ASN RSS https://amnat.org/ Latest press releases and announcements from the ASN en-us Fri, 24 May 2019 05:00:00 GMT 60 “Omnivory in bees: Elevated trophic positions among all major bee families” https://amnat.org/an/newpapers/Sep-Steffan.html Read the Article (Just Accepted) Bees are omnivores, mainly because as larvae, they eat lots of ‘microbial meat’Bees are widely thought to derive all protein directly from floral resources. Recent findings suggest this is largely untrue. It appears that larval bees feed extensively on pollen-borne prey, as well as on the pollen, itself. These prey are the microbes that are suffused throughout a fermenting pollen-provision. Because the microbes are actively consuming the pollen, these herbivorous organisms represent ‘microbial meat’ within the pollen-provision. When a larval bee consumes aged pollen, the bee is consuming both microbial and plant biomass, assimilating the amino acids of microbial prey as well as those of the plant material—analogous to eating bacon bits in a salad. The degree to which a bee assimilates microbe-derived amino acids can be measured empirically as the trophic position of the bee (the more meat consumed, the higher the trophic position). Importantly, gut microbiota do not elevate the hosting animal’s trophic position. To assess the pervasiveness of bee omnivory, the trophic positions of bees representing the six major bee families on Earth were examined. Adult bees were collected over the course of two years, from the cranberry marshlands of Wisconsin to the forests of New York. There was consistent, significant evidence of elevated trophic positions among all the bees in the study (54 specimens across 14 species, 12 genera), suggesting that most bees, if not all, are omnivorous. Such reliance on microbial nutrition also suggests that pollen-borne microbes represent true symbionts for bees; thus, to conserve bee fauna, their microbial symbionts will require attention, too. Abstract As pollen- and nectar-foragers, bees have long been considered strictly herbivorous. Their pollen-provisions, however, are host to abundant microbial communities, which feed on the pollen before/while it is consumed by bee larvae. In the process, microbes convert pollen into a complex of plant and microbial components. Since microbes are analogous to metazoan consumers within trophic hierarchies, the pollen-eating microbes are, functionally, herbivores. When bee larvae consume a microbe-rich pollen complex, they ingest proteins from plant and microbial sources, thus should register as omnivores on the trophic “ladder.” We tested this hypothesis by examining the isotopic compositions of amino acids extracted from native bees collected in North America over multiple years. We measured bee trophic position across the six major bee families. Our findings indicate that bee trophic identity was consistently and significantly higher than that of strict herbivores, providing the first evidence that omnivory is ubiquitous among bee fauna. Such omnivory suggests that pollen-borne microbes represent an important protein source for larval bees, which introduces new questions as to the link between floral fungicide residues and bee development. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704281">Read the Article</a></i> (Just Accepted)</p> <p><b>Bees are omnivores, mainly because as larvae, they eat lots of ‘microbial meat’</b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">B</span>ees are widely thought to derive all protein directly from floral resources. Recent findings suggest this is largely untrue. It appears that larval bees feed extensively on pollen-borne prey, as well as on the pollen, itself. These prey are the microbes that are suffused throughout a fermenting pollen-provision. Because the microbes are actively consuming the pollen, these herbivorous organisms represent ‘microbial meat’ within the pollen-provision. When a larval bee consumes aged pollen, the bee is consuming both microbial and plant biomass, assimilating the amino acids of microbial prey as well as those of the plant material—analogous to eating bacon bits in a salad. The degree to which a bee assimilates microbe-derived amino acids can be measured empirically as the trophic position of the bee (the more meat consumed, the higher the trophic position). Importantly, gut microbiota do not elevate the hosting animal’s trophic position. To assess the pervasiveness of bee omnivory, the trophic positions of bees representing the six major bee families on Earth were examined. Adult bees were collected over the course of two years, from the cranberry marshlands of Wisconsin to the forests of New York. There was consistent, significant evidence of elevated trophic positions among all the bees in the study (54 specimens across 14 species, 12 genera), suggesting that most bees, if not all, are omnivorous. Such reliance on microbial nutrition also suggests that pollen-borne microbes represent true symbionts for bees; thus, to conserve bee fauna, their microbial symbionts will require attention, too. </p> <hr /><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>s pollen- and nectar-foragers, bees have long been considered strictly herbivorous. Their pollen-provisions, however, are host to abundant microbial communities, which feed on the pollen before/while it is consumed by bee larvae. In the process, microbes convert pollen into a complex of plant and microbial components. Since microbes are analogous to metazoan consumers within trophic hierarchies, the pollen-eating microbes are, functionally, herbivores. When bee larvae consume a microbe-rich pollen complex, they ingest proteins from plant and microbial sources, thus should register as omnivores on the trophic “ladder.” We tested this hypothesis by examining the isotopic compositions of amino acids extracted from native bees collected in North America over multiple years. We measured bee trophic position across the six major bee families. Our findings indicate that bee trophic identity was consistently and significantly higher than that of strict herbivores, providing the first evidence that omnivory is ubiquitous among bee fauna. Such omnivory suggests that pollen-borne microbes represent an important protein source for larval bees, which introduces new questions as to the link between floral fungicide residues and bee development. </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 May 2019 05:00:00 GMT “Antagonistic responses of exposure to sublethal temperatures: Adaptive phenotypic plasticity coincides with a reduction in organismal performance” https://amnat.org/an/newpapers/Sep-Gilbert.html Read the Article (Just Accepted) Exposure to stressful temperatures induces adaptive plasticity but constrains ecological and organismal performance Anthropogenic climate change is exposing populations to new environmental pressures that can lead to a variety of physiological, genetic, or behavioral responses. When novel environmental conditions cause phenotypic shifts in the absence of genetic change (i.e. phenotypic plasticity), oftentimes researchers only consider quantifying how traits-of-interest shift, without considering that particularly stressful stimuli might lead to other unforeseen phenotypic outcomes. Because many species are now predisposed to higher incidences of heat waves within their environment, exposure to sublethal temperatures is considered to be a trigger of adaptive phenotypic plasticity, otherwise called ‘heat hardening’. Heat hardening occurs when an individual is exposed to sublethal temperatures, and as a result they can temporarily tolerate higher temperatures than they could prior to heat shock. However, because the trigger of heat hardening is a stressful increase in body temperatures close to upper thermal tolerance limits, organisms might exhibit unforeseen physiological consequences. In this study, Gilbert and Miles show that for tree lizards in the Sonoran Desert, when heat hardening is expressed, lizards prefer cooler temperatures when they thermoregulate, and exhibit reductions in locomotor performance (maximal speed) throughout the response. They also find that because of these physiological costs, tree lizards are not fully able to exploit the adaptive nature of a higher heat tolerance, thus weakening their reliance on phenotypic plasticity as a buffer from temperature extremes. This study demonstrates that even though plasticity can be adaptive and beneficial, when organisms are exposed to extreme environmental stimuli, these stimuli might induce maladaptive responses in other traits leading to antagonistic interactions between the phenotypic shifts triggered by new environments. Abstract A&nbsp;fitness benefit of phenotypic plasticity is the ability of an organism to survive short-term, deleterious environmental fluctuations. Yet, the influence of selection on plasticity in modulating shifts in phenotypic traits remains unclear. Short-term phenotypic plasticity in thermal tolerance traits is attained by exposure to sublethal hot or cold temperatures (i.e. the hardening response). Heat hardening is expected to buffer organisms from the unpredictability of extreme thermal fluctuations in the environment so as to minimize interruptions in activity and enhance survival. However, exposure to sublethal temperatures might entail other phenotypic costs that constrain or inhibit the prolonged use of hardening responses across longer timescales. Here, we estimated the onset of the heat hardening response, physiological and behavioral shifts during heat hardening, and geographic variation in heat hardening using tree lizards (Urosaurus ornatus). Peak heat hardening occurred 6h after exposure to sublethal temperatures. We found that both preferred body temperatures and locomotor performance diminished following exposure to sublethal temperatures, and performance levels did not approach pre-exposure levels until after the peak hardening response. We also found support for intraspecific variation in the hardening response along an environmental gradient, where populations in more thermally variable environments exhibited stronger plastic responses and populations with higher baseline heat tolerances exhibited weaker plastic responses. Sublethal temperature exposure might induce adaptive plasticity in thermal tolerance, however we find that these responses entail other phenotypic shifts that might curtail chronic reliance on plasticity in thermal traits as a mechanism of responding to changes in thermal environments induced by climate warming. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704208">Read the Article</a></i> (Just Accepted)</p> <p><b>Exposure to stressful temperatures induces adaptive plasticity but constrains ecological and organismal performance </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>nthropogenic climate change is exposing populations to new environmental pressures that can lead to a variety of physiological, genetic, or behavioral responses. When novel environmental conditions cause phenotypic shifts in the absence of genetic change (i.e. phenotypic plasticity), oftentimes researchers only consider quantifying how traits-of-interest shift, without considering that particularly stressful stimuli might lead to other unforeseen phenotypic outcomes. Because many species are now predisposed to higher incidences of heat waves within their environment, exposure to sublethal temperatures is considered to be a trigger of adaptive phenotypic plasticity, otherwise called ‘heat hardening’. Heat hardening occurs when an individual is exposed to sublethal temperatures, and as a result they can temporarily tolerate higher temperatures than they could prior to heat shock. However, because the trigger of heat hardening is a stressful increase in body temperatures close to upper thermal tolerance limits, organisms might exhibit unforeseen physiological consequences. In this study, Gilbert and Miles show that for tree lizards in the Sonoran Desert, when heat hardening is expressed, lizards prefer cooler temperatures when they thermoregulate, and exhibit reductions in locomotor performance (maximal speed) throughout the response. They also find that because of these physiological costs, tree lizards are not fully able to exploit the adaptive nature of a higher heat tolerance, thus weakening their reliance on phenotypic plasticity as a buffer from temperature extremes. This study demonstrates that even though plasticity can be adaptive and beneficial, when organisms are exposed to extreme environmental stimuli, these stimuli might induce maladaptive responses in other traits leading to antagonistic interactions between the phenotypic shifts triggered by new environments. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>&nbsp;fitness benefit of phenotypic plasticity is the ability of an organism to survive short-term, deleterious environmental fluctuations. Yet, the influence of selection on plasticity in modulating shifts in phenotypic traits remains unclear. Short-term phenotypic plasticity in thermal tolerance traits is attained by exposure to sublethal hot or cold temperatures (i.e. the hardening response). Heat hardening is expected to buffer organisms from the unpredictability of extreme thermal fluctuations in the environment so as to minimize interruptions in activity and enhance survival. However, exposure to sublethal temperatures might entail other phenotypic costs that constrain or inhibit the prolonged use of hardening responses across longer timescales. Here, we estimated the onset of the heat hardening response, physiological and behavioral shifts during heat hardening, and geographic variation in heat hardening using tree lizards (<i>Urosaurus ornatus</i>). Peak heat hardening occurred 6h after exposure to sublethal temperatures. We found that both preferred body temperatures and locomotor performance diminished following exposure to sublethal temperatures, and performance levels did not approach pre-exposure levels until after the peak hardening response. We also found support for intraspecific variation in the hardening response along an environmental gradient, where populations in more thermally variable environments exhibited stronger plastic responses and populations with higher baseline heat tolerances exhibited weaker plastic responses. Sublethal temperature exposure might induce adaptive plasticity in thermal tolerance, however we find that these responses entail other phenotypic shifts that might curtail chronic reliance on plasticity in thermal traits as a mechanism of responding to changes in thermal environments induced by climate warming. </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 May 2019 05:00:00 GMT “Destruction of spider webs and rescue of ensnared nestmates by a granivorous desert ant (Veromessor pergandei)” https://amnat.org/an/newpapers/Sep-Kwapich.html Read the Article (Just Accepted) Ants destroy spider webs and rescue trapped sisters that call for help Few prey species seek out and destroy the traps designed to capture them, and only a handful rescue group members in distress. That is why Kwapich and Hölldobler were surprised to discover that desert seed harvesting ants systematically dismantle spider webs constructed along their foraging routes, and retrieve sisters ensnared in spider silk. Animals that perform rescue behavior typically live in small groups with high-value individuals, but Veromessor pergandei form enormous societies that deploy up to 30,000 foragers each morning. To determine why colonies rescue seemingly disposable workers, the authors calculated the costs and benefits of web removal. They found that the seeds carried by foraging ants become tangled in undetected webs, reducing the total number of foraging trips individuals can take per day. By accounting for the length of a foraging career and number of trips per day, they estimated that unchecked spider predation could cost colonies 65,000 seeds per year. This is a high price to pay, because colonies need to gather enough resources to rear 600 new sisters each day. Many ant species clear debris from their foraging routes, but Kwapich and H&ouml;lldobler showed that V.&nbsp;pergandei foragers ignore novel objects, and even lack an innate ability to detect spider silk. Instead, ensnared ants release a chemical alarm signal, which stimulates a subset of large-bodied nestmates to remove surrounding webbing. Frozen ‘dummies’ marked with the same alarm compound were also rescued, and freed from their silk bindings. In essence, colonies only benefit from the removal of webs when workers are captured in them. Other seed harvesting ant species arrest foraging or change their foraging patterns in response to spiders. The authors propose that foraging on a single route during a limited temperature window, coupled with the necessary scale seed harvesting, led V.&nbsp;pergandei to its unusual defensive strategy. Abstract Prey species rarely seek-out and dismantle traps constructed by their predators. In the current study, we report an instance of targeted trap destruction by an invertebrate, and a novel context for rescue behavior. We found that foragers of the granivorous desert ant, Veromessor pergandei, identify and cooperatively dismantle spider webs (Araneae: Theridiidae, Steatoda spp. and Asagena sp.) During group foraging, workers ensnared in webs are recovered by sisters, who transport them to the nest and groom away their silk bindings. The presence of an ensnared nestmate and chemical alarm signal significantly increased the probability of web removal and nestmate retrieval. A subset of larger-bodied foragers participated in web removal, and 6.3% became tangled or were captured by spiders. Most animals that perform rescue behavior live in small groups, but V.&nbsp;pergandei colonies include tens of thousands of short-lived workers. To maintain their size, large colonies must collect enough seeds to produce 650 new ants each day. We hypothesize that the removal of spider webs allows for an unimpeded income of seeds on a single foraging path, during a brief daily temperature window. Despite the cost to individuals, webs are only recognized and removed when workers are captured in them. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704338">Read the Article</a></i> (Just Accepted) </p> <p><b>Ants destroy spider webs and rescue trapped sisters that call for help </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">F</span>ew prey species seek out and destroy the traps designed to capture them, and only a handful rescue group members in distress. That is why Kwapich and Hölldobler were surprised to discover that desert seed harvesting ants systematically dismantle spider webs constructed along their foraging routes, and retrieve sisters ensnared in spider silk. Animals that perform rescue behavior typically live in small groups with high-value individuals, but <i>Veromessor pergandei</i> form enormous societies that deploy up to 30,000 foragers each morning. </p><p>To determine why colonies rescue seemingly disposable workers, the authors calculated the costs and benefits of web removal. They found that the seeds carried by foraging ants become tangled in undetected webs, reducing the total number of foraging trips individuals can take per day. By accounting for the length of a foraging career and number of trips per day, they estimated that unchecked spider predation could cost colonies 65,000 seeds per year. This is a high price to pay, because colonies need to gather enough resources to rear 600 new sisters each day. </p><p>Many ant species clear debris from their foraging routes, but Kwapich and H&ouml;lldobler showed that <i>V.&nbsp;pergandei</i> foragers ignore novel objects, and even lack an innate ability to detect spider silk. Instead, ensnared ants release a chemical alarm signal, which stimulates a subset of large-bodied nestmates to remove surrounding webbing. Frozen &lsquo;dummies&rsquo; marked with the same alarm compound were also rescued, and freed from their silk bindings. In essence, colonies only benefit from the removal of webs when workers are captured in them. Other seed harvesting ant species arrest foraging or change their foraging patterns in response to spiders. The authors propose that foraging on a single route during a limited temperature window, coupled with the necessary scale seed harvesting, led <i>V.&nbsp;pergandei</i> to its unusual defensive strategy.</p> <hr/><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>rey species rarely seek-out and dismantle traps constructed by their predators. In the current study, we report an instance of targeted trap destruction by an invertebrate, and a novel context for rescue behavior. We found that foragers of the granivorous desert ant, <i>Veromessor pergandei</i>, identify and cooperatively dismantle spider webs (Araneae: Theridiidae, <i>Steatoda</i> spp. and <i>Asagena</i> sp.) During group foraging, workers ensnared in webs are recovered by sisters, who transport them to the nest and groom away their silk bindings. The presence of an ensnared nestmate and chemical alarm signal significantly increased the probability of web removal and nestmate retrieval. A subset of larger-bodied foragers participated in web removal, and 6.3% became tangled or were captured by spiders. Most animals that perform rescue behavior live in small groups, but <i>V.&nbsp;pergandei</i> colonies include tens of thousands of short-lived workers. To maintain their size, large colonies must collect enough seeds to produce 650 new ants each day. We hypothesize that the removal of spider webs allows for an unimpeded income of seeds on a single foraging path, during a brief daily temperature window. Despite the cost to individuals, webs are only recognized and removed when workers are captured in them. </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 May 2019 05:00:00 GMT “Intraspecific variation in worker body size makes North American bumble bees (Bombus spp.) less susceptible to decline” https://amnat.org/an/newpapers/Sep-Austin.html Read the Article (Just Accepted) Intraspecific variation in worker body size makes North American bumble bees less susceptible to population declines Population declines of bees are of broad interest, as bees are important pollinators of much of our wild and agricultural crops. While bee declines are likely caused by many factors, human-induced environmental changes are thought to be key culprits of these declines. A puzzle, however, is that not all bee species are declining – some are in fact thriving – which suggests differences between species in traits that enable responses to rapidly changed environments. In a new paper in The&nbsp;American Naturalist, M.&nbsp;W. Austin and A.&nbsp;S. Dunlap investigate traits in North American bumble bees (Bombus spp.) that may make certain species of bumble bees more susceptible to decline. They study two traits that may be particularly important for bees when encountering rapidly changed environments: 1) the amount of body size variation within a species (i.e. how close in size individual bees are) and 2) head size, a proxy for brain size and behavioral plasticity. High body size variation is likely adaptive within colonies; larger bees are more efficient workers, while smaller bees can withstand starvation for longer periods of time. Behavioral plasticity is thought to benefit species in changed environments, by allowing individuals to plastically change their behavior to novel environmental conditions. Using natural history collections from the Smithsonian, the American Museum of Natural History, the Field Museum, and the Illinois Natural History Survey, along with measures of bumble bee decline from the International Union for Conservation of Nature, the authors find that bumble bee species with low body size variation are more susceptible to decline, while species with higher body size variation are more likely to be thriving. Head size does not appear to affect a species’ likelihood of decline. These results suggest that high variation in body size enables bumble bees to successfully respond to environments altered by human activity, perhaps due to the benefits of body size variation within colonies. This study is part of Austin’s Ph.D. dissertation at the University of Missouri–St. Louis, where he became interested in this topic while considering why closely related species experience divergent population trends. Abstract Population declines have been documented in approximately one-third of bumble bee species. Certain drivers of these declines are known, however less is known about the interspecific trait differences that make certain species more susceptible to decline. Two traits, which have implications for responding to rapidly changed environments, may be particularly consequential for bumble bee populations: intraspecific body size variation and brain size. Bumble bee body size is highly variable and is likely adaptive at the colony level, and brain size correlates with cognitive traits (e.g. behavioral plasticity) in many groups. Trait variation and plasticity may buffer species against negative effects of rapidly changed environments. Using phylogenetically controlled analyses of 31 North American bumble bee species, we find higher intraspecific body size variation is associated with species having increased their relative abundance over time. However, this variation does not significantly interact with tongue length, another trait thought to influence bees’ decline susceptibility. Head size, a proxy for brain size, is not correlated with change in relative abundance. Our results support the hypothesis that variation in body size makes species less susceptible to decline in rapidly altered environments and suggests that this variation is important to the success of bumble bee populations. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704280">Read the Article</a></i> (Just Accepted)</p> <p><b>Intraspecific variation in worker body size makes North American bumble bees less susceptible to population declines </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>opulation declines of bees are of broad interest, as bees are important pollinators of much of our wild and agricultural crops. While bee declines are likely caused by many factors, human-induced environmental changes are thought to be key culprits of these declines. A puzzle, however, is that not all bee species are declining – some are in fact thriving – which suggests differences between species in traits that enable responses to rapidly changed environments. </p><p>In a new paper in <i>The&nbsp;American Naturalist</i>, M.&nbsp;W. Austin and A.&nbsp;S. Dunlap investigate traits in North American bumble bees (<i>Bombus</i> spp.) that may make certain species of bumble bees more susceptible to decline. They study two traits that may be particularly important for bees when encountering rapidly changed environments: 1) the amount of body size variation within a species (i.e. how close in size individual bees are) and 2) head size, a proxy for brain size and behavioral plasticity. High body size variation is likely adaptive within colonies; larger bees are more efficient workers, while smaller bees can withstand starvation for longer periods of time. Behavioral plasticity is thought to benefit species in changed environments, by allowing individuals to plastically change their behavior to novel environmental conditions. </p><p>Using natural history collections from the Smithsonian, the American Museum of Natural History, the Field Museum, and the Illinois Natural History Survey, along with measures of bumble bee decline from the International Union for Conservation of Nature, the authors find that bumble bee species with low body size variation are more susceptible to decline, while species with higher body size variation are more likely to be thriving. Head size does not appear to affect a species’ likelihood of decline. These results suggest that high variation in body size enables bumble bees to successfully respond to environments altered by human activity, perhaps due to the benefits of body size variation within colonies. </p><p>This study is part of Austin’s Ph.D. dissertation at the University of Missouri–St. Louis, where he became interested in this topic while considering why closely related species experience divergent population trends.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>opulation declines have been documented in approximately one-third of bumble bee species. Certain drivers of these declines are known, however less is known about the interspecific trait differences that make certain species more susceptible to decline. Two traits, which have implications for responding to rapidly changed environments, may be particularly consequential for bumble bee populations: intraspecific body size variation and brain size. Bumble bee body size is highly variable and is likely adaptive at the colony level, and brain size correlates with cognitive traits (e.g. behavioral plasticity) in many groups. Trait variation and plasticity may buffer species against negative effects of rapidly changed environments. Using phylogenetically controlled analyses of 31 North American bumble bee species, we find higher intraspecific body size variation is associated with species having increased their relative abundance over time. However, this variation does not significantly interact with tongue length, another trait thought to influence bees’ decline susceptibility. Head size, a proxy for brain size, is not correlated with change in relative abundance. Our results support the hypothesis that variation in body size makes species less susceptible to decline in rapidly altered environments and suggests that this variation is important to the success of bumble bee 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> Wed, 15 May 2019 05:00:00 GMT “Decreasing predator density and activity explain declining predation of insect prey along elevational gradients” https://amnat.org/an/newpapers/Sep-Camacho-A.html Read the Article (Just Accepted)Abstract Predation, which is a fundamental force in ecosystems, has been found to decrease in intensity with elevation and latitude. The mechanisms behind this pattern, however, remain unaddressed. Using visual sampling of potential predators and live flies as baits, we assessed predation patterns along 4000-meter elevation transects on either side of the equatorial Andes. We found that at the lower elevations around eighty percent of predation events on our insect baits were due to ants. The decline in predation with elevation was mainly driven by a decline in the abundance of ants, whose importance relative to other predators also declined. We show that both predator density and activity (predation rate per individual predator) decreased with elevation, thus ascribing specific mechanisms to known predation patterns. We suggest that changes in these two mechanisms may reflect changes in primary productivity and metabolic rate with temperature, factors of potential relevance across latitudinal and other macroecological gradients, in particular for ectotherm predators and prey. La disminuci&oacute;n en la densidad y actividad de depredadores explican la reducci&oacute;n en la depredaci&oacute;n de insectos presas a lo largo de gradientes de elevaci&oacute;n La depredaci&oacute;n, una fuerza fundamental en los ecosistemas, se ha encontrado que decrece en intensidad con la elevaci&oacute;n y la latitud. Los mecanismos detr&aacute;s de este patr&oacute;n, sin embargo, no han sido estudiados. En este trabajo, usando muestreos visuales de potenciales depredadores y moscas vivas como cebos, evaluamos patrones de depredaci&oacute;n en transectos realizados con una variaci&oacute;n altitudinal de 4000 metros en las dos caras de los Andes ecuatoriales. Encontramos que, en altitudes bajas, alrededor del ochenta porciento de los eventos de depredaci&oacute;n en nuestros insectos cebo fueron causados por hormigas. El decrecimiento en depredaci&oacute;n asociado con la variaci&oacute;n altitudinal fue principalmente causado por una reducci&oacute;n en la abundancia de hormigas, cuya importancia relativa respecto a otros depredadores tambi&eacute;n disminuy&oacute;. Mostramos que tanto la densidad como la actividad de depredadores (tasa individual de depredaci&oacute;n por depredador) decrecieron con la altitud, atribuyendo mecanismos a patrones de depredaci&oacute;n ya conocidos. Sugerimos que cambios en estos dos mecanismos pueden reflejar cambios en la productividad primaria y en la tasa metab&oacute;lica relacionados con la temperatura, factores potencialmente relevantes a lo largo de gradientes de latitud y otros gradientes macroecol&oacute;gicos, particularmente para presas y depredadores ectotermos. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704279">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">P</span>redation, which is a fundamental force in ecosystems, has been found to decrease in intensity with elevation and latitude. The mechanisms behind this pattern, however, remain unaddressed. Using visual sampling of potential predators and live flies as baits, we assessed predation patterns along 4000-meter elevation transects on either side of the equatorial Andes. We found that at the lower elevations around eighty percent of predation events on our insect baits were due to ants. The decline in predation with elevation was mainly driven by a decline in the abundance of ants, whose importance relative to other predators also declined. We show that both predator density and activity (predation rate per individual predator) decreased with elevation, thus ascribing specific mechanisms to known predation patterns. We suggest that changes in these two mechanisms may reflect changes in primary productivity and metabolic rate with temperature, factors of potential relevance across latitudinal and other macroecological gradients, in particular for ectotherm predators and prey.</p> <h4>La disminuci&oacute;n en la densidad y actividad de depredadores explican la reducci&oacute;n en la depredaci&oacute;n de insectos presas a lo largo de gradientes de elevaci&oacute;n</h4> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">L</span>a depredaci&oacute;n, una fuerza fundamental en los ecosistemas, se ha encontrado que decrece en intensidad con la elevaci&oacute;n y la latitud. Los mecanismos detr&aacute;s de este patr&oacute;n, sin embargo, no han sido estudiados. En este trabajo, usando muestreos visuales de potenciales depredadores y moscas vivas como cebos, evaluamos patrones de depredaci&oacute;n en transectos realizados con una variaci&oacute;n altitudinal de 4000 metros en las dos caras de los Andes ecuatoriales. Encontramos que, en altitudes bajas, alrededor del ochenta porciento de los eventos de depredaci&oacute;n en nuestros insectos cebo fueron causados por hormigas. El decrecimiento en depredaci&oacute;n asociado con la variaci&oacute;n altitudinal fue principalmente causado por una reducci&oacute;n en la abundancia de hormigas, cuya importancia relativa respecto a otros depredadores tambi&eacute;n disminuy&oacute;. Mostramos que tanto la densidad como la actividad de depredadores (tasa individual de depredaci&oacute;n por depredador) decrecieron con la altitud, atribuyendo mecanismos a patrones de depredaci&oacute;n ya conocidos. Sugerimos que cambios en estos dos mecanismos pueden reflejar cambios en la productividad primaria y en la tasa metab&oacute;lica relacionados con la temperatura, factores potencialmente relevantes a lo largo de gradientes de latitud y otros gradientes macroecol&oacute;gicos, particularmente para presas y depredadores ectotermos.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 May 2019 05:00:00 GMT “Plastic senescence in the honeybee and the disposable soma theory” https://amnat.org/an/newpapers/Sep-da-Silva.html Read the Article (Just Accepted) The lifespan differences between honeybee castes help distinguish between different evolutionary theories of ageing Honeybee workers have much shorter lifespans than the queen not simply because they live more dangerous lives, but because they age faster. This tells us that ageing evolves as a consequence of an organism’s life history being adapted to its environment. Designation of an individual as a worker or a queen is not based on different sets of genes but on nutrition – a larva that is fed a protein-rich diet develops into a queen, otherwise she develops into a worker. As a worker, a bee ages so rapidly that she typically lives for only one month. In contrast, a queen may live for two years. But why should workers age more rapidly? Evolutionary theories of ageing tell us that natural selection becomes weaker with age simply because any individual has a lower probability of surviving to an old age than to a young age for reasons unrelated to ageing, such as accidental death. As a result, natural selection is less efficient at removing mutations that reduce survival or fertility at older ages, which may explain ageing. It follows from this that species that live more dangerous lives should age more rapidly. This logic also applies to honeybee workers, who perform high-risk duties outside the hive. However, since the designation of a worker is not based on a genetic difference from the queen, its higher rate of ageing must be due to different genes being turned on. The genes that are turned on in a worker are thought to invest the energy in its food in maintaining the bee’s body just enough to keep it functioning for its expected short lifespan, and as a result the bee ages rapidly. Any greater investment in maintenance would be wasteful. These results support an evolutionary theory of ageing, known as the disposable soma theory, that explains ageing as the consequence of organisms evolving an optimal strategy of investment in maintaining their bodies. Abstract The demonstration of lifespan plasticity in natural populations would provide a powerful test of evolutionary theories of senescence. Plastic senescence is not easily explained by mutation accumulation or antagonistic pleiotropy but is a corollary of the disposable soma theory. The lifespan differences among castes of the eusocial Hymenoptera are potentially some of the most striking and extreme examples of lifespan plasticity. Although these differences are often assumed to be plastic, this has never been demonstrated conclusively because differences in lifespan may be caused by the proximate effects of different levels of environmental hazard experienced by castes. Here, age-dependent and age-independent components of instantaneous mortality rates of the honeybee (Apis mellifera) were estimated from published lifetables for natural and semi-natural populations to determine whether differences in lifespan between queens and workers and between different types workers are indeed plastic. These differences in lifespan were found to be due to differences in the rate of actuarial senescence, which correlate positively with the rate of extrinsic mortality, in accordance with the central prediction of evolutionary theories of senescence. Although all three evolutionary theories of senescence could, in principle, explain such plastic senescence, given differential gene expression between castes or life stages, only the disposable soma theory adequately explains the adaptive regulation of somatic maintenance in response to different environmental conditions that appears to underlie lifespan plasticity. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704220">Read the Article</a></i> (Just Accepted)</p> <p><b>The lifespan differences between honeybee castes help distinguish between different evolutionary theories of ageing </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">H</span>oneybee workers have much shorter lifespans than the queen not simply because they live more dangerous lives, but because they age faster. This tells us that ageing evolves as a consequence of an organism’s life history being adapted to its environment. </p><p>Designation of an individual as a worker or a queen is not based on different sets of genes but on nutrition – a larva that is fed a protein-rich diet develops into a queen, otherwise she develops into a worker. As a worker, a bee ages so rapidly that she typically lives for only one month. In contrast, a queen may live for two years. But why should workers age more rapidly? Evolutionary theories of ageing tell us that natural selection becomes weaker with age simply because any individual has a lower probability of surviving to an old age than to a young age for reasons unrelated to ageing, such as accidental death. As a result, natural selection is less efficient at removing mutations that reduce survival or fertility at older ages, which may explain ageing. It follows from this that species that live more dangerous lives should age more rapidly. This logic also applies to honeybee workers, who perform high-risk duties outside the hive. However, since the designation of a worker is not based on a genetic difference from the queen, its higher rate of ageing must be due to different genes being turned on. The genes that are turned on in a worker are thought to invest the energy in its food in maintaining the bee’s body just enough to keep it functioning for its expected short lifespan, and as a result the bee ages rapidly. Any greater investment in maintenance would be wasteful. These results support an evolutionary theory of ageing, known as the disposable soma theory, that explains ageing as the consequence of organisms evolving an optimal strategy of investment in maintaining their bodies. </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 demonstration of lifespan plasticity in natural populations would provide a powerful test of evolutionary theories of senescence. Plastic senescence is not easily explained by mutation accumulation or antagonistic pleiotropy but is a corollary of the disposable soma theory. The lifespan differences among castes of the eusocial Hymenoptera are potentially some of the most striking and extreme examples of lifespan plasticity. Although these differences are often assumed to be plastic, this has never been demonstrated conclusively because differences in lifespan may be caused by the proximate effects of different levels of environmental hazard experienced by castes. Here, age-dependent and age-independent components of instantaneous mortality rates of the honeybee (<i>Apis mellifera</i>) were estimated from published lifetables for natural and semi-natural populations to determine whether differences in lifespan between queens and workers and between different types workers are indeed plastic. These differences in lifespan were found to be due to differences in the rate of actuarial senescence, which correlate positively with the rate of extrinsic mortality, in accordance with the central prediction of evolutionary theories of senescence. Although all three evolutionary theories of senescence could, in principle, explain such plastic senescence, given differential gene expression between castes or life stages, only the disposable soma theory adequately explains the adaptive regulation of somatic maintenance in response to different environmental conditions that appears to underlie lifespan plasticity. </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 May 2019 05:00:00 GMT “Ecological release of the Anna’s Hummingbird during a northern range expansion” https://amnat.org/an/newpapers/Sep-Battey.html Read the Article (Just Accepted) Anna’s Hummingbird populations are booming in the northwest: A century of survey records shows how they got thereIn the early twentieth century, Anna’s Hummingbirds nested in coastal California and the Baja Peninsula, but today their breeding range extends from Arizona to British Columbia. How and when did they spread across western North America? New research conducted by Dr. C.&nbsp;J. Battey at the University of Washington used a century of survey and museum records to track the range and population growth of Anna’s Hummingbirds over time, and found that populations in the Pacific Northwest have been growing exponentially since the region was first colonized in the middle of the twentieth century. By comparing historic and modern climate records, the study shows that climate change is unlikely to explain the initial phases of the range expansion, but may play an increasingly important role in shaping the species’ range in the future. Instead, a combination of introduced plants and supplemental feeding appear to have allowed the species to escape limits on population growth in its native range and establish new breeding populations across Arizona and the Pacific Northwest during the 1960s and 70s. In one sign that populations may already be adapting to their new ranges, nest reports suggest that northern populations now delay the beginning of the nesting season by at least 16 days. The study provides a detailed historical record of this remarkable range expansion, and is a reminder of the profound ways in which humans have shaped the ranges and populations of native species over the last century. Abstract During range expansions species can experience rapid population growth if changes in climate or interspecific interactions remove limits on growth rates in novel habitats. Here I document a century of range expansion in the Anna’s Hummingbird (Calypte anna) and investigate the causes of its recent abundance through a combination of demographic, climatic, and phenological analyses. Christmas Bird Count records indicate that populations have been growing in California since the early twentieth century. Sites across the Pacific Northwest show striking fits to simple models of exponential growth following colonization in the 1960s and ’70s, and nest records indicate that the species now delays the start of the nesting season by at least 16 days in the north. Although the species now occurs in a much wider range of climates than prior to the range expansion, the fastest growing populations in the northwest are in regions with minimum breeding season temperatures similar to those occupied by the species in its native range. Range expansions in the Anna’s Hummingbird thus reflect an ecological release likely caused by a mix of introduced plants, human facilitation, and phenological acclimation that allowed a California native to expand across western North America. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704249">Read the Article</a></i> (Just Accepted)</p> <p><b>Anna’s Hummingbird populations are booming in the northwest: A century of survey records shows how they got there</b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n the early twentieth century, Anna’s Hummingbirds nested in coastal California and the Baja Peninsula, but today their breeding range extends from Arizona to British Columbia. How and when did they spread across western North America? New research conducted by Dr. C.&nbsp;J. Battey at the University of Washington used a century of survey and museum records to track the range and population growth of Anna’s Hummingbirds over time, and found that populations in the Pacific Northwest have been growing exponentially since the region was first colonized in the middle of the twentieth century. By comparing historic and modern climate records, the study shows that climate change is unlikely to explain the initial phases of the range expansion, but may play an increasingly important role in shaping the species’ range in the future. Instead, a combination of introduced plants and supplemental feeding appear to have allowed the species to escape limits on population growth in its native range and establish new breeding populations across Arizona and the Pacific Northwest during the 1960s and 70s. In one sign that populations may already be adapting to their new ranges, nest reports suggest that northern populations now delay the beginning of the nesting season by at least 16 days. The study provides a detailed historical record of this remarkable range expansion, and is a reminder of the profound ways in which humans have shaped the ranges and populations of native species over the last century.</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;">D</span>uring range expansions species can experience rapid population growth if changes in climate or interspecific interactions remove limits on growth rates in novel habitats. Here I document a century of range expansion in the Anna’s Hummingbird (<i>Calypte anna</i>) and investigate the causes of its recent abundance through a combination of demographic, climatic, and phenological analyses. Christmas Bird Count records indicate that populations have been growing in California since the early twentieth century. Sites across the Pacific Northwest show striking fits to simple models of exponential growth following colonization in the 1960s and ’70s, and nest records indicate that the species now delays the start of the nesting season by at least 16 days in the north. Although the species now occurs in a much wider range of climates than prior to the range expansion, the fastest growing populations in the northwest are in regions with minimum breeding season temperatures similar to those occupied by the species in its native range. Range expansions in the Anna’s Hummingbird thus reflect an ecological release likely caused by a mix of introduced plants, human facilitation, and phenological acclimation that allowed a California native to expand across western North America. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 08 May 2019 05:00:00 GMT “The equivocal mean age of parents in a cohort” https://amnat.org/an/newpapers/AugBienvenu.html Read the Article (Just Accepted) The mean age of parents of offspring produced by a cohort is not a good measure of the mean age at reproduction Open any demography textbook and you will find information on how to quantify reproductive timing. In particular, you should find an expression for the mean age at reproduction of a typical individual. This classic formula has been used for decades and is one of the most popular measures of generation time. Unfortunately, its well-accepted interpretation is incorrect; and the difference between what some reseachers have in mind and what they actually compute can be quite large in practice. By detailing the rigorous interpretation of the formula and providing an alternative expression for the mean age at reproduction, this article points out the need to think more deeply about what we mean by “average age at giving birth”. Abstract The mean age at which parents give birth is an important notion in demography, ecology and evolution, where it is used as a measure of generation time. A standard way to quantify it is to compute the mean age of the parents of all offspring produced by a cohort, and the resulting measure is thought to represent the mean age at which a typical parent produces offspring. In this note, I explain why this interpretation is problematic. I also introduce a new measure of the mean age at reproduction and show that it can be very different from the mean age of parents of offspring of a cohort. In particular, the mean age of parents of offspring of a cohort systematically overestimates the mean age at reproduction, and can even be greater than the expected lifespan of parents. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704110">Read the Article</a></i> (Just Accepted)</p> <p><b>The mean age of parents of offspring produced by a cohort is not a good measure of the mean age at reproduction </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">O</span>pen any demography textbook and you will find information on how to quantify reproductive timing. In particular, you should find an expression for the mean age at reproduction of a typical individual. This classic formula has been used for decades and is one of the most popular measures of generation time.</p> <p>Unfortunately, its well-accepted interpretation is incorrect; and the difference between what some reseachers have in mind and what they actually compute can be quite large in practice. By detailing the rigorous interpretation of the formula and providing an alternative expression for the mean age at reproduction, this article points out the need to think more deeply about what we mean by “average age at giving birth”.</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 mean age at which parents give birth is an important notion in demography, ecology and evolution, where it is used as a measure of generation time. A standard way to quantify it is to compute the mean age of the parents of all offspring produced by a cohort, and the resulting measure is thought to represent the mean age at which a typical parent produces offspring. In this note, I explain why this interpretation is problematic. I also introduce a new measure of the mean age at reproduction and show that it can be very different from the mean age of parents of offspring of a cohort. In particular, the mean age of parents of offspring of a cohort systematically overestimates the mean age at reproduction, and can even be greater than the expected lifespan of parents. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 07 May 2019 05:00:00 GMT “Experimental evidence that metamorphosis alleviates genomic conflict” https://amnat.org/an/newpapers/Sep-Goedert.html Read the Article (Just Accepted) Metamorphosis changes integration between traits and alleviates ontogenetic conflict across amphibian life stages Metamorphosis is a remarkable characteristic of many amphibians, marking the transition from an aquatic to a terrestrial life stage. Metamorphosis is a complex and costly process and the benefits of metamorphosis have long puzzled biologists. One possibility is that the morphological changes that occur during metamorphosis allow natural selection to shape the two life stages independently of each other in their respective habitats. Given that tadpoles and frogs are life stages of a single individual, and must be formed from the same genetic material, one might wonder whether it is possible to adapt to one environment without paying a cost of adaptation in the other. In this study, Goedert and Calsbeek use wood frogs to investigate the so-called ‘adaptive decoupling hypothesis’. The researchers performed controlled mattings in the laboratory and reared hundreds of tadpoles through metamorphosis. Their breeding design allowed them to test for patterns of integration in the inheritance of tadpole and frog morphology – for instance, the researchers were able to ask whether having genes for a long tail as a tadpole would lead to long legged frogs. They showed that, although there is some genetic integration between tadpole and frog morphologies, the degree of such integration was much lower between life stages than within either tadpoles or frogs. This study provides some of the first evidence that metamorphosis may have evolved to allow natural selection to shape a single genome into two very different life forms. Abstract Whenever genetically correlated traits experience antagonistic selection, an adaptive response in one trait can lead to a maladaptive response in the correlated trait. This is a form of genome-level conflict that can have important evolutionary consequences by impeding organisms from reaching their adaptive optima. Antagonistic selection should be pervasive in organisms with complex life histories because larval and adult life stages specialize in dramatically different environments. Since individuals express larval and adult morphologies from a single genome, genomic conflict across ontogenetic stages should also be prevalent. Using wood frogs as a study system, we measured natural selection on larval and post-metamorphic life stages, and estimated genetic correlations among traits. Alternative life stages experienced a mix of both antagonistic and congruent viability selection. The integration between traits changed over the course of metamorphosis, reducing genetic correlations that cause conflict. Our results provide novel experimental evidence that metamorphosis can alleviate genomic conflict by partitioning life history stages into modules that can more readily respond to selection. These results highlight the adaptive potential of metamorphosis as a means to avoid ecological specialization trade-offs. Moreover, they provide insights into the prevalence and evolutionary maintenance of complex life cycles. Evidência experimental de que a metamorfose reduz conflito genômico Quando pressões seletivas antagonistas atuam em características geneticamente correlacionadas, a resposta adaptativa de uma dessas características pode resultar em uma resposta maladaptativa na característica correlacionada. Tal situação representa uma forma de conflito genômico que pode ter importantes consequências evolutivas ao impedir organismos de atingir seu valor adaptativo máximo. Espera-se que seleção antagonista seja comum em organismos com ciclo de vida complexos, porque estágios larvais e adultos são especialistas em ambientes muito diferentes. Além disso, como indivíduos expressam morfologias de larva e adulto utilizando um mesmo genoma, o conflito genômico entre esses estágios ontogenéticos deve ser prevalente. Usando sapos (Rana sylvatica) como organismo modelo, medimos seleção natural tanto no estágio larval quanto em estágios pós-metamorfose, e estimamos correlações genéticas entre características de ambos estágios. Os diferentes estágios ontogenéticos apresentaram uma combinação de seleção de viabilidade em direções antagonistas e congruentes. O nível de integração entre características variou ao longo do processo de metamorfose, havendo redução de correlações genéticas que poderiam causar conflito genômico. Nossos resultados demostram evidência de que o processo de metamorfose pode aliviar o conflito genômico ao particionar os estágios ontogenéticos em módulos, permitindo que estes respondam mais rapidamente a forças seletivas. Esses resultados enfatizam o potencial adaptativo da metamorfose como uma forma de evitar demandas conflitantes durante especialização ecológica dos estágios de vida. Mais ainda, esses resultados contribuem para o entendimento da prevalência e manutenção evolutiva de ciclos de vida complexos. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704183">Read the Article</a></i> (Just Accepted) </p> <p><b>Metamorphosis changes integration between traits and alleviates ontogenetic conflict across amphibian life stages </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>etamorphosis is a remarkable characteristic of many amphibians, marking the transition from an aquatic to a terrestrial life stage. Metamorphosis is a complex and costly process and the benefits of metamorphosis have long puzzled biologists. One possibility is that the morphological changes that occur during metamorphosis allow natural selection to shape the two life stages independently of each other in their respective habitats. Given that tadpoles and frogs are life stages of a single individual, and must be formed from the same genetic material, one might wonder whether it is possible to adapt to one environment without paying a cost of adaptation in the other. </p> <p>In this study, Goedert and Calsbeek use wood frogs to investigate the so-called ‘adaptive decoupling hypothesis’. The researchers performed controlled mattings in the laboratory and reared hundreds of tadpoles through metamorphosis. Their breeding design allowed them to test for patterns of integration in the inheritance of tadpole and frog morphology – for instance, the researchers were able to ask whether having genes for a long tail as a tadpole would lead to long legged frogs. They showed that, although there is some genetic integration between tadpole and frog morphologies, the degree of such integration was much lower between life stages than within either tadpoles or frogs. This study provides some of the first evidence that metamorphosis may have evolved to allow natural selection to shape a single genome into two very different life forms. </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>henever genetically correlated traits experience antagonistic selection, an adaptive response in one trait can lead to a maladaptive response in the correlated trait. This is a form of genome-level conflict that can have important evolutionary consequences by impeding organisms from reaching their adaptive optima. Antagonistic selection should be pervasive in organisms with complex life histories because larval and adult life stages specialize in dramatically different environments. Since individuals express larval and adult morphologies from a single genome, genomic conflict across ontogenetic stages should also be prevalent. Using wood frogs as a study system, we measured natural selection on larval and post-metamorphic life stages, and estimated genetic correlations among traits. Alternative life stages experienced a mix of both antagonistic and congruent viability selection. The integration between traits changed over the course of metamorphosis, reducing genetic correlations that cause conflict. Our results provide novel experimental evidence that metamorphosis can alleviate genomic conflict by partitioning life history stages into modules that can more readily respond to selection. These results highlight the adaptive potential of metamorphosis as a means to avoid ecological specialization trade-offs. Moreover, they provide insights into the prevalence and evolutionary maintenance of complex life cycles. </p> <h4>Evidência experimental de que a metamorfose reduz conflito genômico</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;">Q</span>uando pressões seletivas antagonistas atuam em características geneticamente correlacionadas, a resposta adaptativa de uma dessas características pode resultar em uma resposta maladaptativa na característica correlacionada. Tal situação representa uma forma de conflito genômico que pode ter importantes consequências evolutivas ao impedir organismos de atingir seu valor adaptativo máximo. Espera-se que seleção antagonista seja comum em organismos com ciclo de vida complexos, porque estágios larvais e adultos são especialistas em ambientes muito diferentes. Além disso, como indivíduos expressam morfologias de larva e adulto utilizando um mesmo genoma, o conflito genômico entre esses estágios ontogenéticos deve ser prevalente. Usando sapos (<i>Rana sylvatica</i>) como organismo modelo, medimos seleção natural tanto no estágio larval quanto em estágios pós-metamorfose, e estimamos correlações genéticas entre características de ambos estágios. Os diferentes estágios ontogenéticos apresentaram uma combinação de seleção de viabilidade em direções antagonistas e congruentes. O nível de integração entre características variou ao longo do processo de metamorfose, havendo redução de correlações genéticas que poderiam causar conflito genômico. Nossos resultados demostram evidência de que o processo de metamorfose pode aliviar o conflito genômico ao particionar os estágios ontogenéticos em módulos, permitindo que estes respondam mais rapidamente a forças seletivas. Esses resultados enfatizam o potencial adaptativo da metamorfose como uma forma de evitar demandas conflitantes durante especialização ecológica dos estágios de vida. Mais ainda, esses resultados contribuem para o entendimento da prevalência e manutenção evolutiva de ciclos de vida complexos. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 30 Apr 2019 05:00:00 GMT “Can community structure causally determine dynamics of constituent species? A test using a host-parasite community” https://amnat.org/an/newpapers/Sep-Langendorf.html Read the Article (Just Accepted) Are community structures causal? Downward causation in a host-parasite community inferred from observational data Ecologists have long struggled with how features of an entire community – such as diversity or structural complexity – influence the functioning and dynamics of the member species. These community properties are do not exist physically, outside of the complex arrangements and dynamics of multiple species. How, if not mechanically, are they then able to influence the dynamics of the populations that constitute them? And more practically, how can ecologists test for this kind of causation down the organizational scales of an ecosystem? In this upcoming paper, Langendorf and Doak tackle these questions with observational data and causal discovery, applying the increasingly popular Convergent Cross Mapping method of inferring causality to time series data of a Slovakian host-parasite community where species abundances were recorded along with their interactions. They find that the populations of three host species were affected by how connected, clustered, and evenly-distributed interactions were across the entire community. This work offers evidence that structures in the configurations of ecological interactions affect constituent species. Just as importantly, it develops and demonstrates a method for identifying which community features are important to a given species of interest. Abstract Structures of communities have been widely studied with the assumption that they are not only a useful bookkeeping tool, but also can causally influence dynamics of the populations from which they emerge. However, convincing tests of this assumption have remained elusive, because generally the only way to alter a community property is by manipulating its constituent populations, thereby preventing independent measurements of effects on those populations. There is a growing body of evidence that methods like Convergent Cross Mapping (CCM) can be used to make inferences about causal interactions using state space reconstructions of coupled time series, a method that relies only on observational data. Here we show that CCM can be used to test the causal effects of community properties using a well-studied Slovakian rodent-ectoparasite community. CCM identified causal drivers across the organizational scales of this community, including evidence that host dynamics were influenced by the degree to which the community at large was connected and clustered. Our findings add to the growing literature on the importance of community structures in disease dynamics and argue for a broader use of causal inference in the analysis of community dynamics. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704182">Read the Article</a></i> (Just Accepted)</p> <p><b>Are community structures causal? Downward causation in a host-parasite community inferred from observational data </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>cologists have long struggled with how features of an entire community – such as diversity or structural complexity – influence the functioning and dynamics of the member species. These community properties are do not exist physically, outside of the complex arrangements and dynamics of multiple species. How, if not mechanically, are they then able to influence the dynamics of the populations that constitute them? And more practically, how can ecologists test for this kind of causation down the organizational scales of an ecosystem? In this upcoming paper, Langendorf and Doak tackle these questions with observational data and causal discovery, applying the increasingly popular Convergent Cross Mapping method of inferring causality to time series data of a Slovakian host-parasite community where species abundances were recorded along with their interactions. They find that the populations of three host species were affected by how connected, clustered, and evenly-distributed interactions were across the entire community. This work offers evidence that structures in the configurations of ecological interactions affect constituent species. Just as importantly, it develops and demonstrates a method for identifying which community features are important to a given species of interest. </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>tructures of communities have been widely studied with the assumption that they are not only a useful bookkeeping tool, but also can causally influence dynamics of the populations from which they emerge. However, convincing tests of this assumption have remained elusive, because generally the only way to alter a community property is by manipulating its constituent populations, thereby preventing independent measurements of effects on those populations. There is a growing body of evidence that methods like Convergent Cross Mapping (CCM) can be used to make inferences about causal interactions using state space reconstructions of coupled time series, a method that relies only on observational data. Here we show that CCM can be used to test the causal effects of community properties using a well-studied Slovakian rodent-ectoparasite community. CCM identified causal drivers across the organizational scales of this community, including evidence that host dynamics were influenced by the degree to which the community at large was connected and clustered. Our findings add to the growing literature on the importance of community structures in disease dynamics and argue for a broader use of causal inference in the analysis of community dynamics. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 30 Apr 2019 05:00:00 GMT “Beta diversity patterns derived from island biogeography theory” https://amnat.org/an/newpapers/Sep-Lu.html Read the Article (Just Accepted) Beta diversity (Jaccard) is independent of the size of mainland species pool in the Island Biogeography Theory The island biogeography theory pioneered by MacArthur and Wilson has served as a foundation to understand the drivers of species richness for more than 50 years, but never tells us about what shapes beta diversity, i.e. the spatial variation of community composition among islands. A theoretical synthesis of island biogeography theory and beta diversity finally emerged at the call of a unified metacommunity framework to link ecological processes to more ecological patterns. Following MacArthur and Wilson’s original formulation (assuming species-equivalency), Muyang Lu, David Vasseur, and Walter Jetz first show that pairwise beta diversity (Jaccard dissimilarity) of two random islands is only determined by colonization and extinction rates of a species and independent of the size of species pool. This result runs counter to the prevailing belief that beta diversity increases with the size of species pool, with simulations further corroborating the conclusions under non-neutral scenarios. They further use an empirical bird dataset in Thousand Island Lake, China to demonstrate that beta diversity patterns is more powerful in detecting non-neutral processes than species richness. By adding a new dimension to the predictions of the half-century old island biogeography theory, this study opens the gate to investigate community assembly processes in a more systematic way and paves the way for a unified metacommunity theory. Abstract Metacommunity theory and its constituent Theory of Island Biogeography (TIB) have the potential to unify ecology across different scales. TIB has been successful in predicting alpha diversity patterns such as species-area relationships and species-abundance distributions, but lags behind in predicting spatial beta diversity patterns. In this study we use island biogeography theory as the starting point to integrate spatial beta diversity patterns into metacommunity theory. We first derive theoretical predictions for the expected beta diversity patterns under the classic MacArthur and Wilson framework where all species have equal colonization and extinction rates. We then test these predictions for the avian community composition of 42 islands (and 93 species) in the Thousand Island Lake, China. Our theoretical results corroborate that longer distance and smaller area lead to lower beta diversity, and further reveal that pairwise beta diversity is independent of the size of mainland species pool. We also find that for the partitioned pairwise beta diversity components, the turnover component increases with the ratio of extinction rates and colonization rates, while the nestedness component is a monotonic function of the ratio of extinction rates and colonization rates. For the empirical island system, we find that beta diversity patterns better distinguish a species-equivalent model from a species-nonequivalent model than alpha diversity patterns. Our findings suggest that beta diversity patterns provide a powerful tool in detecting non-neutral processes and our model has the potential to incorporate more biological realism in future analyses. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704181">Read the Article</a></i> (Just Accepted)</p> <p><b>Beta diversity (Jaccard) is independent of the size of mainland species pool in the Island Biogeography Theory </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he island biogeography theory pioneered by MacArthur and Wilson has served as a foundation to understand the drivers of species richness for more than 50 years, but never tells us about what shapes beta diversity, i.e. the spatial variation of community composition among islands. A theoretical synthesis of island biogeography theory and beta diversity finally emerged at the call of a unified metacommunity framework to link ecological processes to more ecological patterns. Following MacArthur and Wilson’s original formulation (assuming species-equivalency), Muyang Lu, David Vasseur, and Walter Jetz first show that pairwise beta diversity (Jaccard dissimilarity) of two random islands is only determined by colonization and extinction rates of a species and independent of the size of species pool. This result runs counter to the prevailing belief that beta diversity increases with the size of species pool, with simulations further corroborating the conclusions under non-neutral scenarios. They further use an empirical bird dataset in Thousand Island Lake, China to demonstrate that beta diversity patterns is more powerful in detecting non-neutral processes than species richness. By adding a new dimension to the predictions of the half-century old island biogeography theory, this study opens the gate to investigate community assembly processes in a more systematic way and paves the way for a unified metacommunity theory.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>etacommunity theory and its constituent Theory of Island Biogeography (TIB) have the potential to unify ecology across different scales. TIB has been successful in predicting alpha diversity patterns such as species-area relationships and species-abundance distributions, but lags behind in predicting spatial beta diversity patterns. In this study we use island biogeography theory as the starting point to integrate spatial beta diversity patterns into metacommunity theory. We first derive theoretical predictions for the expected beta diversity patterns under the classic MacArthur and Wilson framework where all species have equal colonization and extinction rates. We then test these predictions for the avian community composition of 42 islands (and 93 species) in the Thousand Island Lake, China. Our theoretical results corroborate that longer distance and smaller area lead to lower beta diversity, and further reveal that pairwise beta diversity is independent of the size of mainland species pool. We also find that for the partitioned pairwise beta diversity components, the turnover component increases with the ratio of extinction rates and colonization rates, while the nestedness component is a monotonic function of the ratio of extinction rates and colonization rates. For the empirical island system, we find that beta diversity patterns better distinguish a species-equivalent model from a species-nonequivalent model than alpha diversity patterns. Our findings suggest that beta diversity patterns provide a powerful tool in detecting non-neutral processes and our model has the potential to incorporate more biological realism in future analyses. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 30 Apr 2019 05:00:00 GMT “Coevolution creates complex mosaics across large landscapes” https://amnat.org/an/newpapers/AugFernandes.html Read the Article (Just Accepted)Does our understanding of the interplay between species interactions and patterns of diversity still apply when we go from local to regional or continental scales? It is now widely recognized that species interactions play a major role in influencing evolutionary rates, trajectories, and outcomes, but how does the spatial organization of these interactions affect the way species’ traits are distributed in space? Using mathematical models to describe coevolutionary dynamics in a landscape where the interactions vary from mutualism to antagonism, Fernandes and collaborators investigate how coevolution affects the spatial patterns of phenotypes, when considering large spatial scales and different structures of geographic mosaics of selection. One of the main results of this work is the formation of large clusters of phenotypes, in many cases much larger than the spatial aggregation of sites with the same interaction outcome. This result leads to the implications that (i) phenotype distributions can not be directly obtained from the outcomes of local interactions, and that (ii) local interactions can not be simply inferred from local patterns of trait distributions alone. Focusing on how the magnitude of selection, the spatial distribution of interactions and gene flow influence the spatial patterns of phenotypes, this work calls attention to the importance of comprehending coevolutionary dynamics in this context, and also the many ways in which these dynamics can be affected by human-driven habitat fragmentation in natural landscapes. Abstract The spatial distribution of populations can influence the evolutionary outcome of species interactions. The variation in direction and strength of selection across local communities creates geographic selection mosaics that, when combined with gene flow and genomic processes such as genome duplication or hybridization, can fuel ongoing coevolution. A fundamental problem to solve is how coevolution proceeds when many populations that vary in their ecological outcomes are connected across large landscapes. Here we use a lattice model to explore this problem. Our results show that the complex interrelationships among the elements of the geographic mosaic of coevolution can lead to the formation of clusters of populations with similar phenotypes that are larger than expected by local selection. Our results indicate that neither the spatial distribution of phenotypes nor the spatial differences in magnitude and direction of selection alone dictate coevolutionary dynamics: the geographic mosaic of coevolution affects formation of phenotypic clusters, which in turn affect the spatial and temporal dynamics of coevolution. Because the formation of large phenotypic clusters depends on gene flow, we predict current habitat fragmentation will change the outcomes of geographic mosaics, coupling spatial patterns in selection and phenotypes. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704157">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;">D</span>oes our understanding of the interplay between species interactions and patterns of diversity still apply when we go from local to regional or continental scales? It is now widely recognized that species interactions play a major role in influencing evolutionary rates, trajectories, and outcomes, but how does the spatial organization of these interactions affect the way species’ traits are distributed in space? Using mathematical models to describe coevolutionary dynamics in a landscape where the interactions vary from mutualism to antagonism, Fernandes and collaborators investigate how coevolution affects the spatial patterns of phenotypes, when considering large spatial scales and different structures of geographic mosaics of selection. One of the main results of this work is the formation of large clusters of phenotypes, in many cases much larger than the spatial aggregation of sites with the same interaction outcome. This result leads to the implications that (i) phenotype distributions can not be directly obtained from the outcomes of local interactions, and that (ii) local interactions can not be simply inferred from local patterns of trait distributions alone. Focusing on how the magnitude of selection, the spatial distribution of interactions and gene flow influence the spatial patterns of phenotypes, this work calls attention to the importance of comprehending coevolutionary dynamics in this context, and also the many ways in which these dynamics can be affected by human-driven habitat fragmentation in natural landscapes. </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 spatial distribution of populations can influence the evolutionary outcome of species interactions. The variation in direction and strength of selection across local communities creates geographic selection mosaics that, when combined with gene flow and genomic processes such as genome duplication or hybridization, can fuel ongoing coevolution. A fundamental problem to solve is how coevolution proceeds when many populations that vary in their ecological outcomes are connected across large landscapes. Here we use a lattice model to explore this problem. Our results show that the complex interrelationships among the elements of the geographic mosaic of coevolution can lead to the formation of clusters of populations with similar phenotypes that are larger than expected by local selection. Our results indicate that neither the spatial distribution of phenotypes nor the spatial differences in magnitude and direction of selection alone dictate coevolutionary dynamics: the geographic mosaic of coevolution affects formation of phenotypic clusters, which in turn affect the spatial and temporal dynamics of coevolution. Because the formation of large phenotypic clusters depends on gene flow, we predict current habitat fragmentation will change the outcomes of geographic mosaics, coupling spatial patterns in selection and phenotypes. </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, 29 Apr 2019 05:00:00 GMT “Generation time measures the trade-off between survival and reproduction in a life cycle” https://amnat.org/an/newpapers/AugGiaimo.html Read the Article (Just Accepted) Generation time measures the trade-off between survival and reproduction in a life cycle The African elephant or the desert tortoise can live up to 80 years in a dangerous world without medicine: Shouldn’t we do genetics of longevity on them to get their secret? Yes, in principle. But it would very impractical. Looking at differences between only two generations of these animals would exceed the life expectancy of a human researcher and the usual horizon of science funding. For this reason too, animal models of aging and longevity, like the fruit fly and the mice, are usually chosen that are fast-lived in comparison to humans. Mutations that extend lifespan in these animals are isolated in the hope of finding similar human genes. But results from this approach may not transfer smoothly to humans. Mutants with longer life are often less fertile. Optimization theory shows that the reproductive cost of a slightly increased longevity in a species is measured by the average age at parenthood in the species, the so-called generation time. A 1% increase in survival, for example, imposes a percentage cost in reproduction equal to the generation time. But fruit flies usually give birth at around 11 days, while humans need on average 20 to 30 years. Therefore, studies on animal models may underestimate the fertility price of enhanced longevity in humans. While short-lived animals are likely to remain important and very useful models in the genetics of longevity, this result helps us to better understand their potential limitations. Abstract Survival and fertility are the two most basic components of fitness and they drive the evolution of a life cycle. A trade-off between them is usually present: when survival increases, fertility decreases – and vice versa. Here we show that, at an evolutionary optimum, the generation time is a measure of the strength of the trade-off between overall survival and overall fertility in a life cycle. Our result both helps to explain the known fact that the generation time describes the speed of living in the slow-fast continuum of life cycles and may have implications for the extrapolation from model organisms of longevity to humans. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704155">Read the Article</a></i> (Just Accepted)</p> <p><b>Generation time measures the trade-off between survival and reproduction in a life cycle </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he African elephant or the desert tortoise can live up to 80 years in a dangerous world without medicine: Shouldn’t we do genetics of longevity on them to get their secret? Yes, in principle. But it would very impractical. Looking at differences between only two generations of these animals would exceed the life expectancy of a human researcher and the usual horizon of science funding. For this reason too, animal models of aging and longevity, like the fruit fly and the mice, are usually chosen that are fast-lived in comparison to humans. Mutations that extend lifespan in these animals are isolated in the hope of finding similar human genes. But results from this approach may not transfer smoothly to humans. </p> <p>Mutants with longer life are often less fertile. Optimization theory shows that the reproductive cost of a slightly increased longevity in a species is measured by the average age at parenthood in the species, the so-called generation time. A 1% increase in survival, for example, imposes a percentage cost in reproduction equal to the generation time. But fruit flies usually give birth at around 11 days, while humans need on average 20 to 30 years. Therefore, studies on animal models may underestimate the fertility price of enhanced longevity in humans. While short-lived animals are likely to remain important and very useful models in the genetics of longevity, this result helps us to better understand their potential limitations.</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>urvival and fertility are the two most basic components of fitness and they drive the evolution of a life cycle. A trade-off between them is usually present: when survival increases, fertility decreases – and vice versa. Here we show that, at an evolutionary optimum, the generation time is a measure of the strength of the trade-off between overall survival and overall fertility in a life cycle. Our result both helps to explain the known fact that the generation time describes the speed of living in the slow-fast continuum of life cycles and may have implications for the extrapolation from model organisms of longevity to humans. </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, 29 Apr 2019 05:00:00 GMT “Dormancy in metacommunities” https://amnat.org/an/newpapers/AugWisnoski.html Read the Article (Just Accepted)Metacommunity ecology has primarily focused on how dispersal influences biodiversity across a landscape. However, many species possess the ability to engage in dormancy, a reversible state of reduced metabolism, which allows them to “disperse through time”. As a result, colonization of a local community can occur from an internal “seed bank” of dormant organisms, not just from other habitat patches, as is commonly assumed in metacommunity theory. Using simulation models, the authors show that dormancy can modify patterns of biodiversity across spatial scales in the metacommunity. The influence of dormancy on these patterns may further depend on whether dispersal and dormancy are correlated (positively or negatively). In an analysis of aquatic invertebrates that live in tropical bromeliads, the authors find evidence for correlations between dispersal and dormancy strategies. Evidence from the literature suggests colonization from the seed bank is typically most important following local disturbances or in spatially isolated communities where dispersal is limiting. Our work also has implications for understanding and predicting species invasions. More broadly, dormancy in the context of metacommunity ecology may provide alternative explanations for commonly observed biodiversity patterns and could improve our understanding of eco-evolutionary dynamics and ecosystem functioning across spatial scales. Abstract Although metacommunity ecology has improved our understanding of how dispersal affects community structure and dynamics across spatial scales, it has yet to adequately account for dormancy. Dormancy is a reversible state of reduced metabolic activity that enables temporal dispersal within the metacommunity. Dormancy is also a metacommunity-level process because it can covary with spatial dispersal and affect diversity across spatial scales. We develop a framework to integrate dispersal and dormancy, focusing on the covariation they exhibit, to predict how dormancy modifies the importance of species interactions, dispersal, and historical contingencies in metacommunities. We used empirical and modeling approaches to demonstrate the utility of this framework. We examined case studies of microcrustaceans in ephemeral ponds, where dormancy underlies metacommunity dynamics, and identified constraints on the dispersal and dormancy strategies of bromeliad-dwelling invertebrates. Using simulations, we showed that dormancy can alter classic metacommunity patterns of diversity in ways that depend on dispersal–dormancy covariation and spatiotemporal environmental variability. We propose that dormancy may also facilitate evolution-mediated priority effects if locally adapted seed banks prevent colonization by more dispersal-limited species. Last, we present testable predictions for the implications of dormancy in metacommunities, some of which may fundamentally alter our understanding of metacommunity ecology. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704168">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>etacommunity ecology has primarily focused on how dispersal influences biodiversity across a landscape. However, many species possess the ability to engage in dormancy, a reversible state of reduced metabolism, which allows them to “disperse through time”. As a result, colonization of a local community can occur from an internal “seed bank” of dormant organisms, not just from other habitat patches, as is commonly assumed in metacommunity theory. </p><p>Using simulation models, the authors show that dormancy can modify patterns of biodiversity across spatial scales in the metacommunity. The influence of dormancy on these patterns may further depend on whether dispersal and dormancy are correlated (positively or negatively). In an analysis of aquatic invertebrates that live in tropical bromeliads, the authors find evidence for correlations between dispersal and dormancy strategies. Evidence from the literature suggests colonization from the seed bank is typically most important following local disturbances or in spatially isolated communities where dispersal is limiting. Our work also has implications for understanding and predicting species invasions. More broadly, dormancy in the context of metacommunity ecology may provide alternative explanations for commonly observed biodiversity patterns and could improve our understanding of eco-evolutionary dynamics and ecosystem functioning across spatial scales.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>lthough metacommunity ecology has improved our understanding of how dispersal affects community structure and dynamics across spatial scales, it has yet to adequately account for dormancy. Dormancy is a reversible state of reduced metabolic activity that enables temporal dispersal within the metacommunity. Dormancy is also a metacommunity-level process because it can covary with spatial dispersal and affect diversity across spatial scales. We develop a framework to integrate dispersal and dormancy, focusing on the covariation they exhibit, to predict how dormancy modifies the importance of species interactions, dispersal, and historical contingencies in metacommunities. We used empirical and modeling approaches to demonstrate the utility of this framework. We examined case studies of microcrustaceans in ephemeral ponds, where dormancy underlies metacommunity dynamics, and identified constraints on the dispersal and dormancy strategies of bromeliad-dwelling invertebrates. Using simulations, we showed that dormancy can alter classic metacommunity patterns of diversity in ways that depend on dispersal–dormancy covariation and spatiotemporal environmental variability. We propose that dormancy may also facilitate evolution-mediated priority effects if locally adapted seed banks prevent colonization by more dispersal-limited species. Last, we present testable predictions for the implications of dormancy in metacommunities, some of which may fundamentally alter our understanding of metacommunity 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> Mon, 29 Apr 2019 05:00:00 GMT “Lifetime fitness, sex-specific life history, and the maintenance of a polyphenism” https://amnat.org/an/newpapers/AugLackey.html Read the Article (Just Accepted) Long-term data (27 years) reveals lifetime fitness differs between the sexes of each morph of tiger salamanders Studying survival and reproduction within populations provides windows into the processes and mechanisms that underlie the evolutionary origins and maintenance of diversity. Lackey et al. examine a striking type of variation within some salamander populations where a larva can develop into one of two morphs based on its body size and competition: one morph undergoes metamorphosis to become a terrestrial adult, whereas the other retains its larval characteristics and matures as an aquatic adult. While these morphs have long fascinated evolutionary biologists, even gracing the cover of Gould’s landmark Ontogeny and Phylogeny (1977), long-term studies of lifetime costs and benefits are necessary to determine which factors promote the maintenance of two morphs within the same population. Howard Whiteman spearheaded an ongoing long-term research program in 1990 in a population of Arizona Tiger Salamanders in the Rocky Mountains of Colorado. Lackey et al. use 27 years of data from this population to test for differences between each morph and sex in (1) lifetime reproduction, (2) timing of development and reproduction, and (3) consequences of environmental variation across time and space. The authors find that males of the aquatic morph and females of the terrestrial morph have higher lifetime reproduction than the other morph-sex combinations. Thus, sex-specific payoffs likely contribute to maintaining the two morphs in this population. Intriguingly, the morphs achieve these outcomes via different developmental and reproductive strategies. Although the environment shapes which morph a larva becomes, it seems to have little effect on differences between morphs in lifetime reproduction. These results demonstrate how differences in lifetime reproduction can contribute to maintaining trait variation within a population and emphasize the importance of studying reproductive differences between the sexes. Abstract Polyphenisms, alternative morphs produced through plasticity, can reveal the evolutionary and ecological processes that initiate and maintain diversity within populations. We examined lifetime fitness consequences of two morphs in a polyphenic population of Arizona Tiger Salamanders using a 27-year data set with 1,317 adults and 6,862 captures across eight generations. Larval salamanders develop into either an aquatic paedomorph that retains larval traits and stays in its natal pond or a terrestrial metamorph that undergoes metamorphosis. To evaluate the adaptive significance of this polyphenism, we compared lifetime reproductive success of each morph and assessed how life history strategies and spatiotemporal variation explained fitness. We found sex-specific differences in lifetime fitness between morphs. For males, paedomorphs had more reproductive opportunities than metamorphs when we accounted for the potential mating advantage of larger males. For females, in contrast, metamorphs had higher estimated egg production than paedomorphs. Life history strategies differed between morphs largely because the morphs maximized different ends of the trade-off between age at first reproduction and longevity. Spatiotemporal variation affected larval more than adult life history traits with little to no effect on lifetime fitness. Thus, environmental variation likely explains differences in morph production across time and space but contributes little to lifetime fitness differences between morphs and sexes. Our long-term study and measures of lifetime fitness provide unique insight into the complex selective regimes potentially acting on each morph and sex. Our findings motivate future work to examine how sex-specific selection may contribute to the maintenance of polyphenism. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704156">Read the Article</a></i> (Just Accepted) </p> <p><b>Long-term data (27 years) reveals lifetime fitness differs between the sexes of each morph of tiger salamanders </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>tudying survival and reproduction within populations provides windows into the processes and mechanisms that underlie the evolutionary origins and maintenance of diversity. Lackey et al. examine a striking type of variation within some salamander populations where a larva can develop into one of two morphs based on its body size and competition: one morph undergoes metamorphosis to become a terrestrial adult, whereas the other retains its larval characteristics and matures as an aquatic adult. While these morphs have long fascinated evolutionary biologists, even gracing the cover of Gould’s landmark <i>Ontogeny and Phylogeny</i> (1977), long-term studies of lifetime costs and benefits are necessary to determine which factors promote the maintenance of two morphs within the same population. Howard Whiteman spearheaded an ongoing long-term research program in 1990 in a population of Arizona Tiger Salamanders in the Rocky Mountains of Colorado. Lackey et al. use 27 years of data from this population to test for differences between each morph and sex in (1) lifetime reproduction, (2) timing of development and reproduction, and (3) consequences of environmental variation across time and space. The authors find that males of the aquatic morph and females of the terrestrial morph have higher lifetime reproduction than the other morph-sex combinations. Thus, sex-specific payoffs likely contribute to maintaining the two morphs in this population. Intriguingly, the morphs achieve these outcomes via different developmental and reproductive strategies. Although the environment shapes which morph a larva becomes, it seems to have little effect on differences between morphs in lifetime reproduction. These results demonstrate how differences in lifetime reproduction can contribute to maintaining trait variation within a population and emphasize the importance of studying reproductive differences between the sexes.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>olyphenisms, alternative morphs produced through plasticity, can reveal the evolutionary and ecological processes that initiate and maintain diversity within populations. We examined lifetime fitness consequences of two morphs in a polyphenic population of Arizona Tiger Salamanders using a 27-year data set with 1,317 adults and 6,862 captures across eight generations. Larval salamanders develop into either an aquatic paedomorph that retains larval traits and stays in its natal pond or a terrestrial metamorph that undergoes metamorphosis. To evaluate the adaptive significance of this polyphenism, we compared lifetime reproductive success of each morph and assessed how life history strategies and spatiotemporal variation explained fitness. We found sex-specific differences in lifetime fitness between morphs. For males, paedomorphs had more reproductive opportunities than metamorphs when we accounted for the potential mating advantage of larger males. For females, in contrast, metamorphs had higher estimated egg production than paedomorphs. Life history strategies differed between morphs largely because the morphs maximized different ends of the trade-off between age at first reproduction and longevity. Spatiotemporal variation affected larval more than adult life history traits with little to no effect on lifetime fitness. Thus, environmental variation likely explains differences in morph production across time and space but contributes little to lifetime fitness differences between morphs and sexes. Our long-term study and measures of lifetime fitness provide unique insight into the complex selective regimes potentially acting on each morph and sex. Our findings motivate future work to examine how sex-specific selection may contribute to the maintenance of polyphenism. </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, 29 Apr 2019 05:00:00 GMT “Playing out Liem’s Paradox: opportunistic piscivory across Lake Tanganyikan cichlids” https://amnat.org/an/newpapers/Aug-Golcher-Benavides.html Read the Article (Just Accepted) Researchers report diet switching by morphologically specialized cichlids as consequence of unusual concentrations of clupeidsCichlid fishes are celebrated for their often extreme feeding adaptations and unique feeding strategies: Lobochilotes labiatus extracts invertebrates from rock crevices using its enlarged lips, Perissodus microlepis’s feeding on scales from other fishes is linked to their striking mouth asymmetry, Tropheus duboisi crops algae growing on the rocky substrate using teeth located at the jaw-edges of their subterminal mouths. Karel Liem (1980) first noted that cichlid fishes are not only remarkable dietary specialists, but also can act as jacks-of-all-trades. However, evidence for the dietary flexibility of cichlids comes from laboratory studies, and it is unclear whether cichlid fishes in the wild actually feed on resources other than the ones they have adaptations for. We report field observations of dietary switching by multiple cichlid species in Lake Tanganyika as a consequence of a transient school of juvenile sardines; and discuss this evidence in the framework of Liem’s paradox. Robinson and Wilson (1998) solved Liem’s paradox by demonstrating that extreme dietary specializations can theoretically be maintained as long as they do not preclude the ability to exploit other broadly accessible food resources. Rare pulses of “easy prey” could determine the fate of endemic species with small population size across ecosystems. Abstract Trophic specialization is a key feature of the diversity of cichlid fish adaptive radiations. However, Liem (1980) observed that even species with highly specialized trophic morphologies have dietary flexibility, enabling them to exploit episodic food resources opportunistically. Evidence for dietary flexibility comes largely from laboratory studies, and it is unclear whether cichlid fishes undergo diet shifts in the wild. We report observations of diet switching by multiple cichlid species in Lake Tanganyika as a consequence of unusual concentrations of schooling juvenile clupeid fishes. Fish species with varying degrees of trophic specialization converged on a single prey: juvenile sardines that are also endemic to Lake Tanganyika (Stolothrissa tanganicae and Limnothrissa miodon). We provide evidence for cichlid species acting as jacks-of-all-trades and discuss this evidence in the framework of Liem’s classic paradox: that trophic specialization does not preclude dietary flexibility. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704169">Read the Article</a></i> (Just Accepted)</p> <p><b>Researchers report diet switching by morphologically specialized cichlids as consequence of unusual concentrations of clupeids</b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">C</span>ichlid fishes are celebrated for their often extreme feeding adaptations and unique feeding strategies: <i>Lobochilotes labiatus</i> extracts invertebrates from rock crevices using its enlarged lips, <i>Perissodus microlepis</i>&rsquo;s feeding on scales from other fishes is linked to their striking mouth asymmetry, <i>Tropheus duboisi</i> crops algae growing on the rocky substrate using teeth located at the jaw-edges of their subterminal mouths. Karel Liem (1980) first noted that cichlid fishes are not only remarkable dietary specialists, but also can act as jacks-of-all-trades. However, evidence for the dietary flexibility of cichlids comes from laboratory studies, and it is unclear whether cichlid fishes in the wild actually feed on resources other than the ones they have adaptations for. We report field observations of dietary switching by multiple cichlid species in Lake Tanganyika as a consequence of a transient school of juvenile sardines; and discuss this evidence in the framework of Liem&rsquo;s paradox. Robinson and Wilson (1998) solved Liem&rsquo;s paradox by demonstrating that extreme dietary specializations can theoretically be maintained as long as they do not preclude the ability to exploit other broadly accessible food resources. Rare pulses of &ldquo;easy prey&rdquo; could determine the fate of endemic species with small population size across ecosystems.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">T</span>rophic specialization is a key feature of the diversity of cichlid fish adaptive radiations. However, Liem (1980) observed that even species with highly specialized trophic morphologies have dietary flexibility, enabling them to exploit episodic food resources opportunistically. Evidence for dietary flexibility comes largely from laboratory studies, and it is unclear whether cichlid fishes undergo diet shifts in the wild. We report observations of diet switching by multiple cichlid species in Lake Tanganyika as a consequence of unusual concentrations of schooling juvenile clupeid fishes. Fish species with varying degrees of trophic specialization converged on a single prey: juvenile sardines that are also endemic to Lake Tanganyika (<i>Stolothrissa tanganicae</i> and <i>Limnothrissa miodon</i>). We provide evidence for cichlid species acting as jacks-of-all-trades and discuss this evidence in the framework of Liem&rsquo;s classic paradox: that trophic specialization does not preclude dietary flexibility.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 29 Apr 2019 05:00:00 GMT “Resolving the paradox of environmental quality and sociality: the ecological causes and consequences of cooperative breeding in two lineages of birds” https://amnat.org/an/newpapers/AugLin-A.html Read the Article (Just Accepted) Social animals occupy larger species range size Abstract Cooperatively breeding animals occur in virtually every ecosystem on earth. Comparative and biogeographic studies suggest that both benign and harsh, as well as stable and fluctuating, environments can favor the evolution of cooperative breeding behavior. The fact that cooperative societies occur in environments of such contrasting quality creates a paradox of environmental quality and sociality. The dual-benefits framework—which leads to the prediction that the ecological consequences of sociality (e.g. range size) vary depending on the benefits that individuals of each species receive by forming social groups—offers a potential resolution to this paradox. Here we use a case study of two avian lineages, starlings (Sturnidae) and hornbills (Bucerotidae), in which environmental unpredictability appears to have opposite effects on the evolution of cooperation to test the dual-benefits framework. Consistent with previous work, harsh and unpredictable environments promote cooperative breeding behavior in starlings, which in turn leads to larger geographic ranges. However, cooperatively breeding hornbills occur in benign and stable environments, but sociality does not influence range size. Our study suggests that the paradox of environmental quality and sociality arises largely because cooperative breeding is an umbrella term, encompassing social species that form groups for different reasons. We demonstrate that differentiating among the functional causes of social group formation is critical for developing a predictive framework for understanding the evolution of cooperative breeding behavior. 解決環境品質和社會性演化的悖論：促進兩類鳥類類群中合作生殖演化的生態原因與其後果 林宇恆，詹仕凡，Dustin R. Rubenstein，劉彥廷，沈聖峰 地球上幾乎每個生態系統均可見合作生殖的動物。比較研究和生物地理學研究顯示，良好與嚴苛、以及穩定和變動的環境皆有利於合作生殖行為的演化。合作生殖物種在這些品質相異的環境中存在的事實造成了環境品質和社會性演化的悖論。我們的雙重群體利益理論預測：社會性的生態後果（例如物種的地理分布範圍大小）取決於每個物種的個體透過組成社會群體所獲得的利益，因此這理論提供了對這一悖論的潛在解決方案。由於環境不可預測性對椋鳥科和犀鳥科這兩個鳥類類群合作生殖的演化，有相反的影響，我們就使用兩個鳥類類群，進行案例研究以測試雙重群體利益理論。與過去的研究結果一致的是，嚴酷和不可預測的環境促進了椋鳥的合作繁殖行為，因而使椋鳥有更大的物種地理分布範圍。然而，合作繁殖的犀鳥在良好和穩定的環境中出現，但其合作生殖與否則不影響物種的分布範圍大小。我們的研究表明，環境品質和社會性演化的悖論的形成主要是因為合作生殖是一個概括性術語，包含因不同生態原因而形成群體的社會性物種。我們的研究證明，區分社會群體形成的生態原因，對於進一步發展用於理解合作生殖行為演化的預測理論至為關鍵。 More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704090">Read the Article</a></i> (Just Accepted)</p> <p><strong>Social animals occupy larger species range size </strong></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>ooperatively breeding animals occur in virtually every ecosystem on earth. Comparative and biogeographic studies suggest that both benign and harsh, as well as stable and fluctuating, environments can favor the evolution of cooperative breeding behavior. The fact that cooperative societies occur in environments of such contrasting quality creates a paradox of environmental quality and sociality. The dual-benefits framework—which leads to the prediction that the ecological consequences of sociality (e.g. range size) vary depending on the benefits that individuals of each species receive by forming social groups—offers a potential resolution to this paradox. Here we use a case study of two avian lineages, starlings (Sturnidae) and hornbills (Bucerotidae), in which environmental unpredictability appears to have opposite effects on the evolution of cooperation to test the dual-benefits framework. Consistent with previous work, harsh and unpredictable environments promote cooperative breeding behavior in starlings, which in turn leads to larger geographic ranges. However, cooperatively breeding hornbills occur in benign and stable environments, but sociality does not influence range size. Our study suggests that the paradox of environmental quality and sociality arises largely because cooperative breeding is an umbrella term, encompassing social species that form groups for different reasons. We demonstrate that differentiating among the functional causes of social group formation is critical for developing a predictive framework for understanding the evolution of cooperative breeding behavior. </p> <h4>解決環境品質和社會性演化的悖論：促進兩類鳥類類群中合作生殖演化的生態原因與其後果</h4> <p>林宇恆，詹仕凡，Dustin R. Rubenstein，劉彥廷，沈聖峰</p> <p>地球上幾乎每個生態系統均可見合作生殖的動物。比較研究和生物地理學研究顯示，良好與嚴苛、以及穩定和變動的環境皆有利於合作生殖行為的演化。合作生殖物種在這些品質相異的環境中存在的事實造成了環境品質和社會性演化的悖論。我們的雙重群體利益理論預測：社會性的生態後果（例如物種的地理分布範圍大小）取決於每個物種的個體透過組成社會群體所獲得的利益，因此這理論提供了對這一悖論的潛在解決方案。由於環境不可預測性對椋鳥科和犀鳥科這兩個鳥類類群合作生殖的演化，有相反的影響，我們就使用兩個鳥類類群，進行案例研究以測試雙重群體利益理論。與過去的研究結果一致的是，嚴酷和不可預測的環境促進了椋鳥的合作繁殖行為，因而使椋鳥有更大的物種地理分布範圍。然而，合作繁殖的犀鳥在良好和穩定的環境中出現，但其合作生殖與否則不影響物種的分布範圍大小。我們的研究表明，環境品質和社會性演化的悖論的形成主要是因為合作生殖是一個概括性術語，包含因不同生態原因而形成群體的社會性物種。我們的研究證明，區分社會群體形成的生態原因，對於進一步發展用於理解合作生殖行為演化的預測理論至為關鍵。</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, 24 Apr 2019 05:00:00 GMT “Phenotypic diversity arises from secondary signal loss in the elaborate visual displays of toucans and barbets” https://amnat.org/an/newpapers/AugMiles.html Read the Article (Just Accepted) Secondary loss of signals underlies the evolution of display diversity in toucans The evolution of complexity and diversity are two defining characteristics of life on Earth, but how they relate to each other is still largely a mystery. To address this question, we modeled how a communication system evolved as its individual components were gained and lost throughout evolutionary time. We specifically looked at the visual displays of toucans and barbets, a group of birds found across the continental tropics. Species in the group are mostly known for their big beaks and colorful plumage, but some are a bit more drab. When reading about the birds, we also noticed a common emphasis on tail-based displays. For example, in many species a bird will cock its tail up (and sometimes wave it around) to display, exposing feathers on the rump and undertail. Coincidentally, many species also have contrasting feather patches in the same regions. Some species also ruffle up the rump feathers to display—indeed, including many with a color patch on the rump. Yet others displayed with either gesture (or both) without any special ornaments on the tail. The small number of traits in this system made it perfect for discrete trait modeling, which we used to explore coevolution between gesture and color—and how coevolution influences the evolutionary trajectory toward phenotypic complexity (e.g., a species that has gained many colors and gestures) and diversity (i.e., the range of unique gesture-color combinations present in species today). Indeed, gestures tend to co-evolve with the color patches they emphasize. However, a species with no display whatsoever is only likely to gain a tail-cocking gesture. The chance of gaining a color ornament first was almost zero! Color ornaments were instead gained by lineages that already tail-cock. As a result, we found only a few likely ways that a species’ display evolves from minimum complexity (no gestures, no ornaments) to maximum complexity. Instead, many displays we see today must have evolved as different signal combinations were lost instead: there are only a few ways to become complex, but many routes to diversity. Abstract Complexity and diversity are fundamental characteristics of life, but the relationship between the two remains murky. For example, both gaining and losing complexity can support diversity—so how exactly does complexity influence the emergence of unique phenotypes? Here we address this question by examining how complexity underlies the diversity of elaborate visual displays in an avian clade (Ramphastides, the toucans and barbets). These species communicate in part using body movement and colorful ornaments on the tail. We find that sexual size dimorphism predicts the evolution of one specific signal, the tail-cock gesture, implying that tail-cocking is more likely to evolve under stronger sexual selection. We also discovered process-level constraints on the evolution of complexity: signals are gained along a strict order of operations, where the tail-cock gesture arises before other colors and gestures. Yet virtually any signal can be lost at any time. As a result, many extant phenotypes were more likely to arise through loss of complexity, highlighting the importance of secondary signal loss to phenotypic diversity. Collectively, our results demonstrate how sexual selection catalyzes the evolution of complex phenotypes, which indirectly support diversity by allowing different traits to be modified or lost in the future. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704088">Read the Article</a></i> (Just Accepted)</p> <p><b>Secondary loss of signals underlies the evolution of display diversity in toucans </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he evolution of complexity and diversity are two defining characteristics of life on Earth, but <i>how</i> they relate to each other is still largely a mystery. To address this question, we modeled how a communication system evolved as its individual components were gained and lost throughout evolutionary time. We specifically looked at the visual displays of toucans and barbets, a group of birds found across the continental tropics. Species in the group are mostly known for their big beaks and colorful plumage, but some are a bit more drab. When reading about the birds, we also noticed a common emphasis on tail-based displays. For example, in many species a bird will cock its tail up (and sometimes wave it around) to display, exposing feathers on the rump and undertail. Coincidentally, many species also have contrasting feather patches in the same regions. Some species also ruffle up the rump feathers to display—indeed, including many with a color patch on the rump. Yet others displayed with either gesture (or both) without any special ornaments on the tail. </p><p>The small number of traits in this system made it perfect for discrete trait modeling, which we used to explore coevolution between gesture and color—and how coevolution influences the evolutionary trajectory toward phenotypic complexity (e.g., a species that has gained many colors and gestures) and diversity (i.e., the range of unique gesture-color combinations present in species today). Indeed, gestures tend to co-evolve with the color patches they emphasize. However, a species with no display whatsoever is <i>only likely to gain a tail-cocking gesture</i>. The chance of gaining a color ornament first was almost zero! Color ornaments were instead gained by lineages that already tail-cock. As a result, we found only a few likely ways that a species’ display evolves from minimum complexity (no gestures, no ornaments) to maximum complexity. Instead, many displays we see today must have evolved as different signal combinations were lost instead: there are only a few ways to become complex, but many routes to diversity. </p> <hr /><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>omplexity and diversity are fundamental characteristics of life, but the relationship between the two remains murky. For example, both gaining and losing complexity can support diversity—so how exactly does complexity influence the emergence of unique phenotypes? Here we address this question by examining how complexity underlies the diversity of elaborate visual displays in an avian clade (Ramphastides, the toucans and barbets). These species communicate in part using body movement and colorful ornaments on the tail. We find that sexual size dimorphism predicts the evolution of one specific signal, the tail-cock gesture, implying that tail-cocking is more likely to evolve under stronger sexual selection. We also discovered process-level constraints on the evolution of complexity: signals are gained along a strict order of operations, where the tail-cock gesture arises before other colors and gestures. Yet virtually any signal can be lost at any time. As a result, many extant phenotypes were more likely to arise through <i>loss</i> of complexity, highlighting the importance of secondary signal loss to phenotypic diversity. Collectively, our results demonstrate how sexual selection catalyzes the evolution of complex phenotypes, which indirectly support diversity by allowing different traits to be modified or lost in the future. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 23 Apr 2019 05:00:00 GMT “Are pheromones key to unlocking cryptic lizard diversity?” https://amnat.org/an/newpapers/AugZozaya-A.html Read the Article (Just Accepted) Abstract Animals use mating traits to compete for, attract, and choose mates. Because mating traits influence mate choice, the divergence of mating traits between populations can result in reproductive isolation. This can occur without associated morphological divergence, producing reproductively isolated ‘cryptic species’ that are visually indistinguishable. Thus, identifying the mating traits in morphologically conservative groups is key to resolving diversity and speciation processes. Lizards contain many such groups, with phylogeographic studies often revealing highly divergent but morphologically cryptic lineages within species. Considering that cryptic lizard species can be sympatric but morphologically indistinguishable, we hypothesize that candidate species will exhibit divergent pheromones and that pheromones will have typically diverged more than morphology. To test this, we used gas chromatography to characterize pheromones (epidermal pore secretions) from 10 genetically divergent lineages of the Bynoe’s gecko (Heteronotia binoei) species complex in northern Australia. Multivariate analyses of pheromone blends and morphology indicate that pheromones are lineage-specific and have diverged relatively more than morphology. Such specificity suggests that pheromones influence behavioral isolation in this morphologically conservative lizard radiation. These results suggest that pheromone data may unlock the tremendous ‘cryptic’ diversity currently being uncovered in many lizard groups. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704059">Read the Article</a></i> (Just Accepted)</p> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>nimals use mating traits to compete for, attract, and choose mates. Because mating traits influence mate choice, the divergence of mating traits between populations can result in reproductive isolation. This can occur without associated morphological divergence, producing reproductively isolated &lsquo;cryptic species&rsquo; that are visually indistinguishable. Thus, identifying the mating traits in morphologically conservative groups is key to resolving diversity and speciation processes. Lizards contain many such groups, with phylogeographic studies often revealing highly divergent but morphologically cryptic lineages within species. Considering that cryptic lizard species can be sympatric but morphologically indistinguishable, we hypothesize that candidate species will exhibit divergent pheromones and that pheromones will have typically diverged more than morphology. To test this, we used gas chromatography to characterize pheromones (epidermal pore secretions) from 10 genetically divergent lineages of the Bynoe&rsquo;s gecko (<em>Heteronotia binoei</em>) species complex in northern Australia. Multivariate analyses of pheromone blends and morphology indicate that pheromones are lineage-specific and have diverged relatively more than morphology. Such specificity suggests that pheromones influence behavioral isolation in this morphologically conservative lizard radiation. These results suggest that pheromone data may unlock the tremendous &lsquo;cryptic&rsquo; diversity currently being uncovered in many lizard groups.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: georgia; font-size: large;"><em>More forthcoming papers</em> &raquo;</span></a></div> Tue, 23 Apr 2019 05:00:00 GMT “Individual variation in the social plasticity of water dragons” https://amnat.org/an/newpapers/AugStrickland-A.html Read the Article (Just Accepted)Abstract Individuals should alter when they socially associate with conspecifics to avoid potentially costly interactions. Moreover, individuals may vary in their propensity to use information about conspecifics when making such social decisions. However, surprisingly little is known about either the determinants of, or individual variation in, such ‘social plasticity’. We show here that eastern water dragons (Intellegama lesueurii lesueurii) may simultaneously use information from different components of their social environment when deciding whether or not to socially associate. In particular, we found that individuals altered when they socially associated with conspecifics according to the levels of potential conflict and competition in their social environment; both sexes socially associated more at higher local density than would be expected under increased random encounters. Further, females were more likely to socially associate during the breeding season, and when there were more males and/or conspecifics whom they typically avoided in their social environment. This suggests that females may seek safety in numbers when the potential for intra-sexual conflict or sexual harassment is high. Using a behavioral reaction-norm framework, we also provide novel evidence to show that individuals vary in the extent and direction of their social plasticity, and that males varied more than females. Our study thus implies that individuals use multiple cues in their environment when deciding to socially associate, and that the resulting social plasticity varies between the sexes and between individuals. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704089">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>ndividuals should alter when they socially associate with conspecifics to avoid potentially costly interactions. Moreover, individuals may vary in their propensity to use information about conspecifics when making such social decisions. However, surprisingly little is known about either the determinants of, or individual variation in, such ‘social plasticity’. We show here that eastern water dragons (<i>Intellegama lesueurii lesueurii</i>) may simultaneously use information from different components of their social environment when deciding whether or not to socially associate. In particular, we found that individuals altered when they socially associated with conspecifics according to the levels of potential conflict and competition in their social environment; both sexes socially associated more at higher local density than would be expected under increased random encounters. Further, females were more likely to socially associate during the breeding season, and when there were more males and/or conspecifics whom they typically avoided in their social environment. This suggests that females may seek safety in numbers when the potential for intra-sexual conflict or sexual harassment is high. Using a behavioral reaction-norm framework, we also provide novel evidence to show that individuals vary in the extent and direction of their social plasticity, and that males varied more than females. Our study thus implies that individuals use multiple cues in their environment when deciding to socially associate, and that the resulting social plasticity varies between the sexes and between individuals.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 23 Apr 2019 05:00:00 GMT “Nineteen years of consistently positive and strong female mate preferences despite individual variation” https://amnat.org/an/newpapers/AugRyan.html Read the Article (Just Accepted)Female mate choice generates some of the most spectacular biological diversity in the animal kingdom. Or does it? Alfred Wallace was no supporter of Darwin’s sexual selection theory because he could not imagine females showing persistent preferences for the same details of sexual beauty over generations. Julian Huxley, another critic, voiced some similar concerns. For female choice to be an important driver of sexual beauty, it has been argued, it must be strong and it must be consistent—fickle preferences won’t cut it. Amazingly, there are very few studies of female mate choice across a substantial number of generations. A group of researchers has been studying sexual selection in túngara frogs in Panama for several decades. Although the foci of this research program are varied, the hallmark has been the female’s preference for complex calls over simple calls. Simple calls are adequate to attract a mate but complex calls are preferred. But is this preference strong and consistent? Nineteen consecutive years of more than 5000 female mate choice tests have shown an average preference for the complex call of 0.86—more than a five-fold preference! Clearly it is strong, but is it consistent? Yes. There is very little variation in this strength of preference across years. Does this consistency across years mean there is similar consistency among females? No. Although most females have strong preferences for the complex call there is significant variation amongst females within years, much more so than the variation among years. Although other female preferences in this frog and female preferences in other species are known to be fickle, the preference for complex calls is strong and consistent just as Darwin suggested when he posited that females have a taste for the beautiful. Abstract Sexual selection driven by mate choice has generated some of the most astounding diversity in nature, suggesting population-level preferences should be strong and consistent over many generations. On the other hand, mating preferences are among the least repeatable components of an individual animal’s phenotype, suggesting low consistency across an animal’s lifetime. Despite decades of intensive study of sexual selection there is almost no information about the strength and consistency of preferences across many years. In this study we present the results of over 5000 mate choice tests with a species of wild frog conducted over 19 consecutive years. Results show that preferences are positive and strong and vary little across years. This consistency is despite the fact that there are substantial differences among females in their strength of preference. We also suggest mate preferences in populations that are primarily the result of sensory exploitation might be more stable over time compared to preferences that are primarily involved in assessing male quality. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704103">Read the Article</a></i> (Just Accepted)</p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">F</span>emale mate choice generates some of the most spectacular biological diversity in the animal kingdom. Or does it? Alfred Wallace was no supporter of Darwin’s sexual selection theory because he could not imagine females showing persistent preferences for the same details of sexual beauty over generations. Julian Huxley, another critic, voiced some similar concerns. For female choice to be an important driver of sexual beauty, it has been argued, it must be strong and it must be consistent—fickle preferences won’t cut it. Amazingly, there are very few studies of female mate choice across a substantial number of generations.</p> <p>A group of researchers has been studying sexual selection in túngara frogs in Panama for several decades. Although the foci of this research program are varied, the hallmark has been the female’s preference for complex calls over simple calls. Simple calls are adequate to attract a mate but complex calls are preferred. But is this preference strong and consistent? Nineteen consecutive years of more than 5000 female mate choice tests have shown an average preference for the complex call of 0.86—more than a five-fold preference! Clearly it is strong, but is it consistent? Yes. There is very little variation in this strength of preference across years. Does this consistency across years mean there is similar consistency among females? No. Although most females have strong preferences for the complex call there is significant variation amongst females within years, much more so than the variation among years. Although other female preferences in this frog and female preferences in other species are known to be fickle, the preference for complex calls is strong and consistent just as Darwin suggested when he posited that females have a <i>taste for the beautiful</i>.</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 driven by mate choice has generated some of the most astounding diversity in nature, suggesting population-level preferences should be strong and consistent over many generations. On the other hand, mating preferences are among the least repeatable components of an individual animal’s phenotype, suggesting low consistency across an animal’s lifetime. Despite decades of intensive study of sexual selection there is almost no information about the strength and consistency of preferences across many years. In this study we present the results of over 5000 mate choice tests with a species of wild frog conducted over 19 consecutive years. Results show that preferences are positive and strong and vary little across years. This consistency is despite the fact that there are substantial differences among females in their strength of preference. We also suggest mate preferences in populations that are primarily the result of sensory exploitation might be more stable over time compared to preferences that are primarily involved in assessing male quality. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 23 Apr 2019 05:00:00 GMT “A general explanation for the persistence of reproductive interference” https://amnat.org/an/newpapers/AugDrury.html Read the Article (Just Accepted) Why is reproductive interference so common? A new study suggests animals may be caught in an evolutionary ‘catch-22’ Why do animals sometimes attempt to mate with members of other species, even though doing so is wasteful? A new study by Drury and colleagues offers an answer to this question. Investigators generally assume that wasteful interspecific matings—known as ‘reproductive interference’—will either be eliminated by natural selection or result in one species going locally extinct. Yet, examples of reproductive interference abound, even in species that seem to coexist over long periods of time. In this study, Drury and colleagues argue that such species might be caught in an ‘evolutionary catch-22’. That is, because females of different species often look similar, males are unable to distinguish between females of their own species and females of another species when they come into contact. As a result, natural selection cannot drive divergence in female phenotypes via reproductive character displacement, which requires that males can differentiate between species. Yet, males cannot evolve the ability to differentiate between females until female phenotypes diverge, meaning that reproductive interference persists indefinitely. The study then goes on to demonstrate that the catch-22 explanation is a viable explanation for ongoing reproductive interference in a clade of damselflies distributed throughout North and Central America in which species similarity in female phenotypes predicts levels of reproductive isolation. In particular, they find that in cases where reproductive isolation is high, this isolation cannot be explained by reproductive character displacement, and is better explained by divergence prior to secondary contact. The evolutionary ‘catch-22’ provides a previously undocumented reason why reproductive interference is widespread. Abstract Reproductive interference is widespread, despite the theoretical expectation that it should be eliminated by reproductive character displacement (RCD). A possible explanation is that females of sympatric species are too similar phenotypically for males to distinguish between them, resulting in a type of evolutionary dilemma or “catch-22” in which reproductive interference persists because male mate recognition (MR) cannot evolve until female phenotypes diverge further, and vice versa. Here we illustrate, and test, this hypothesis with data on rubyspot damselflies (Hetaerina spp.). First, reproductive isolation owing to male MR breaks down with increasing interspecific similarity in female phenotypes. Second, comparing allopatric and sympatric populations yielded no evidence for RCD, suggesting that parallel divergence in female coloration and male MR in allopatry determines the level of reproductive isolation upon secondary contact. Whenever reproductive isolation depends on male mate recognition and females of sympatric species are phenotypically similar, the evolutionary catch-22 hypothesis offers an explanation for the persistence of reproductive interference. Una explicación general para la persistencia de la interferencia reproductiva La interferencia reproductiva es común a pesar de la expectativa teórica de que esta debería ser eliminada por el desplazamiento del carácter reproductivo. Una posible explicación sugiere que cuando las hembras de especies simpátricas son muy similares fenotípicamente los machos no pueden distinguir entre ellas, causando así un tipo de dilema evolutivo o “catch-22”. En este caso la interferencia reproductiva persiste debido a que el reconocimiento de pareja por los machos no puede evolucionar hasta cuando se desarrolle una divergencia notoria en el fenotipo de las hembras, y viceversa. En este estudio ilustramos y probamos esta hipótesis con datos obtenidos en libélulas del género Hetaerina spp. Primero, el aislamiento reproductivo debido al reconocimiento de pareja por los machos disminuye con el aumento en la similitud fenotípica interespecífica de las hembras. Segundo, la comparación entre poblaciones alopátricas y simpátricas no mostró evidencia en el desplazamiento del carácter reproductivo. Esto sugiriere que la divergencia paralela en la coloración de las hembras y el reconocimiento de pareja por parte de los machos en alopatría determina el nivel de aislamiento reproductivo al contacto secundario. Cuando las hembras de especies simpátricas son fenotípicamente similares y el aislamiento reproductivo depende del reconocimiento por parte de los machos, la hipótesis evolutiva “catch-22” ofrece una explicación para la persistencia de la interferencia reproductiva. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704102">Read the Article</a></i> (Just Accepted)</p> <p><b>Why is reproductive interference so common? A new study suggests animals may be caught in an evolutionary &lsquo;catch-22&rsquo; </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>hy do animals sometimes attempt to mate with members of other species, even though doing so is wasteful? A new study by Drury and colleagues offers an answer to this question. Investigators generally assume that wasteful interspecific matings—known as ‘reproductive interference’—will either be eliminated by natural selection or result in one species going locally extinct. Yet, examples of reproductive interference abound, even in species that seem to coexist over long periods of time. In this study, Drury and colleagues argue that such species might be caught in an ‘evolutionary catch-22’. That is, because females of different species often look similar, males are unable to distinguish between females of their own species and females of another species when they come into contact. As a result, natural selection cannot drive divergence in female phenotypes via reproductive character displacement, which requires that males can differentiate between species. Yet, males cannot evolve the ability to differentiate between females until female phenotypes diverge, meaning that reproductive interference persists indefinitely. The study then goes on to demonstrate that the catch-22 explanation is a viable explanation for ongoing reproductive interference in a clade of damselflies distributed throughout North and Central America in which species similarity in female phenotypes predicts levels of reproductive isolation. In particular, they find that in cases where reproductive isolation is high, this isolation cannot be explained by reproductive character displacement, and is better explained by divergence prior to secondary contact. The evolutionary ‘catch-22’ provides a previously undocumented reason why reproductive interference is widespread.</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>eproductive interference is widespread, despite the theoretical expectation that it should be eliminated by reproductive character displacement (RCD). A possible explanation is that females of sympatric species are too similar phenotypically for males to distinguish between them, resulting in a type of evolutionary dilemma or “catch-22” in which reproductive interference persists because male mate recognition (MR) cannot evolve until female phenotypes diverge further, and vice versa. Here we illustrate, and test, this hypothesis with data on rubyspot damselflies (<i>Hetaerina</i> spp.). First, reproductive isolation owing to male MR breaks down with increasing interspecific similarity in female phenotypes. Second, comparing allopatric and sympatric populations yielded no evidence for RCD, suggesting that parallel divergence in female coloration and male MR in allopatry determines the level of reproductive isolation upon secondary contact. Whenever reproductive isolation depends on male mate recognition and females of sympatric species are phenotypically similar, the evolutionary catch-22 hypothesis offers an explanation for the persistence of reproductive interference. </p> <h4>Una explicación general para la persistencia de la interferencia reproductiva</h4> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">L</span>a interferencia reproductiva es común a pesar de la expectativa teórica de que esta debería ser eliminada por el desplazamiento del carácter reproductivo. Una posible explicación sugiere que cuando las hembras de especies simpátricas son muy similares fenotípicamente los machos no pueden distinguir entre ellas, causando así un tipo de dilema evolutivo o “catch-22”. En este caso la interferencia reproductiva persiste debido a que el reconocimiento de pareja por los machos no puede evolucionar hasta cuando se desarrolle una divergencia notoria en el fenotipo de las hembras, y viceversa. En este estudio ilustramos y probamos esta hipótesis con datos obtenidos en libélulas del género <i>Hetaerina</i> spp. Primero, el aislamiento reproductivo debido al reconocimiento de pareja por los machos disminuye con el aumento en la similitud fenotípica interespecífica de las hembras. Segundo, la comparación entre poblaciones alopátricas y simpátricas no mostró evidencia en el desplazamiento del carácter reproductivo. Esto sugiriere que la divergencia paralela en la coloración de las hembras y el reconocimiento de pareja por parte de los machos en alopatría determina el nivel de aislamiento reproductivo al contacto secundario. Cuando las hembras de especies simpátricas son fenotípicamente similares y el aislamiento reproductivo depende del reconocimiento por parte de los machos, la hipótesis evolutiva “catch-22” ofrece una explicación para la persistencia de la interferencia reproductiva. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 23 Apr 2019 05:00:00 GMT “Environmental veto synchronizes mast seeding in four contrasting tree species” https://amnat.org/an/newpapers/AugBogdziewicz.html Read the Article (Just Accepted) Adverse weather events can synchronize trees reproduction Variable, synchronized seed production, called masting, is a widespread reproductive strategy in plants. How plants are able to synchronize reproduction is a longstanding question. One leading idea is that plants need to accumulate sufficient resources after depletion following seeding, which creates annual variability of reproduction. Synchrony is then induced by the efficiency of mass flowering for outcross pollination. Plants that reproduce asynchronously do not spent resources on seeds due to pollination failure, so they flower again and again until other plants do it as well, when flowers can get pollinated. Similar resource carry-over can be induced by external factors preventing reproduction – environmental veto – like frost or other adverse weather events. In this case, preventing plants from developing seeds in one year helps to put all plants on the same reproductive schedule. The authors of this study used four species differing in their masting strategies: Two species (pine and rowan) are “flowering masting” species, i.e. plants where mast seeding is driven by variable production of flowers. Two other species were oaks, and these are “fruiting masting” species, i.e. species where annual variation in seed production is a consequence of variable ripening with relatively constant flower production. Based on that difference in life history, they predicted that synchronization in the “flowering masting” species would be driven by density-dependent pollination success, while in the second group by correlated environmental veto. Indeed, positive density-dependence of pollination was much stronger in rowan and pine, while veto was much more frequent in oaks. However, in all four species, the veto was strong enough to drive synchrony without the need to invoke any other mechanism. Susceptibility to adverse weather conditions may benefit masting species, as it allows them to synchronize seed production. Abstract Synchronized and variable reproduction by perennial plants, called mast seeding, is a major reproductive strategy of trees. The need to accumulate sufficient resources after depletion following fruiting (resource budget), the efficiency of mass flowering for outcross pollination (pollen coupling), or the external factors preventing reproduction (environmental veto) could all synchronize masting. We used seed production data for four species (Quercus ilex, Q.&nbsp;humilis, Sorbus aucuparia, Pinus albicaulis) to parametrize resource budget models of masting. Based on species life history characteristics, we hypothesized that pollen coupling should synchronize reproduction in S.&nbsp;aucuparia and P.&nbsp;albicaulis, while in Q.&nbsp;ilex and Q.&nbsp;humilis environmental veto should be a major factor. Pollen coupling was stronger in S.&nbsp;aucuparia and P.&nbsp;albicaulis than in oaks, while veto was more frequent in the latter. Yet, in all species, costs of reproduction were too small to impose a replenishment period. A synchronous environmental veto, in the presence of environmental stochasticity, was sufficient to produce observed variability and synchrony in reproduction. In the past, vetoes like frost events that prevent reproduction have been perceived as negative for plants. In fact, they could be selectively favored as a way to create mast seeding. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704111">Read the Article</a></i> (Just Accepted)</p> <p><b>Adverse weather events can synchronize trees reproduction </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">V</span>ariable, synchronized seed production, called masting, is a widespread reproductive strategy in plants. How plants are able to synchronize reproduction is a longstanding question. One leading idea is that plants need to accumulate sufficient resources after depletion following seeding, which creates annual variability of reproduction. Synchrony is then induced by the efficiency of mass flowering for outcross pollination. Plants that reproduce asynchronously do not spent resources on seeds due to pollination failure, so they flower again and again until other plants do it as well, when flowers can get pollinated. Similar resource carry-over can be induced by external factors preventing reproduction – environmental veto – like frost or other adverse weather events. In this case, preventing plants from developing seeds in one year helps to put all plants on the same reproductive schedule. </p><p>The authors of this study used four species differing in their masting strategies: Two species (pine and rowan) are “flowering masting” species, i.e. plants where mast seeding is driven by variable production of flowers. Two other species were oaks, and these are “fruiting masting” species, i.e. species where annual variation in seed production is a consequence of variable ripening with relatively constant flower production. Based on that difference in life history, they predicted that synchronization in the “flowering masting” species would be driven by density-dependent pollination success, while in the second group by correlated environmental veto. Indeed, positive density-dependence of pollination was much stronger in rowan and pine, while veto was much more frequent in oaks. However, in all four species, the veto was strong enough to drive synchrony without the need to invoke any other mechanism. Susceptibility to adverse weather conditions may benefit masting species, as it allows them to synchronize seed production.</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>ynchronized and variable reproduction by perennial plants, called mast seeding, is a major reproductive strategy of trees. The need to accumulate sufficient resources after depletion following fruiting (resource budget), the efficiency of mass flowering for outcross pollination (pollen coupling), or the external factors preventing reproduction (environmental veto) could all synchronize masting. We used seed production data for four species (<i>Quercus ilex, Q.&nbsp;humilis, Sorbus aucuparia, Pinus albicaulis</i>) to parametrize resource budget models of masting. Based on species life history characteristics, we hypothesized that pollen coupling should synchronize reproduction in <i>S.&nbsp;aucuparia</i> and <i>P.&nbsp;albicaulis</i>, while in <i>Q.&nbsp;ilex</i> and <i>Q.&nbsp;humilis</i> environmental veto should be a major factor. Pollen coupling was stronger in <i>S.&nbsp;aucuparia</i> and <i>P.&nbsp;albicaulis</i> than in oaks, while veto was more frequent in the latter. Yet, in all species, costs of reproduction were too small to impose a replenishment period. A synchronous environmental veto, in the presence of environmental stochasticity, was sufficient to produce observed variability and synchrony in reproduction. In the past, vetoes like frost events that prevent reproduction have been perceived as negative for plants. In fact, they could be selectively favored as a way to create mast seeding. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 23 Apr 2019 05:00:00 GMT “Individual and population differences shape species interactions and natural selection” https://amnat.org/an/newpapers/AugStart-A.html Read the Article (Just Accepted) Small differences among individuals rewire foodwebs and shape natural selection Abstract Trait variation is central to our understanding of species interactions, and trait variation arising within species is increasingly recognized as an important component of community ecology. Ecologists generally consider intraspecific variation either among or within populations, yet these differences can interact to create patterns of species interactions. These differences can also affect species interactions by altering processes occurring at distinct scales. Specifically, intraspecific variation may shape species interactions simply by shifting a population’s position along a trait-function map, or by shifting the relationship between traits and their ecological function. I test these ideas by manipulating within- and among-population intraspecific variation in wild populations of a gall-forming insect, before quantifying species interactions and phenotypic selection. Within- and among-population differences in gall size interact to affect attack rates by an enemy community, but among-population differences were far more consequential. Intraspecific differences shaped species interactions both by shifting the position of populations along the trait-function map, and by altering the relationship between traits and their function, with ultimate consequences for patterns of natural selection. I suggest that intraspecific variation can affect communities and natural selection by acting through individual- and population-level mechanisms. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704060">Read the Article</a></i> (Just Accepted)</p> <p><b>Small differences among individuals rewire foodwebs and shape natural selection </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>rait variation is central to our understanding of species interactions, and trait variation arising within species is increasingly recognized as an important component of community ecology. Ecologists generally consider intraspecific variation either among or within populations, yet these differences can interact to create patterns of species interactions. These differences can also affect species interactions by altering processes occurring at distinct scales. Specifically, intraspecific variation may shape species interactions simply by shifting a population’s position along a trait-function map, or by shifting the relationship between traits and their ecological function. I test these ideas by manipulating within- and among-population intraspecific variation in wild populations of a gall-forming insect, before quantifying species interactions and phenotypic selection. Within- and among-population differences in gall size interact to affect attack rates by an enemy community, but among-population differences were far more consequential. Intraspecific differences shaped species interactions both by shifting the position of populations along the trait-function map, and by altering the relationship between traits and their function, with ultimate consequences for patterns of natural selection. I suggest that intraspecific variation can affect communities and natural selection by acting through individual- and population-level mechanisms. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 23 Apr 2019 05:00:00 GMT “Dense dwarfs versus gelatinous giants: The trade-offs and physiological limits determining the body plan of planktonic filter feeders” https://amnat.org/an/newpapers/AugDoelger.html Read the Article (Just Accepted)Gelatinous plankton form a special group of marine organisms due to their distinctly watery bodies with low carbon content. We find the gelatinous body plan mainly in large, centimeter-sized plankton who feed by filtering their micron-sized prey out of the water instead of perceiving it at a distance. Why do such planktonic giants tend to be gelatinous while microbes (dwarfs) that filter feed on the same prey stay dense? A marine biologist and two physicists in the Centre for Ocean Life at the Technical University of Denmark have resolved this question by developing a new theoretical model. By modeling the energy budget of filter feeders, the authors show that the interplay between gain and cost of energy has the key implication that a minimum filter area is necessary to collect enough food to sustain a living. Through comparison of their model predictions and existing data on filter feeders, the authors conclude that filter feeders need to be either small or if they are large to increase the filter area by being gelatinous in order to survive in dilute oceanic environments. Large plankton that are non-gelatinous also exist, but they either live in prey-rich environments or compensate by sensing their prey at a distance. Such understanding of planktonic survival strategies is essential to model and predict the global distributions of plankton. It directly connects to the main goal of the Centre for Ocean Life where marine ecologists, physicists, chemists, and mathematicians are working jointly to build a trait-based description of life in the ocean. Abstract Most marine plankton have a high energy (carbon) density, but some are gelatinous with approximately hundred times more watery bodies. How do those distinctly different body plans emerge and what are the trade-offs? We address this question by modeling the energy budget of planktonic filter feeders across life forms from micron-sized unicellular microbes like choanoflagellates to centimeter-sized gelatinous tunicates such as salps. We find two equally successful strategies, one being small with high energy density (dense dwarf), and the other being large with low energy density (gelatinous giant). The constraint that forces large – but not small – filter feeders to be gelatinous is identified as a lower limit to the size-specific filter area, below which the energy costs lead to starvation. A further limit is found from the maximum size-specific motor force that restricts the access to optimum strategies. The quantified constraints are discussed in the context of other resource acquisition strategies. We argue that interception feeding strategies can only be accessed by large organisms if they are gelatinous. On the other hand, organisms that use remote prey sensing do not need to be gelatinous, even if they are large. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703656">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;">G</span>elatinous plankton form a special group of marine organisms due to their distinctly watery bodies with low carbon content. We find the gelatinous body plan mainly in large, centimeter-sized plankton who feed by filtering their micron-sized prey out of the water instead of perceiving it at a distance. Why do such planktonic giants tend to be gelatinous while microbes (dwarfs) that filter feed on the same prey stay dense? A marine biologist and two physicists in the Centre for Ocean Life at the Technical University of Denmark have resolved this question by developing a new theoretical model. </p><p>By modeling the energy budget of filter feeders, the authors show that the interplay between gain and cost of energy has the key implication that a minimum filter area is necessary to collect enough food to sustain a living. Through comparison of their model predictions and existing data on filter feeders, the authors conclude that filter feeders need to be either small or if they are large to increase the filter area by being gelatinous in order to survive in dilute oceanic environments. Large plankton that are non-gelatinous also exist, but they either live in prey-rich environments or compensate by sensing their prey at a distance. </p><p>Such understanding of planktonic survival strategies is essential to model and predict the global distributions of plankton. It directly connects to the main goal of the Centre for Ocean Life where marine ecologists, physicists, chemists, and mathematicians are working jointly to build a trait-based description of life in the ocean. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>ost marine plankton have a high energy (carbon) density, but some are gelatinous with approximately hundred times more watery bodies. How do those distinctly different body plans emerge and what are the trade-offs? We address this question by modeling the energy budget of planktonic filter feeders across life forms from micron-sized unicellular microbes like choanoflagellates to centimeter-sized gelatinous tunicates such as salps. We find two equally successful strategies, one being small with high energy density (dense dwarf), and the other being large with low energy density (gelatinous giant). The constraint that forces large – but not small – filter feeders to be gelatinous is identified as a lower limit to the size-specific filter area, below which the energy costs lead to starvation. A further limit is found from the maximum size-specific motor force that restricts the access to optimum strategies. The quantified constraints are discussed in the context of other resource acquisition strategies. We argue that interception feeding strategies can only be accessed by large organisms if they are gelatinous. On the other hand, organisms that use remote prey sensing do not need to be gelatinous, even if they are large. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 17 Apr 2019 05:00:00 GMT “Consistent associations between body size and hidden contrasting color signals across a range of insect taxa” https://amnat.org/an/newpapers/JulyLoefflerHenry.html Read the Article (Just Accepted) The evolution of hidden contrasting coloration is associated with body size in insects Coloration frequently serves to protect insects from visual predators through crypsis, warning signals, and mimicry. While these color patterns are often permanently displayed, some insect species use their anti-predatory color signals more dynamically: they normally remain camouflaged, but reveal conspicuous colors transiently upon approach by predators. Recent studies have demonstrated that such flash (in moving prey) and deimatic (in stationary prey) conspicuous displays are more effective in deterring predators when exhibited by larger prey than smaller prey. Thus, one might expect that hidden conspicuous color signals would be more likely to be found in large than small prey species. The collaborative research team between Carleton University and Mokpo National University tested this hypothesis in five different insect groups that are known to utilize hidden conspicuous color signals: Orthoptera, Mantidae, Phasmatidae, Saturniidae, and Sphingidae. Our findings suggest that after controlling for the effect of shared ancestry, the presence of hidden conspicuous color signals is indeed associated with large size in most of the studied insect taxa. These results therefore provide further evidence that anti-predator traits in insects is at least in part mediated by body size. Abstract While there have been a number of recent advances in our understanding of the evolution of animal color patterns, much of this work has focused on color patterns that are constantly displayed. However, some animals hide functional color signals and only display them transiently through behavioral displays. These displays are widely employed as a secondary defense following detection when fleeing (flash display) or when stationary (deimatic display). Yet if displays of hidden colors are so effective in deterring predation, why have not all species evolved them? An earlier study suggested that the hidden anti-predatory color signals in insects are more likely to have evolved in species with large size because either (or both): i) large cryptic prey are more frequently detected and pursued and ii) hidden color signals in large prey are more effective in deterring predation than small prey. These arguments should apply universally to any prey that use hidden signals so the association between large size and hidden contrasting color signals should be evident across diverse groups of prey. In this study, we tested this prediction in five different groups of insects. Using phylogenetically controlled analysis to elucidate the relationship between body size and color contrast between forewings and hindwings, we found evidence for the predicted size-color contrast associations in four different groups of insects, namely Orthoptera, Phasmatidae, Mantidae, Saturniidae, but not in Sphingidae. Collectively, our study indicates that body size plays an important role in explaining variation in the evolution of hidden contrasting color signals in insects. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703535">Read the Article</a></i> (Just Accepted)</p> <p><b>The evolution of hidden contrasting coloration is associated with body size in insects </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>oloration frequently serves to protect insects from visual predators through crypsis, warning signals, and mimicry. While these color patterns are often permanently displayed, some insect species use their anti-predatory color signals more dynamically: they normally remain camouflaged, but reveal conspicuous colors transiently upon approach by predators. Recent studies have demonstrated that such flash (in moving prey) and deimatic (in stationary prey) conspicuous displays are more effective in deterring predators when exhibited by larger prey than smaller prey. Thus, one might expect that hidden conspicuous color signals would be more likely to be found in large than small prey species. The collaborative research team between Carleton University and Mokpo National University tested this hypothesis in five different insect groups that are known to utilize hidden conspicuous color signals: Orthoptera, Mantidae, Phasmatidae, Saturniidae, and Sphingidae. Our findings suggest that after controlling for the effect of shared ancestry, the presence of hidden conspicuous color signals is indeed associated with large size in most of the studied insect taxa. These results therefore provide further evidence that anti-predator traits in insects is at least in part mediated by body size. </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 there have been a number of recent advances in our understanding of the evolution of animal color patterns, much of this work has focused on color patterns that are constantly displayed. However, some animals hide functional color signals and only display them transiently through behavioral displays. These displays are widely employed as a secondary defense following detection when fleeing (flash display) or when stationary (deimatic display). Yet if displays of hidden colors are so effective in deterring predation, why have not all species evolved them? An earlier study suggested that the hidden anti-predatory color signals in insects are more likely to have evolved in species with large size because either (or both): i) large cryptic prey are more frequently detected and pursued and ii) hidden color signals in large prey are more effective in deterring predation than small prey. These arguments should apply universally to any prey that use hidden signals so the association between large size and hidden contrasting color signals should be evident across diverse groups of prey. In this study, we tested this prediction in five different groups of insects. Using phylogenetically controlled analysis to elucidate the relationship between body size and color contrast between forewings and hindwings, we found evidence for the predicted size-color contrast associations in four different groups of insects, namely Orthoptera, Phasmatidae, Mantidae, Saturniidae, but not in Sphingidae. Collectively, our study indicates that body size plays an important role in explaining variation in the evolution of hidden contrasting color signals in insects. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 17 Apr 2019 05:00:00 GMT “Phytoplankton species richness along coastal and estuarine salinity continua” https://amnat.org/an/newpapers/AugOlli.html Read the Article (Just Accepted) Phytoplankton diversity-salinity relation follows Remane curve: High richness at fresh and saline ends, low at brackish Throughout the evolutionary time scales, the boundary between freshwater and ocean salinity has been a tough one for aquatic organisms to cross. Compared to freshwater and the ocean, a lower number of species thrive at brackish salinity. This textbook knowledge stems from the classical work by Adolf Remane with benthic macro-invertebrate diversity in the Baltic Sea, and has shaped our understanding of species richness along the salinity gradient for 85 years. When it comes to phytoplankton, the base of the aquatic food chain, it is surprising how little scrutiny the matter has received. This is partly due to the rareness of high-quality phytoplankton data sets covering the full salinity range from fresh water to the ocean. Recently some researchers have proposed a reversal of Remane’s concept for protists and phytoplankton, with a richness maximum at brackish salinities. Analysis of sizeable phytoplankton data sets from two large coastal ecosystems, the Chesapeake Bay and the Baltic Sea, unambiguously corroborated the validity of the Remane concept in terms of both alpha and gamma species richness. These analyses, based on >15,000 phytoplankton samples, revealed in both data sets minima in species richness at salinities around 7-9, and increasing diversity towards both limbs of the salinity gradient. Why does this matter? Biodiversity is the basis of ecosystem functioning and services; hence, understanding the drivers of biodiversity become mandatory for human wellbeing. Our results support the idea that ecological scaling rules apply to microbial diversity in ways similar to what is known from the macrobial realm. The results enable us to predict changes in diversity, and the associated ecosystem functions, in the era of global change, where coastal and estuarine salinity gradients are shifting due to changes in precipitation and hydrology. Abstract High number of freshwater species at low salinity, and a corresponding high number of marine species at high salinity, enveloping a conspicuous richness minimum at intermediate salinities, has shaped our basic understanding of biodiversity along a coastal salinity gradient for almost 80 years. Visualized as the ‘Remane curve’, this iconic concept was originally based on sedentary macroinvertebrates in the Baltic Sea. To what extent the concept can be generalized, particularly to free-drifting organisms, is currently debated. Here we use ca 16,000 phytoplankton samples from 2 large coastal ecosystems, the Baltic Sea and the Chesapeake Bay, to analyze the relationship between salinity and phytoplankton species richness. Alpha diversity showed a consistent variation along the salinity gradient, with a minimum at mesohaline salinities at around 7 – 9. Rarefied species pools at narrow salinity intervals also showed reduced diversity at intermediate salinities, surrounded by high richness towards both ends of the gradient. The cumulative likelihood of species presence validated the minimum at intermediate salinities. Community composition changed abruptly at the α diversity minimum in the Baltic Sea, while it changed gradually along the salinity gradient in the Chesapeake Bay. We conclude that the Remane concept is in every respect valid for phytoplankton. Fütoplaktoni liigirikkus rannikumere ja estuaari soolsusgradientidel Ligi 80 aastat on meie arusaama vee organismide liigirikkusest soolsusgradiendil kujundanud paradigmaks muutunud Remane kõver. Selle järgi on magevee liigirikkus suur, suur on liigirikkus ka ookeanis, kuid vahepealses riimveelises osas on tuntav liigirikkuse madalseis. Adolf Remane sedastas oma seaduspära uurides põhjaeluliste suurselgrootute liigirikkust Läänemeres. Kas ja millisel määral on seaduspära kehtiv teiste organismirühmade puhul, eriti vabalt hõljuvate plankterite puhul, ei ole teada. Me analüüsisime ligi 16,000 fütoplanktoni proovi liigirikkust kahe suure ökosüsteemi, Läänemere ja Chesapeake Lahe soolsusgradientidel. Proovide liigirikkus oli madalaim gradiendi mesohaliinses piirkonnas, soolsusel 7 – 9. Ka harvenduskõverad kitsastes soolsusvahemikes näitasid madalat liigirikkust mesohaliinses piirkonnas ja fütoplanktoni liigirikkus suurenemist nii magevee, kui ookeani soolsuse suunal. Liikide kumulatiivne esinemise tõenäosus soolsuse gradiendil näitas samuti liigirikkuse miinimumi riimveelises osas. Chesapeake Lahes muutub fütoplanktoni kooslus mageveelisest mereliseks sujuvalt kogu soolsusgradiendil. Kontrastina, Läänemere eripäraks on fütoplanktoni koosluse järsk muutus liigirikkuse miinimumi piirkonnas. Analüüsi tulemused näitavad, et Remane printsiip on täiel määral kehtiv ka fütoplanktoni puhul. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703657">Read the Article</a></i> (Just Accepted)</p> <p><b>Phytoplankton diversity-salinity relation follows Remane curve: High richness at fresh and saline ends, low at brackish </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>hroughout the evolutionary time scales, the boundary between freshwater and ocean salinity has been a tough one for aquatic organisms to cross. Compared to freshwater and the ocean, a lower number of species thrive at brackish salinity. This textbook knowledge stems from the classical work by Adolf Remane with benthic macro-invertebrate diversity in the Baltic Sea, and has shaped our understanding of species richness along the salinity gradient for 85 years. </p><p>When it comes to phytoplankton, the base of the aquatic food chain, it is surprising how little scrutiny the matter has received. This is partly due to the rareness of high-quality phytoplankton data sets covering the full salinity range from fresh water to the ocean. Recently some researchers have proposed a reversal of Remane’s concept for protists and phytoplankton, with a richness maximum at brackish salinities. </p><p>Analysis of sizeable phytoplankton data sets from two large coastal ecosystems, the Chesapeake Bay and the Baltic Sea, unambiguously corroborated the validity of the Remane concept in terms of both alpha and gamma species richness. These analyses, based on &gt;15,000 phytoplankton samples, revealed in both data sets minima in species richness at salinities around 7-9, and increasing diversity towards both limbs of the salinity gradient. </p><p>Why does this matter? Biodiversity is the basis of ecosystem functioning and services; hence, understanding the drivers of biodiversity become mandatory for human wellbeing. Our results support the idea that ecological scaling rules apply to microbial diversity in ways similar to what is known from the macrobial realm. The results enable us to predict changes in diversity, and the associated ecosystem functions, in the era of global change, where coastal and estuarine salinity gradients are shifting due to changes in precipitation and hydrology. </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;">H</span>igh number of freshwater species at low salinity, and a corresponding high number of marine species at high salinity, enveloping a conspicuous richness minimum at intermediate salinities, has shaped our basic understanding of biodiversity along a coastal salinity gradient for almost 80 years. Visualized as the ‘Remane curve’, this iconic concept was originally based on sedentary macroinvertebrates in the Baltic Sea. To what extent the concept can be generalized, particularly to free-drifting organisms, is currently debated. Here we use ca 16,000 phytoplankton samples from 2 large coastal ecosystems, the Baltic Sea and the Chesapeake Bay, to analyze the relationship between salinity and phytoplankton species richness. Alpha diversity showed a consistent variation along the salinity gradient, with a minimum at mesohaline salinities at around 7 – 9. Rarefied species pools at narrow salinity intervals also showed reduced diversity at intermediate salinities, surrounded by high richness towards both ends of the gradient. The cumulative likelihood of species presence validated the minimum at intermediate salinities. Community composition changed abruptly at the α diversity minimum in the Baltic Sea, while it changed gradually along the salinity gradient in the Chesapeake Bay. We conclude that the Remane concept is in every respect valid for phytoplankton. </p> <h4>Fütoplaktoni liigirikkus rannikumere ja estuaari soolsusgradientidel</h4> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">L</span>igi 80 aastat on meie arusaama vee organismide liigirikkusest soolsusgradiendil kujundanud paradigmaks muutunud Remane kõver. Selle järgi on magevee liigirikkus suur, suur on liigirikkus ka ookeanis, kuid vahepealses riimveelises osas on tuntav liigirikkuse madalseis. Adolf Remane sedastas oma seaduspära uurides põhjaeluliste suurselgrootute liigirikkust Läänemeres. Kas ja millisel määral on seaduspära kehtiv teiste organismirühmade puhul, eriti vabalt hõljuvate plankterite puhul, ei ole teada. Me analüüsisime ligi 16,000 fütoplanktoni proovi liigirikkust kahe suure ökosüsteemi, Läänemere ja Chesapeake Lahe soolsusgradientidel. Proovide liigirikkus oli madalaim gradiendi mesohaliinses piirkonnas, soolsusel 7 – 9. Ka harvenduskõverad kitsastes soolsusvahemikes näitasid madalat liigirikkust mesohaliinses piirkonnas ja fütoplanktoni liigirikkus suurenemist nii magevee, kui ookeani soolsuse suunal. Liikide kumulatiivne esinemise tõenäosus soolsuse gradiendil näitas samuti liigirikkuse miinimumi riimveelises osas. Chesapeake Lahes muutub fütoplanktoni kooslus mageveelisest mereliseks sujuvalt kogu soolsusgradiendil. Kontrastina, Läänemere eripäraks on fütoplanktoni koosluse järsk muutus liigirikkuse miinimumi piirkonnas. Analüüsi tulemused näitavad, et Remane printsiip on täiel määral kehtiv ka fütoplanktoni puhul. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 17 Apr 2019 05:00:00 GMT “Eco-evolutionary dynamics in the wild: clonal turnover and stability in Daphnia populations” https://amnat.org/an/newpapers/JulySteiner-A.html Read the Article Abstract There is increasing recognition of the importance of rapid adaptation in the dynamics of populations and communities. While the effects of rapid adaptation on the stability of populations have been shown in experimental systems, demonstration of their impacts in natural populations are rare. We examined the relationship between clonal dynamics and population stability of natural Daphnia pulex populations experiencing seasonal environmental variation. We show that the degree of asynchrony in a population&#39;s clonal dynamics is tightly linked to its population-level stability. Populations whose clonal abundances were more asynchronous were more stable temporally. Variation in asynchrony was related to variability in primary productivity, and experiments using clones from the study populations revealed significant genotype by environment interactions in response to food level. This suggests that clonal turnover was not due to neutral dynamics alone but may be linked to variation in functional traits associated with resource acquisition and conversion. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703484">Read the Article</a></i></p> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>here is increasing recognition of the importance of rapid adaptation in the dynamics of populations and communities. While the effects of rapid adaptation on the stability of populations have been shown in experimental systems, demonstration of their impacts in natural populations are rare. We examined the relationship between clonal dynamics and population stability of natural <em>Daphnia pulex</em> populations experiencing seasonal environmental variation. We show that the degree of asynchrony in a population&#39;s clonal dynamics is tightly linked to its population-level stability. Populations whose clonal abundances were more asynchronous were more stable temporally. Variation in asynchrony was related to variability in primary productivity, and experiments using clones from the study populations revealed significant genotype by environment interactions in response to food level. This suggests that clonal turnover was not due to neutral dynamics alone but may be linked to variation in functional traits associated with resource acquisition and conversion.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: georgia; font-size: large;"><em>More forthcoming papers</em> &raquo;</span></a></div> Wed, 17 Apr 2019 05:00:00 GMT “Host responses to foreign eggs across the avian visual color space” https://amnat.org/an/newpapers/JulyHanley.html Read the Article Scientists detect color biases in the rejection behavior of the blackbird Painting eggs using vibrant colors may conjure pleasant springtime childhood memories for many people. A team of scientists led by Dr. Daniel Hanley of Long Island University–Post do this every season for science. Dr. Hanley and his lab are interested in natural colors: how they are used and how they evolve. Birds’ eggs range from blue-green to brown and can be variably speckled, and birds examine their own eggs for many reasons. One such reason is that some birds will lay their eggs in other birds’ nests. No bird wants to come back to their nest and find an additional mouth to feed, especially when that foster child may evict and kill its foster siblings. The appearance of an imposter egg is one way that birds evaluate whether an egg belongs to them or another bird. Traditional theory assumes that if the egg appears quite similar to their own a bird will likely accept it, but if it differs considerably the bird will reject it. In a paper appearing in The&nbsp;American Naturalist, Dr. Hanley and his colleagues Dr. Mark Hauber (University of Illinois Urbana-Champaign), Tom&aacute;&scaron; Grim, and Karel Gern used an experimental approach to study how the common blackbird, an European species, responds to an unprecedented range of colors. Since birds can see a far greater range of colors than humans can, Dr. Hanley and co-author Karel Gern (shown above) made a bird-specific color wheel to paint eggs, manipulating the three main components of color: hue (e.g., blue, aquamarine, magenta, etc.), saturation (i.e. intensity), and brightness. They found that birds responded strongly to a far greater array of colors than had been previously tested. In addition, they found that the components of color interacted, such that birds may respond to one hue but only if it were an intense color. This group has also shown that hosts in North America, Europe, and South America all remove brown eggs at a much higher rate than blue-green eggs, despite how different they appear from their own eggs. These findings illustrate that we have a lot to learn about how wild birds use color information in their decision making; however, studies such as these are slowly closing that gap. Abstract Despite extensive research on the sensory and cognitive processes of host rejection of avian brood parasites’ eggs, the underlying perceptual and cognitive mechanisms are not sufficiently understood. Historically, most studies of host egg discrimination assumed that hosts rejected a parasite’s egg from their nest based on the perceived color and pattern differences between the parasite’s egg and their own. A recent study used a continuous range of parasitic egg colors and discovered that hosts were more likely to reject browner foreign eggs than foreign eggs that were more blue-green, even when their absolute perceived color differences from the hosts’ own egg colors were similar. However, the extent of these color biases across the avian perceivable color space remains unclear. Therefore, we built upon this previous study by testing European blackbirds’ (Turdus merula) responses to model eggs spanning an unprecedented volume of the avian color space. We found that host decisions depended on avian perceived hue, saturation, and luminance of the parasite’s egg; hosts generally accepted eggs that were bluer or more blue-green, and more often rejected eggs that were less saturated or darker. We suggest that future studies investigate the underlying mechanisms of foreign egg discrimination in other host lineages to determine the prevalence and phylogenetic conservation of such perceptual biases among birds. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703534">Read the Article</a></i></p> <p><b>Scientists detect color biases in the rejection behavior of the blackbird </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>ainting eggs using vibrant colors may conjure pleasant springtime childhood memories for many people. A team of scientists led by Dr. Daniel Hanley of Long Island University&ndash;Post do this every season for science. Dr. Hanley and his lab are interested in natural colors: how they are used and how they evolve. Birds&rsquo; eggs range from blue-green to brown and can be variably speckled, and birds examine their own eggs for many reasons. One such reason is that some birds will lay their eggs in other birds&rsquo; nests. No bird wants to come back to their nest and find an additional mouth to feed, especially when that foster child may evict and kill its foster siblings. The appearance of an imposter egg is one way that birds evaluate whether an egg belongs to them or another bird. Traditional theory assumes that if the egg appears quite similar to their own a bird will likely accept it, but if it differs considerably the bird will reject it.</p> <p>In a paper appearing in <em>The&nbsp;American Naturalist</em>, Dr. Hanley and his colleagues Dr. Mark Hauber (University of Illinois Urbana-Champaign), Tom&aacute;&scaron; Grim, and Karel Gern used an experimental approach to study how the common blackbird, an European species, responds to an unprecedented range of colors. Since birds can see a far greater range of colors than humans can, Dr. Hanley and co-author Karel Gern (shown above) made a bird-specific color wheel to paint eggs, manipulating the three main components of color: hue (e.g., blue, aquamarine, magenta, etc.), saturation (i.e. intensity), and brightness. They found that birds responded strongly to a far greater array of colors than had been previously tested. In addition, they found that the components of color interacted, such that birds may respond to one hue but only if it were an intense color. This group has also shown that hosts in North America, Europe, and South America all remove brown eggs at a much higher rate than blue-green eggs, despite how different they appear from their own eggs. These findings illustrate that we have a lot to learn about how wild birds use color information in their decision making; however, studies such as these are slowly closing that gap.</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;">D</span>espite extensive research on the sensory and cognitive processes of host rejection of avian brood parasites&rsquo; eggs, the underlying perceptual and cognitive mechanisms are not sufficiently understood. Historically, most studies of host egg discrimination assumed that hosts rejected a parasite&rsquo;s egg from their nest based on the perceived color and pattern differences between the parasite&rsquo;s egg and their own. A recent study used a continuous range of parasitic egg colors and discovered that hosts were more likely to reject browner foreign eggs than foreign eggs that were more blue-green, even when their absolute perceived color differences from the hosts&rsquo; own egg colors were similar. However, the extent of these color biases across the avian perceivable color space remains unclear. Therefore, we built upon this previous study by testing European blackbirds&rsquo; (<em>Turdus merula</em>) responses to model eggs spanning an unprecedented volume of the avian color space. We found that host decisions depended on avian perceived hue, saturation, and luminance of the parasite&rsquo;s egg; hosts generally accepted eggs that were bluer or more blue-green, and more often rejected eggs that were less saturated or darker. We suggest that future studies investigate the underlying mechanisms of foreign egg discrimination in other host lineages to determine the prevalence and phylogenetic conservation of such perceptual biases among birds.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family:georgia; font-size:large"><em>More forthcoming papers</em> &raquo;</span></a></div> Wed, 17 Apr 2019 05:00:00 GMT “Evolutionary hysteresis and ratchets in the evolution of periodical cicadas” https://amnat.org/an/newpapers/JulyToivonen.html Read the Article Evolutionary hysteresis and ratchets promote the evolution of long synchronous life cycles in periodical cicadas The authors show how two interesting evolutionary mechanisms, hysteresis and ratchets, promote the evolution of long and synchronous life-cycles in the periodical cicadas. Evolutionary hysteresis is a phenomenon wherein evolution not only depends on the current environmental conditions but also on the history of environmental change. Evolutionary ratchets are mechanisms that cause evolution to become “locked” such that it can only proceed in one direction. The authors show that the evolution of perfectly synchronous life-cycles in the periodical cicadas is unlikely in contemporary climates. However, the harsh environmental conditions encountered during past ice ages may have been instrumental in the evolution of synchronicity. Further, once a synchronous life-cycle is attained it cannot be lost even when the environmental conditions become favorable again (evolutionary hysteresis). The authors show that once periodical cicadas evolved synchronous life cycles they would only have been able to develop ever longer life cycles and it became impossible for them to return to non-synchronous or shorter life cycles (evolutionary ratchet). While this paper concentrates on a specific case study, the authors hope to inspire others to look for evolutionary ratchets and hysteresis in other contexts as well. Abstract It has been previously hypothesized that the perfectly synchronized mass emergence of periodical cicadas (Magicicada spp.) evolved as a result of a switch from size-based to age-based emergence. In the former case cicada nymphs emerge immediately (at the first opportunity) upon reaching maturity whereas in the latter case nymphs wait in order to emerge at a specific age. Here we use an individual-based model to simulate the cicada life cycle and to study the evolution of periodicity. We find that if age-based emergence evolves in a constant abiotic environment, it typically results in a population that is proto-periodic and synchronous emergence of the whole population is not achieved. However, perfect periodicity and synchronous emergence can be attained, if the abiotic environment changes back-and-forth between favorable and unfavorable conditions (hysteresis). Furthermore, once age-based emergence evolves, generally it can only be invaded by other age-based emergence strategies with longer cycle lengths (evolutionary ratchet). Together, these mechanisms promote the evolution of long periodic life cycles and synchronous emergence in the \textit{Magicicada}. We discuss how our results connect to previous theories and recent phylogenetic studies on Magicicada evolution. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703563">Read the Article</a></i></p> <p><b>Evolutionary hysteresis and ratchets promote the evolution of long synchronous life cycles in periodical cicadas </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he authors show how two interesting evolutionary mechanisms, hysteresis and ratchets, promote the evolution of long and synchronous life-cycles in the periodical cicadas. Evolutionary hysteresis is a phenomenon wherein evolution not only depends on the current environmental conditions but also on the history of environmental change. Evolutionary ratchets are mechanisms that cause evolution to become “locked” such that it can only proceed in one direction. </p> <p>The authors show that the evolution of perfectly synchronous life-cycles in the periodical cicadas is unlikely in contemporary climates. However, the harsh environmental conditions encountered during past ice ages may have been instrumental in the evolution of synchronicity. Further, once a synchronous life-cycle is attained it cannot be lost even when the environmental conditions become favorable again (evolutionary hysteresis). The authors show that once periodical cicadas evolved synchronous life cycles they would only have been able to develop ever longer life cycles and it became impossible for them to return to non-synchronous or shorter life cycles (evolutionary ratchet). </p> <p>While this paper concentrates on a specific case study, the authors hope to inspire others to look for evolutionary ratchets and hysteresis in other contexts as well.</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>t has been previously hypothesized that the perfectly synchronized mass emergence of periodical cicadas (<i>Magicicada</i> spp.) evolved as a result of a switch from size-based to age-based emergence. In the former case cicada nymphs emerge immediately (at the first opportunity) upon reaching maturity whereas in the latter case nymphs wait in order to emerge at a specific age. Here we use an individual-based model to simulate the cicada life cycle and to study the evolution of periodicity. We find that if age-based emergence evolves in a constant abiotic environment, it typically results in a population that is proto-periodic and synchronous emergence of the whole population is not achieved. However, perfect periodicity and synchronous emergence can be attained, if the abiotic environment changes back-and-forth between favorable and unfavorable conditions (hysteresis). Furthermore, once age-based emergence evolves, generally it can only be invaded by other age-based emergence strategies with longer cycle lengths (evolutionary ratchet). Together, these mechanisms promote the evolution of long periodic life cycles and synchronous emergence in the \textit{Magicicada}. We discuss how our results connect to previous theories and recent phylogenetic studies on Magicicada 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> Wed, 17 Apr 2019 05:00:00 GMT “Bimodal pollination systems in Andean Melastomataceae involving birds, bats, and rodents” https://amnat.org/an/newpapers/JulyDellinger.html Read the Article Biomodal pollination systems in the Andes: nectar adaptations to birds, South African scent compounds in rodent flowers A&nbsp;flower pollinated only by a single animal species is the most extreme case of specialization in plant-pollinator interactions and this flower will show specific adaptations to its pollinator to maximize reproductive output. On the other extreme, generalized pollination systems involve many different animal species (often of different groups, e.g. beetles, flies, butterflies) and generalist flowers are adapted to make use of all of these different pollinators simultaneously. Flowers visited by two pollinator groups (e.g. hummingbirds and bats), such as documented in a new paper in The&nbsp;American Naturalist by Dellinger et al., lie between these extremes and may help understand when and how specialized or generalized pollination systems evolve. In her PhD project, Dellinger investigated floral adaptations to variable combinations of two different pollinator groups in four closely related South American plant species. She conducted pollinator observations and experiments in three different cloud forest sites in Ecuador. Dellinger et al. found that all investigated species were effectively pollinated by one diurnally active pollinator group and a nocturnally active one (hummingbirds/bats, hummingbirds/rodents, flowerpiercers/rodents). All species have widely open flowers, which allow access to the nectar reward to both pollinator groups at all times. Nectar sugar composition shows typical adaptations to diurnal bird pollinators while scent profiles indicate adaptation to nocturnal bat/rodent pollinators. Dellinger et al. conclude that these pollination systems are specialized rather than generalized and exhibit ‘bimodal’ adaptations to exploit two different pollinator groups. Apparently, being specialized on these pollinator combinations is advantageous and outweighs costs (trade-offs) reported for other pollination systems involving more than one pollinator group. Abstract Floral adaptation to a single most effective functional pollinator group leads to specialized pollination syndromes. However, adaptations allowing for pollination by two functional groups (bimodal pollination systems) remain a conundrum rarely investigated. We tested if floral scent and nectar traits of species visited by two functional pollinator groups indicate specialization on either one of the two or (intermediate) bimodal systems. We studied pollination biology in four species of Meriania (Melastomataceae) in the Ecuadorian Andes. Pollinator observations and exclusion experiments showed that each species was effectively pollinated by two functional groups (hummingbirds/bats; hummingbirds/rodents; flowerpiercers/rodents), nectar composition followed known bird preferences and scent profiles gave mixed support for specialization on bats and rodents. Our results suggest that nectar rewarding Meriania species have evolved stable bimodal pollination strategies with parallel adaptations to two functional pollinator groups. The discovery of rodent pollination is particularly important given its rarity outside of South Africa. Síndromes florales bimodales en Melastomataceae Andinas incluyendo aves, murcielagos y ratones La adaptación a solo un grupo funcional de polinizadores lleva a síndromes florales especializados, pero todavía no se entiende bien cómo las flores pueden adaptarse a la polinización por dos grupos de polinizadores (síndromes bimodales). Analizamos el olor floral y características del néctar de cuatro especies de Meriania (Melastomataceae) visitadas por dos grupos distintos de polinizadores, para evaluar si hay síndromes de polinización a un solo grupo funcional de polinizadores o muestra síndromes bimodales. Nuestros experimentos mostraron que en cada especie de Meriania dos grupos de polinizadores (colibríes/murciélagos; colibríes/ratones; pinchaflores/ratones) son eficientes en el transporte de polen. La composición del néctar indicó especialización a los polinizadores diurnos (colibríes, pinchaflores), mientras que el olor de las flores mostró más especialización por los polinizadores nocturnos (murciélagos y ratones). Nuestros resultados sugieren que especies nectaríferas de Meriania evolucionaron síndromes bimodales estables con adaptaciones paralelas a dos grupos funcionales de polinizadores. El descubrimiento de polinización por ratones es especialmente importante por la rareza con que ocurre fuera de Sudáfrica. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703517">Read the Article</a></i></p> <p><b>Biomodal pollination systems in the Andes: nectar adaptations to birds, South African scent compounds in rodent flowers </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>&nbsp;flower pollinated only by a single animal species is the most extreme case of specialization in plant-pollinator interactions and this flower will show specific adaptations to its pollinator to maximize reproductive output. On the other extreme, generalized pollination systems involve many different animal species (often of different groups, e.g. beetles, flies, butterflies) and generalist flowers are adapted to make use of all of these different pollinators simultaneously. Flowers visited by two pollinator groups (e.g. hummingbirds and bats), such as documented in a new paper in <i>The&nbsp;American Naturalist</i> by Dellinger et al., lie between these extremes and may help understand when and how specialized or generalized pollination systems evolve. </p><p>In her PhD project, Dellinger investigated floral adaptations to variable combinations of two different pollinator groups in four closely related South American plant species. She conducted pollinator observations and experiments in three different cloud forest sites in Ecuador. Dellinger et al. found that all investigated species were effectively pollinated by one diurnally active pollinator group and a nocturnally active one (hummingbirds/bats, hummingbirds/rodents, flowerpiercers/rodents). All species have widely open flowers, which allow access to the nectar reward to both pollinator groups at all times. Nectar sugar composition shows typical adaptations to diurnal bird pollinators while scent profiles indicate adaptation to nocturnal bat/rodent pollinators. Dellinger et al. conclude that these pollination systems are specialized rather than generalized and exhibit ‘bimodal’ adaptations to exploit two different pollinator groups. Apparently, being specialized on these pollinator combinations is advantageous and outweighs costs (trade-offs) reported for other pollination systems involving more than one pollinator group. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">F</span>loral adaptation to a single most effective functional pollinator group leads to specialized pollination syndromes. However, adaptations allowing for pollination by two functional groups (bimodal pollination systems) remain a conundrum rarely investigated. We tested if floral scent and nectar traits of species visited by two functional pollinator groups indicate specialization on either one of the two or (intermediate) bimodal systems. We studied pollination biology in four species of <i>Meriania</i> (Melastomataceae) in the Ecuadorian Andes. Pollinator observations and exclusion experiments showed that each species was effectively pollinated by two functional groups (hummingbirds/bats; hummingbirds/rodents; flowerpiercers/rodents), nectar composition followed known bird preferences and scent profiles gave mixed support for specialization on bats and rodents. Our results suggest that nectar rewarding <i>Meriania</i> species have evolved stable bimodal pollination strategies with parallel adaptations to two functional pollinator groups. The discovery of rodent pollination is particularly important given its rarity outside of South Africa. </p> <h4>Síndromes florales bimodales en Melastomataceae Andinas incluyendo aves, murcielagos y ratones</h4> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">L</span>a adaptación a solo un grupo funcional de polinizadores lleva a síndromes florales especializados, pero todavía no se entiende bien cómo las flores pueden adaptarse a la polinización por dos grupos de polinizadores (síndromes bimodales). Analizamos el olor floral y características del néctar de cuatro especies de <i>Meriania</i> (Melastomataceae) visitadas por dos grupos distintos de polinizadores, para evaluar si hay síndromes de polinización a un solo grupo funcional de polinizadores o muestra síndromes bimodales. Nuestros experimentos mostraron que en cada especie de <i>Meriania</i> dos grupos de polinizadores (colibríes/murciélagos; colibríes/ratones; pinchaflores/ratones) son eficientes en el transporte de polen. La composición del néctar indicó especialización a los polinizadores diurnos (colibríes, pinchaflores), mientras que el olor de las flores mostró más especialización por los polinizadores nocturnos (murciélagos y ratones). Nuestros resultados sugieren que especies nectaríferas de <i>Meriania</i> evolucionaron síndromes bimodales estables con adaptaciones paralelas a dos grupos funcionales de polinizadores. El descubrimiento de polinización por ratones es especialmente importante por la rareza con que ocurre fuera de Sudáfrica. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 17 Apr 2019 05:00:00 GMT “Why so variable: can genetic variance in flowering thresholds be maintained by fluctuating selection?” https://amnat.org/an/newpapers/JulyRees.html Read the Article (Just Accepted) Why populations are genetically variable is a puzzle: Here is why fluctuating selection might hold the key Many processes are thought to allow the maintenance of genetic variation in natural populations. However, determining which ones operate in the wild is difficult. The authors’ previous work exploring the evolution of flowering thresholds (the critical size a plant must achieve before it can flower) suggested that even in a variable environment, where the conditions for growth, survival, and reproduction vary from year to year, a single strategy was best and so the maintenance of genetic variation was not possible. Here the researchers extend their models to include quantitative genetic variation and ask whether a gene which increases the mutation rate would be adaptive. For one species where they assume a constant environment, selection does not favor an increase in mutation rate, and genetic variation in the threshold size for flowering is maladaptive. In contrast, for the other species where they assume a variable environment, an increase in mutation rate is adaptive. The authors suggest this is a consequence of disruptive selection which favors genotypes in the tails of the flowering threshold distribution. They suspect this mechanism may operate in many natural systems. Abstract We use integral projection models (IPM) and individual-based simulations to study the evolution of genetic variance in two monocarpic plant systems. Previous approaches combining IPMs with an Adaptive Dynamics-style invasion analysis predicted that genetic variability in the size threshold for flowering will not be maintained, which conflicts with empirical evidence. We ask if this discrepancy can be resolved by making more realistic assumptions about the underlying genetic architecture: assuming a multilocus quantitative trait in an outcrossing diploid species. To do this, we embed the infinitesimal model of quantitative genetics into an IPM for a sizestructured cosexual plant species. The resulting IPM describes the joint dynamics of individual size and breeding value of the evolving trait. We apply this general framework to the monocarpic perennials Oenothera glazioviana and Carlina vulgaris. The evolution of heritable variation in threshold size is explored, in both individual-based models (IBMs) and IPMs, using a mutation rate modifier approach. In the Oenothera model, where the environment is constant, there is selection against producing genetically variable offspring. In the Carlina model, where the environment varies between years, genetically variable offspring provide a selective advantage, allowing the maintenance of genetic variability. The contrasting predictions of Adaptive Dynamics and Quantitative Genetics models for the same system suggest that fluctuating selection may be more effective at maintaining genetic variation than previously thought. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703436">Read the Article</a></i> (Just Accepted)</p> <p><b>Why populations are genetically variable is a puzzle: Here is why fluctuating selection might hold the key </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>any processes are thought to allow the maintenance of genetic variation in natural populations. However, determining which ones operate in the wild is difficult. The authors’ previous work exploring the evolution of flowering thresholds (the critical size a plant must achieve before it can flower) suggested that even in a variable environment, where the conditions for growth, survival, and reproduction vary from year to year, a single strategy was best and so the maintenance of genetic variation was not possible. </p><p>Here the researchers extend their models to include quantitative genetic variation and ask whether a gene which increases the mutation rate would be adaptive. For one species where they assume a constant environment, selection does not favor an increase in mutation rate, and genetic variation in the threshold size for flowering is maladaptive. In contrast, for the other species where they assume a variable environment, an increase in mutation rate is adaptive. The authors suggest this is a consequence of disruptive selection which favors genotypes in the tails of the flowering threshold distribution. They suspect this mechanism may operate in many natural systems.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>e use integral projection models (IPM) and individual-based simulations to study the evolution of genetic variance in two monocarpic plant systems. Previous approaches combining IPMs with an Adaptive Dynamics-style invasion analysis predicted that genetic variability in the size threshold for flowering will not be maintained, which conflicts with empirical evidence. We ask if this discrepancy can be resolved by making more realistic assumptions about the underlying genetic architecture: assuming a multilocus quantitative trait in an outcrossing diploid species. To do this, we embed the infinitesimal model of quantitative genetics into an IPM for a sizestructured cosexual plant species. The resulting IPM describes the joint dynamics of individual size and breeding value of the evolving trait. We apply this general framework to the monocarpic perennials <i>Oenothera glazioviana</i> and <i>Carlina vulgaris</i>. The evolution of heritable variation in threshold size is explored, in both individual-based models (IBMs) and IPMs, using a mutation rate modifier approach. In the <i>Oenothera</i> model, where the environment is constant, there is selection against producing genetically variable offspring. In the <i>Carlina</i> model, where the environment varies between years, genetically variable offspring provide a selective advantage, allowing the maintenance of genetic variability. The contrasting predictions of Adaptive Dynamics and Quantitative Genetics models for the same system suggest that fluctuating selection may be more effective at maintaining genetic variation than previously thought. </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, 15 Apr 2019 05:00:00 GMT “The critical role of infectious disease in compensatory population growth in response to culling” https://amnat.org/an/newpapers/JulyTanner-A.html Read the Article (Just Accepted) Using mathematical models we show how culling populations harboring endemic disease can lead to compensatory growth Abstract Despite the ubiquity of disease in nature, the role that disease dynamics play in the compensatory growth response to harvesting has been ignored. We use a mathematical approach to show that harvesting can lead to compensatory growth due to a release from disease-induced mortality. Our findings imply that culling in systems that harbor virulent parasites can reduce disease prevalence and increase population density. Our models predict that this compensation occurs for a broad range of infectious disease characteristics unless disease induces long-lasting immunity in hosts. Our key insight is that a population can be regulated at a similar density by disease or at reduced prevalence by a combination of culling and disease. We illustrate our predictions with a system-specific model representing wild boar tuberculosis infection, parameterized for central Spain, and find significant compensation to culling. Given that few wildlife diseases are likely to induce long-lived immunity, populations with virulent diseases may often be resilient to harvesting. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703437">Read the Article</a></i> (Just Accepted)</p> <p><b>Using mathematical models we show how culling populations harboring endemic disease can lead to compensatory growth </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">D</span>espite the ubiquity of disease in nature, the role that disease dynamics play in the compensatory growth response to harvesting has been ignored. We use a mathematical approach to show that harvesting can lead to compensatory growth due to a release from disease-induced mortality. Our findings imply that culling in systems that harbor virulent parasites can reduce disease prevalence and increase population density. Our models predict that this compensation occurs for a broad range of infectious disease characteristics unless disease induces long-lasting immunity in hosts. Our key insight is that a population can be regulated at a similar density by disease or at reduced prevalence by a combination of culling and disease. We illustrate our predictions with a system-specific model representing wild boar tuberculosis infection, parameterized for central Spain, and find significant compensation to culling. Given that few wildlife diseases are likely to induce long-lived immunity, populations with virulent diseases may often be resilient to harvesting. </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, 15 Apr 2019 05:00:00 GMT “Lagging adaptation to climate change supersedes local adaptation to herbivory in an annual monkeyflower” https://amnat.org/an/newpapers/AugKooyers.html Read the Article Adaptation lag! Elevation-matched California monkeyflowers populations have higher fitness in Oregon sites than Oregon monkeyflowers In the western US, climate change is causing the timing of growing seasons to shift. Spring is starting earlier on average, and consequently populations are experiencing seasonal conditions more characteristic of habitats to their south. In addition, precipitation is falling more often as rain rather than as snow, which deprives plant populations in mountainous areas of the snowmelt that serves as a dependable water source into summer. A team led by Nicholas Kooyers and Benjamin Blackman examined how well annual populations of the common monkeyflower, a widespread species in the western US, are adapting to cope with these environmental shifts. At both low and high elevation field sites, they find that local Oregon populations are less well adapted to their current environment than populations sampled from >500 miles south in California at equivalent elevations. Thus, their results are consistent with what is known as an adaptation lag, a pattern where local populations fare worse in current climates than populations whose historical climates better match current climates. What gave the California populations the advantage? The team found that they possessed several trait differences that fostered success in earlier growing seasons through timing reproduction to occur at more favorable times at each site. Oregon plants did have at least one home court advantage though. They sustained less damage from herbivores than the more heavily chewed on California plants, suggesting future years at these sites may also feature mismatches between Oregon herbivore communities and California-like growing seasons. Although they did not thrive as well as the California populations, the Oregon populations are not yet facing a truly dire threat from the changing climate. They still produced sufficient seed to sustain positive population growth rates even in the drastically early year when the team completed their study. Nonetheless, that the team observed patterns consistent with an adaptation lag even in this species, which has all the qualities like a short generation time and vast reservoirs of genetic variation that should favor rapid adaptation to changing climates, is dismaying for the many species that lack such evolutionary advantages. Abstract While native populations are often adapted to historical biotic and abiotic conditions at their home site, populations from other locations in the range may be better adapted to current conditions due to changing climates or extreme conditions in a single year. We examine whether local populations of a widespread species maintain a relative advantage over distant populations that have evolved at sites better matching the current climate. Specifically, we grew lines derived from low and high elevation annual populations in California and Oregon of the common monkeyflower (Erythranthe guttata), and conducted phenotypic selection analyses in low and high elevation common gardens in Oregon to examine relative fitness and the traits mediating relative fitness. Californian low elevation populations have the highest relative fitness in the low elevation site and Californian high elevation populations have the highest relative fitness in the high elevation site. Relative fitness differences are mediated by selection for properly timed transitions to flowering with selection favoring more rapid growth rates at the low elevation site and greater vegetative biomass prior to flowering at the high elevation site. Fitness advantages for Californian plants occur despite incurring higher herbivory at both sites than the native Oregonian plants. Our findings suggest a lag in adaptation causes maladaptation in extreme years that may be more prevalent in future climates, but local populations still have high growth rates and thus are not yet threatened. More forthcoming papers &raquo; <!-- <p><i>The DOI will be https://dx.doi.org/10.1086/702312 </i></p> --> <p><i><a href="https://dx.doi.org/10.1086/702312">Read the Article</a></i> </p> <p><b>Adaptation lag! Elevation-matched California monkeyflowers populations have higher fitness in Oregon sites than Oregon monkeyflowers </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n the western US, climate change is causing the timing of growing seasons to shift. Spring is starting earlier on average, and consequently populations are experiencing seasonal conditions more characteristic of habitats to their south. In addition, precipitation is falling more often as rain rather than as snow, which deprives plant populations in mountainous areas of the snowmelt that serves as a dependable water source into summer. </p><p>A team led by Nicholas Kooyers and Benjamin Blackman examined how well annual populations of the common monkeyflower, a widespread species in the western US, are adapting to cope with these environmental shifts. At both low and high elevation field sites, they find that local Oregon populations are less well adapted to their current environment than populations sampled from >500 miles south in California at equivalent elevations. Thus, their results are consistent with what is known as an adaptation lag, a pattern where local populations fare worse in current climates than populations whose historical climates better match current climates. </p><p>What gave the California populations the advantage? The team found that they possessed several trait differences that fostered success in earlier growing seasons through timing reproduction to occur at more favorable times at each site. Oregon plants did have at least one home court advantage though. They sustained less damage from herbivores than the more heavily chewed on California plants, suggesting future years at these sites may also feature mismatches between Oregon herbivore communities and California-like growing seasons. </p><p>Although they did not thrive as well as the California populations, the Oregon populations are not yet facing a truly dire threat from the changing climate. They still produced sufficient seed to sustain positive population growth rates even in the drastically early year when the team completed their study. Nonetheless, that the team observed patterns consistent with an adaptation lag even in this species, which has all the qualities like a short generation time and vast reservoirs of genetic variation that should favor rapid adaptation to changing climates, is dismaying for the many species that lack such evolutionary advantages. </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 native populations are often adapted to historical biotic and abiotic conditions at their home site, populations from other locations in the range may be better adapted to current conditions due to changing climates or extreme conditions in a single year. We examine whether local populations of a widespread species maintain a relative advantage over distant populations that have evolved at sites better matching the current climate. Specifically, we grew lines derived from low and high elevation annual populations in California and Oregon of the common monkeyflower (<i>Erythranthe guttata</i>), and conducted phenotypic selection analyses in low and high elevation common gardens in Oregon to examine relative fitness and the traits mediating relative fitness. Californian low elevation populations have the highest relative fitness in the low elevation site and Californian high elevation populations have the highest relative fitness in the high elevation site. Relative fitness differences are mediated by selection for properly timed transitions to flowering with selection favoring more rapid growth rates at the low elevation site and greater vegetative biomass prior to flowering at the high elevation site. Fitness advantages for Californian plants occur despite incurring higher herbivory at both sites than the native Oregonian plants. Our findings suggest a lag in adaptation causes maladaptation in extreme years that may be more prevalent in future climates, but local populations still have high growth rates and thus are not yet threatened. </p> <div style="float: right;"><za 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, 15 Apr 2019 05:00:00 GMT “Maladaptive shifts in life history in a changing environment” https://amnat.org/an/newpapers/AugCotto.html Read the Article Maladaptation can induce false-adaptive shifts in life history if different trait values maximize different vital rates As climate warms, the performance of many organisms is affected, with negative effects on some aspects of their life cycle, but also of positive effects on others. Should we interpret such cases of improved performance as evidence for climate change facilitating the persistence of those populations? A model by researchers from CNRS, the University of Montpellier (France) and the University of British Columbia (Canada) suggests caution in doing so. In some birds, breeding earlier in the season increases the number of chicks raised in that year, but compromises the parent prospects of survival. Similarly, in some plants, flowering early is associated with the production of a higher number of fruits, but increases the risk of being grazed. The seasonal timing of key events in the life cycle of many organisms has already been modified by the warming of temperatures. Further genetic evolution of populations will be necessary to adapt this timing to future climates. How will the conflicting consequences of altered timing on different aspects of the life cycle affect this adaptive race? The model predicts that even adapting populations will lag behind the climate. Such lags in adaptation however have unforeseen consequences for the life cycle of these organisms, with negative effects on some aspects of performance (e.g. on fecundity) and, more surprisingly, positive effects on others (e.g. on survival). Increased performance in some aspects of the life cycle under a changing climate may reflect the population inability to evolve fast enough and may be observed in populations on the verge of extinction. Lags in adaptation may also trigger drastic changes in the life cycle, with some populations evolving to reproduce only once during an individual’s lifetime. This study therefore suggests that consequences of climate change should be integrated over the whole life cycle to conclude about the persistence prospects of populations. Abstract Many species facing climate change have complex life cycles, with individuals in different stages differing in their sensitivity to a changing climate and their contribution to population growth. We use a quantitative genetics model to predict the dynamics of adaptation in a stage-structured population confronted with a steadily changing environment. Our model assumes that different optimal phenotypic values maximize different fitness components, consistent with many empirical observations. In a constant environment, the population evolves towards an equilibrium phenotype, which represents the best compromise given the trade-off between vital rates. In a changing environment however, the mean phenotype in the population will lag behind this optimal compromise. We show that this lag may result in a shift along the trade-off between vital rates, with negative consequences for some fitness components, but, less intuitively, improvements in some others. Complex eco-evolutionary dynamics can emerge in our model due to feedbacks between population demography and adaptation. Because of such feedbacks loops, selection may favor further shifts in life history in the same direction as caused by maladaptive lags. These shifts in life history could be wrongly interpreted as adaptations to the new environment, while they only reflect the inability of the population to adapt fast enough. More forthcoming papers &raquo; <!-- <p><i>The DOI will be https://dx.doi.org/10.1086/702716 </i></p> --> <p><i><a href="https://dx.doi.org/10.1086/702716">Read the Article</a></i> </p> <p><b>Maladaptation can induce false-adaptive shifts in life history if different trait values maximize different vital rates </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>s climate warms, the performance of many organisms is affected, with negative effects on some aspects of their life cycle, but also of positive effects on others. Should we interpret such cases of improved performance as evidence for climate change facilitating the persistence of those populations? A model by researchers from CNRS, the University of Montpellier (France) and the University of British Columbia (Canada) suggests caution in doing so. </p><p>In some birds, breeding earlier in the season increases the number of chicks raised in that year, but compromises the parent prospects of survival. Similarly, in some plants, flowering early is associated with the production of a higher number of fruits, but increases the risk of being grazed. The seasonal timing of key events in the life cycle of many organisms has already been modified by the warming of temperatures. Further genetic evolution of populations will be necessary to adapt this timing to future climates. How will the conflicting consequences of altered timing on different aspects of the life cycle affect this adaptive race? The model predicts that even adapting populations will lag behind the climate. Such lags in adaptation however have unforeseen consequences for the life cycle of these organisms, with negative effects on some aspects of performance (e.g. on fecundity) and, more surprisingly, positive effects on others (e.g. on survival). Increased performance in some aspects of the life cycle under a changing climate may reflect the population inability to evolve fast enough and may be observed in populations on the verge of extinction. Lags in adaptation may also trigger drastic changes in the life cycle, with some populations evolving to reproduce only once during an individual’s lifetime. This study therefore suggests that consequences of climate change should be integrated over the whole life cycle to conclude about the persistence prospects of populations.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>any species facing climate change have complex life cycles, with individuals in different stages differing in their sensitivity to a changing climate and their contribution to population growth. We use a quantitative genetics model to predict the dynamics of adaptation in a stage-structured population confronted with a steadily changing environment. Our model assumes that different optimal phenotypic values maximize different fitness components, consistent with many empirical observations. In a constant environment, the population evolves towards an equilibrium phenotype, which represents the best compromise given the trade-off between vital rates. In a changing environment however, the mean phenotype in the population will lag behind this optimal compromise. We show that this lag may result in a shift along the trade-off between vital rates, with negative consequences for some fitness components, but, less intuitively, improvements in some others. Complex eco-evolutionary dynamics can emerge in our model due to feedbacks between population demography and adaptation. Because of such feedbacks loops, selection may favor further shifts in life history in the same direction as caused by maladaptive lags. These shifts in life history could be wrongly interpreted as adaptations to the new environment, while they only reflect the inability of the population to adapt fast enough. </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, 15 Apr 2019 05:00:00 GMT “Unpacking conditional neutrality: genomic signatures of selection on conditionally beneficial and conditionally deleterious mutations” https://amnat.org/an/newpapers/AugMee-A.html Abstract It is common to look for signatures of local adaptation in genomes by identifying loci with extreme levels of allele frequency divergence among populations. This approach to finding genes associated with local adaptation often assumes antagonistic pleiotropy, wherein alternative alleles are strongly favored in alternative environments. Conditional neutrality has been proposed as an alternative to antagonistic pleiotropy, but conditionally neutral polymorphisms are transient and it is unclear how much outlier signal would be maintained under different forms of conditional neutrality. Here, we use individual-based simulations and a simple analytical heuristic to show that a pattern that mimics local adaptation at the phenotypic level, where each genotype has the highest fitness in its home environment, can be produced by the accumulation of mutations that are neutral in their home environment and deleterious in non-local environments. Because conditionally deleterious mutations likely arise at a rate many times higher than conditionally beneficial mutations, they can have a significant cumulative effect on fitness even when individual effect sizes are small. We show that conditionally deleterious mutations driving non-local maladaptation may be undetectable by even the most powerful genome scans, as differences in allele frequency between populations are typically small. We also explore the evolutionary effects of conditionally-beneficial mutations and find that they can maintain significant signals of local adaptation, and they would be more readily detectable than conditionally deleterious mutations using conventional genome scan approaches. We discuss implications for interpreting outcomes of transplant experiments and genome scans that are used to study the genetic basis of local adaptation. More forthcoming papers &raquo; <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>t is common to look for signatures of local adaptation in genomes by identifying loci with extreme levels of allele frequency divergence among populations. This approach to finding genes associated with local adaptation often assumes antagonistic pleiotropy, wherein alternative alleles are strongly favored in alternative environments. Conditional neutrality has been proposed as an alternative to antagonistic pleiotropy, but conditionally neutral polymorphisms are transient and it is unclear how much outlier signal would be maintained under different forms of conditional neutrality. Here, we use individual-based simulations and a simple analytical heuristic to show that a pattern that mimics local adaptation at the phenotypic level, where each genotype has the highest fitness in its home environment, can be produced by the accumulation of mutations that are neutral in their home environment and deleterious in non-local environments. Because conditionally deleterious mutations likely arise at a rate many times higher than conditionally beneficial mutations, they can have a significant cumulative effect on fitness even when individual effect sizes are small. We show that conditionally deleterious mutations driving non-local maladaptation may be undetectable by even the most powerful genome scans, as differences in allele frequency between populations are typically small. We also explore the evolutionary effects of conditionally-beneficial mutations and find that they can maintain significant signals of local adaptation, and they would be more readily detectable than conditionally deleterious mutations using conventional genome scan approaches. We discuss implications for interpreting outcomes of transplant experiments and genome scans that are used to study the genetic basis of local adaptation. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 15 Apr 2019 05:00:00 GMT 2019 American Naturalist Student Paper Award https://amnat.org/announcements/ANNStuPaperAwa.html The American Naturalist Student Paper Award is for work that was published in 2018 and that was performed primarily by the first author and primarily while she or he was an undergraduate or graduate student. There were over seventy eligible papers. The recipient of the 2019 Student Paper Award is Marta Strecker Shocket, for her paper "Temperature drives epidemics in a zooplankton-fungus disease system: a trait-driven approach points to transmission via host foraging” (April 2018, 191(4):435-451), co-authored with Alexander Strauss, Jessica Hite, Maja Ijivar, ZDavid Civitello, Meghan Duffy, Carla C&atilde;ceres, and Spencer Hall. This is a remarkable combination of experimental work, modeling, and observational natural history rolled into one. Dr. Shocket and collaborators asked how climate warming will affect the dynamics of disease outbreaks. They emphasize the need for a mechanistic understanding of host-parasite interactions and the role of temperature to generate effective predictions. They develop a trait-based model that considers how temperature affects host foraging rates in a Daphnia-fungus interaction, and parameterized the model with laboratory experiments. They found that warming increased Daphnia foraging rates, which in turn increased fungal transmission success and epidemic size. The Editors appreciated the well-integrated mix of field data, lab experiments, mesocosm experiments, and theory, in service of a mechanistic understanding of species interactions. This paper has the potential to set a new standard for studies of the role of temperature-dependence in disease dynamics. Nicolas Schnedler-Meyer, for his paper “Evolution of complex asexual reproductive strategies in jellyfish”, coauthored with Simone Pigolotti and Patizio Mariani (July 2018, 192(1):72-80). This paper stood out to us because it presents a simple but elegant model of life history evolution that was solidly grounded in natural history (jellyfish life cycles). The study considers the diversity of asexual modes of reproduction in scyphozoan jellyfish, to describe tradeoffs among dispersal, dormancy, and local spread. Which life history strategy dominates depends on the nature of environmental variation, as the authors demonstrate with an Evolutionary Stable Strategy analysis. Not only do they effectively model which life histories should evolve in which environmental settings for jellyfish, but they do an excellent job of linking their findings to similar kinds of variance discounting adaptations in plants and other animals. They very effectively relate their model results back to published empirical literature, in ways that both provide compelling support for their approach and raise new testable hypotheses. Amanda Gibson, for her paper “Periodic, parasite-mediated selection for and against sex”, co-authored with Lynda Delph, Daniela Vergara, and Curt Lively (November 2018, 192(5):537-551). This is an impressive exploration of the maintenance of polymorphic reproductive strategies (sexual or asexual) via frequency-dependent co-evolution between host and pathogen. The authors fuse long-term field data and mescocosm experiments to demonstrate that a parasite Microphallus evolves to specialize on whichever host snail type (sexual or asexual) is most common, thereby maintaining host polymorphism. The fusion of experimental and field data is impressive, and yields a major contribution to a fundamental and long-standing subject in evolutionary biology, the maintenance of sexual reproduction. Daniel I. Bolnick, Editor-in-Chief Russell Bonduriansky, Editor Alice Winn, Editor with the 2017 editors who handled many of the 2018 papers, Judith Bronstein, former Editor-in-Chief Yannis Michilakis, former Editor <p><em>The American Naturalist</em> Student Paper Award is for work that was published in 2018 and that was performed primarily by the first author and primarily while she or he was an undergraduate or graduate student. There were over seventy eligible papers.</p> <p>The recipient of the 2019 Student Paper Award is Marta Strecker Shocket, for her paper <a href="https://www.journals.uchicago.edu/doi/full/10.1086/696096">&quot;Temperature drives epidemics in a zooplankton-fungus disease system: a trait-driven approach points to transmission via host foraging&rdquo;</a> (April 2018, 191(4):435-451), co-authored with Alexander Strauss, Jessica Hite, Maja Ijivar, ZDavid Civitello, Meghan Duffy, Carla C&atilde;ceres, and Spencer Hall. This is a remarkable combination of experimental work, modeling, and observational natural history rolled into one. Dr. Shocket and collaborators asked how climate warming will affect the dynamics of disease outbreaks. They emphasize the need for a mechanistic understanding of host-parasite interactions and the role of temperature to generate effective predictions. They develop a trait-based model that considers how temperature affects host foraging rates in a Daphnia-fungus interaction, and parameterized the model with laboratory experiments. They found that warming increased Daphnia foraging rates, which in turn increased fungal transmission success and epidemic size. The Editors appreciated the well-integrated mix of field data, lab experiments, mesocosm experiments, and theory, in service of a mechanistic understanding of species interactions. This paper has the potential to set a new standard for studies of the role of temperature-dependence in disease dynamics.</p><ul> <li><strong>Nicolas Schnedler-Meyer</strong>, for his paper <a href="https://www.journals.uchicago.edu/doi/full/10.1086/697538">&ldquo;Evolution of complex asexual reproductive strategies in jellyfish&rdquo;</a>, coauthored with Simone Pigolotti and Patizio Mariani (July 2018, 192(1):72-80). This paper stood out to us because it presents a simple but elegant model of life history evolution that was solidly grounded in natural history (jellyfish life cycles). The study considers the diversity of asexual modes of reproduction in scyphozoan jellyfish, to describe tradeoffs among dispersal, dormancy, and local spread. Which life history strategy dominates depends on the nature of environmental variation, as the authors demonstrate with an Evolutionary Stable Strategy analysis. Not only do they effectively model which life histories should evolve in which environmental settings for jellyfish, but they do an excellent job of linking their findings to similar kinds of variance discounting adaptations in plants and other animals. They very effectively relate their model results back to published empirical literature, in ways that both provide compelling support for their approach and raise new testable hypotheses.</li> <li><strong>Amanda Gibson,</strong> for her paper <a href="https://www.journals.uchicago.edu/doi/full/10.1086/699829">&ldquo;Periodic, parasite-mediated selection for and against sex&rdquo;</a>, co-authored with Lynda Delph, Daniela Vergara, and Curt Lively (November 2018, 192(5):537-551). This is an impressive exploration of the maintenance of polymorphic reproductive strategies (sexual or asexual) via frequency-dependent co-evolution between host and pathogen. The authors fuse long-term field data and mescocosm experiments to demonstrate that a parasite Microphallus evolves to specialize on whichever host snail type (sexual or asexual) is most common, thereby maintaining host polymorphism. The fusion of experimental and field data is impressive, and yields a major contribution to a fundamental and long-standing subject in evolutionary biology, the maintenance of sexual reproduction.</li> </ul> <p><br /> Daniel I. Bolnick, Editor-in-Chief<br /> Russell Bonduriansky, Editor<br /> Alice Winn, Editor</p> <p>with the 2017 editors who handled many of the 2018 papers,<br /> Judith Bronstein, former Editor-in-Chief<br /> Yannis Michilakis, former Editor</p> Mon, 15 Apr 2019 05:00:00 GMT Call for ASN Graduate Student Representatives https://amnat.org/announcements/NomGCtoECRep.html The American Society of Naturalists Graduate Student Council invites applications for two to three new graduate student representatives to join us! As a member of the Graduate Student Council you have the chance to participate in the workings of the society and interact with many of the great researchers who are members of the ASN. The ASN is committed to developing a variety of initiatives to provide more valuable services to its student members. Representatives take part in several committees that include choosing ASN-sponsored workshops, helping choose winners of the annual student research grant, organizing student events at conferences, participating in various committees, and running the website for grad student ASN members at http://asngrads.com/. Each year we seek new members to join for a 3-year term. We are also open to new roles or ideas for things you think the Grad Council could do to encourage student involvement and interaction among researchers. If you are interested in joining, please email Shengpei Wang (swang74@syr.edu) by June 30th with the subject line “ASN GC application” and attach a single pdf document containing your CV and a short paragraph (less than 1 page) about what you hope to contribute and why you want to join the grad council.Kim Gilbert&nbsp;(GC rep 2014-2015): "Serving on the ASN grad council is a fantastic opportunity to not only meet faculty, post-docs, and students from a wide range of universities, but to become more involved in a great community of researchers in ecology and evolution. You learn about how journal societies run, as well as the ins and outs of organizing conference events. You also serve as an important representative for all graduate student members of the ASN to ensure the society is doing its best to meet student&#39;s needs at conferences or through other opportunities." Emily Weiss (GC rep 2013-2014): Serving on the Grad Council really was an incredibly enriching experience for me, and I hope that many other students will apply and get to have that experience too. Rafael Maia&nbsp;(GC rep 2013-2014): "I served the council for a couple years and strongly recommend it. Great society, exciting possibilities!" Courtney Fitzpatrick&nbsp;(founding GC rep): "Grad students: excellent opportunity to get involved, meet collaborators/mentors, and learn about your scientific society!" <p>The American Society of Naturalists Graduate Student Council invites applications for two to three new graduate student representatives to join us!</p> <p>As a member of the Graduate Student Council you have the chance to participate in the workings of the society and interact with many of the great researchers who are members of the ASN. The ASN is committed to developing a variety of initiatives to provide more valuable services to its student members.</p> <p>Representatives take part in several committees that include choosing ASN-sponsored workshops, helping choose winners of the annual student research grant, organizing student events at conferences, participating in various committees, and running the website for grad student ASN members at <a href="http://asngrads.com/">http://asngrads.com/</a>.</p> <p>Each year we seek new members to join for a 3-year term. We are also open to new roles or ideas for things you think the Grad Council could do to encourage student involvement and interaction among researchers.</p> <p>If you are interested in joining, please email Shengpei Wang (<a href="mailto:swang74@syr.edu?subject=ASN%20GC%20application&amp;body=%20">swang74@syr.edu</a>) by June 30<sup>th</sup> with the subject line &ldquo;ASN GC application&rdquo; and attach a single pdf document containing your CV and a short paragraph (less than 1 page) about what you hope to contribute and why you want to join the grad council.</p><p><strong>Kim Gilbert&nbsp;</strong>(GC rep 2014-2015):<br /> &quot;Serving on the ASN grad council is a fantastic opportunity to not only meet faculty, post-docs, and students from a wide range of universities, but to become more involved in a great community of researchers in ecology and evolution. You learn about how journal societies run, as well as the ins and outs of organizing conference events. You also serve as an important representative for all graduate student members of the ASN to ensure the society is doing its best to meet student&#39;s needs at conferences or through other opportunities.&quot;</p> <p><strong>Emily Weiss (</strong>GC rep 2013-2014):<br /> Serving on the Grad Council really was an incredibly enriching experience for me, and I hope that many other students will apply and get to have that experience too.</p> <p><strong>Rafael Maia&nbsp;</strong>(GC rep 2013-2014):<br /> &quot;I served the council for a couple years and strongly recommend it. Great society, exciting possibilities!&quot;</p> <p><strong>Courtney Fitzpatrick</strong>&nbsp;(founding GC rep):<br /> &quot;Grad students: excellent opportunity to get involved, meet collaborators/mentors, and learn about your scientific society!&quot;</p> Mon, 15 Apr 2019 05:00:00 GMT 2019 Presidential Award https://amnat.org/announcements/ANNPresAwa.html The recipients of the Presidential Award for 2018 are Meike J. Wittmann and Tadashi Fukami, for their paper Eco-Evolutionary Buffering: Rapid Evolution Facilitates Regional Species Coexistence despite Local Priority Effects in the June 2018 issue. The Presidential Award is chosen by the President of the American Society of Naturalists from all of the papers published in The American Naturalist&nbsp;during the preceding calendar year. This paper is a fine example of the synthetic tradition of The American Naturalist, wedding ecology and evolution. Weitmann and Fukami propose an evolutionary hypothesis to solve an ecological conundrum: how can species diversity persist with strong priority effects? They develop a metacommunity model that includes evolution of a costly resistance to interference competition from other species. With the possibility of such evolution, a species which becomes common may evolve to become more invadable by other species, thereby retaining the diversity of the system. With evolution, the regional coexistence of species is possible even with local priority effects. &nbsp; Michael C. Whitlock President, American Society of Naturalists <p>The recipients of the Presidential Award for 2018 are Meike J. Wittmann and Tadashi Fukami, for their paper<a href="https://www.journals.uchicago.edu/doi/full/10.1086/697187"> Eco-Evolutionary Buffering: Rapid Evolution Facilitates Regional Species Coexistence despite Local Priority Effects</a> in the June 2018 issue. The Presidential Award is chosen by the President of the American Society of Naturalists from all of the papers published in <em>The American Naturalist</em>&nbsp;during the preceding calendar year.</p> <p>This paper is a fine example of the synthetic tradition of <em>The American Naturalist, </em>wedding ecology and evolution. Weitmann and Fukami propose an evolutionary hypothesis to solve an ecological conundrum: how can species diversity persist with strong priority effects? They develop a metacommunity model that includes evolution of a costly resistance to interference competition from other species. With the possibility of such evolution, a species which becomes common may evolve to become more invadable by other species, thereby retaining the diversity of the system. With evolution, the regional coexistence of species is possible even with local priority effects.</p> <p>&nbsp;</p> <p>Michael C. Whitlock<br /> President, American Society of Naturalists</p> Mon, 15 Apr 2019 05:00:00 GMT “Seed masting causes fluctuations in optimum litter size and lag load in a seed predator” https://amnat.org/an/newpapers/AugMcAdam.html Read the Article (Just Accepted) Boom-bust cycles in seed production increase seed escape by inducing maladaptation in seed predators Instead of producing similar amounts of seeds each year, some plant species produce very few seeds for several years followed by a bumper seed crop. This boom-bust pattern of seed production is called ‘masting’ and is thought to increase tree fitness by alternately swamping and starving seed predators. In this study, the authors proposed a new idea – perhaps masting causes natural selection on seed predators to differ between these feast and famine conditions. If this changeable selection reduces the abundance of seed predators, this could further increase the benefits of masting. The authors tested this hypothesis using 28 years of data on North American red squirrels in the Yukon Territory of Canada. In many organisms, it is best to produce an intermediate number of offspring. Produce too many and each will be too small to survive. Produce too few and each will survive well, but there won’t be many of them. An intermediate number of offspring optimally balances these two processes. In this study, the authors found that optimum litter size in red squirrels depends on whether it is a mast year for white spruce cones, their main source of food. In bust years for cones, litter sizes of red squirrels closely match optimum litter sizes. But during mast years, when food is plentiful, the optimum litter size is much larger. Red squirrels somehow know when a mast year is coming and produce larger litters in the spring of mast years, but this increase is small compared to the large increase in optimum litter size during mast years. As a result, squirrels don’t recruit as many offspring during mast years as they would have if they had produced larger litters, which is good for tree fitness. So, in addition to swamping and starving seed predators, boom-bust patterns of seed production can also cause seed predators to evolve more frugal life histories that are well suited to common years of low food abundance, but are poorly adapted to less common, resource-rich mast years. Abstract The episodic production of large seed crops by some perennial plants (masting) is known to increase seed escape by alternately starving and swamping seed predators. These pulses of resources might also act as an agent of selection on the life histories of seed predators, which could indirectly enhance seed escape by inducing an evolutionary load on seed predator populations. We measured natural selection on litter size of female North American red squirrels (Tamiasciurus hudsonicus) across 28 years and five white spruce (Picea glauca) masting events. Observed litter sizes were similar to optimum litter sizes during non-mast years but were well below optimum litter sizes during mast years. Mast events, therefore, caused selection for larger litters (β′ = 0.25) and a lag load (L = 0.25) on red squirrels during mast years. Reduced juvenile recruitment associated with this lag load increased the number of spruce cones escaping squirrel predation. Although, offspring and parents often experienced opposite environments with respect to the mast, we found no effect of environmental mismatches across generations on either offspring survival or population growth. Instead, squirrels plastically increased litter sizes in anticipation of mast events, which partially, although not completely, reduced the lag load resulting from this change in food availability. These results, therefore, suggest that in addition to ecological and behavioral effects on seed predators, mast seed production can further enhance seed escape by inducing maladaptation in seed predators through fluctuations in optimal trait values. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703743">Read the Article</a></i> (Just Accepted)</p> <p><b>Boom-bust cycles in seed production increase seed escape by inducing maladaptation in seed predators </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>nstead of producing similar amounts of seeds each year, some plant species produce very few seeds for several years followed by a bumper seed crop. This boom-bust pattern of seed production is called ‘masting’ and is thought to increase tree fitness by alternately swamping and starving seed predators. In this study, the authors proposed a new idea – perhaps masting causes natural selection on seed predators to differ between these feast and famine conditions. If this changeable selection reduces the abundance of seed predators, this could further increase the benefits of masting. </p> <p>The authors tested this hypothesis using 28 years of data on North American red squirrels in the Yukon Territory of Canada. In many organisms, it is best to produce an intermediate number of offspring. Produce too many and each will be too small to survive. Produce too few and each will survive well, but there won’t be many of them. An intermediate number of offspring optimally balances these two processes. In this study, the authors found that optimum litter size in red squirrels depends on whether it is a mast year for white spruce cones, their main source of food. In bust years for cones, litter sizes of red squirrels closely match optimum litter sizes. But during mast years, when food is plentiful, the optimum litter size is much larger. Red squirrels somehow know when a mast year is coming and produce larger litters in the spring of mast years, but this increase is small compared to the large increase in optimum litter size during mast years. As a result, squirrels don’t recruit as many offspring during mast years as they would have if they had produced larger litters, which is good for tree fitness. </p><p>So, in addition to swamping and starving seed predators, boom-bust patterns of seed production can also cause seed predators to evolve more frugal life histories that are well suited to common years of low food abundance, but are poorly adapted to less common, resource-rich mast years. </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 episodic production of large seed crops by some perennial plants (masting) is known to increase seed escape by alternately starving and swamping seed predators. These pulses of resources might also act as an agent of selection on the life histories of seed predators, which could indirectly enhance seed escape by inducing an evolutionary load on seed predator populations. We measured natural selection on litter size of female North American red squirrels (<i>Tamiasciurus hudsonicus</i>) across 28 years and five white spruce (<i>Picea glauca</i>) masting events. Observed litter sizes were similar to optimum litter sizes during non-mast years but were well below optimum litter sizes during mast years. Mast events, therefore, caused selection for larger litters (<i>β′</i> = 0.25) and a lag load (<i>L</i> = 0.25) on red squirrels during mast years. Reduced juvenile recruitment associated with this lag load increased the number of spruce cones escaping squirrel predation. Although, offspring and parents often experienced opposite environments with respect to the mast, we found no effect of environmental mismatches across generations on either offspring survival or population growth. Instead, squirrels plastically increased litter sizes in anticipation of mast events, which partially, although not completely, reduced the lag load resulting from this change in food availability. These results, therefore, suggest that in addition to ecological and behavioral effects on seed predators, mast seed production can further enhance seed escape by inducing maladaptation in seed predators through fluctuations in optimal trait values. </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, 15 Apr 2019 05:00:00 GMT “Ecological and evolutionary stabilities of biotrophism, necrotrophism, and saprotrophism” https://amnat.org/an/newpapers/JulySuzuki.html Read the Article Diverse trophic strategies of fungi are studied theoretically, revealing novel insight into their control and evolution Fungi have diverse strategies for utilizing plants as their nutrient resources. For example, obligate biotrophs like wheat leaf rust reproduce in living hosts, obligate necrotrophs like take-all fungi kill infected hosts and reproduce in dead material, while obligate saprotrophs like fairy ring mushrooms reproduce only in dead plant residues in the environment. What is the most efficient trophic strategy for fungi to utilize a given plant population while ecologically sustaining it? How have such diverse trophic strategies evolved in fungi? To tackle these questions, Sayaki U. Suzuki at CARC/NARO and Akira Sasaki at SOKENDAI attempted to construct an epidemiological model that explores three trophic modes (biotrophic, necrotrophic and saprotrophic transmissions) for fungi to utilize plants. Although their model is simple, consisting only of four states of host plants (susceptible living plant, infected living plant, uninfected dead plant, and infected dead plant), it adequately describes the ecological behavior of plant pathogenic fungi. Using this model, they obtained the threshold condition for the spread of the disease epidemic and reorganized the conventional physiological classification of fungi from the ecological perspective. They then proposed four types of ecological groups corresponding to the patterns of dependence on nutrient resources, either living or dead plants. It is also possible to draw guidelines from this model for controlling crop diseases suitable for each fungal type of nutrient dependency. By analyzing the evolution of virulence in their plant-fungi model, they found that a milder fungal virulence in living plants is always selected for if plant-fungi populations are in a stable (endemic) state. However, with a sufficiently strong necrotrophic transmission rate, the host population densities show sustained cycles, which promotes the evolution towards higher virulence. They refer to this self-reinforcement towards highly virulent necrotrophs as “necrotrophic spiral”. Abstract Fungi have multiple trophic behaviors including biotrophism (parasitism on living hosts), necrotrophism (parasitism through killing host tissues), and saprotrophism (feeding on decaying organic matter). Historical classifications of plant pathogens are based on many different axes, including their trophic dependence on living and dead plants, their pathogenicity and mutualistic relationship to host plants, and their transmission pathways and infection mechanisms. Such diverse classifications are sometimes conflicting with each other. Clarifying the delineations among these groups would promote synthesis of fungal biology with current ecological and evolutionary concepts. To ask when biotrophic, necrotrophic, or saprotrophic fungi are maintained and are favored by selection, we constructed an epidemiological model that describes the transitions between four states of host plants: susceptible living plant (S), infected living plant (I), uninfected dead plant (D), and infected dead plant, or plant residue (R). S and D represent two kinds of resource—living and dead plant tissues—for fungal inocula (I and R). We obtained values for the basic reproductive number (R0), which defines the persistence criteria of fungi. Based on our results, we propose four types of ecological groups corresponding to the patterns of dependence on nutrient resources: (i) parasitism-dependent fungi, characterized by their critical dependence on living plants; (ii) saprotrophism-dependent fungi, characterized by their critical dependence on dead plants; (iii) facultatively dependent fungi, which are neither parasitism nor saprotrophism dependent; and (iv) doubly dependent fungi, which are neither wholly parasitism dependent nor wholly saprotrophism dependent. This grouping can be used to suggest principles for effective pest control. Our model also reveals simple conditions for the evolution of fungal trophic behaviors. We found that, in the absence of a trade-off between virulence and other life history parameters, milder fungal virulence in living plants is always selected for if plant–fungus population dynamics are stable. However, with sufficiently strong necrotrophic transmission, the host population densities show sustained cycles, which promotes the evolution of higher virulence. Epidemiological synthesis of diverse trophism in plant-fungi relationship in our model thus opens the way to discuss the evolution of fungal lifestyles as a function of ecological conditions. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703485">Read the Article</a></i></p> <p><b>Diverse trophic strategies of fungi are studied theoretically, revealing novel insight into their control and evolution </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">F</span>ungi have diverse strategies for utilizing plants as their nutrient resources. For example, <i>obligate biotrophs</i> like wheat leaf rust reproduce in living hosts, <i>obligate necrotrophs</i> like take-all fungi kill infected hosts and reproduce in dead material, while <i>obligate saprotrophs</i> like fairy ring mushrooms reproduce only in dead plant residues in the environment. What is the most efficient trophic strategy for fungi to utilize a given plant population while ecologically sustaining it? How have such diverse trophic strategies evolved in fungi? To tackle these questions, Sayaki U. Suzuki at CARC/NARO and Akira Sasaki at SOKENDAI attempted to construct an epidemiological model that explores three trophic modes (biotrophic, necrotrophic and saprotrophic transmissions) for fungi to utilize plants. Although their model is simple, consisting only of four states of host plants (susceptible living plant, infected living plant, uninfected dead plant, and infected dead plant), it adequately describes the ecological behavior of plant pathogenic fungi. </p><p>Using this model, they obtained the threshold condition for the spread of the disease epidemic and reorganized the conventional physiological classification of fungi from the ecological perspective. They then proposed four types of ecological groups corresponding to the patterns of dependence on nutrient resources, either living or dead plants. It is also possible to draw guidelines from this model for controlling crop diseases suitable for each fungal type of nutrient dependency. </p><p>By analyzing the evolution of virulence in their plant-fungi model, they found that a milder fungal virulence in living plants is always selected for if plant-fungi populations are in a stable (endemic) state. However, with a sufficiently strong necrotrophic transmission rate, the host population densities show sustained cycles, which promotes the evolution towards higher virulence. They refer to this self-reinforcement towards highly virulent necrotrophs as “necrotrophic spiral”.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">F</span>ungi have multiple trophic behaviors including biotrophism (parasitism on living hosts), necrotrophism (parasitism through killing host tissues), and saprotrophism (feeding on decaying organic matter). Historical classifications of plant pathogens are based on many different axes, including their trophic dependence on living and dead plants, their pathogenicity and mutualistic relationship to host plants, and their transmission pathways and infection mechanisms. Such diverse classifications are sometimes conflicting with each other. Clarifying the delineations among these groups would promote synthesis of fungal biology with current ecological and evolutionary concepts. To ask when biotrophic, necrotrophic, or saprotrophic fungi are maintained and are favored by selection, we constructed an epidemiological model that describes the transitions between four states of host plants: susceptible living plant (S), infected living plant (I), uninfected dead plant (D), and infected dead plant, or plant residue (R). S and D represent two kinds of resource—living and dead plant tissues—for fungal inocula (I and R). We obtained values for the basic reproductive number (R0), which defines the persistence criteria of fungi. Based on our results, we propose four types of ecological groups corresponding to the patterns of dependence on nutrient resources: (i) <i>parasitism-dependent fungi</i>, characterized by their critical dependence on living plants; (ii) <i>saprotrophism-dependent fungi</i>, characterized by their critical dependence on dead plants; (iii) <i>facultatively dependent fungi</i>, which are neither parasitism nor saprotrophism dependent; and (iv) <i>doubly dependent fungi</i>, which are neither wholly parasitism dependent nor wholly saprotrophism dependent. This grouping can be used to suggest principles for effective pest control. Our model also reveals simple conditions for the evolution of fungal trophic behaviors. We found that, in the absence of a trade-off between virulence and other life history parameters, milder fungal virulence in living plants is always selected for if plant–fungus population dynamics are stable. However, with sufficiently strong necrotrophic transmission, the host population densities show sustained cycles, which promotes the evolution of higher virulence. Epidemiological synthesis of diverse trophism in plant-fungi relationship in our model thus opens the way to discuss the evolution of fungal lifestyles as a function of ecological conditions. </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, 15 Apr 2019 05:00:00 GMT “Phenotypic plasticity and local adaptation in a wild hibernator evaluated through reciprocal translocation” https://amnat.org/an/newpapers/AugLane-A.html Read the Article Abstract Phenological shifts are the most commonly reported ecological responses to climate change, and can be produced rapidly by phenotypic plasticity. However, both the limits of plasticity, and whether it will be sufficient to maintain local adaptation (or even lead to maladaptation) are less clear. Increased winter precipitation has been shown to lead to phenological delays and corresponding annual decreases in fitness in Columbian ground squirrels (Urocitellus columbianus). We took advantage of natural phenological variation (across elevations) in this species to better assess the extent of phenotypic plasticity in emergence dates and the relationships between emergence dates and individual annual fitness. We coupled a reciprocal translocation experiment with natural monitoring across two populations separated by approximately 500 m in elevation. Individuals in both populations responded plastically to both spring temperature and winter precipitation. Translocated individuals adjusted their emergence dates to approach those of individuals in their adoptive populations, but did differ significantly in their emergence dates from residents. There were no differences in annual fitness among treatment groups, nor selection on emergent date within a year. Phenotypic plasticity is thus sufficient to allow individuals to respond to broad environmental gradients, but the influence of variation in emergence dates on annual fitness requires further investigation. More forthcoming papers &raquo; <!-- <p><i>The DOI will be https://dx.doi.org/10.1086/702313</i></p> --> <p><i><a href="https://dx.doi.org/10.1086/702313">Read the Article</a></i> </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>henological shifts are the most commonly reported ecological responses to climate change, and can be produced rapidly by phenotypic plasticity. However, both the limits of plasticity, and whether it will be sufficient to maintain local adaptation (or even lead to maladaptation) are less clear. Increased winter precipitation has been shown to lead to phenological delays and corresponding annual decreases in fitness in Columbian ground squirrels (<i>Urocitellus columbianus</i>). We took advantage of natural phenological variation (across elevations) in this species to better assess the extent of phenotypic plasticity in emergence dates and the relationships between emergence dates and individual annual fitness. We coupled a reciprocal translocation experiment with natural monitoring across two populations separated by approximately 500 m in elevation. Individuals in both populations responded plastically to both spring temperature and winter precipitation. Translocated individuals adjusted their emergence dates to approach those of individuals in their adoptive populations, but did differ significantly in their emergence dates from residents. There were no differences in annual fitness among treatment groups, nor selection on emergent date within a year. Phenotypic plasticity is thus sufficient to allow individuals to respond to broad environmental gradients, but the influence of variation in emergence dates on annual fitness requires further investigation. </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, 15 Apr 2019 05:00:00 GMT “Hidden Markov models reveal tactical adjustment of temporally-clustered courtship displays in response to the behaviors of a robotic female” https://amnat.org/an/newpapers/JulyPerry.html Read the ArticleTo convince females to mate, males in many species spend a great deal of energy producing vocal and dance displays during courtship. In order to put on a good show for females that are likely to mate with them, males may have to be tactical in how they spend that energy. One way they may do this is by responding to female behaviors that indicate interest (or lack of interest) in mating. Investigators at the University of California, Davis studied whether male greater sage-grouse (Centrocercus urophasianus) adjust their display effort in response to female behaviors. To do so, they tested males on their display grounds in Wyoming with a robotic female, which either imitated the behaviors of real females uninterested in mating (pecking at the ground) or females becoming interested in mating (standing upright and looking toward the male). To determine whether males adjusted their display effort in response to these female behaviors, they analyzed the timing of males’ displays using a hidden Markov model (or HMM). HMMs are a versatile statistical tool that can be adapted to accommodate different types of time series data. Like many species of birds, frogs, and insects, male sage-grouse display in bouts separated by intervals of inactivity. The HMM enabled the researchers to determine that male sage-grouse primarily respond to female behaviors by adjusting their display persistence (rather than their display rate). They also found that these adjustments were directly related to males’ success in convincing real females to mate. Males with more matings were more persistent regardless of robot behavior, while males with fewer matings tended to reserve their display effort for when the robotic female already looked interested. Two simpler statistical techniques that are commonly used to quantify animals’ display effort were much less effective at analyzing the same data set. This study demonstrates that HMMs can be very useful for quantifying changes in animals’ display bout behavior, which will benefit researchers interested in broad questions about the evolution of animal sexual displays. Abstract We present a statistical approach—a custom-built hidden Markov model (HMM)—that is broadly applicable to the analysis of temporally-clustered display events, as found in many animals, including birds, orthopterans, and anurans. This HMM can simultaneously estimate both the expected lengths of each animal’s display bouts and also their within-bout display rates. We highlight the HMM’s ability to estimate changes in animals’ display effort over time and across different social contexts, using data from male greater sage-grouse (Centrocercus urophasianus). Male display effort was modeled across three sites in two experimental treatments (robotic female simulating interested or uninterested behavior) and in the presence or absence of live females. Across contexts, we show that sage-grouse males primarily adjust their bout lengths, rather than their within-bout display rates. Males’ responses to female behavior were correlated with male mating success: males with more matings showed high display persistence regardless of female behavior, while males with fewer matings tended to invest selectively in females that were already showing interest in mating. Additionally, males with higher mating success responded more to female presence versus absence. We conclude with suggestions for adapting our HMM approach for use in other animal systems. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703518">Read the Article</a></i></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>o convince females to mate, males in many species spend a great deal of energy producing vocal and dance displays during courtship. In order to put on a good show for females that are likely to mate with them, males may have to be tactical in how they spend that energy. One way they may do this is by responding to female behaviors that indicate interest (or lack of interest) in mating. Investigators at the University of California, Davis studied whether male greater sage-grouse (<i>Centrocercus urophasianus</i>) adjust their display effort in response to female behaviors. To do so, they tested males on their display grounds in Wyoming with a robotic female, which either imitated the behaviors of real females uninterested in mating (pecking at the ground) or females becoming interested in mating (standing upright and looking toward the male). To determine whether males adjusted their display effort in response to these female behaviors, they analyzed the timing of males’ displays using a hidden Markov model (or HMM). HMMs are a versatile statistical tool that can be adapted to accommodate different types of time series data. </p><p>Like many species of birds, frogs, and insects, male sage-grouse display in bouts separated by intervals of inactivity. The HMM enabled the researchers to determine that male sage-grouse primarily respond to female behaviors by adjusting their display persistence (rather than their display rate). They also found that these adjustments were directly related to males’ success in convincing real females to mate. Males with more matings were more persistent regardless of robot behavior, while males with fewer matings tended to reserve their display effort for when the robotic female already looked interested. Two simpler statistical techniques that are commonly used to quantify animals’ display effort were much less effective at analyzing the same data set. This study demonstrates that HMMs can be very useful for quantifying changes in animals’ display bout behavior, which will benefit researchers interested in broad questions about the evolution of animal sexual displays. </p><hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>e present a statistical approach—a custom-built hidden Markov model (HMM)—that is broadly applicable to the analysis of temporally-clustered display events, as found in many animals, including birds, orthopterans, and anurans. This HMM can simultaneously estimate both the expected lengths of each animal’s display bouts and also their within-bout display rates. We highlight the HMM’s ability to estimate changes in animals’ display effort over time and across different social contexts, using data from male greater sage-grouse (<i>Centrocercus urophasianus</i>). Male display effort was modeled across three sites in two experimental treatments (robotic female simulating interested or uninterested behavior) and in the presence or absence of live females. Across contexts, we show that sage-grouse males primarily adjust their bout lengths, rather than their within-bout display rates. Males’ responses to female behavior were correlated with male mating success: males with more matings showed high display persistence regardless of female behavior, while males with fewer matings tended to invest selectively in females that were already showing interest in mating. Additionally, males with higher mating success responded more to female presence versus absence. We conclude with suggestions for adapting our HMM approach for use in other animal systems. </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, 15 Apr 2019 05:00:00 GMT “A residence time theory for biodiversity” https://amnat.org/an/newpapers/JulyLocey-A.html Read the ArticleAbstract From microorganisms to the largest macroorganisms, much of Earth’s biodiversity is subject to forces of physical turnover. Residence time is the ratio of an ecosystem’s size to its rate of flow and provides a means for understanding the influence of physical turnover on biological systems. Despite its use across scientific disciplines, residence time has not been integrated into the broader understanding of biodiversity, life history, and the assembly of ecological communities. Here, we propose a residence time theory for the growth, activity, abundance, and diversity of traits and taxa in complex ecological systems. Using thousands of stochastic individual-based models to simulate energetically constrained life history processes, we show that our predictions are conceptually sound, mutually compatible, and support ecological relationships that underpin much of biodiversity theory. We discuss the importance of residence time across the ecological hierarchy and propose how residence time can be integrated into theories ranging from population genetics to macroecology. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703456">Read the Article</a></i></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">F</span>rom microorganisms to the largest macroorganisms, much of Earth’s biodiversity is subject to forces of physical turnover. Residence time is the ratio of an ecosystem’s size to its rate of flow and provides a means for understanding the influence of physical turnover on biological systems. Despite its use across scientific disciplines, residence time has not been integrated into the broader understanding of biodiversity, life history, and the assembly of ecological communities. Here, we propose a residence time theory for the growth, activity, abundance, and diversity of traits and taxa in complex ecological systems. Using thousands of stochastic individual-based models to simulate energetically constrained life history processes, we show that our predictions are conceptually sound, mutually compatible, and support ecological relationships that underpin much of biodiversity theory. We discuss the importance of residence time across the ecological hierarchy and propose how residence time can be integrated into theories ranging from population genetics to macroecology. </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, 15 Apr 2019 05:00:00 GMT “Evolution of stress-induced mutagenesis in the presence of horizontal gene transfer” https://amnat.org/an/newpapers/JulyRam.html Read the Article Stress-induced mutagenesis can evolve and increase the adaptation rate even in the presence of horizontal gene transfer Mutations are usually considered random events. However, over the last 20 years it has become apparent that some microbes generate more mutations under stress conditions such as starvation, DNA damage, and antibiotics. In 2012, Ram and Hadany used mathematical models and computer simulations to show that stress-induced mutation is likely to evolve. Their models focused on microbes that do not exchange genes – that is, asexual microbes, as far as we can think of sex as the exchange of genetic material between unrelated individuals. However, several molecular mechanisms in microbes can lead to a primitive kind of sex called horizontal gene transfer, in which small pieces of DNA are transmitted between cells. For example, some microbes will take up DNA molecules from their environment and incorporate it to their genome in a process called transformation. Theory suggests that horizontal gene transfer will decrease the evolutionary advantage of generating new mutations: why should a cell risk mutating, when most mutations are harmful, if instead it can just pick up an advantageous mutation from another cell? In new research published in The&nbsp;American Naturalist, Ram and Hadany test if stress-induced mutation can evolve even in the presence of horizontal gene transfer. They find that although horizontal gene transfer reduces the evolutionary advantage of stress-induced mutation, the latter can still be evolutionary advantageous, especially if horizontal gene transfer is also induced by stress. Moreover, they show that stress-induced mutation accelerates adaptation to new environments. Therefore, the authors suggest that mutation and horizontal gene transfer can complement rather than exclude each other, and that mutation is likely to be correlated with stressful conditions even in microbes that undergo horizontal gene transfer. Abstract Stress-induced mutagenesis has been observed in multiple species of bacteria and yeast. It has been suggested that in asexual populations, a mutator allele that increases the mutation rate during stress can sweep to fixation with the beneficial mutations it generates. However, even asexual microbes can undergo horizontal gene transfer and rare recombination, which typically interfere with the spread of mutator alleles. Here we examine the effect of horizontal gene transfer on the evolutionary advantage of stress-induced mutator alleles. Our results demonstrate that stress-induced mutator alleles are favored by selection even in the presence of horizontal gene transfer, and more so when the mutator alleles also increase the rate of horizontal gene transfer. We suggest that when regulated by stress, mutation and horizontal gene transfer can be complementary, rather than competing, adaptive strategies, and that stress-induced mutagenesis has important implications for evolutionary biology, ecology, and epidemiology, even in the presence of horizontal gene transfer and rare recombination. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703457">Read the Article</a></i></p> <p><b>Stress-induced mutagenesis can evolve and increase the adaptation rate even in the presence of horizontal gene transfer </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>utations are usually considered random events. However, over the last 20 years it has become apparent that some microbes generate more mutations under stress conditions such as starvation, DNA damage, and antibiotics. In 2012, Ram and Hadany used mathematical models and computer simulations to show that stress-induced mutation is likely to evolve. Their models focused on microbes that do not exchange genes – that is, asexual microbes, as far as we can think of sex as the exchange of genetic material between unrelated individuals. However, several molecular mechanisms in microbes can lead to a primitive kind of sex called <i>horizontal gene transfer</i>, in which small pieces of DNA are transmitted between cells. For example, some microbes will take up DNA molecules from their environment and incorporate it to their genome in a process called <i>transformation</i>. Theory suggests that horizontal gene transfer will decrease the evolutionary advantage of generating new mutations: why should a cell risk mutating, when most mutations are harmful, if instead it can just pick up an advantageous mutation from another cell?</p> <p>In new research published in <i>The&nbsp;American Naturalist</i>, Ram and Hadany test if stress-induced mutation can evolve even in the presence of horizontal gene transfer. They find that although horizontal gene transfer reduces the evolutionary advantage of stress-induced mutation, the latter can still be evolutionary advantageous, especially if horizontal gene transfer is also induced by stress. Moreover, they show that stress-induced mutation accelerates adaptation to new environments. Therefore, the authors suggest that mutation and horizontal gene transfer can complement rather than exclude each other, and that mutation is likely to be correlated with stressful conditions even in microbes that undergo horizontal gene transfer. </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>tress-induced mutagenesis has been observed in multiple species of bacteria and yeast. It has been suggested that in asexual populations, a mutator allele that increases the mutation rate during stress can sweep to fixation with the beneficial mutations it generates. However, even asexual microbes can undergo horizontal gene transfer and rare recombination, which typically interfere with the spread of mutator alleles. Here we examine the effect of horizontal gene transfer on the evolutionary advantage of stress-induced mutator alleles. Our results demonstrate that stress-induced mutator alleles are favored by selection even in the presence of horizontal gene transfer, and more so when the mutator alleles also increase the rate of horizontal gene transfer. We suggest that when regulated by stress, mutation and horizontal gene transfer can be complementary, rather than competing, adaptive strategies, and that stress-induced mutagenesis has important implications for evolutionary biology, ecology, and epidemiology, even in the presence of horizontal gene transfer and rare recombination.</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, 15 Apr 2019 05:00:00 GMT “Phenotype-environment matching predicts both positive and negative effects of intraspecific variation” https://amnat.org/an/newpapers/JulyDibble-A.html Read the Article Phenotype matching predicts effects of intraspecific variation on population dynamics and disease epidemics Abstract Natural populations can vary considerably in their genotypic and/or phenotypic diversity. Differences in this intraspecific diversity can have important consequences for contemporary ecological dynamics, but the direction and magnitude of these effects appear inconsistent across studies and systems. Here we proposed and tested the hypothesis that context-dependent ecological effects of altering phenotypic variance are predictable and arise from the relationship between a population’s mean phenotype and the local environmental optimum. By factorially manipulating the mean and variance of a key host trait in environments with and without a lethal parasite, we demonstrate that increasing phenotypic variance can have beneficial effects for host populations (e.g. smaller disease epidemics), but only when the population’s initial phenotype was poorly-matched to the local environment. When phenotypes were initially well-suited to environmental conditions, in contrast, greater phenotypic variance led to larger disease epidemics. Significant reductions in individual susceptibility occurred in both contexts over time, but the mechanisms leading to those reductions differed; strong selection was caused by either a ‘suboptimal’ trait mean and insufficient trait variance, or a ‘near-optimal’ trait mean and too much trait variance. Increasing intraspecific variation is clearly not always beneficial for populations, instead producing predictable ecological and evolutionary effects that depend on environmental context and biological interactions. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/703483">Read the Article</a></i></p> <p><b>Phenotype matching predicts effects of intraspecific variation on population dynamics and disease epidemics </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">N</span>atural populations can vary considerably in their genotypic and/or phenotypic diversity. Differences in this intraspecific diversity can have important consequences for contemporary ecological dynamics, but the direction and magnitude of these effects appear inconsistent across studies and systems. Here we proposed and tested the hypothesis that context-dependent ecological effects of altering phenotypic variance are predictable and arise from the relationship between a population’s mean phenotype and the local environmental optimum. By factorially manipulating the mean and variance of a key host trait in environments with and without a lethal parasite, we demonstrate that increasing phenotypic variance can have beneficial effects for host populations (e.g. smaller disease epidemics), but only when the population’s initial phenotype was poorly-matched to the local environment. When phenotypes were initially well-suited to environmental conditions, in contrast, greater phenotypic variance led to larger disease epidemics. Significant reductions in individual susceptibility occurred in both contexts over time, but the mechanisms leading to those reductions differed; strong selection was caused by either a ‘suboptimal’ trait mean and insufficient trait variance, or a ‘near-optimal’ trait mean and too much trait variance. Increasing intraspecific variation is clearly not always beneficial for populations, instead producing predictable ecological and evolutionary effects that depend on environmental context and biological interactions. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Mon, 15 Apr 2019 05:00:00 GMT The ASN Student Research Award Recipients for 2019 https://amnat.org/announcements/ANNStuResearchAWA.html First Last &nbsp;Research Gaurav Kandlikar Quantifying the effects of soil microbes on California annual plant community dynamics Ken Thompson Biomechanical incompatibilities and mutation-order speciation Katherine Holmes How do community context and plasticity contribute to local adaptation in plants? Kara Million MHC diversity and patterns of parasite infection in Darters (Etheostoma) of Indiana Jessie Mutz The evolvability of density: effects of multiple traits and their evolutionary potential on the density phenotype Andre Moncrieff Multiple hybrid zones in a widespread Amazonian bird reveal different evolutionary processes Sheela Turbek Explaining mismatches between genetic and phenotypic divergence in a rapid radiation of finch-like birds Linyi Zhang Testing the repeatability of ecological speciation under divergent host use across a community of gall -forming insects Suad Yoon Novel immunological interactions as an overlooked aspect of global change: insights from the host range expansion of Lycaeides melissa William Booker The Evolutionary Dynamics of Gene Duplications in Structured Populations 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:100%"> <tbody> <tr> <td>First</td> <td>Last</td> <td>&nbsp;Research</td> </tr> <tr> <td>Gaurav</td> <td>Kandlikar</td> <td>Quantifying the effects of soil microbes on California annual plant community dynamics</td> </tr> <tr> <td>Ken</td> <td>Thompson</td> <td>Biomechanical incompatibilities and mutation-order speciation</td> </tr> <tr> <td>Katherine</td> <td>Holmes</td> <td>How do community context and plasticity contribute to local adaptation in plants?</td> </tr> <tr> <td>Kara</td> <td>Million</td> <td>MHC diversity and patterns of parasite infection in Darters (Etheostoma) of Indiana</td> </tr> <tr> <td>Jessie</td> <td>Mutz</td> <td>The evolvability of density: effects of multiple traits and their evolutionary potential on the density phenotype</td> </tr> <tr> <td>Andre</td> <td>Moncrieff</td> <td>Multiple hybrid zones in a widespread Amazonian bird reveal different evolutionary processes</td> </tr> <tr> <td>Sheela</td> <td>Turbek</td> <td>Explaining mismatches between genetic and phenotypic divergence in a rapid radiation of finch-like birds</td> </tr> <tr> <td>Linyi</td> <td>Zhang</td> <td>Testing the repeatability of ecological speciation under divergent host use across a community of gall -forming insects</td> </tr> <tr> <td>Suad</td> <td>Yoon</td> <td>Novel immunological interactions as an overlooked aspect of global change: insights from the host range expansion of <em>Lycaeides melissa</em></td> </tr> <tr> <td>William</td> <td>Booker</td> <td>The Evolutionary Dynamics of Gene Duplications in Structured Populations</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> Wed, 10 Apr 2019 05:00:00 GMT Outside the Distribution--Pitch your story! Come to the Show! https://amnat.org/announcements/ANNCollider.html Stories are powerful. Whether hilarious or heartbreaking, subversive or soothing, it matters who takes the stage and what stories are told. On June 23, 2019, The Story Collider will host a very special live show at the Evolution Meetings in Providence. This event is co-organized by the Diversity Committees of the ASN, SSB, and SSE with the goal of highlighting the diverse voices of evolutionary biology! Tickets for this event are $15 and available for purchase via the conference registration site.The Story Collider producers and event organizers are now recruiting submissions from story tellers! We are searching for five people to share true, personal stories on the theme Outside the Distribution. All you need at this point is the seed of an idea for your story. It can be about almost anything—an important experiment, a rough day in the field, misadventure, love, loss, and more; but it must be about you. Our format does not include slides or props. It’s not the place for lectures. It’s about lived experiences. Exotic locations and exciting action never hurt, but what we care about is how you’ve grown as a result of the events in your life. If you’re selected for the show, experienced Story Collider producers will work with you for more than a month to help you prepare. Send a brief pitch to stories@storycollider.org&nbsp; with “Evolution Story Idea” in the subject. The deadline for pitches is May 3, 2019. If you are curious or would like some inspiration, read more at https://www.storycollider.org/submissions or browse The Story Collider podcast archive at http://soundcloud.com/the-story-collider. <p>Stories are powerful. Whether hilarious or heartbreaking, subversive or soothing, it matters who takes the stage and what stories are told. On June 23, 2019, The Story Collider will host a very special live show at the Evolution Meetings in Providence. This event is co-organized by the Diversity Committees of the ASN, SSB, and SSE with the goal of highlighting the diverse voices of evolutionary biology!</p> <p>Tickets for this event are$15 and available for purchase via the conference registration site.</p><p>The Story Collider producers and event organizers are now recruiting submissions from story tellers! We are searching for five people to share true, personal stories on the theme <strong>Outside the Distribution</strong>.</p> <p>All you need at this point is the seed of an idea for your story. It can be about almost anything&mdash;an important experiment, a rough day in the field, misadventure, love, loss, and more; but it must be about you. Our format does not include slides or props. It&rsquo;s not the place for lectures. It&rsquo;s about lived experiences. Exotic locations and exciting action never hurt, but what we care about is how you&rsquo;ve grown as a result of the events in your life. If you&rsquo;re selected for the show, experienced Story Collider producers will work with you for more than a month to help you prepare.</p> <p>Send a brief pitch to <a href="mailto:stories@storycollider.org?subject=Evolution%20Story%20Idea">stories@storycollider.org</a>&nbsp; with &ldquo;Evolution Story Idea&rdquo; in the subject. The deadline for pitches is <strong>May 3, 2019</strong>. If you are curious or would like some inspiration, read more at <a href="https://www.storycollider.org/submissions">https://www.storycollider.org/submissions</a> or browse The Story Collider podcast archive at <a href="http://soundcloud.com/the-story-collider.">http://soundcloud.com/the-story-collider.</a></p> Wed, 10 Apr 2019 05:00:00 GMT