ASN RSS https://amnat.org/ Latest press releases and announcements from the ASN en-us Sat, 30 May 2020 05:00:00 GMT 60 “Deconstructing the impact of malaria vector diversity on disease risk” https://amnat.org/an/newpapers/Sep-Hoi.html Amber Gigi Hoi, Benjamin Gilbert, and Nicole Mideo (Sep 2020) Mosquitoes are not flying syringes—researchers at UofT dissects how mosquito diversity amplify malaria risk Read the Article (Just Accepted) A &nbsp;growing body of research explores how the structure of diverse host communities mediates the spread of infectious diseases; however, much less is known about the influence of vector communities despite their being major targets for disease control. In a new paper published in The&nbsp;American Naturalist, researchers at the University of Toronto, Amber Gigi Hoi, Benjamin Gilbert, and Nicole Mideo, present the first empirical evidence of mosquito diversity amplifying malaria prevalence. The parasites that cause malaria, one of the world’s deadliest vector-borne diseases, can be transmitted by more than 70 species of mosquitoes. Comparing mosquito communities around the globe, the precise number of species, and their relative abundances, vary considerably. These mosquito species also encompass substantial diversity in seasonal activity, habitat, and feeding preferences. Mosquitoes are not simply flying syringes (although it is sometimes convenient to think of them this way), and so nuances of their ecology and the structure of vector communities will influence disease risk. Amber and coauthors use publicly available mosquito and malaria survey data to tease apart the direct and indirect influences of total mosquito abundance, the number of species present, and the relative abundance of those species on malaria risk. They find that increasing the number of mosquito species directly increases malaria prevalence, though this effect is weakened slightly by more diverse mosquito communities harboring a lower relative abundance of the most ‘competent’ vector species. Total mosquito abundance is only indirectly associated with malaria prevalence through its relationship with these other measures of diversity. The researchers speculate that this is a consequence of species being active at different times of the year, prolonging the period over which disease transmission occurs. These results are consistent with previous theoretical work that predicts diverse vector communities will promote disease spread, and the study emphasizes the importance of understanding vector community ecology for designing sound vector management strategies. Abstract Recent years have seen significant progress in understanding the impact of host community assemblage on disease risk, yet diversity in disease vectors has rarely been investigated. Using published malaria and mosquito surveys from Kenya, we analyzed the relationship between malaria prevalence and multiple axes of mosquito diversity: abundance, species richness, and composition. We found a net amplification of malaria prevalence by vector species richness, a result of a strong direct positive association between richness and prevalence alongside a weak indirect negative association between the two, mediated through mosquito community composition. One plausible explanation of these patterns is species niche complementarity, whereby less competent vector species contribute to disease transmission by filling spatial or temporal gaps in transmission left by dominant vectors. A greater understanding of vector community assemblage and function, as well as any interactions between host and vector biodiversity, could offer insights to both fundamental and applied ecology. More forthcoming papers &raquo; <p>Amber Gigi Hoi, Benjamin Gilbert, and Nicole Mideo (Sep 2020) </p> <p><b>Mosquitoes are <i>not</i> flying syringes&mdash;researchers at UofT dissects how mosquito diversity amplify malaria risk </b></p> <p><i><a href="https://dx.doi.org/10.1086/710005">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> &nbsp;growing body of research explores how the structure of diverse host communities mediates the spread of infectious diseases; however, much less is known about the influence of vector communities despite their being major targets for disease control. In a new paper published in <i>The&nbsp;American Naturalist</i>, researchers at the University of Toronto, Amber Gigi Hoi, Benjamin Gilbert, and Nicole Mideo, present the first empirical evidence of mosquito diversity amplifying malaria prevalence. The parasites that cause malaria, one of the world’s deadliest vector-borne diseases, can be transmitted by more than 70 species of mosquitoes. Comparing mosquito communities around the globe, the precise number of species, and their relative abundances, vary considerably. These mosquito species also encompass substantial diversity in seasonal activity, habitat, and feeding preferences. Mosquitoes are not simply flying syringes (although it is sometimes convenient to think of them this way), and so nuances of their ecology and the structure of vector communities will influence disease risk. </p><p>Amber and coauthors use publicly available mosquito and malaria survey data to tease apart the direct and indirect influences of total mosquito abundance, the number of species present, and the relative abundance of those species on malaria risk. They find that increasing the number of mosquito species directly increases malaria prevalence, though this effect is weakened slightly by more diverse mosquito communities harboring a lower relative abundance of the most ‘competent’ vector species. Total mosquito abundance is only indirectly associated with malaria prevalence through its relationship with these other measures of diversity. The researchers speculate that this is a consequence of species being active at different times of the year, prolonging the period over which disease transmission occurs. These results are consistent with previous theoretical work that predicts diverse vector communities will promote disease spread, and the study emphasizes the importance of understanding vector community ecology for designing sound vector management strategies. </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;">R</span>ecent years have seen significant progress in understanding the impact of host community assemblage on disease risk, yet diversity in disease vectors has rarely been investigated. Using published malaria and mosquito surveys from Kenya, we analyzed the relationship between malaria prevalence and multiple axes of mosquito diversity: abundance, species richness, and composition. We found a net amplification of malaria prevalence by vector species richness, a result of a strong direct positive association between richness and prevalence alongside a weak indirect negative association between the two, mediated through mosquito community composition. One plausible explanation of these patterns is species niche complementarity, whereby less competent vector species contribute to disease transmission by filling spatial or temporal gaps in transmission left by dominant vectors. A greater understanding of vector community assemblage and function, as well as any interactions between host and vector biodiversity, could offer insights to both fundamental and applied ecology. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 29 May 2020 05:00:00 GMT “Defensive symbiosis and the evolution of virulence” https://amnat.org/an/newpapers/Sep-Nelson-A.html Paul Nelson and Georgiana May (Sep 2020) Symbiont defense of the host can protect against pathogens, but it may sometimes lead to the loss of mutualism Read the Article (Just Accepted) Abstract A&nbsp;microbiome rife with enemies of the host should cause selection for defensive traits in symbionts yet such complex environments are also predicted to select for greater symbiont virulence. Why then do we so often observe defensive mutualists that protect hosts while causing little to no damage? To address this question, we build a symbiont-centered model that incorporates the evolution of two independent symbiont traits: defense and virulence. Virulence is modeled as a continuous trait spanning parasitism (positive virulence) and mutualism (negative virulence), thus accounting for the entire range of direct effects that symbionts have on host mortality. Defense is modeled as a continuous trait that ameliorates the costs to the host associated with infection by a deleterious parasite. We show that the evolution of increased defense in one symbiont may lead to the evolution of lower virulence in both symbionts and even facilitate pathogens evolving to mutualism. However, results are context-dependent, and when defensive traits are costly, the evolution of greater defense may also lead to the evolution of greater virulence, breaking the common expectation that defensive symbionts are necessarily mutualists towards the host. More forthcoming papers &raquo; <p>Paul Nelson and Georgiana May (Sep 2020) </p> <p><b>Symbiont defense of the host can protect against pathogens, but it may sometimes lead to the loss of mutualism </b></p> <p><i><a href="https://dx.doi.org/10.1086/709962">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>&nbsp;microbiome rife with enemies of the host should cause selection for defensive traits in symbionts yet such complex environments are also predicted to select for greater symbiont virulence. Why then do we so often observe defensive mutualists that protect hosts while causing little to no damage? To address this question, we build a symbiont-centered model that incorporates the evolution of two independent symbiont traits: defense and virulence. Virulence is modeled as a continuous trait spanning parasitism (positive virulence) and mutualism (negative virulence), thus accounting for the entire range of direct effects that symbionts have on host mortality. Defense is modeled as a continuous trait that ameliorates the costs to the host associated with infection by a deleterious parasite. We show that the evolution of increased defense in one symbiont may lead to the evolution of lower virulence in both symbionts and even facilitate pathogens evolving to mutualism. However, results are context-dependent, and when defensive traits are costly, the evolution of greater defense may also lead to the evolution of greater virulence, breaking the common expectation that defensive symbionts are necessarily mutualists towards the host. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 29 May 2020 05:00:00 GMT “Consumer responses to experimental pulsed subsidies in isolated vs. connected habitats” https://amnat.org/an/newpapers/Sep-Wright-A.html Amber N. Wright, Louie H. Yang, Jonah Piovia-Scott, David A. Spiller, and Thomas W. Schoener (Sep 2020) Pulsed subsidies may facilitate establishment Read the Article (Just Accepted) Abstract Increases in consumer abundance following a resource pulse can be driven by diet shifts, aggregation, and reproductive responses, with combined responses expected to result in faster response times and larger numerical increases. Previous work in plots on large Bahamian islands has shown that lizards (Anolis sagrei) increased in abundance following pulses of seaweed deposition, which provide additional prey (i.e., seaweed detritivores). Numerical responses were associated with rapid diet shifts and aggregation, followed by increased reproduction. These dynamics are likely different on isolated small islands where lizards cannot readily immigrate or emigrate. To test this, we manipulated the frequency and magnitude of seaweed resource pulses on whole small islands and in plots within large islands, and monitored lizard diet and numerical responses over four years. We found that seaweed addition caused persistent increases in lizard abundance on small islands regardless of pulse frequency or magnitude. Increased abundance may have occurred because the initial pulse facilitated population establishment, possibly via enhanced overwinter survival. In contrast with a previous experiment, we did not detect numerical responses in plots on large islands, despite lizards consuming more marine resources in subsidized plots. This lack of a numerical response may be due to rapid aggregation followed by disaggregation, or stronger suppression of A.&nbsp;sagrei by their predators on large islands in this study. Our results highlight the importance of habitat connectivity in governing ecological responses to resource pulses and suggest that disaggregation and changes in survivorship may be underappreciated drivers of pulse-associated dynamics. More forthcoming papers &raquo; <p>Amber N. Wright, Louie H. Yang, Jonah Piovia-Scott, David A. Spiller, and Thomas W. Schoener (Sep 2020) </p> <p><b>Pulsed subsidies may facilitate establishment </b></p> <p><i><a href="https://dx.doi.org/10.1086/710040">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>ncreases in consumer abundance following a resource pulse can be driven by diet shifts, aggregation, and reproductive responses, with combined responses expected to result in faster response times and larger numerical increases. Previous work in plots on large Bahamian islands has shown that lizards (<i>Anolis sagrei</i>) increased in abundance following pulses of seaweed deposition, which provide additional prey (i.e., seaweed detritivores). Numerical responses were associated with rapid diet shifts and aggregation, followed by increased reproduction. These dynamics are likely different on isolated small islands where lizards cannot readily immigrate or emigrate. To test this, we manipulated the frequency and magnitude of seaweed resource pulses on whole small islands and in plots within large islands, and monitored lizard diet and numerical responses over four years. We found that seaweed addition caused persistent increases in lizard abundance on small islands regardless of pulse frequency or magnitude. Increased abundance may have occurred because the initial pulse facilitated population establishment, possibly via enhanced overwinter survival. In contrast with a previous experiment, we did not detect numerical responses in plots on large islands, despite lizards consuming more marine resources in subsidized plots. This lack of a numerical response may be due to rapid aggregation followed by disaggregation, or stronger suppression of <i>A.&nbsp;sagrei</i> by their predators on large islands in this study. Our results highlight the importance of habitat connectivity in governing ecological responses to resource pulses and suggest that disaggregation and changes in survivorship may be underappreciated drivers of pulse-associated dynamics. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 29 May 2020 05:00:00 GMT “The origin and spread of locally adaptive seasonal camouflage in snowshoe hares” https://amnat.org/an/newpapers/Sep-Jones-A.html Matthew R. Jones, L. Scott Mills, Jeffrey D. Jensen, and Jeffrey M. Good (Sep 2020) Hybridization, selection, and genetic dominance interact to shape range edge adaptation in snowshoe hares Read the Article (Just Accepted) Abstract Adaptation is central to population persistence in the face of environmental change, yet we seldom precisely understand the origin and spread of adaptive variation in natural populations. Snowshoe hares (Lepus americanus) along the Pacific Northwest (PNW) coast have evolved brown winter camouflage through positive selection on recessive variation at the Agouti pigmentation gene introgressed from black-tailed jackrabbits (L.&nbsp;californicus). Here we combine new and published whole genome and exome sequences with targeted genotyping of Agouti in order to investigate the evolutionary history of local seasonal camouflage adaptation in the PNW. We find evidence of significantly elevated inbreeding and mutational load in coastal winter-brown hares, consistent with a recent range expansion into temperate coastal environments that incurred indirect fitness costs. The genome-wide distribution of introgression tract lengths supports a pulse of hybridization near the end of the last glacial maximum, which may have facilitated range expansion via introgression of winter-brown camouflage variation. However, signatures of a selective sweep at Agouti indicate a much more recent spread of winter-brown camouflage. Through simulations we show that the delay between the hybrid origin and subsequent selective sweep of the recessive winter-brown allele can be largely attributed to the limits of natural selection imposed by simple allelic dominance. We argue that while hybridization during periods of environmental change may provide a critical reservoir of adaptive variation at range edges, the probability and pace of local adaptation will strongly depend on population demography and the genetic architecture of introgressed variation. More forthcoming papers &raquo; <p>Matthew R. Jones, L. Scott Mills, Jeffrey D. Jensen, and Jeffrey M. Good (Sep 2020) </p> <p><b>Hybridization, selection, and genetic dominance interact to shape range edge adaptation in snowshoe hares </b></p> <p><i><a href="https://dx.doi.org/10.1086/710022">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>daptation is central to population persistence in the face of environmental change, yet we seldom precisely understand the origin and spread of adaptive variation in natural populations. Snowshoe hares (<i>Lepus americanus</i>) along the Pacific Northwest (PNW) coast have evolved brown winter camouflage through positive selection on recessive variation at the<i> Agouti</i> pigmentation gene introgressed from black-tailed jackrabbits (<i>L.&nbsp;californicus</i>). Here we combine new and published whole genome and exome sequences with targeted genotyping of <i>Agouti</i> in order to investigate the evolutionary history of local seasonal camouflage adaptation in the PNW. We find evidence of significantly elevated inbreeding and mutational load in coastal winter-brown hares, consistent with a recent range expansion into temperate coastal environments that incurred indirect fitness costs. The genome-wide distribution of introgression tract lengths supports a pulse of hybridization near the end of the last glacial maximum, which may have facilitated range expansion via introgression of winter-brown camouflage variation. However, signatures of a selective sweep at <i>Agouti</i> indicate a much more recent spread of winter-brown camouflage. Through simulations we show that the delay between the hybrid origin and subsequent selective sweep of the recessive winter-brown allele can be largely attributed to the limits of natural selection imposed by simple allelic dominance. We argue that while hybridization during periods of environmental change may provide a critical reservoir of adaptive variation at range edges, the probability and pace of local adaptation will strongly depend on population demography and the genetic architecture of introgressed variation. </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, 29 May 2020 05:00:00 GMT “The Minimum Environmental Perturbation Principle: A New Perspective on Niche Theory” https://amnat.org/an/newpapers/Sep-Marsland-A.html Robert Marsland III, Wenping Cui, and Pankaj Mehta (Sep 2020) A new generalization of MacArthur&#39;s Minimization Principle produces an interpretable community-level objective function Read the Article (Just Accepted) Abstract Fifty years ago, Robert MacArthur showed that stable equilibria optimize quadratic functions of the population sizes in several important ecological models. Here, we generalize this finding to a broader class of systems within the framework of contemporary niche theory, and precisely state the conditions under which an optimization principle (not necessarily quadratic) can be obtained. We show that conducting the optimization in the space of environmental states instead of population sizes leads to a universal and transparent physical interpretation of the objective function. Specifically, the equilibrium state minimizes the perturbation of the environment induced by the presence of the competing species, subject to the constraint that no species has a positive net growth rate. We use this “minimum environmental perturbation principle” to make new predictions for evolution and community assembly, where the minimum perturbation increases monotonically under invasion by new species. We also describe a simple experimental setting where the conditions of validity for this optimization principle have been empirically tested. More forthcoming papers &raquo; <p>Robert Marsland III, Wenping Cui, and Pankaj Mehta (Sep 2020)</p> <p><b>A new generalization of MacArthur&#39;s Minimization Principle produces an interpretable community-level objective function </b></p> <p><i><a href="https://dx.doi.org/10.1086/710093">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;">F</span>ifty years ago, Robert MacArthur showed that stable equilibria optimize quadratic functions of the population sizes in several important ecological models. Here, we generalize this finding to a broader class of systems within the framework of contemporary niche theory, and precisely state the conditions under which an optimization principle (not necessarily quadratic) can be obtained. We show that conducting the optimization in the space of environmental states instead of population sizes leads to a universal and transparent physical interpretation of the objective function. Specifically, the equilibrium state minimizes the perturbation of the environment induced by the presence of the competing species, subject to the constraint that no species has a positive net growth rate. We use this &ldquo;minimum environmental perturbation principle&rdquo; to make new predictions for evolution and community assembly, where the minimum perturbation increases monotonically under invasion by new species. We also describe a simple experimental setting where the conditions of validity for this optimization principle have been empirically tested.</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, 29 May 2020 05:00:00 GMT “Male-male competition causes parasite-mediated sexual selection for local adaptation” https://amnat.org/an/newpapers/Sep-Gomez-Llano.html Miguel Gómez-Llano, Aaditya Narasimhan, and Erik Svensson (Sep 2020) Read the Article (Just Accepted) Parasites can affect species in a myriad of ways, one of these is by reducing their reproductive success. In this study, the authors found that male mating success was reduced when they were infected with parasites, but interestingly female fecundity was not. Further experiments showed that males with parasites were less able to compete with healthy males for access to females. Because mating success of infected males was reduced, local adaptation to become more resistant to parasites evolved, as shown by a long-term monitoring program. While working in a system of ponds in Southern Sweden, the authors of this study noticed that in a population of the common blue tail damselfly (Ischnura elegans), particularly heavily infested with parasite mites, males with parasites were usually found as singles while males with no parasites were, seemingly, more likely to be found mating. With this idea in mind, the authors design a series of experiments to test if this idea. They not only show that this was true and parasitized males were less likely to reproduce, they also show that the main mechanism behind this was competition between males. Because parasites reduce male condition, infected males are less likely to succeed when competing with other males for access to females. This area of Sweden has been thoroughly studied and a database of the population exists from the last 15 years. This data allowed the authors to test if parasite resistance (individuals are less likely to be infected) and tolerance (individuals get less affected by parasites) has evolve as a response to the reduced reproductive success of parasitized males. Their results show evidence for adaptation due to a reduced reproductive success of parasitized males in a wild insect population. Abstract Sexual selection has been suggested to accelerate local adaptation and promote evolutionary rescue through several ecological and genetic mechanisms. Condition-dependent sexual selection has mainly been studied in laboratory settings while data from natural populations are lacking. One ecological factor that can cause condition-dependent sexual selection is parasitism. Here, we quantified ectoparasite load (Arrenurus water mites) in a natural population of the common bluetail damselfly (Ischnura elegans) over 15 years. We quantified the strength of sexual selection against parasite load in both sexes and experimentally investigated the mechanisms behind such selection. Then, we investigated how parasite resistance and tolerance changed over time to understand how they might influence population density. Parasites reduced mating success in both sexes, and sexual selection was stronger in males than in females. Experiments show that male-male competition is a strong force causing precopulatory sexual selection against parasite load. Although parasite resistance and male parasite tolerance increased over time, suggestive of increasing local adaptation against parasites, no signal of evolutionary rescue could be found. We suggest that condition-dependent sexual selection facilitates local adaptation against parasites and discuss its effects in evolutionary rescue. La competencia entre machos causa selecci&oacute;n sexual mediada por par&aacute;sitos, promoviendo la adaptaci&oacute;n Se ha sugerido que la selecci&oacute;n sexual puede acelerar la adaptaci&oacute;n y facilitar el rescate evolutivo a trav&eacute;s de diversos mecanismos ecol&oacute;gicos y gen&eacute;ticos. La selecci&oacute;n sexual sobre la condici&oacute;n ha sido estudiada principalmente en el laboratorio, mientras existe una escasez de datos de poblaciones silvestres. Un factor ecol&oacute;gico que puede causar selecci&oacute;n sexual sobre la condici&oacute;n es el parasitismo. En este estudio cuantificamos la carga de ectopar&aacute;sitos (&aacute;caros acu&aacute;ticos Arrenurus) en una poblaci&oacute;n silvestre de una especie de odonatos (Ischnura elegans) por 15 a&ntilde;os. Cuantificamos la fuerza de la selecci&oacute;n sexual en contra de individuos parasitados en ambos sexos e investigamos los mecanismos detr&aacute;s de dicha selecci&oacute;n. Posteriormente investigamos como la resistencia y tolerancia al par&aacute;sito ha cambiado a lo largo del tiempo y como puede influenciar la densidad poblacional. Los par&aacute;sitos redujeron el &eacute;xito reproductivo de ambos sexos, y la selecci&oacute;n sexual fue m&aacute;s fuerte en machos que en hembras. Los experimentos sugieren que la selecci&oacute;n sexual fue mediada principalmente por competencia entre machos, con poco o ning&uacute;n efecto de elecci&oacute;n de pareja. Aunque la resistencia y tolerancia al par&aacute;sito incrementaron con el tiempo, sugiriendo adaptaci&oacute;n al par&aacute;sito, no se encontraron se&ntilde;ales de rescate evolutivo. Sugerimos que la selecci&oacute;n sexual sobre la condici&oacute;n facilita la adaptaci&oacute;n al par&aacute;sito y discutimos sus efectos en el rescate evolutivo. More forthcoming papers &raquo; <p>Miguel Gómez-Llano, Aaditya Narasimhan, and Erik Svensson (Sep 2020) </p> <p><i><a href="https://dx.doi.org/10.1086/710039">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>arasites can affect species in a myriad of ways, one of these is by reducing their reproductive success. In this study, the authors found that male mating success was reduced when they were infected with parasites, but interestingly female fecundity was not. Further experiments showed that males with parasites were less able to compete with healthy males for access to females. Because mating success of infected males was reduced, local adaptation to become more resistant to parasites evolved, as shown by a long-term monitoring program.</p> <p>While working in a system of ponds in Southern Sweden, the authors of this study noticed that in a population of the common blue tail damselfly (<i>Ischnura elegans</i>), particularly heavily infested with parasite mites, males with parasites were usually found as singles while males with no parasites were, seemingly, more likely to be found mating. With this idea in mind, the authors design a series of experiments to test if this idea. They not only show that this was true and parasitized males were less likely to reproduce, they also show that the main mechanism behind this was competition between males. Because parasites reduce male condition, infected males are less likely to succeed when competing with other males for access to females.</p> <p>This area of Sweden has been thoroughly studied and a database of the population exists from the last 15 years. This data allowed the authors to test if parasite resistance (individuals are less likely to be infected) and tolerance (individuals get less affected by parasites) has evolve as a response to the reduced reproductive success of parasitized males. Their results show evidence for adaptation due to a reduced reproductive success of parasitized males in a wild insect 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>exual selection has been suggested to accelerate local adaptation and promote evolutionary rescue through several ecological and genetic mechanisms. Condition-dependent sexual selection has mainly been studied in laboratory settings while data from natural populations are lacking. One ecological factor that can cause condition-dependent sexual selection is parasitism. Here, we quantified ectoparasite load (<i>Arrenurus</i> water mites) in a natural population of the common bluetail damselfly (<i>Ischnura elegans</i>) over 15 years. We quantified the strength of sexual selection against parasite load in both sexes and experimentally investigated the mechanisms behind such selection. Then, we investigated how parasite resistance and tolerance changed over time to understand how they might influence population density. Parasites reduced mating success in both sexes, and sexual selection was stronger in males than in females. Experiments show that male-male competition is a strong force causing precopulatory sexual selection against parasite load. Although parasite resistance and male parasite tolerance increased over time, suggestive of increasing local adaptation against parasites, no signal of evolutionary rescue could be found. We suggest that condition-dependent sexual selection facilitates local adaptation against parasites and discuss its effects in evolutionary rescue.</p> <h4>La competencia entre machos causa selecci&oacute;n sexual mediada por par&aacute;sitos, promoviendo la adaptaci&oacute;n</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;">S</span>e ha sugerido que la selecci&oacute;n sexual puede acelerar la adaptaci&oacute;n y facilitar el rescate evolutivo a trav&eacute;s de diversos mecanismos ecol&oacute;gicos y gen&eacute;ticos. La selecci&oacute;n sexual sobre la condici&oacute;n ha sido estudiada principalmente en el laboratorio, mientras existe una escasez de datos de poblaciones silvestres. Un factor ecol&oacute;gico que puede causar selecci&oacute;n sexual sobre la condici&oacute;n es el parasitismo. En este estudio cuantificamos la carga de ectopar&aacute;sitos (&aacute;caros acu&aacute;ticos <i>Arrenurus</i>) en una poblaci&oacute;n silvestre de una especie de odonatos (<i>Ischnura elegans</i>) por 15 a&ntilde;os. Cuantificamos la fuerza de la selecci&oacute;n sexual en contra de individuos parasitados en ambos sexos e investigamos los mecanismos detr&aacute;s de dicha selecci&oacute;n. Posteriormente investigamos como la resistencia y tolerancia al par&aacute;sito ha cambiado a lo largo del tiempo y como puede influenciar la densidad poblacional. Los par&aacute;sitos redujeron el &eacute;xito reproductivo de ambos sexos, y la selecci&oacute;n sexual fue m&aacute;s fuerte en machos que en hembras. Los experimentos sugieren que la selecci&oacute;n sexual fue mediada principalmente por competencia entre machos, con poco o ning&uacute;n efecto de elecci&oacute;n de pareja. Aunque la resistencia y tolerancia al par&aacute;sito incrementaron con el tiempo, sugiriendo adaptaci&oacute;n al par&aacute;sito, no se encontraron se&ntilde;ales de rescate evolutivo. Sugerimos que la selecci&oacute;n sexual sobre la condici&oacute;n facilita la adaptaci&oacute;n al par&aacute;sito y discutimos sus efectos en el rescate evolutivo.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 28 May 2020 05:00:00 GMT “Phenotypic plasticity for desiccation resistance, climate change and future species distributions: will plasticity have much impact?” https://amnat.org/an/newpapers/Sep-Kellermann.html Vanessa Kellermann, Shane F. McEvey, Carla M. Sgrò, and Ary A. Hoffmann (Sep 2020) Phenotypic plasticity in desiccation resistance does not contribute much to climate change responses Read the Article (Just Accepted) Phenotypic plasticity, the ability of an organism to rapidly adjust traits, has been proposed as an important way organisms can buffer the impacts of climate change. This is because plasticity is a way of rapidly shifting traits (within a generation) in comparison to evolution (change in allele frequencies), which is likely slower. Despite the vital role plasticity could play in how species respond to climate change, our current methods for measuring the impact of climate change – distributional models that base future suitability of environments on current distributions – rarely take plasticity into account. Researchers from Monash University in Australia set out to test the relative importance of phenotypic plasticity in buffering species from climate change in Drosophila species. The researchers firstly determined how much species could increase their desiccation resistance (ability to tolerate dry environments a trait linked to climate change resilience) via plasticity. Then, using a semi-mechanistic distributional model (modeling species distributions from traits and distributional data), they examined whether the addition of plasticity could limit the impact of climate change. If plasticity is an important buffer, they expected species to retain more of their distribution under climate change than models without plasticity. While the researchers found species could shift their desiccation resistance considerably (i.e., these traits showed plasticity), adding plasticity to their models had only a small impact on the retention of species distributions under climate change. Although some of the largest shifts in plasticity were observed in tropically restricted species, reductions in the suitability of environments under climate change for this group of species were still observed. This suggests that plasticity for desiccation resistance is unlikely to buffer this vulnerable group of species from climate change. Abstract While species distribution models (SDMs) are widely used to predict the vulnerability of species to climate change, they do not explicitly indicate the extent to which plastic responses ameliorate climate change impacts. Here we use data on plastic responses of 32 species of Drosophila to desiccation stress to suggest that basal resistance rather than adult hardening is relatively more important in determining species differences in desiccation resistance and sensitivity to climate change. We go on to show, using the semi-mechanistic SDM CLIMEX, that the inclusion of plasticity has some impact on current species distributions and future vulnerability for widespread species, but has little impact on the distribution of arguably more vulnerable tropically-restricted species. More forthcoming papers &raquo; <p>Vanessa Kellermann, Shane F. McEvey, Carla M. Sgrò, and Ary A. Hoffmann (Sep 2020) </p> <p><b>Phenotypic plasticity in desiccation resistance does not contribute much to climate change responses </b></p> <p><i><a href="https://dx.doi.org/10.1086/710006">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>henotypic plasticity, the ability of an organism to rapidly adjust traits, has been proposed as an important way organisms can buffer the impacts of climate change. This is because plasticity is a way of rapidly shifting traits (within a generation) in comparison to evolution (change in allele frequencies), which is likely slower. Despite the vital role plasticity could play in how species respond to climate change, our current methods for measuring the impact of climate change – distributional models that base future suitability of environments on current distributions – rarely take plasticity into account. Researchers from Monash University in Australia set out to test the relative importance of phenotypic plasticity in buffering species from climate change in <i>Drosophila</i> species. The researchers firstly determined how much species could increase their desiccation resistance (ability to tolerate dry environments a trait linked to climate change resilience) via plasticity. Then, using a semi-mechanistic distributional model (modeling species distributions from traits and distributional data), they examined whether the addition of plasticity could limit the impact of climate change. If plasticity is an important buffer, they expected species to retain more of their distribution under climate change than models without plasticity. While the researchers found species could shift their desiccation resistance considerably (i.e., these traits showed plasticity), adding plasticity to their models had only a small impact on the retention of species distributions under climate change. Although some of the largest shifts in plasticity were observed in tropically restricted species, reductions in the suitability of environments under climate change for this group of species were still observed. This suggests that plasticity for desiccation resistance is unlikely to buffer this vulnerable group of species from climate change. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hile species distribution models (SDMs) are widely used to predict the vulnerability of species to climate change, they do not explicitly indicate the extent to which plastic responses ameliorate climate change impacts. Here we use data on plastic responses of 32 species of <i>Drosophila</i> to desiccation stress to suggest that basal resistance rather than adult hardening is relatively more important in determining species differences in desiccation resistance and sensitivity to climate change. We go on to show, using the semi-mechanistic SDM CLIMEX, that the inclusion of plasticity has some impact on current species distributions and future vulnerability for widespread species, but has little impact on the distribution of arguably more vulnerable tropically-restricted species. </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, 27 May 2020 05:00:00 GMT “Partner fidelity and asymmetric specialization in ecological networks” https://amnat.org/an/newpapers/Sep-Fortuna-A.html Miguel A. Fortuna, Arxhina Nagavci, Matthew A. Barbour, and Jordi Bascompte (Sep 2020) Asymmetric specialization leaves a pervasive signature on the biogeography of mutualistic interactions Read the Article (Just Accepted) Abstract Species are embedded in complex networks of interdependencies that may change across geographic locations. Yet, most approaches to investigate the architecture of this entangled web of life have considered exclusively local communities. In order to quantify to what extent species interactions change at a biogeographic scale, we need to shed light on how among-community variation affects the occurrence of species interactions. Here, we quantify the probability for two partners to interact wherever they co-occur (i.e., partner fidelity) by analyzing the most extensive database on species interaction networks worldwide. We found that mutualistic species show more fidelity in their interactions than antagonistic ones when there is asymmetric specialization (i.e., when specialist species interact with generalist partners). Moreover, resources (e.g., plants in plant-pollinator mutualisms or hosts in host-parasite interactions) show a higher partner fidelity in mutualistic than in antagonistic interactions, which can be explained neither by sampling effort, nor by phylogenetic constraints developed during their evolutionary histories. In spite of the general belief that mutualistic interactions among free-living species are labile, asymmetric specialization is very much conserved across large geographic areas. More forthcoming papers &raquo; <p>Miguel A. Fortuna, Arxhina Nagavci, Matthew A. Barbour, and Jordi Bascompte (Sep 2020) </p> <p><b>Asymmetric specialization leaves a pervasive signature on the biogeography of mutualistic interactions </b></p> <p><i><a href="https://dx.doi.org/10.1086/709961">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>pecies are embedded in complex networks of interdependencies that may change across geographic locations. Yet, most approaches to investigate the architecture of this entangled web of life have considered exclusively local communities. In order to quantify to what extent species interactions change at a biogeographic scale, we need to shed light on how among-community variation affects the occurrence of species interactions. Here, we quantify the probability for two partners to interact wherever they co-occur (i.e., partner fidelity) by analyzing the most extensive database on species interaction networks worldwide. We found that mutualistic species show more fidelity in their interactions than antagonistic ones when there is asymmetric specialization (i.e., when specialist species interact with generalist partners). Moreover, resources (e.g., plants in plant-pollinator mutualisms or hosts in host-parasite interactions) show a higher partner fidelity in mutualistic than in antagonistic interactions, which can be explained neither by sampling effort, nor by phylogenetic constraints developed during their evolutionary histories. In spite of the general belief that mutualistic interactions among free-living species are labile, asymmetric specialization is very much conserved across large geographic areas. </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, 27 May 2020 05:00:00 GMT “What do ecology, evolution, and behavior have in common? The organism in the middle” https://amnat.org/an/newpapers/Aug-Ketterson.html Ellen D. Ketterson (Aug 2020) Read the Article (Just Accepted) Scientists at early stages in their careers can wonder how to go about shaping a research path. Major influences will include past experiences (undergrad research), people you know well as a graduate student (advisors, fellow lab members, faculty committee members), issues being addressed in the current literature, and chance encounters at meetings or workshops. Reading about the unfolding of careers of other biologists can be reassuring. In this account, the author looks back over nearly 50&nbsp;years of research to identify turning points in her research history. In her case, a persistent theme was the study organism and a curiosity about how mechanism and function work together. The research focused on the dark-eyed junco, a north-temperate passerine, and how its natural history could be used to address common themes in ecology, evolution, and animal behavior. The article describes research questions posed, including blind alleys, and those that proved more informative. The topics addressed include animal migrations (differential migration, site-fidelity, site recognition), hormone-mediated life history trade-offs (phenotypic engineering, hormonal pleiotropy, adaptation and constraint, phenotypic integration), and a return to migration as a contributing factor to population divergence (allochrony, heteropatry, photoperiodic thresholds, and mate choice). Unanswered questions are posed, including one of how reproductive timing will respond to environmental change and influence future species distributions. Very little of how Dr. Ketterson’s research turned out could have been foreseen, so the message to those starting out is to go bravely. Abstract Biologists who publish in The&nbsp;American Naturalist are drawn to its unifying mission of covering research in the fields of ecology, evolution, behavior, and integrative biology. Presented here is one scientist’s attempt to straddle these fields by focusing on a single organism. It is also an account of how time spent in the field stimulates a naturalist to wonder ‘why did that animal just do that?’ and how research is guided by chance and intention interacting with the scientific literature and the people one meets along the way. With respect to the science, the examples come from bird migration, hormones and their connection to phenotypic integration, sexual and natural selection, and urban ecology. They also come from research on the impact of environmental change on timing of reproduction and the potential for allochrony in migratory species to influence population divergence. More forthcoming papers &raquo; <p>Ellen D. Ketterson (Aug 2020) </p> <p><i><a href="https://dx.doi.org/10.1086/709699">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>cientists at early stages in their careers can wonder how to go about shaping a research path. Major influences will include past experiences (undergrad research), people you know well as a graduate student (advisors, fellow lab members, faculty committee members), issues being addressed in the current literature, and chance encounters at meetings or workshops. Reading about the unfolding of careers of other biologists can be reassuring. In this account, the author looks back over nearly 50&nbsp;years of research to identify turning points in her research history. In her case, a persistent theme was the study organism and a curiosity about how mechanism and function work together. The research focused on the dark-eyed junco, a north-temperate passerine, and how its natural history could be used to address common themes in ecology, evolution, and animal behavior. The article describes research questions posed, including blind alleys, and those that proved more informative. The topics addressed include animal migrations (differential migration, site-fidelity, site recognition), hormone-mediated life history trade-offs (phenotypic engineering, hormonal pleiotropy, adaptation and constraint, phenotypic integration), and a return to migration as a contributing factor to population divergence (allochrony, heteropatry, photoperiodic thresholds, and mate choice). Unanswered questions are posed, including one of how reproductive timing will respond to environmental change and influence future species distributions. Very little of how Dr. Ketterson’s research turned out could have been foreseen, so the message to those starting out is to go bravely. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">B</span>iologists who publish in <i>The&nbsp;American Naturalist</i> are drawn to its unifying mission of covering research in the fields of ecology, evolution, behavior, and integrative biology. Presented here is one scientist&rsquo;s attempt to straddle these fields by focusing on a single organism. It is also an account of how time spent in the field stimulates a naturalist to wonder &lsquo;why did that animal just do that?&rsquo; and how research is guided by chance and intention interacting with the scientific literature and the people one meets along the way. With respect to the science, the examples come from bird migration, hormones and their connection to phenotypic integration, sexual and natural selection, and urban ecology. They also come from research on the impact of environmental change on timing of reproduction and the potential for allochrony in migratory species to influence population divergence.</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, 15 May 2020 05:00:00 GMT “Shifts in reproductive investment in response to competitors lowers male reproductive success” https://amnat.org/an/newpapers/Sep-Spagopoulou.html Foteini Spagopoulou, Regina Vega-Trejo, Megan L. Head, and Michael D. Jennions (Sep 2020) The presence of sexual competition lowers male reproductive success in the G. holbrooki mosquitofish Read the Article (Just Accepted) Males of many species are exposed to highly variable social environments, where the presence and intensity of competition for access to females often change. In response, males can strategically adjust their investment in behavioral or morphological traits associated with higher mating or fertilization success. For instance, males can perceive an overabundance of other males as a signal for increased sexual competition and scale up investment in sexually selected traits. However, does such an increase in investment always lead to higher reproductive success? In a new study, Foteini Spagopoulou, Regina Vega-Trejo, Megan Head, and Michael Jennions from Uppsala University and the Australian National University, use the eastern mosquitofish (Gambusia holbrooki) to investigate whether a competitive environment drives males to increase their investment in sexually selected traits and ultimately maximize their reproductive success. Males are housed for a full spermatogenesis cycle in either a competitive treatment, by continually being exposed to cues that rivals are present, which mimics mating competition, or in a control treatment where such cues are absent. The authors first collect sperm measurements and then allow the males, following sperm replenishment, to compete freely with a similar-sized male (from the alternative treatment) for female access and copulations. Moreover, in contrast to previous studies, the authors specifically ask how male investment in sperm and mating traits ultimately translates in reproductive success using paternity testing. Contrary to theoretical expectations, the authors observe that males from the competitive treatment have slower swimming sperm, make fewer copulation attempts and courtship displays, and most importantly, sire fewer offspring. The unanticipated outcome of exposure to cues from rivals is, therefore, making males less, rather than more, reproductively successful. The authors discuss several possible explanations and highlight the importance of exposure duration to rivals. Moreover, these findings shed a critical perspective on experimental design and stress the need of testing whether observed changes in sexual traits elevate reproductive success. Abstract In many species, males exhibit phenotypic plasticity in sexually selected traits when exposed to social cues about the intensity of sexual competition. To date, however, few studies have tested how this plasticity affects male reproductive success. We initially tested whether male mosquitofish, Gambusia holbrooki (Poeciliidae), change their investment in traits under pre- and post- copulatory sexual selection depending on the social environment. Focal males were exposed, for a full spermatogenesis cycle, to visual and chemical cues of rivals that were either present (competitive treatment) or absent (control). Males from the competitive treatment had significantly slower swimming sperm, but did not differ in sperm count from control males. When two males competed for a female, competitive treatment males also made significantly fewer copulation attempts and courtship displays than control males. Further, paternity analysis of 708 offspring from 148 potential sires, testing whether these changes in reproductive traits affected male reproductive success, showed that males previously exposed to cues about the presence of rivals sired significantly fewer offspring when competing with a control male. We discuss several possible explanations for these unusual findings. More forthcoming papers &raquo; <p>Foteini Spagopoulou, Regina Vega-Trejo, Megan L. Head, and Michael D. Jennions (Sep 2020) </p> <p><b>The presence of sexual competition lowers male reproductive success in the <i>G. holbrooki</i> mosquitofish </b></p> <p><i><a href="https://dx.doi.org/10.1086/709821">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>ales of many species are exposed to highly variable social environments, where the presence and intensity of competition for access to females often change. In response, males can strategically adjust their investment in behavioral or morphological traits associated with higher mating or fertilization success. For instance, males can perceive an overabundance of other males as a signal for increased sexual competition and scale up investment in sexually selected traits. However, does such an increase in investment always lead to higher reproductive success? </p><p>In a new study, Foteini Spagopoulou, Regina Vega-Trejo, Megan Head, and Michael Jennions from Uppsala University and the Australian National University, use the eastern mosquitofish (<i>Gambusia holbrooki</i>) to investigate whether a competitive environment drives males to increase their investment in sexually selected traits and ultimately maximize their reproductive success. Males are housed for a full spermatogenesis cycle in either a competitive treatment, by continually being exposed to cues that rivals are present, which mimics mating competition, or in a control treatment where such cues are absent. The authors first collect sperm measurements and then allow the males, following sperm replenishment, to compete freely with a similar-sized male (from the alternative treatment) for female access and copulations. Moreover, in contrast to previous studies, the authors specifically ask how male investment in sperm and mating traits ultimately translates in reproductive success using paternity testing. </p><p>Contrary to theoretical expectations, the authors observe that males from the competitive treatment have slower swimming sperm, make fewer copulation attempts and courtship displays, and most importantly, sire fewer offspring. The unanticipated outcome of exposure to cues from rivals is, therefore, making males less, rather than more, reproductively successful. The authors discuss several possible explanations and highlight the importance of exposure duration to rivals. Moreover, these findings shed a critical perspective on experimental design and stress the need of testing whether observed changes in sexual traits elevate reproductive success. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n many species, males exhibit phenotypic plasticity in sexually selected traits when exposed to social cues about the intensity of sexual competition. To date, however, few studies have tested how this plasticity affects male reproductive success. We initially tested whether male mosquitofish, <i>Gambusia holbrooki</i> (Poeciliidae), change their investment in traits under pre- and post- copulatory sexual selection depending on the social environment. Focal males were exposed, for a full spermatogenesis cycle, to visual and chemical cues of rivals that were either present (competitive treatment) or absent (control). Males from the competitive treatment had significantly slower swimming sperm, but did not differ in sperm count from control males. When two males competed for a female, competitive treatment males also made significantly fewer copulation attempts and courtship displays than control males. Further, paternity analysis of 708 offspring from 148 potential sires, testing whether these changes in reproductive traits affected male reproductive success, showed that males previously exposed to cues about the presence of rivals sired significantly fewer offspring when competing with a control male. We discuss several possible explanations for these unusual findings. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 14 May 2020 05:00:00 GMT “Selection and constraints in the ecomorphological adaptive evolution of the skull of living Canidae (Carnivora, Mammalia)” https://amnat.org/an/newpapers/Aug-Machado-A.html Fabio Andrade Machado (Aug 2020) Evolution of cranial morphology was shaped by selection and constraints in Canidae (Carnivora) Read the Article (Just Accepted)Abstract The association between phenotype and ecology is essential for understanding the environmental drivers of morphological evolution. This is a particularly challenging task when dealing with complex traits such as the skull, where multiple selective pressures are at play and evolution might be constrained by ontogenetic and genetic factors. In the present contribution I integrate morphometric tools, comparative methods and quantitative genetics to investigate how ontogenetic constraints and selection might have interacted during the evolution of the skull in extant Canidae. The results confirm that the evolution of cranial morphology was largely adaptive and molded by changes in diet composition. While the investigation of the adaptive landscape reveals two main Selective Lines of Least Resistance (one associated with size and one associated with functional shape features), rates of evolution along size were higher than those found for shape dimensions, suggesting the influence of constraints on morphological evolution. Structural Modeling Analyses revealed that size, which is the line of most genetic/phenotypic variation, might have acted as a constraint, negatively impacting dietary evolution. Constraints might have been overcome in the case of selection for the consumption of large prey, by associating strong selection along both size and shape directions. The results obtained here show that microevolutionary constraints may have played a role in shaping macroevolutionary patterns of morphological evolution. More forthcoming papers &raquo; <p>Fabio Andrade Machado (Aug 2020)</p> <p><b>Evolution of cranial morphology was shaped by selection and constraints in Canidae (Carnivora) </b></p> <p><i><a href="https://dx.doi.org/10.1086/709610">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he association between phenotype and ecology is essential for understanding the environmental drivers of morphological evolution. This is a particularly challenging task when dealing with complex traits such as the skull, where multiple selective pressures are at play and evolution might be constrained by ontogenetic and genetic factors. In the present contribution I integrate morphometric tools, comparative methods and quantitative genetics to investigate how ontogenetic constraints and selection might have interacted during the evolution of the skull in extant Canidae. The results confirm that the evolution of cranial morphology was largely adaptive and molded by changes in diet composition. While the investigation of the adaptive landscape reveals two main Selective Lines of Least Resistance (one associated with size and one associated with functional shape features), rates of evolution along size were higher than those found for shape dimensions, suggesting the influence of constraints on morphological evolution. Structural Modeling Analyses revealed that size, which is the line of most genetic/phenotypic variation, might have acted as a constraint, negatively impacting dietary evolution. Constraints might have been overcome in the case of selection for the consumption of large prey, by associating strong selection along both size and shape directions. The results obtained here show that microevolutionary constraints may have played a role in shaping macroevolutionary patterns of morphological evolution. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 14 May 2020 05:00:00 GMT “Mammal community structure through the Paleocene-Eocene Thermal Maximum” https://amnat.org/an/newpapers/Sep-Fraser-A.html Danielle Fraser and S. Kathleen Lyons (Sep 2020) Despite increasing richness due to invasion and rapid climate change, PETM mammal community structure was unchanged Read the Article (Just Accepted) Abstract Human-mediated species invasion and climate change are leading to global extinctions and are predicted to result in the loss of important axes of phylogenetic and functional diversity. However, the long-term robustness of modern communities to invasion is unknown, given the limited timescales over which they can be studied. Using the fossil record of the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma) in North America, we evaluate mammalian community-level response to a rapid global warming event (5° to 8°C) and invasion by three Eurasian mammalian orders and by species undergoing northward range shifts. We assembled a database of 144 species body sizes and created a time scaled composite phylogeny. We calculated the phylogenetic and functional diversity of all communities before, during, and after the PETM. Despite increases in the phylogenetic diversity of the regional species pool, phylogenetic diversity of mammalian communities remained relatively unchanged, a pattern that is invariant to the tree dating method, uncertainty in tree topology, and resolution. Similarly, body size dispersion and the degree of spatial taxonomic turnover of communities remained similar across the PETM. We suggest that invasion by new taxa had little impact on Paleocene-Eocene mammal communities because niches were not saturated. Our findings are consistent with the numerous studies of modern communities that record little change in community-scale richness despite turnover in taxonomic composition during invasion. What remains unknown is whether long-term robustness to biotic and abiotic perturbation are retained by modern communities given global anthropogenic landscape modification. More forthcoming papers &raquo; <p>Danielle Fraser and S. Kathleen Lyons (Sep 2020) </p> <p><b>Despite increasing richness due to invasion and rapid climate change, PETM mammal community structure was unchanged </b></p> <p><i><a href="https://dx.doi.org/10.1086/709819">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;">H</span>uman-mediated species invasion and climate change are leading to global extinctions and are predicted to result in the loss of important axes of phylogenetic and functional diversity. However, the long-term robustness of modern communities to invasion is unknown, given the limited timescales over which they can be studied. Using the fossil record of the Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma) in North America, we evaluate mammalian community-level response to a rapid global warming event (5° to 8°C) and invasion by three Eurasian mammalian orders and by species undergoing northward range shifts. We assembled a database of 144 species body sizes and created a time scaled composite phylogeny. We calculated the phylogenetic and functional diversity of all communities before, during, and after the PETM. Despite increases in the phylogenetic diversity of the regional species pool, phylogenetic diversity of mammalian communities remained relatively unchanged, a pattern that is invariant to the tree dating method, uncertainty in tree topology, and resolution. Similarly, body size dispersion and the degree of spatial taxonomic turnover of communities remained similar across the PETM. We suggest that invasion by new taxa had little impact on Paleocene-Eocene mammal communities because niches were not saturated. Our findings are consistent with the numerous studies of modern communities that record little change in community-scale richness despite turnover in taxonomic composition during invasion. What remains unknown is whether long-term robustness to biotic and abiotic perturbation are retained by modern communities given global anthropogenic landscape modification. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 07 May 2020 05:00:00 GMT Results of the 2020 Election https://amnat.org/announcements/ANNelectionResults.html Election Statement The ASN represents everything I love most in science. From the first time I opened Am Nat as a college junior and realized how an ecologist could spend her life, to the ASN stand-alone meetings that have energized and reinvigorated my research, to the final paper I handled as Am Nat Editor in Chief, the ASN has occupied the center of my career. My research focuses on the ecology and evolution of interspecific interactions, particularly on mutualisms. My career-long goal has been to build a solid conceptual foundation for the study of these poorly understood interactions. Using a combination of field observations, experiments, and theory, my lab examines how population processes, abiotic conditions, and the community context determine net effects of interactions for each participant species. I received my BA from Brown University, and my MSc and PhD in Ecology and Evolutionary Biology from the University of Michigan. I currently hold the rank of University Distinguished Professor in the Department of Ecology and Evolutionary Biology at the University of Arizona, with a joint appointment in the Department of Entomology. I’ve received several other university honors, including a Distinguished Career Teaching Award, as well as a Distinguished Service Award from the National Science Foundation. I was elected Fellow of the Ecological Society of America in 2016. I’ve served as an NSF Program Officer and in leadership positions for the Ecological Society of America and the Smithsonian Institution, but my most relevant service has been to the ASN. I served as Secretary in 2004-2006. I joined the American Naturalist Editorial Board in 2004, became one of the three Editors in 2010, and then served as the (first and only female) Editor in Chief from 2013 to 2017. I’m particularly proud of the efforts we made to diversify the Editorial Board during this period. I initiated the popular “Countdown” series that highlights significant but overlooked Am Nat papers of the past. Melding my interests in diversity and Am Nat’s own history, I was lead author on a 2018 paper highlighting the biographies and contributions of its earliest women authors. The landscape of science, scientific societies, publishing, and the world itself are all changing rapidly. ASN can and must continue to show the intellectual leadership it’s been demonstrating so effectively in recent years, while remaining the model egalitarian and diverse organization that it’s recently become. Further, we will be experiencing some critical personnel transitions in the next few years, notably in both the Managing Editor and Editor in Chief positions at Am Nat. I think it’s fair to say that I know ASN and our flagship journal inside and out. I believe that I can gently spearhead pragmatic responses to the challenges and opportunities ahead.Election Statement I want to know how organisms adapt to new environments, and how adaptive processes influence molecular evolution. Current themes in my lab include understanding: (1) dietary niche shifts in insect pests, (2) the evolution of the bacterial translation machinery, (3) the evolutionary consequences of new mutations, and (4) the evolution of host-bacterial associations. I completed my Bachelors in Microbiology at Abasaheb Garware College Pune, India (2003); and my PhD in Ecology, Evolution and Behaviour at the University of Texas at Austin (2009). After a postdoctoral fellowship at Harvard University, I started my independent group in Bangalore in 2012. I recently received a Women Excellence Award (for female scientists under 40) from the President of India and have successfully competed for several national and international research grants and fellowships. I count my efforts to increase the visibility of evolutionary biology in India as my most important service. I have organized several meetings and student workshops (e.g. the long-running ICTS Schools on Population Genetics and Evolution), and participated in various outreach efforts (e.g. public Science Caf&eacute; talks, radio and television programs, and talks at smaller colleges and Universities in the country). I also serve as associate editor of Molecular Biology and Evolution (since 2015) and Evolution (since 2020); on the diversity committee of the ASN (since 2018); and the international committee of the SSE (since 2018). The ASN and the American Naturalist are quite special for me: my first paper was published in the American Naturalist, and experiencing peer review at its best (thanks to AE George Gilchrist) shaped how I approach my current roles as reviewer and editor. I also won the Editor’s award for best student paper, and the book grant from ASN let me buy truly beautiful books that I could not otherwise afford. Since then, I have continued to enjoy the high quality of science that is discussed at ASN meetings and published in the American Naturalist. I hope to connect the ASN to the Indian community and increase the breadth and reach of the ASN. This link would be mutually beneficial, given the incredible biodiversity in my part of the world but the relatively small local community of evolutionary biologists and ecologists. For the VP symposium, I would like to consider two areas: how to bridge across micro and macro-evolution, and the early evolution and establishment of host-microbiome interactions. <p><strong>Election Statement</strong></p> <p>The ASN represents everything I love most in science. From the first time I opened Am Nat as a college junior and realized how an ecologist could spend her life, to the ASN stand-alone meetings that have energized and reinvigorated my research, to the final paper I handled as Am Nat Editor in Chief, the ASN has occupied the center of my career. My research focuses on the ecology and evolution of interspecific interactions, particularly on mutualisms. My career-long goal has been to build a solid conceptual foundation for the study of these poorly understood interactions. Using a combination of field observations, experiments, and theory, my lab examines how population processes, abiotic conditions, and the community context determine net effects of interactions for each participant species.</p> <p>I received my BA from Brown University, and my MSc and PhD in Ecology and Evolutionary Biology from the University of Michigan. I currently hold the rank of University Distinguished Professor in the Department of Ecology and Evolutionary Biology at the University of Arizona, with a joint appointment in the Department of Entomology. I&rsquo;ve received several other university honors, including a Distinguished Career Teaching Award, as well as a Distinguished Service Award from the National Science Foundation. I was elected Fellow of the Ecological Society of America in 2016. I&rsquo;ve served as an NSF Program Officer and in leadership positions for the Ecological Society of America and the Smithsonian Institution, but my most relevant service has been to the ASN. I served as Secretary in 2004-2006. I joined the American Naturalist Editorial Board in 2004, became one of the three Editors in 2010, and then served as the (first and only female) Editor in Chief from 2013 to 2017. I&rsquo;m particularly proud of the efforts we made to diversify the Editorial Board during this period. I initiated the popular &ldquo;Countdown&rdquo; series that highlights significant but overlooked Am Nat papers of the past. Melding my interests in diversity and Am Nat&rsquo;s own history, I was lead author on a 2018 paper highlighting the biographies and contributions of its earliest women authors.</p> <p>The landscape of science, scientific societies, publishing, and the world itself are all changing rapidly. ASN can and must continue to show the intellectual leadership it&rsquo;s been demonstrating so effectively in recent years, while remaining the model egalitarian and diverse organization that it&rsquo;s recently become. Further, we will be experiencing some critical personnel transitions in the next few years, notably in both the Managing Editor and Editor in Chief positions at Am Nat. I think it&rsquo;s fair to say that I know ASN and our flagship journal inside and out. I believe that I can gently spearhead pragmatic responses to the challenges and opportunities ahead.</p><p><strong>Election Statement</strong></p> <p>I want to know how organisms adapt to new environments, and how adaptive processes influence molecular evolution. Current themes in my lab include understanding: (1) dietary niche shifts in insect pests, (2) the evolution of the bacterial translation machinery, (3) the evolutionary consequences of new mutations, and (4) the evolution of host-bacterial associations.</p> <p>I completed my Bachelors in Microbiology at Abasaheb Garware College Pune, India (2003); and my PhD in Ecology, Evolution and Behaviour at the University of Texas at Austin (2009). After a postdoctoral fellowship at Harvard University, I started my independent group in Bangalore in 2012. I recently received a Women Excellence Award (for female scientists under 40) from the President of India and have successfully competed for several national and international research grants and fellowships.</p> <p>I count my efforts to increase the visibility of evolutionary biology in India as my most important service. I have organized several meetings and student workshops (e.g. the long-running ICTS Schools on Population Genetics and Evolution), and participated in various outreach efforts (e.g. public Science Caf&eacute; talks, radio and television programs, and talks at smaller colleges and Universities in the country). I also serve as associate editor of Molecular Biology and Evolution (since 2015) and Evolution (since 2020); on the diversity committee of the ASN (since 2018); and the international committee of the SSE (since 2018).</p> <p>The ASN and the American Naturalist are quite special for me: my first paper was published in the American Naturalist, and experiencing peer review at its best (thanks to AE George Gilchrist) shaped how I approach my current roles as reviewer and editor. I also won the Editor&rsquo;s award for best student paper, and the book grant from ASN let me buy truly beautiful books that I could not otherwise afford. Since then, I have continued to enjoy the high quality of science that is discussed at ASN meetings and published in the American Naturalist.</p> <p>I hope to connect the ASN to the Indian community and increase the breadth and reach of the ASN. This link would be mutually beneficial, given the incredible biodiversity in my part of the world but the relatively small local community of evolutionary biologists and ecologists. For the VP symposium, I would like to consider two areas: how to bridge across micro and macro-evolution, and the early evolution and establishment of host-microbiome interactions.</p> Mon, 04 May 2020 05:00:00 GMT Survey on Having Virtual Evolution 2020 https://amnat.org/announcements/VirtualEvolution.html We are all saddened that we will not be able to gather in June in Cleveland to talk science with our ASN, SSB, and SSE friends and colleagues.&nbsp; Currently, we are exploring the possibility of hosting a VIRTUAL meeting so we can keep our scientific conversations going.&nbsp; Because the program must be much more limited than what we would have done in Cleveland, we want to especially focus on engagement by graduate students, postdoctoral associates, and very early career scientists in our societies.&nbsp; We also want to use this as an opportunity to possibly explore new types of interactions that we might be able to have in such a format. One bright spot is that a virtual meeting will greatly reduce our meeting’s carbon footprint.&nbsp; And this will be the first or second professional society meeting that you will attend that is free, and you can sleep in your own bed each night. We would appreciate if you would complete our online questionnaire so that we can gauge the interest in such a meeting. You can find the questionnaire at https://forms.gle/Ky5DvVS1VduZSSTz5 If you have any questions or further suggestions about this meeting, or would like to volunteer to help out, please email Mark McPeek.&nbsp; &nbsp; Thank you for helping us plan, Susan Kalisz, President American Society of Naturalists &nbsp; <p style="margin-right:0in; margin-left:0in"><span style="font-size:11pt"><span style="font-family:&quot;Calibri&quot;,sans-serif"><span style="font-family:&quot;Times New Roman&quot;,serif">We are all saddened that we will not be able to gather in June in Cleveland to talk science with our ASN, SSB, and SSE friends and colleagues.&nbsp; Currently, we are exploring the possibility of hosting a VIRTUAL meeting so we can keep our scientific conversations going.&nbsp;<br /> <br /> Because the program must be much more limited than what we would have done in Cleveland, we want to especially focus on engagement by graduate students, postdoctoral associates, and very early career scientists in our societies.&nbsp; We also want to use this as an opportunity to possibly explore new types of interactions that we might be able to have in such a format.<br /> <br /> One bright spot is that a virtual meeting will greatly reduce our meeting&rsquo;s carbon footprint.&nbsp; And this will be the first or second professional society meeting that you will attend that is free, and you can sleep in your own bed each night.<br /> <br /> We would appreciate if you would complete our online questionnaire so that we can gauge the interest in such a meeting.</span></span></span></p> <p style="margin-right:0in; margin-left:0in"><span style="font-size:11pt"><span style="font-family:&quot;Calibri&quot;,sans-serif"><span style="font-family:&quot;Times New Roman&quot;,serif">You can find the questionnaire at <a href="https://forms.gle/Ky5DvVS1VduZSSTz5" style="color:#0563c1; text-decoration:underline">https://forms.gle/Ky5DvVS1VduZSSTz5</a></span></span></span></p> <p style="margin-right:0in; margin-left:0in"><span style="font-size:11pt"><span style="font-family:&quot;Calibri&quot;,sans-serif"><span style="font-family:&quot;Times New Roman&quot;,serif">If you have any questions or further suggestions about this meeting, or would like to volunteer to help out, please email <a href="mailto:mark.mcpeek@dartmouth.edu?subject=ASN%20Virtual%20Conference" style="color:#0563c1; text-decoration:underline">Mark McPeek</a>.&nbsp; </span></span></span></p> <p style="margin-right:0in; margin-left:0in">&nbsp;</p> <p style="margin-right:0in; margin-left:0in"><span style="font-size:11pt"><span style="font-family:&quot;Calibri&quot;,sans-serif"><span style="font-family:&quot;Times New Roman&quot;,serif">Thank you for helping us plan,</span></span></span></p> <p style="margin-right:0in; margin-left:0in"><span style="font-size:11pt"><span style="font-family:&quot;Calibri&quot;,sans-serif"><span style="font-family:&quot;Times New Roman&quot;,serif">Susan Kalisz, President</span></span></span></p> <p style="margin-right:0in; margin-left:0in"><span style="font-size:11pt"><span style="font-family:&quot;Calibri&quot;,sans-serif"><span style="font-family:&quot;Times New Roman&quot;,serif">American Society of Naturalists</span></span></span></p> <p style="margin:0in 0in 0.0001pt; margin-right:0in; margin-left:0in">&nbsp;</p> Tue, 28 Apr 2020 05:00:00 GMT “Common field data limitations can substantially bias sexual selection metrics” https://amnat.org/an/newpapers/Aug-Cramer.html Emily R. A. Cramer, Sara A. Kaiser, Michael S. Webster, and T. Brandt Ryder (Aug 2020) Estimating sexual selection metrics from standard field data may result in substantial levels of bias Read the Article (Just Accepted) Comparing sexual selection across species and populations is key to test the evolutionary causes and consequences of this process. However, a paper appearing in The&nbsp;American Naturalist shows that metrics used in such comparisons are likely to be strongly biased in typical field studies, particularly for metrics that require estimating the number of copulation partners. Most field studies infer the number of copulation partners an individual has by using genetic tools to assign parentage of sampled offspring. Copulations that fail to fertilize eggs are not detected, so mating partners are consistently under-estimated. Furthermore, this approach creates an artificially high correlation between the number of detected mating partners and the number of offspring. Researchers were already concerned about such bias, and several empirical studies on captive individuals, where copulations could be directly observed, supported that concern. However, the extent of the issue had not been thoroughly explored. In this study, researchers examine how data limitations inherent in studies of wild bird populations affect the accuracy of the four most widely used sexual selection metrics. The authors generate 39,000 computer-simulated populations of socially monogamous breeding pairs, belonging to 15&nbsp;species with varying levels of extra-pair paternity to evaluate several types of field data limitations, using a range of biologically relevant values. They found substantial bias when copulations are inferred from parentage outcomes rather than being observed directly. The degree of bias differs among species and due to factors such as male infertility, nest predation, and incomplete sampling of extra-pair offspring. In addition to providing code for other researchers to assess data limitations within their own study populations, these authors suggest using this tool to make informed choices when selecting and interpreting sexual selection metrics. Abstract Sexual selection studies widely estimate several metrics, but values may be inaccurate because standard field methods for studying wild populations produce limited data (e.g., incomplete sampling, inability to observe copulations directly). We compared four selection metrics (Bateman gradient, opportunity for sexual selection, opportunity for selection, and s′max) estimated with simulated complete and simulated limited data for 15 socially monogamous songbird species with extra-pair paternity (4-54% extra-pair offspring). Inferring copulation success from offspring parentage creates non-independence between these variables and systematically underestimates copulation success. We found that this introduces substantial bias for the Bateman gradient, opportunity for sexual selection, and s′max. Notably, 47.5% of detected Bateman gradients were significantly positive for females, suggesting selection on females to copulate with multiple males, though the true Bateman gradient was zero. Bias generally increased with the extent of other sources of data limitations tested (nest predation, male infertility, and unsampled floater males). Incomplete offspring sampling introduced bias for all metrics except the Bateman gradient, while incomplete sampling of extra-pair sires did not introduce additional bias when sires were a random subset of breeding males. Overall, our findings demonstrate how biases due to field data limitations can strongly impact the study of sexual selection. More forthcoming papers &raquo; <p>Emily R. A. Cramer, Sara A. Kaiser, Michael S. Webster, and T. Brandt Ryder (Aug 2020) </p> <p><b>Estimating sexual selection metrics from standard field data may result in substantial levels of bias </b></p> <p><i><a href="https://dx.doi.org/10.1086/709547">Read the Article</a></i> (Just Accepted) </p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>omparing sexual selection across species and populations is key to test the evolutionary causes and consequences of this process. However, a paper appearing in <i>The&nbsp;American Naturalist</i> shows that metrics used in such comparisons are likely to be strongly biased in typical field studies, particularly for metrics that require estimating the number of copulation partners. Most field studies infer the number of copulation partners an individual has by using genetic tools to assign parentage of sampled offspring. Copulations that fail to fertilize eggs are not detected, so mating partners are consistently under-estimated. Furthermore, this approach creates an artificially high correlation between the number of detected mating partners and the number of offspring. Researchers were already concerned about such bias, and several empirical studies on captive individuals, where copulations could be directly observed, supported that concern. However, the extent of the issue had not been thoroughly explored. In this study, researchers examine how data limitations inherent in studies of wild bird populations affect the accuracy of the four most widely used sexual selection metrics. The authors generate 39,000 computer-simulated populations of socially monogamous breeding pairs, belonging to 15&nbsp;species with varying levels of extra-pair paternity to evaluate several types of field data limitations, using a range of biologically relevant values. They found substantial bias when copulations are inferred from parentage outcomes rather than being observed directly. The degree of bias differs among species and due to factors such as male infertility, nest predation, and incomplete sampling of extra-pair offspring. In addition to providing code for other researchers to assess data limitations within their own study populations, these authors suggest using this tool to make informed choices when selecting and interpreting sexual selection metrics. </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>exual selection studies widely estimate several metrics, but values may be inaccurate because standard field methods for studying wild populations produce limited data (e.g., incomplete sampling, inability to observe copulations directly). We compared four selection metrics (Bateman gradient, opportunity for sexual selection, opportunity for selection, and <i>s′<span style="font-size:70%; position:relative; bottom:-0.3em;">max</span></i>) estimated with simulated complete and simulated limited data for 15 socially monogamous songbird species with extra-pair paternity (4-54% extra-pair offspring). Inferring copulation success from offspring parentage creates non-independence between these variables and systematically underestimates copulation success. We found that this introduces substantial bias for the Bateman gradient, opportunity for sexual selection, and <i>s′<span style="font-size:70%; position:relative; bottom:-0.3em;">max</span></i>. Notably, 47.5% of detected Bateman gradients were significantly positive for females, suggesting selection on females to copulate with multiple males, though the true Bateman gradient was zero. Bias generally increased with the extent of other sources of data limitations tested (nest predation, male infertility, and unsampled floater males). Incomplete offspring sampling introduced bias for all metrics except the Bateman gradient, while incomplete sampling of extra-pair sires did not introduce additional bias when sires were a random subset of breeding males. Overall, our findings demonstrate how biases due to field data limitations can strongly impact the study of sexual selection. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 23 Apr 2020 05:00:00 GMT “Transformational mimicry in a myrmecomorphic spider” https://amnat.org/an/newpapers/Aug-Pekar.html Stano Pekár, Yun-Yun Tsai, and Radek Michalko (Aug 2020) Leptorchestes berolinensis is an ant-mimicking spider with all stages being accurate mimics Read the Article (Just Accepted) There are few species of spiders that look alike ants during their entire lives. Such spiders cannot imitate the same ant species because spiders grow in size but ant imagoes do not. A hundred years ago naturalists observed, for the first time, that ant-like spiders change their shape and coloration as they grow in size and thus imitate different ant species – small ant species when they are juvenile and large ant species when they are adult. The phenomenon has been dubbed transformational mimicry. Strangely, it has not been tested whether these successive mimetic appearances are similarly protected from predators. Researchers from the Masaryk University in Czechia tested the hypotheses of transformational mimicry in the ant-mimicking jumping spider Leptorchestes berolinensis. The research was conducted in a meadow area with old oak tree trunks which are inhabited by ants and the ant-mimicking spiders. The researchers quantified the mimetic resemblance of different ontogenetic stages to potential ant models. They measured movement, body shape, body size, and coloration. Analysis revealed spider adults to possess more accurate resemblance to ants than juveniles. Adults were similar to smaller morphs of Camponotus or Lasius ants, whereas juveniles were more similar to Lasius and Colobopsis ants. Then the scientists tested whether co-occurring natural predators – mantises and Pisaura spiders – were deceived by juvenile and adult mimics after having experience with ant models. These predators never captured any ant or mimic. The researchers conclude that Leptorchestes berolinensis is a mimic of ants undergoing transformational mimicry, with all stages being similarly protected from predators. This study shows that even less accurate resemblance to ants is sufficient to protect ant-mimicking spiders from predators. Abstract Species that are Batesian mimics during post-embryonic development shift between mimetic models as they grow in size. However, it has not yet been tested whether these successive mimetic phenotypes are similarly protected from predators. Early instar phenotypes could represent an inaccurate phenotype or an accurate phenotype because of selection from different predators. Here, we tested the hypotheses of transformational Batesian mimicry in the ant-mimicking jumping spider Leptochestes berolinensis. We quantified the mimetic accuracy of different ontogenetic stages to potential ant models by using an multi-trait approach. We measured movement, body profile, body size, and coloration. Analysis revealed adults to be more accurate mimics than juveniles. Adults were similar to smaller morphs of Camponotus or Lasius ants, whereas juveniles were more similar to Lasius and Colobopsis ants. We tested whether predators, mantises and Pisaura spiders, were deceived by mimics after having experience with ant models. These predators never captured any ant or a mimic, but always captured the non-myrmecomorphic spider. We conclude that Leptorchestes berolinensis is a Batesian mimic of ants undergoing transformational mimicry with all stages being accurate mimics. More forthcoming papers &raquo; <p>Stano Pekár, Yun-Yun Tsai, and Radek Michalko (Aug 2020) </p> <p><b><i>Leptorchestes berolinensis</i> is an ant-mimicking spider with all stages being accurate mimics </b></p> <p><i><a href="https://www.journals.uchicago.edu/doi/abs/10.1086/709426">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>here are few species of spiders that look alike ants during their entire lives. Such spiders cannot imitate the same ant species because spiders grow in size but ant imagoes do not. A hundred years ago naturalists observed, for the first time, that ant-like spiders change their shape and coloration as they grow in size and thus imitate different ant species – small ant species when they are juvenile and large ant species when they are adult. The phenomenon has been dubbed transformational mimicry. Strangely, it has not been tested whether these successive mimetic appearances are similarly protected from predators. Researchers from the Masaryk University in Czechia tested the hypotheses of transformational mimicry in the ant-mimicking jumping spider <i>Leptorchestes berolinensis</i>. The research was conducted in a meadow area with old oak tree trunks which are inhabited by ants and the ant-mimicking spiders. The researchers quantified the mimetic resemblance of different ontogenetic stages to potential ant models. They measured movement, body shape, body size, and coloration. Analysis revealed spider adults to possess more accurate resemblance to ants than juveniles. Adults were similar to smaller morphs of <i>Camponotus</i> or <i>Lasius</i> ants, whereas juveniles were more similar to <i>Lasius</i> and <i>Colobopsis</i> ants. Then the scientists tested whether co-occurring natural predators – mantises and <i>Pisaura</i> spiders – were deceived by juvenile and adult mimics after having experience with ant models. These predators never captured any ant or mimic. The researchers conclude that <i>Leptorchestes berolinensis</i> is a mimic of ants undergoing transformational mimicry, with all stages being similarly protected from predators. This study shows that even less accurate resemblance to ants is sufficient to protect ant-mimicking spiders from predators. </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>pecies that are Batesian mimics during post-embryonic development shift between mimetic models as they grow in size. However, it has not yet been tested whether these successive mimetic phenotypes are similarly protected from predators. Early instar phenotypes could represent an inaccurate phenotype or an accurate phenotype because of selection from different predators. Here, we tested the hypotheses of transformational Batesian mimicry in the ant-mimicking jumping spider Leptochestes berolinensis. We quantified the mimetic accuracy of different ontogenetic stages to potential ant models by using an multi-trait approach. We measured movement, body profile, body size, and coloration. Analysis revealed adults to be more accurate mimics than juveniles. Adults were similar to smaller morphs of Camponotus or Lasius ants, whereas juveniles were more similar to Lasius and Colobopsis ants. We tested whether predators, mantises and Pisaura spiders, were deceived by mimics after having experience with ant models. These predators never captured any ant or a mimic, but always captured the non-myrmecomorphic spider. We conclude that Leptorchestes berolinensis is a Batesian mimic of ants undergoing transformational mimicry with all stages being accurate mimics.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 23 Apr 2020 05:00:00 GMT “Incorporating the connectivity timescale in metapopulation partitioning” https://amnat.org/an/newpapers/Aug-Aiken.html Christopher M. Aiken and Sergio A. Navarrete (Aug 2020) A new subpopulation scheme that considers the number of generations is developed Read the Article (Just Accepted) The distribution of organisms across the landscape tends to be neither homogeneous nor neatly clumped, but rather somewhere in between. To be able to manage a species, however, it is often useful to divide the individuals into groups, based on how strongly they interact with their neighbours. This study, undertaken by scientists from the Coastal Marine Research Station in Las Cruces, Chile, takes a new look at how best to partition a group of individuals – a “metapopulation” – into some small number of “compartments” or “subpopulations”. The study's novelty resides in the consideration of generations – quantifying the degree of interaction between groups of individuals by the number of generations required for genes to get from one to another. By redefining the metapopulation partitoning problem following this basic concept, a consistent and simple way to calculate the compartments is shown to be possible. By way of example a simple and efficient algorithm is used to partition the deep ocean based on the time required to drift from one point to another, as determined from drifting ocean buoys. After multiple one year generations the initial complex pattern of deep ocean connectivity gives way to a remarkably coherent spatial pattern of groupings. The example is used to discuss challenges for conservation of the orange roughy fisheries of the northen and southern hemisphere, given the large number of generations required for genetic information to transit between the two subpopulations. Abstract The often complex spatial patterns of propagule dispersal across a metapopulation present a challenge for species management, motivating efforts to represent the connectivity in more simple but meaningful ways. The reduction of complexity may be achieved by partitioning the metapopulation into groups of highly connected patches, called “subpopulations”. In order to have relevance for management, these subunits must be defined from ecological or evolutionary principles. The probabilities of dispersal-mediated propagule interchange between sites, commonly organized into a connectivity matrix, entail a timescale that is usually ignored in subpopulation analyses, limiting their utility and possibly leading to misinterpretation and wrong management decisions. Recognition of the essentially dynamical role played by metapopulation connectivity leads naturally to the incorporation of the generational timescale into the partitioning analysis. An algorithm is proposed to determine the subpopulations – both their cardinality and composition – as a function of the generational timescale and of a limiting probability of connection, illustrated with a novel empirical estimate of mesopelagic connectivity. The proposed framework allows the unambiguous determination of the timescales corresponding to dispersal barriers, and the identification of effective ecological units across the spectrum of management-relevant time horizons. More forthcoming papers &raquo; <p>Christopher M. Aiken and Sergio A. Navarrete (Aug 2020) </p> <p><b>A new subpopulation scheme that considers the number of generations is developed </b></p> <p><i><a href="https://dx.doi.org/10.1086/709548">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 distribution of organisms across the landscape tends to be neither homogeneous nor neatly clumped, but rather somewhere in between. To be able to manage a species, however, it is often useful to divide the individuals into groups, based on how strongly they interact with their neighbours. This study, undertaken by scientists from the Coastal Marine Research Station in Las Cruces, Chile, takes a new look at how best to partition a group of individuals &ndash; a “metapopulation” &ndash; into some small number of “compartments” or “subpopulations”. The study's novelty resides in the consideration of generations &ndash; quantifying the degree of interaction between groups of individuals by the number of generations required for genes to get from one to another. By redefining the metapopulation partitoning problem following this basic concept, a consistent and simple way to calculate the compartments is shown to be possible. By way of example a simple and efficient algorithm is used to partition the deep ocean based on the time required to drift from one point to another, as determined from drifting ocean buoys. After multiple one year generations the initial complex pattern of deep ocean connectivity gives way to a remarkably coherent spatial pattern of groupings. The example is used to discuss challenges for conservation of the orange roughy fisheries of the northen and southern hemisphere, given the large number of generations required for genetic information to transit between the two subpopulations. </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 often complex spatial patterns of propagule dispersal across a metapopulation present a challenge for species management, motivating efforts to represent the connectivity in more simple but meaningful ways. The reduction of complexity may be achieved by partitioning the metapopulation into groups of highly connected patches, called “subpopulations”. In order to have relevance for management, these subunits must be defined from ecological or evolutionary principles. The probabilities of dispersal-mediated propagule interchange between sites, commonly organized into a connectivity matrix, entail a timescale that is usually ignored in subpopulation analyses, limiting their utility and possibly leading to misinterpretation and wrong management decisions. Recognition of the essentially dynamical role played by metapopulation connectivity leads naturally to the incorporation of the generational timescale into the partitioning analysis. An algorithm is proposed to determine the subpopulations – both their cardinality and composition – as a function of the generational timescale and of a limiting probability of connection, illustrated with a novel empirical estimate of mesopelagic connectivity. The proposed framework allows the unambiguous determination of the timescales corresponding to dispersal barriers, and the identification of effective ecological units across the spectrum of management-relevant time horizons. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 23 Apr 2020 05:00:00 GMT “Metabolic rate interacts with resource availability to determine individual variation in microhabitat use in the wild” https://amnat.org/an/newpapers/Aug-Auer-A.html Sonya K. Auer, Ronald D. Bassar, Daniel Turek, Graeme J. Anderson, Simon McKelvey, John D. Armstrong, Keith H. Nislow, Helen K. Downie, Thomas A. J. Morgan, Darryl McLennan, and Neil B. Metcalfe (Aug 2020) Metabolic rate interacts with resource availability to determine individual variation in microhabitat use in the wild Read the Article (Just Accepted) Abstract Ecological pressures such as competition can lead individuals within a population to partition resources or habitats, but the underlying intrinsic mechanisms that determine an individual’s resource use are not well understood. Here we show that an individual’s own energy demand and associated competitive ability influence its resource use, but only when food is more limiting. We tested whether intraspecific variation in metabolic rate leads to microhabitat partitioning among juvenile Atlantic salmon (Salmo salar) in natural streams subjected to manipulated nutrient levels and subsequent per capita food availability. We found that individual salmon from families with a higher baseline (standard) metabolic rate (which is associated with greater competitive ability) tended to occupy faster flowing water, but only in streams with lower per capita food availability. Faster flowing microhabitats yield more food, but high metabolic rate fish only benefited from faster growth in streams with high food levels, presumably because in low food environments the cost of a high metabolism offset the benefits of acquiring a productive microhabitat. The benefits of a given metabolic rate were thus context-dependent. These results demonstrate that intraspecific variation in metabolic rate can interact with resource availability to determine the spatial structuring of wild populations. More forthcoming papers &raquo; <p>Sonya K. Auer, Ronald D. Bassar, Daniel Turek, Graeme J. Anderson, Simon McKelvey, John D. Armstrong, Keith H. Nislow, Helen K. Downie, Thomas A. J. Morgan, Darryl McLennan, and Neil B. Metcalfe (Aug 2020) </p> <p><b>Metabolic rate interacts with resource availability to determine individual variation in microhabitat use in the wild </b></p> <p><i><a href="https://dx.doi.org/10.1086/709479">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>cological pressures such as competition can lead individuals within a population to partition resources or habitats, but the underlying intrinsic mechanisms that determine an individual&rsquo;s resource use are not well understood. Here we show that an individual&rsquo;s own energy demand and associated competitive ability influence its resource use, but only when food is more limiting. We tested whether intraspecific variation in metabolic rate leads to microhabitat partitioning among juvenile Atlantic salmon (<i>Salmo salar</i>) in natural streams subjected to manipulated nutrient levels and subsequent per capita food availability. We found that individual salmon from families with a higher baseline (standard) metabolic rate (which is associated with greater competitive ability) tended to occupy faster flowing water, but only in streams with lower per capita food availability. Faster flowing microhabitats yield more food, but high metabolic rate fish only benefited from faster growth in streams with high food levels, presumably because in low food environments the cost of a high metabolism offset the benefits of acquiring a productive microhabitat. The benefits of a given metabolic rate were thus context-dependent. These results demonstrate that intraspecific variation in metabolic rate can interact with resource availability to determine the spatial structuring of wild populations.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 20 Apr 2020 05:00:00 GMT “Relative brain size is predicted by the intensity of intrasexual competition in frogs” https://amnat.org/an/newpapers/Aug-Mai.html Chun Lan Mai (麦春兰), Wen Bo Liao (廖文波), Stefan Lüpold, and Alexander Kotrschal (Aug 2020) Read the Article (Just Accepted) It is widely known that it takes brains for males to learn complex songs or behaviors that they use to charm females into mating. But what about species in which males fight over access to mates rather than attracting them with elaborate courtship or ornaments? Some studies suggest that even fighting males might benefit from better cognitive abilities, because they may be better able to predict when defeat becomes inevitable and it is time to back off to avoid being harmed. But others indicate that investing in physical attributes like weapons or muscles, to increase success in fights, might come at the cost of brain development because of energetic constraints. So, male mate competition could drive the evolution of both larger and smaller brains. But which is more likely? Our study tested these predictions against each other in a sample of 30 different Chinese species of frogs and toads, using several predictors of mate-competition intensity: the ratio between breeding males and females, spawning-site density and group size, and the weight of male arm muscles. More males per spawning site, and especially more males per available female, enhance the aggression and likelihood of wrestling matches between them. And stronger arms increase the success in such contests. Accounting for variation in body size and relatedness between species, we found males of species with a greater surplus of males, denser populations and stronger arms—that is, with more intense male competition—to have larger brains than those species with weaker competition. Our clearest evidence for a link between mate competition and brain size, however, was that male brains showed a stronger response than female brains to our most important indicators of mate competition: sex ratio and arm muscles. Our study thus provides strong evidence that not just wooing females but also fighting for them can drive the evolution of brainier males. Abstract Competition over mates is a powerful force shaping trait evolution. For instance, better cognitive abilities may be beneficial in male−male competition and thus be selected for by intrasexual selection. Alternatively, investment in physical attributes favoring male performance in competition for mates may lower the resources available for brain development, and more intense male mate competition would coincide with smaller brains. To date, only indirect evidence for such relationships exists and most studies are heavily biased towards primates and other homoeothermic vertebrates. We tested the association between male brain size (relative to body size) and male−male competition across N=30 species of Chinese anurans. Three indicators of the intensity of male mate competition—operational sex ratio (OSR), spawning-site density and male forelimb muscle mass—were positively associated with relative brain size, whereas the absolute spawning-group size was not. The relationship with the OSR and male forelimb muscle mass was stronger for the male than the female brains. Taken together, our findings suggest that the increased cognitive abilities of larger brains are beneficial in male−male competition. This study adds taxonomic breadth to the mounting evidence for a prominent role of sexual selection in vertebrate brain evolution. 两栖动物雄性间配偶竞争强度预测脑大小变异 争夺配偶是动物性状进化的强有力驱动者。例如,良好的认知能力有利于雄性个体赢得配偶竞争,从而被性选择所青睐。另一方面,如果雄性分配更多能量到那些有利于其获得配偶的身体性状,他们将减少用于脑发育的能量投入;由此推测,更激烈的配偶竞争将使得雄性拥有更小的脑。目前,支持这一预测的证据是间接的,且多集中在灵长类以及其他恒温动物。使用30种来自中国的无尾两栖类,我们检验了雄性脑大小(相对于身体大小)与雄性间配偶竞争强度的关系。结果表明,相对脑大小与三个雄性配偶竞争强度指标,即有效性比、产卵点密度和雄性前臂肌肉重,显著正相关,而与产卵地群体大小无关。我们还发现,雄性脑大小与有效性比和前臂肌肉重的相关性明显强于雌性。总之,我们的发现表明,大的脑,这意味着更好的认知能力,在雄性间配偶竞争中是有利的。我们的发现也在类群上拓展了性选择在脊椎动物脑进化中所起的突出作用。 More forthcoming papers &raquo; <p>Chun Lan Mai (麦春兰), Wen Bo Liao (廖文波), Stefan Lüpold, and Alexander Kotrschal (Aug 2020) </p> <p><i><a href="https://dx.doi.org/10.1086/709465">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>t is widely known that it takes brains for males to learn complex songs or behaviors that they use to charm females into mating. But what about species in which males fight over access to mates rather than attracting them with elaborate courtship or ornaments? Some studies suggest that even fighting males might benefit from better cognitive abilities, because they may be better able to predict when defeat becomes inevitable and it is time to back off to avoid being harmed. But others indicate that investing in physical attributes like weapons or muscles, to increase success in fights, might come at the cost of brain development because of energetic constraints. So, male mate competition could drive the evolution of both larger and smaller brains. But which is more likely? Our study tested these predictions against each other in a sample of 30 different Chinese species of frogs and toads, using several predictors of mate-competition intensity: the ratio between breeding males and females, spawning-site density and group size, and the weight of male arm muscles. More males per spawning site, and especially more males per available female, enhance the aggression and likelihood of wrestling matches between them. And stronger arms increase the success in such contests. Accounting for variation in body size and relatedness between species, we found males of species with a greater surplus of males, denser populations and stronger arms—that is, with more intense male competition—to have larger brains than those species with weaker competition. Our clearest evidence for a link between mate competition and brain size, however, was that male brains showed a stronger response than female brains to our most important indicators of mate competition: sex ratio and arm muscles. Our study thus provides strong evidence that not just wooing females but also fighting for them can drive the evolution of brainier males. </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>ompetition over mates is a powerful force shaping trait evolution. For instance, better cognitive abilities may be beneficial in male−male competition and thus be selected for by intrasexual selection. Alternatively, investment in physical attributes favoring male performance in competition for mates may lower the resources available for brain development, and more intense male mate competition would coincide with smaller brains. To date, only indirect evidence for such relationships exists and most studies are heavily biased towards primates and other homoeothermic vertebrates. We tested the association between male brain size (relative to body size) and male−male competition across <i>N</i>=30 species of Chinese anurans. Three indicators of the intensity of male mate competition—operational sex ratio (OSR), spawning-site density and male forelimb muscle mass—were positively associated with relative brain size, whereas the absolute spawning-group size was not. The relationship with the OSR and male forelimb muscle mass was stronger for the male than the female brains. Taken together, our findings suggest that the increased cognitive abilities of larger brains are beneficial in male−male competition. This study adds taxonomic breadth to the mounting evidence for a prominent role of sexual selection in vertebrate brain evolution. </p> <h4>两栖动物雄性间配偶竞争强度预测脑大小变异</h4> <p>争夺配偶是动物性状进化的强有力驱动者。例如,良好的认知能力有利于雄性个体赢得配偶竞争,从而被性选择所青睐。另一方面,如果雄性分配更多能量到那些有利于其获得配偶的身体性状,他们将减少用于脑发育的能量投入;由此推测,更激烈的配偶竞争将使得雄性拥有更小的脑。目前,支持这一预测的证据是间接的,且多集中在灵长类以及其他恒温动物。使用30种来自中国的无尾两栖类,我们检验了雄性脑大小(相对于身体大小)与雄性间配偶竞争强度的关系。结果表明,相对脑大小与三个雄性配偶竞争强度指标,即有效性比、产卵点密度和雄性前臂肌肉重,显著正相关,而与产卵地群体大小无关。我们还发现,雄性脑大小与有效性比和前臂肌肉重的相关性明显强于雌性。总之,我们的发现表明,大的脑,这意味着更好的认知能力,在雄性间配偶竞争中是有利的。我们的发现也在类群上拓展了性选择在脊椎动物脑进化中所起的突出作用。 </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 20 Apr 2020 05:00:00 GMT “A stochastic model for predicting age and mass at maturity of insects” https://amnat.org/an/newpapers/Aug-Legault.html Geoffrey Legault and Joel G. Kingsolver (Aug 2020) A stochastic model of insect development predicts complex dependencies between age and mass at maturity Read the Article (Just Accepted) Two key questions in ecology and evolutionary biology are: (1) How long does it take individuals to mature (i.e., become adults)? and (2) How big are they when they do? Age at maturity is important because it determines when adults become active in the environment, which affects the timing of interactions such as herbivory and pollination. Mass at maturity is important because it affects demographic traits such as fecundity, hardiness, and dispersal ability. Finally, trade-offs between age and mass at maturity (e.g., fast maturation = small mass) are important because they determine which life history strategies are optimal. Biologists Geoffrey Legault (University of British Columbia) and Joel Kingsolver (University of North Carolina at Chapel Hill) propose a new method for predicting the age and mass at maturity of insects. Their approach, which combines the theory of stochastic processes with the well known developmental biology of insects, reveals that variation during development can produce complex and previously unknown trade-offs between age and mass at maturity. Though their results focus on insect growth and maturation, they argue that similar trade-offs could occur in a wide variety of organisms with complex developmental processes. Abstract Variation in age and mass at maturity is commonly observed in populations, even among individuals with the same genetic and environmental backgrounds. Accounting for such individual variation with a stochastic model is important for estimating optimal evolutionary strategies and for understanding potential trade-offs among life history traits. However, most studies employ stochastic models that are either phenomenological or account for variation in only one life history trait. We propose a model based on the developmental biology of the moth Manduca sexta that accounts for stochasticity in two key life history traits, age and mass at maturity. The model is mechanistic, describing feeding behavior and common insect developmental processes including the degradation of juvenile hormone prior to molting. We derive a joint probability density function for the model and explore how the distribution of age and mass at maturity is affected by different parameter values. We find that the joint distribution is generally non-normal and highly sensitive to parameter values. In addition, our model predicts previously observed effects of temperature change and nutritional quality on the expected values of insect age and mass. Our results highlight the importance of integrating multiple sources of stochasticity into life history models. More forthcoming papers &raquo; <p>Geoffrey Legault and Joel G. Kingsolver (Aug 2020) </p> <p><b>A stochastic model of insect development predicts complex dependencies between age and mass at maturity </b></p> <p><i><a href="https://dx.doi.org/10.1086/709503">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>wo key questions in ecology and evolutionary biology are: (1) How long does it take individuals to mature (i.e., become adults)? and (2) How big are they when they do? Age at maturity is important because it determines when adults become active in the environment, which affects the timing of interactions such as herbivory and pollination. Mass at maturity is important because it affects demographic traits such as fecundity, hardiness, and dispersal ability. Finally, trade-offs between age and mass at maturity (e.g., fast maturation = small mass) are important because they determine which life history strategies are optimal. </p><p>Biologists Geoffrey Legault (University of British Columbia) and Joel Kingsolver (University of North Carolina at Chapel Hill) propose a new method for predicting the age and mass at maturity of insects. Their approach, which combines the theory of stochastic processes with the well known developmental biology of insects, reveals that variation during development can produce complex and previously unknown trade-offs between age and mass at maturity. Though their results focus on insect growth and maturation, they argue that similar trade-offs could occur in a wide variety of organisms with complex developmental processes. </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;">V</span>ariation in age and mass at maturity is commonly observed in populations, even among individuals with the same genetic and environmental backgrounds. Accounting for such individual variation with a stochastic model is important for estimating optimal evolutionary strategies and for understanding potential trade-offs among life history traits. However, most studies employ stochastic models that are either phenomenological or account for variation in only one life history trait. We propose a model based on the developmental biology of the moth <i>Manduca sexta</i> that accounts for stochasticity in two key life history traits, age and mass at maturity. The model is mechanistic, describing feeding behavior and common insect developmental processes including the degradation of juvenile hormone prior to molting. We derive a joint probability density function for the model and explore how the distribution of age and mass at maturity is affected by different parameter values. We find that the joint distribution is generally non-normal and highly sensitive to parameter values. In addition, our model predicts previously observed effects of temperature change and nutritional quality on the expected values of insect age and mass. Our results highlight the importance of integrating multiple sources of stochasticity into life history models. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 20 Apr 2020 05:00:00 GMT “Effect of stressors on the carrying capacity of spatially distributed metapopulations” https://amnat.org/an/newpapers/Aug-Zhang-A.html Bo Zhang, Donald DeAngelis, Wei-Ming Ni, Yuanshi Wang, Lu Zhai, Alex Kula, Shuang Xu, and David Van Dyken (Aug 2020) We prove mathematically and test empirically that a homogeneous distributed stressor leads to the lowest metapopulation Read the Article (Just Accepted) Abstract Stressors such as antibiotics, herbicides and pollutants are becoming increasingly common in the environment. The effects of stressors on populations are typically studied in homogeneous, non-spatial settings. However, most populations in nature are spatially distributed over environmentally heterogeneous landscapes with spatially-restricted dispersal. Little is known about the effects of stressors in these more realistic settings. Here, we combine laboratory experiments with novel mathematical theory to rigorously investigate how a stressor’s physiological effect and spatial distribution interact with dispersal to influence population dynamics. We prove mathematically that if a stressor increases death rate and/or simultaneously decreases population growth rate and yield, a homogeneous distribution of stressor leads to a lower total population size than if the same amount of stressor was heterogeneously distributed. We experimentally test this prediction on spatially-distributed populations of budding yeast, Saccharomyces cerevisiae. We find that the antibiotic, cycloheximide, increases yeast death rate but reduces growth rate and yield. Consistent with our mathematical predictions, we observe that a homogeneous spatial distribution of cycloheximide minimizes the total equilibrium size of experimental metapopulations, with the magnitude of the effect depending predictably on dispersal rate and geographic pattern of antibiotic heterogeneity. Our study has implications for assessing population risk posed by pollutants, antibiotics, and global change, and in the rational design of strategies for employing toxins to control pathogens and pests. More forthcoming papers &raquo; <p>Bo Zhang, Donald DeAngelis, Wei-Ming Ni, Yuanshi Wang, Lu Zhai, Alex Kula, Shuang Xu, and David Van Dyken (Aug 2020) </p> <p><b>We prove mathematically and test empirically that a homogeneous distributed stressor leads to the lowest metapopulation </b></p> <p><i><a href="https://dx.doi.org/10.1086/709293">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>tressors such as antibiotics, herbicides and pollutants are becoming increasingly common in the environment. The effects of stressors on populations are typically studied in homogeneous, non-spatial settings. However, most populations in nature are spatially distributed over environmentally heterogeneous landscapes with spatially-restricted dispersal. Little is known about the effects of stressors in these more realistic settings. Here, we combine laboratory experiments with novel mathematical theory to rigorously investigate how a stressor’s physiological effect and spatial distribution interact with dispersal to influence population dynamics. We prove mathematically that if a stressor increases death rate and/or simultaneously decreases population growth rate and yield, a homogeneous distribution of stressor leads to a lower total population size than if the same amount of stressor was heterogeneously distributed. We experimentally test this prediction on spatially-distributed populations of budding yeast, <i>Saccharomyces cerevisiae</i>. We find that the antibiotic, cycloheximide, increases yeast death rate but reduces growth rate and yield. Consistent with our mathematical predictions, we observe that a homogeneous spatial distribution of cycloheximide minimizes the total equilibrium size of experimental metapopulations, with the magnitude of the effect depending predictably on dispersal rate and geographic pattern of antibiotic heterogeneity. Our study has implications for assessing population risk posed by pollutants, antibiotics, and global change, and in the rational design of strategies for employing toxins to control pathogens and pests. </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, 15 Apr 2020 05:00:00 GMT The ASN Student Research Award https://amnat.org/announcements/ANNStuResearchAWA.html First Last &nbsp;Research Romain Boisseau The convergent evolution of extreme hindlegs in tree lobster stick insects Matthew Gibson Testing alternative modes of fruit color convergence in an invasive Gal&aacute;pagos tomato Elisa Visher The evolution of host genotype specialization in an insect pathogen Sarah Wolf Telomeres and ecogeographic rules: how latitudinal patterns of telomere dynamics mediate life history evolution George W. Gilchrist, a long-time member of our community, passed away early in 2020. His family requested that a fund be collected to support student research, which he supported in so many ways. George Gilchrist held faculty positions at Clarkson University and the College of William and Mary before becoming a long-time Program Director (Division of Environmental Biology) at the National Science Foundation. For 10 years, George was also the liaison between the Education and Outreach Committees of ASN and SSE. His impact on our science and young scientists has been exceptional. These four applicants for the ASN Student Research Award were singled out for the quality of their research projects and for their relevance to George Gilchrist&#39;s own research interests. First Last &nbsp;Research Amanda Benoit The effects of pollinator predators on self-pollination rates and inbreeding depression of the flowering plant, Calochortus luteus Regan Cross Do species’ habitat breadths narrow toward their range limits? Austin Garner Identifying the mutational basis of reinforcement and the genomic signatures of its evolution in Phlox drummondii with region-specific target capture sequencing Lucas Nell Extreme population fluctuations and genome evolution: a 40-year ecological and genomic time series in a wild population Brandie Quarles Phenological tracking via dormancy: facilitating survival and adaptation to climate change Angel Rivera-Col&oacute;n Comparative and population genomics in the only temperate icefish, Champsocephalus esox S&eacute;bastien Rivest Testing the role of microorganisms in mediating floral evolution Young Ha Suh Tracking movement to understand dispersal and habitat selection Amy Waananen Time is the longest distance: temporal outcrossing in a fragmented environment Yingtong Wu Selection vs. gene flow: the maintenance of species boundaries of an endangered rare species, Maple-Leaf Oak (Quercus acerifolia) The ASN Student Research Awards support research by student members that advances the goals of the society: the conceptual unification of ecology, evolution, or behavior. Each award consists of a $2,000 check to the candidate. An applicant must be a member of the ASN (membership is international), must hold a bachelor’s degree or equivalent, must have passed to candidacy in a Ph.D. program or equivalent, and must be at least one year from completing the PhD. Projects in all types of research (i.e., laboratory, field, theory) are encouraged. Proposals are judged on originality, strength, and significance of the questions being addressed, prospects for significant results, and the match between the proposed research and the ASN mission. <table border="1" cellpadding="1" cellspacing="1" style="width: 455px;"> <tbody> <tr> <td>First</td> <td>Last</td> <td>&nbsp;Research</td> </tr> <tr> <td>Romain</td> <td>Boisseau</td> <td>The convergent evolution of extreme hindlegs in tree lobster stick insects</td> </tr> <tr> <td>Matthew</td> <td>Gibson</td> <td>Testing alternative modes of fruit color convergence in an invasive Gal&aacute;pagos tomato</td> </tr> <tr> <td>Elisa</td> <td>Visher</td> <td>The evolution of host genotype specialization in an insect pathogen</td> </tr> <tr> <td>Sarah</td> <td>Wolf</td> <td>Telomeres and ecogeographic rules: how latitudinal patterns of telomere dynamics mediate life history evolution</td> </tr> </tbody> </table> <p>George W. Gilchrist, a long-time member of our community, passed away early in 2020. His family requested that a fund be collected to support student research, which he supported in so many ways. George Gilchrist held faculty positions at Clarkson University and the College of William and Mary before becoming a long-time Program Director (Division of Environmental Biology) at the National Science Foundation. For 10 years, George was also the liaison between the Education and Outreach Committees of ASN and SSE. His impact on our science and young scientists has been exceptional. These four applicants for the ASN Student Research Award were singled out for the quality of their research projects and for their relevance to George Gilchrist&#39;s own research interests.</p><table border="1" cellpadding="1" cellspacing="1" style="width: 455px;"> <tbody> <tr> <td>First</td> <td>Last</td> <td>&nbsp;Research</td> </tr> <tr> <td>Amanda</td> <td>Benoit</td> <td>The effects of pollinator predators on self-pollination rates and inbreeding depression of the flowering plant, <em>Calochortus luteus</em></td> </tr> <tr> <td>Regan</td> <td>Cross</td> <td>Do species&rsquo; habitat breadths narrow toward their range limits?</td> </tr> <tr> <td>Austin</td> <td>Garner</td> <td>Identifying the mutational basis of reinforcement and the genomic signatures of its evolution in <em>Phlox drummondii</em> with region-specific target capture sequencing</td> </tr> <tr> <td>Lucas</td> <td>Nell</td> <td>Extreme population fluctuations and genome evolution: a 40-year ecological and genomic time series in a wild population</td> </tr> <tr> <td>Brandie</td> <td>Quarles</td> <td>Phenological tracking via dormancy: facilitating survival and adaptation to climate change</td> </tr> <tr> <td>Angel</td> <td>Rivera-Col&oacute;n</td> <td>Comparative and population genomics in the only temperate icefish, <em>Champsocephalus esox</em></td> </tr> <tr> <td>S&eacute;bastien</td> <td>Rivest</td> <td>Testing the role of microorganisms in mediating floral evolution</td> </tr> <tr> <td>Young Ha</td> <td>Suh</td> <td>Tracking movement to understand dispersal and habitat selection</td> </tr> <tr> <td>Amy</td> <td>Waananen</td> <td>Time is the longest distance: temporal outcrossing in a fragmented environment</td> </tr> <tr> <td>Yingtong</td> <td>Wu</td> <td>Selection vs. gene flow: the maintenance of species boundaries of an endangered rare species, Maple-Leaf Oak (<em>Quercus acerifolia</em>)</td> </tr> </tbody> </table> <p>The ASN Student Research Awards support research by student members that advances the goals of the society: the conceptual unification of ecology, evolution, or behavior. Each award consists of a $2,000 check to the candidate. An applicant must be a member of the ASN (membership is international), must hold a bachelor&rsquo;s degree or equivalent, must have passed to candidacy in a Ph.D. program or equivalent, and must be at least one year from completing the PhD.</p> <p>Projects in all types of research (i.e., laboratory, field, theory) are encouraged. Proposals are judged on originality, strength, and significance of the questions being addressed, prospects for significant results, and the match between the proposed research and the ASN mission.</p> Mon, 06 Apr 2020 05:00:00 GMT