una nidada es un rasgo expresado exclusivamente por las hembras. Sin embargo, machos y hembras interact&uacute;an y, como resultado, los machos tambi&eacute;n pueden influir en el inicio de la puesta de huevos. Por ejemplo, los machos de varias especies proporcionan alimentos durante el cortejo. Este cortejo sirve para reforzar el v&iacute;nculo de pareja, y a la vez, al proporcionar m&aacute;s o mejor comida, puede repercutir en una puesta m&aacute;s temprana.</p> <p>Desde un punto de vista evolutivo, no solo es importante investigar si existe un efecto del macho en los rasgos de la hembra, sino tambi&eacute;n si estos tienen un componente gen&eacute;tico, ya que, de ser as&iacute;, pueden facilitar o restringir las respuestas evolutivas a la selecci&oacute;n.</p> <p>Investigadores del Centre d&rsquo;&Eacute;cologie Fonctionnelle et &Eacute;volutive (Francia), el Institute of Avian Research (Alemania) y la Norwegian University of Science and Technology (Noruega) han estudiado los efectos que el macho puede inducir en la fecha de puesta de huevos de la hembra utilizando datos de una poblaci&oacute;n de charranes comunes marcados individualmente, y que han sido estudiados durante sus temporadas de cr&iacute;a en Alemania durante m&aacute;s de 30 a&ntilde;os. Los charranes comunes son aves marinas migratorias y los que se reproducen en Alemania pasan sus inviernos en &Aacute;frica occidental, llegan a la colonia reproductora en abril-mayo y comienzan a reproducirse en mayo-junio.</p> <p>El equipo de investigadores descubri&oacute; que los machos influyen en la fecha de puesta de las hembras, y que este efecto tiene un componente gen&eacute;tico. An&aacute;lisis adicionales revelaron que la fecha de llegada de la migraci&oacute;n del macho era un rasgo subyacente al efecto del macho observado, y que puede explicarse en gran medida por el apareamiento selectivo acorde con la fecha de llegada de migraci&oacute;n. Moiron y sus colaboradores, por lo tanto, argumentan que no solo es importante estudiar los efectos de pareja en la puesta de huevos, sino tambi&eacute;n descubrir las posibles v&iacute;as causales y la existencia de sesgos subyacentes.</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>henological traits, such as the timing of reproduction, are often influenced by social interactions between paired individuals. Such partner effects may occur when pair members affect each other&rsquo;s pre-breeding environment. Partner effects can be environmentally and/or genetically determined, and quantifying direct and indirect genetic effects is important for understanding the evolutionary dynamics of phenological traits. Here, using 26 years of data from a pedigreed population of a migratory seabird, the common tern (<i>Sterna hirundo</i>), we investigate male and female effects on female laying date. We find that female laying date harbors both genetic and environmental variation, and is additionally influenced by the environmental, and, to a lower extent, genetic, component of its mate. We demonstrate this partner effect to be largely explained by male arrival date. Interestingly, analyses of mating patterns with respect to arrival date show mating to be strongly assortative and, using simulations, we show that assortative mating leads to overestimation of partner effects. Our study provides evidence for partner effects on breeding phenology in a long distance migrant, while uncovering the potential causal pathways underlying the observed effects and raising awareness for confounding effects due to assortative mating or other common environmental effects.</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> Fri, 21 Aug 2020 05:00:00 GMT “Life-history modeling reveals the ecological and evolutionary significance of autotomy” https://amnat.org/an/newpapers/Nov-Hoso.html Masaki Hoso and Ichiro K. Shimatani (Dec 2020) Mark-recapture study reveals how much fitness advantage is conferred by snail autotomy against snake predation Read the Article (Just Accepted) When attacked, lizards drop their tails and grasshoppers release their legs. Autotomy, the self-shedding of body parts, is widespread in animals, and its survival benefit seems apparent. But it remains unknown what proportion of deaths is prevented by autotomy in nature. The authors tackled this classic and fundamental question by modeling the invisible process of prey’s life history. They applied their novel approach to a unique predator-prey system in Iriomote Island, Japan, where a land snail autotomizes and regenerates its foot in response to snake bites. Using field and laboratory data, they estimated three properties of the snail prey that have rarely or never been quantified in the wild: (1) how frequently they encountered snake predators; (2) what proportion of their mortality was attributable to snake predation; and (3) how much advantage was conferred by autotomy. Their approach is applicable to a range of predator-prey systems where unsuccessful predation attempts cause identical changes in appearance of prey animals. Abstract Autotomy, the self-amputation of body parts, serves as an anti-predator defense in many taxonomic groups of animals. However, its adaptive value has seldom been quantified. Here, we propose a novel modeling approach for measuring the fitness advantage conferred by the capability for autotomy in the wild. Using a predator-prey system where a land snail autotomizes and regenerates its foot specifically in response to snake bites, we conducted a laboratory behavioral experiment and a 3-year multi-event capture–mark–recapture (CMR) study. Combining these empirical data, we developed a hierarchical model and estimated the basic life history parameters of the snail. Using samples from the posterior distribution, we constructed the snail’s life table as well as that of a snail variant incapable of foot autotomy. As a result of our analyses, we estimated the monthly encounter rate with snake predators at 3.3% (95% CI: 1.6–4.9%), the contribution of snake predation to total mortality until maturity at 43.3% (15.0–95.3%), and the fitness advantage conferred by foot autotomy at 6.5% (2.7–11.5%). This study demonstrated the utility of the multi-method hierarchical modeling approach for the quantitative understanding of the ecological and evolutionary processes of anti-predator defenses in the wild.&emsp; 自切の生態学的および進化学的意義を生活史モデリングによって解き明かす 自切、すなわち身体の一部を自発的に切り離す行動は、さまざまな分類群の動物において被食防御の効果をもつことが知られている。しかし、実際にどの程度、適応度が自切によって向上しているのかは、定量的に評価されたことがほとんどない。そこで我々は、自切する能力を備えることによって向上する適応度を野外で測定する手法を開発し、現実のシステムに対して適用した。用いた動物は、ヘビからの被食に際して特異的に腹足を自切するカタツムリである。我々は、捕食行動実験の結果と3年間におよぶ標識再捕獲データを階層モデルによって統合し、カタツムリの生活史に関わるパラメーターを推定した。また、パラメーターの事後分布を用いたシミュレーションにより生命表を構築した。解析の結果、カタツムリにとってのヘビとの月間遭遇率は 3.3% (95%信用区間: 1.6–4.9%)、成熟に至るまでの死因に占めるヘビからの捕食圧は 43.3% (15.0–95.3%)、そして自切能力によって向上している適応度は 6.5% (2.7–11.5%) と推定された。この研究は、野外における被食防御の生態的および進化的過程を定量的に理解するにあたり、複数のデータを統合する階層モデルの有用性を示すものでもある。 More forthcoming papers &raquo; <p>Masaki Hoso and Ichiro K. Shimatani (Dec 2020) </p> <p><b>Mark-recapture study reveals how much fitness advantage is conferred by snail autotomy against snake predation </b></p> <p><i><a href="https://doi.org/10.1086/711311">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hen attacked, lizards drop their tails and grasshoppers release their legs. Autotomy, the self-shedding of body parts, is widespread in animals, and its survival benefit seems apparent. But it remains unknown what proportion of deaths is prevented by autotomy in nature. The authors tackled this classic and fundamental question by modeling the invisible process of prey&rsquo;s life history. They applied their novel approach to a unique predator-prey system in Iriomote Island, Japan, where a land snail autotomizes and regenerates its foot in response to snake bites. Using field and laboratory data, they estimated three properties of the snail prey that have rarely or never been quantified in the wild: (1) how frequently they encountered snake predators; (2) what proportion of their mortality was attributable to snake predation; and (3) how much advantage was conferred by autotomy. Their approach is applicable to a range of predator-prey systems where unsuccessful predation attempts cause identical changes in appearance of prey animals.</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>utotomy, the self-amputation of body parts, serves as an anti-predator defense in many taxonomic groups of animals. However, its adaptive value has seldom been quantified. Here, we propose a novel modeling approach for measuring the fitness advantage conferred by the capability for autotomy in the wild. Using a predator-prey system where a land snail autotomizes and regenerates its foot specifically in response to snake bites, we conducted a laboratory behavioral experiment and a 3-year multi-event capture&ndash;mark&ndash;recapture (CMR) study. Combining these empirical data, we developed a hierarchical model and estimated the basic life history parameters of the snail. Using samples from the posterior distribution, we constructed the snail&rsquo;s life table as well as that of a snail variant incapable of foot autotomy. As a result of our analyses, we estimated the monthly encounter rate with snake predators at 3.3% (95% CI: 1.6&ndash;4.9%), the contribution of snake predation to total mortality until maturity at 43.3% (15.0&ndash;95.3%), and the fitness advantage conferred by foot autotomy at 6.5% (2.7&ndash;11.5%). This study demonstrated the utility of the multi-method hierarchical modeling approach for the quantitative understanding of the ecological and evolutionary processes of anti-predator defenses in the wild.&emsp;</p> <h4>自切の生態学的および進化学的意義を生活史モデリングによって解き明かす</h4> <p>自切、すなわち身体の一部を自発的に切り離す行動は、さまざまな分類群の動物において被食防御の効果をもつことが知られている。しかし、実際にどの程度、適応度が自切によって向上しているのかは、定量的に評価されたことがほとんどない。そこで我々は、自切する能力を備えることによって向上する適応度を野外で測定する手法を開発し、現実のシステムに対して適用した。用いた動物は、ヘビからの被食に際して特異的に腹足を自切するカタツムリである。我々は、捕食行動実験の結果と3年間におよぶ標識再捕獲データを階層モデルによって統合し、カタツムリの生活史に関わるパラメーターを推定した。また、パラメーターの事後分布を用いたシミュレーションにより生命表を構築した。解析の結果、カタツムリにとってのヘビとの月間遭遇率は 3.3% (95%信用区間: 1.6&ndash;4.9%)、成熟に至るまでの死因に占めるヘビからの捕食圧は 43.3% (15.0&ndash;95.3%)、そして自切能力によって向上している適応度は 6.5% (2.7&ndash;11.5%) と推定された。この研究は、野外における被食防御の生態的および進化的過程を定量的に理解するにあたり、複数のデータを統合する階層モデルの有用性を示すものでもある。</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> Fri, 21 Aug 2020 05:00:00 GMT “Janzen–Connell effects are a weak impediment to competitive exclusion” https://amnat.org/an/newpapers/Nov-Chisholm.html Ryan Chisholm and Tak Fung (Nov 2020) Modeling indicates that Janzen-Connell effects maintain little diversity in the presence of intrinsic fitness variation Read the ArticleStep into a tropical forest and before long something will attack you. A mosquito bites you, a tick latches on, a chigger bores under your skin. You sit on the ground and get a nasty case of worms. Eventually, fungi eat away at your clothes. Such pests and pathogens can make life difficult—not just for humans but for plants and other tropical forest organisms as well. But could these “natural enemies” in fact be essential to the ecosystem, by preventing any one species from getting the upper hand? In a new study, two ecologists from the National University of Singapore tested this idea for tropical forest trees by building mathematical models in which each tree species is attacked by its own specialised enemy. In real tropical forests, there can be dozens or hundreds of tree species in a single hectare. Did their model produce similar diversity? The answer in general was no. Only in a very special case, the ecological equivalent of a pin landing on its head, did they e get such high tree diversity. This special case was when all species were equivalent—they all had the same death rate, same birth rate, and so on. Because pins generally do not land on their heads in nature, this scenario is implausible. The idea that pests and pathogens, through their voracious activities, can maintain forest diversity is vivid and appealing, but it does not stand up to scrutiny. The quest for a rigorous explanation of tropical forest diversity continues. Abstract A&nbsp;goal of ecology is to identify the stabilizing mechanisms that maintain species diversity in the face of competitive exclusion and drift. For tropical forest tree communities, it has been hypothesized that high diversity is maintained via Janzen–Connell effects, whereby host-specific natural enemies prevent any one species from becoming too abundant. Here, we explore the plausibility of this hypothesis with theoretical models. We confirm a previous result that when added to a model with drift but no competitive exclusion, i.e., a neutral model where intrinsic fitnesses are perfectly equalized across species, Janzen–Connell effects maintain very high species richness that scales strongly with community size. However, when competitive exclusion is introduced, i.e., when intrinsic fitnesses vary across species, the number of species maintained by Janzen–Connell effects is substantially reduced, and scales much less strongly with community size. Because fitness variation is pervasive in nature, we conclude that the potential of Janzen–Connell effects to maintain diversity is probably weak, and that the mechanism does not yet provide a sufficient explanation for the observed high diversity of tropical forest tree communities. We also show that, surprisingly, dispersal limitation can further reduce the ability of Janzen–Connell effects to maintain diversity. More forthcoming papers &raquo; <p>Ryan Chisholm and Tak Fung (Nov 2020)</p> <p><b>Modeling indicates that Janzen-Connell effects maintain little diversity in the presence of intrinsic fitness variation </b></p> <p><i><a href="https://doi.org/10.1086/711042">Read the Article</a></i></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>tep into a tropical forest and before long something will attack you. A mosquito bites you, a tick latches on, a chigger bores under your skin. You sit on the ground and get a nasty case of worms. Eventually, fungi eat away at your clothes. Such pests and pathogens can make life difficult—not just for humans but for plants and other tropical forest organisms as well. But could these “natural enemies” in fact be essential to the ecosystem, by preventing any one species from getting the upper hand? In a new study, two ecologists from the National University of Singapore tested this idea for tropical forest trees by building mathematical models in which each tree species is attacked by its own specialised enemy. In real tropical forests, there can be dozens or hundreds of tree species in a single hectare. Did their model produce similar diversity? The answer in general was no. Only in a very special case, the ecological equivalent of a pin landing on its head, did they e get such high tree diversity. This special case was when all species were equivalent—they all had the same death rate, same birth rate, and so on. Because pins generally do not land on their heads in nature, this scenario is implausible. The idea that pests and pathogens, through their voracious activities, can maintain forest diversity is vivid and appealing, but it does not stand up to scrutiny. The quest for a rigorous explanation of tropical forest diversity continues. </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;goal of ecology is to identify the stabilizing mechanisms that maintain species diversity in the face of competitive exclusion and drift. For tropical forest tree communities, it has been hypothesized that high diversity is maintained via Janzen–Connell effects, whereby host-specific natural enemies prevent any one species from becoming too abundant. Here, we explore the plausibility of this hypothesis with theoretical models. We confirm a previous result that when added to a model with drift but no competitive exclusion, i.e., a neutral model where intrinsic fitnesses are perfectly equalized across species, Janzen–Connell effects maintain very high species richness that scales strongly with community size. However, when competitive exclusion is introduced, i.e., when intrinsic fitnesses vary across species, the number of species maintained by Janzen–Connell effects is substantially reduced, and scales much less strongly with community size. Because fitness variation is pervasive in nature, we conclude that the potential of Janzen–Connell effects to maintain diversity is probably weak, and that the mechanism does not yet provide a sufficient explanation for the observed high diversity of tropical forest tree communities. We also show that, surprisingly, dispersal limitation can further reduce the ability of Janzen–Connell effects to maintain 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> Fri, 21 Aug 2020 05:00:00 GMT “Proximate causes of infertility and embryo mortality in captive zebra finches” https://amnat.org/an/newpapers/Nov-Pei.html Yifan Pei, Wolfgang Forstmeier, Daiping Wang, Katrin Martin, Joanna Rutkowska, and Bart Kempenaers (Nov 2020) High rates of infertility and embryo mortality in zebra finches are puzzling but partly explained by sexual antagonism Read the Article (Just Accepted) In a wide range of species, including humans and birds, some couples experience difficulties with reproduction. Are such problems mostly a matter of age, of inbreeding (the pairing of close relatives), or of poor early-life conditions? Is reproductive failure caused by the male, the female, or by the specific combination of both partners? Are reproductive problems encoded in the genes, and if so, why do such detrimental genes exist in the first place? Scientists and the general public alike have long been puzzled by the causes of infertility and embryo mortality. However, thorough quantitative analyses of reproductive failure are rare, even in relatively well-studied species. To answer those questions, researchers from the Max Planck Institute for Ornithology in Germany monitored and studied the fate of more than twenty-three thousand eggs in a captive population of zebra finches. They found that infertility is predominantly a male-specific problem, whereas embryo and nestling mortality are mostly a matter of the female. However, the main causes of infertility and offspring mortality remain unidentified. Age, inbreeding, and early-life conditions all have significant effects on reproductive performance, but explain only a little of the observed individual differences. This study provides further insights into the genetic causes of reproductive failure. Using quantitative genetic analysis, the researchers found that some of the genetic variants underlying male infertility tend to have beneficial effects on females, which might explain why such genetic variants can persist in the population. Abstract Some species show high rates of reproductive failure, which is puzzling because natural selection works against such failure in every generation. Hatching failure is common in both captive and wild zebra finches (Taeniopygia guttata), yet little is known about its proximate causes. Here we analyze data on reproductive performance (fate of >23,000 eggs) based on up to 14 years of breeding of four captive zebra finch populations. We find that virtually all aspects of reproductive performance are negatively affected by inbreeding (mean r&nbsp;=&nbsp;&minus;0.117), by an early-starting, age-related decline (mean r&nbsp;=&nbsp;&minus;0.132), and by poor early-life nutrition (mean r&nbsp;=&nbsp;&minus;0.058). However, these effects together explain only about 3% of the variance in infertility, offspring mortality, fecundity and fitness. In contrast, individual repeatability of different fitness components varied between 15% and 50%. As expected, we found relatively low heritability in fitness components (median: 7% of phenotypic, and 29% of individually repeatable variation). Yet, some of the heritable variation in fitness appears to be maintained by antagonistic pleiotropy (negative genetic correlations) between male fitness traits and female and offspring fitness traits. The large amount of unexplained variation suggests a potentially important role of local dominance and epistasis, including the possibility of segregating genetic incompatibilities. More forthcoming papers &raquo; <p>Yifan Pei, Wolfgang Forstmeier, Daiping Wang, Katrin Martin, Joanna Rutkowska, and Bart Kempenaers (Nov 2020) </p> <p><b>High rates of infertility and embryo mortality in zebra finches are puzzling but partly explained by sexual antagonism </b></p> <p><i><a href="https://dx.doi.org/10.1086/710956">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n a wide range of species, including humans and birds, some couples experience difficulties with reproduction. Are such problems mostly a matter of age, of inbreeding (the pairing of close relatives), or of poor early-life conditions? Is reproductive failure caused by the male, the female, or by the specific combination of both partners? Are reproductive problems encoded in the genes, and if so, why do such detrimental genes exist in the first place? Scientists and the general public alike have long been puzzled by the causes of infertility and embryo mortality. However, thorough quantitative analyses of reproductive failure are rare, even in relatively well-studied species. </p><p>To answer those questions, researchers from the Max Planck Institute for Ornithology in Germany monitored and studied the fate of more than twenty-three thousand eggs in a captive population of zebra finches. They found that infertility is predominantly a male-specific problem, whereas embryo and nestling mortality are mostly a matter of the female. However, the main causes of infertility and offspring mortality remain unidentified. Age, inbreeding, and early-life conditions all have significant effects on reproductive performance, but explain only a little of the observed individual differences. This study provides further insights into the genetic causes of reproductive failure. Using quantitative genetic analysis, the researchers found that some of the genetic variants underlying male infertility tend to have beneficial effects on females, which might explain why such genetic variants can persist in the population. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>ome species show high rates of reproductive failure, which is puzzling because natural selection works against such failure in every generation. Hatching failure is common in both captive and wild zebra finches (<i>Taeniopygia guttata</i>), yet little is known about its proximate causes. Here we analyze data on reproductive performance (fate of &gt;23,000 eggs) based on up to 14 years of breeding of four captive zebra finch populations. We find that virtually all aspects of reproductive performance are negatively affected by inbreeding (mean <i>r</i>&nbsp;=&nbsp;&minus;0.117), by an early-starting, age-related decline (mean <i>r</i>&nbsp;=&nbsp;&minus;0.132), and by poor early-life nutrition (mean <i>r</i>&nbsp;=&nbsp;&minus;0.058). However, these effects together explain only about 3% of the variance in infertility, offspring mortality, fecundity and fitness. In contrast, individual repeatability of different fitness components varied between 15% and 50%. As expected, we found relatively low heritability in fitness components (median: 7% of phenotypic, and 29% of individually repeatable variation). Yet, some of the heritable variation in fitness appears to be maintained by antagonistic pleiotropy (negative genetic correlations) between male fitness traits and female and offspring fitness traits. The large amount of unexplained variation suggests a potentially important role of local dominance and epistasis, including the possibility of segregating genetic incompatibilities. </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, 18 Aug 2020 05:00:00 GMT “Evolution of plasticity in response to ethanol between sister species with different ecological histories (<i>Drosophila melanogaster</i> and <i>D. simulans</i>)” https://amnat.org/an/newpapers/Nov-Signor-A.html Sarah A. Signor (Nov 2020) Drosophila evolves to exploit novel resources through genetic accommodation Read the ArticleAbstract When populations evolve adaptive reaction norms in response to novel environments it can occur through a process termed genetic accommodation. Under this model, the initial response to the environment is widely variable between genotypes due to cryptic genetic variation, which is then refined by selection to a single adaptive response. Here, I empirically test these predictions from genetic accommodation by measuring reaction norms in individual genotypes, and across several time points. I compare two species of Drosophila that differ in their adaptation to ethanol (Drosophila melanogaster and D.&nbsp;simulans). Both species are human commensals with a recent cosmopolitan expansion, but only D.&nbsp;melanogaster is adapted to ethanol exposure. Using gene expression as a phenotype and an approach that combines information about expression and alternative splicing I find that D.&nbsp;simulans exhibits cryptic genetic variation in the response to ethanol, while D.&nbsp;melanogaster has almost no genotype-specific variation in reaction norm. This is evidence for adaptation to ethanol through genetic accommodation, suggesting that the evolution of phenotypic plasticity could be an important contributor to the ability to exploit novel resources. More forthcoming papers &raquo; <p>Sarah A. Signor (Nov 2020)</p> <p><b><i>Drosophila</i> evolves to exploit novel resources through genetic accommodation </b></p> <p><i><a href="https://dx.doi.org/10.1086/710763">Read the Article</a></i></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hen populations evolve adaptive reaction norms in response to novel environments it can occur through a process termed genetic accommodation. Under this model, the initial response to the environment is widely variable between genotypes due to cryptic genetic variation, which is then refined by selection to a single adaptive response. Here, I empirically test these predictions from genetic accommodation by measuring reaction norms in individual genotypes, and across several time points. I compare two species of <i>Drosophila </i> that differ in their adaptation to ethanol (<i>Drosophila melanogaster</i> and <i>D.&nbsp;simulans</i>). Both species are human commensals with a recent cosmopolitan expansion, but only <i>D.&nbsp;melanogaster</i> is adapted to ethanol exposure. Using gene expression as a phenotype and an approach that combines information about expression and alternative splicing I find that <i>D.&nbsp;simulans</i> exhibits cryptic genetic variation in the response to ethanol, while <i>D.&nbsp;melanogaster</i> has almost no genotype-specific variation in reaction norm. This is evidence for adaptation to ethanol through genetic accommodation, suggesting that the evolution of phenotypic plasticity could be an important contributor to the ability to exploit novel resources. </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, 18 Aug 2020 05:00:00 GMT “The complexity of social complexity: a quantitative multidimensional approach for studies on social organization” https://amnat.org/an/newpapers/Nov-Holland.html Jacob George Holland and Guy Bloch (Nov 2020) Social complexity evolution is not ladderlike as assumed: quantifying individual social traits provides better direction Read the ArticleHow did complex animal societies evolve from solitary ancestors? Animals such as species of bees, ants, and wasps, live in social groups which determine many aspects of their biology. In some species these associations are loose, but in others individuals are entirely dependant on one another for daily life. Some of these groups resemble a “superorganism”, with incredible coordination between large numbers of specialised individuals. Many social insects are ecologically significant and economically important, further urging the need to understand their biology. The common research approach has assumed that there is a series of neat stages of social complexity that need to be passed in order to reach the highest level, like climbing rungs on a ladder. We propose that, instead, complexity should be measured separately for multiple social traits, such as colony size or the amount of individual specialisation. We focus on bumble bees, which provide a nice example of limitations in the current approach, because their social complexity has been defined quite differently across studies. Moreover, some of their social traits are relatively simple, such as small colonies, and reproduction by females other than the queen (“worker” bees); whereas other traits are socially complex, such as workers which vary greatly in size and perform different roles. Our approach overcomes these limitations and allows us to distinguish between species that are currently defined as having the same level of social complexity, despite substantial variation in some of their social traits. Our approach also makes it easier to understand how different social traits might be linked to specific molecular or behavioural mechanisms that have been important for the evolution of social complexity. Abstract The rapid increase in “big data” of the post-genomic era makes it crucial to appropriately measure the level of social complexity in comparative studies. We argue that commonly used qualitative classifications lump together species showing a broad range of social complexity, and falsely imply that social evolution always progresses along a single linear stepwise trajectory that can be deduced from comparing extant species. To illustrate this point, we compared widely used social complexity measures in "primitively eusocial" bumble bees with “advanced eusocial” stingless bees, honey bees, and attine ants. We find that a single species can have both higher and lower levels of complexity compared to other taxa, depending on the social trait measured. We propose that measuring the complexity of individual social traits switches focus from semantic discussions and offers several directions for progress. Firstly, quantitative social traits can be correlated with molecular, developmental, and physiological processes within and across lineages of social animals. This approach is particularly promising for identifying processes that influence or have been affected by social evolution. Secondly, key social complexity traits can be combined into multidimensional lineage-specific quantitative indices enabling fine scale comparison across species that are currently bundled within the same level of social complexity. More forthcoming papers &raquo; <p>Jacob George Holland and Guy Bloch (Nov 2020)</p> <p><b>Social complexity evolution is not ladderlike as assumed: quantifying individual social traits provides better direction </b></p> <p><i><a href="https://dx.doi.org/10.1086/710957">Read the Article</a></i></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">H</span>ow did complex animal societies evolve from solitary ancestors? Animals such as species of bees, ants, and wasps, live in social groups which determine many aspects of their biology. In some species these associations are loose, but in others individuals are entirely dependant on one another for daily life. Some of these groups resemble a “superorganism”, with incredible coordination between large numbers of specialised individuals. Many social insects are ecologically significant and economically important, further urging the need to understand their biology. The common research approach has assumed that there is a series of neat stages of social complexity that need to be passed in order to reach the highest level, like climbing rungs on a ladder. We propose that, instead, complexity should be measured separately for multiple social traits, such as colony size or the amount of individual specialisation. We focus on bumble bees, which provide a nice example of limitations in the current approach, because their social complexity has been defined quite differently across studies. Moreover, some of their social traits are relatively simple, such as small colonies, and reproduction by females other than the queen (“worker” bees); whereas other traits are socially complex, such as workers which vary greatly in size and perform different roles. Our approach overcomes these limitations and allows us to distinguish between species that are currently defined as having the same level of social complexity, despite substantial variation in some of their social traits. Our approach also makes it easier to understand how different social traits might be linked to specific molecular or behavioural mechanisms that have been important for the evolution of social complexity. </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 rapid increase in “big data” of the post-genomic era makes it crucial to appropriately measure the level of social complexity in comparative studies. We argue that commonly used qualitative classifications lump together species showing a broad range of social complexity, and falsely imply that social evolution always progresses along a single linear stepwise trajectory that can be deduced from comparing extant species. To illustrate this point, we compared widely used social complexity measures in "primitively eusocial" bumble bees with “advanced eusocial” stingless bees, honey bees, and attine ants. We find that a single species can have both higher and lower levels of complexity compared to other taxa, depending on the social trait measured. We propose that measuring the complexity of individual social traits switches focus from semantic discussions and offers several directions for progress. Firstly, quantitative social traits can be correlated with molecular, developmental, and physiological processes within and across lineages of social animals. This approach is particularly promising for identifying processes that influence or have been affected by social evolution. Secondly, key social complexity traits can be combined into multidimensional lineage-specific quantitative indices enabling fine scale comparison across species that are currently bundled within the same level of social complexity. </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, 18 Aug 2020 05:00:00 GMT