ASN RSS http://amnat.org/ Latest press releases and announcements from the ASN en-us Mon, 08 Jan 2018 06:00:00 GMT 60 “Oxygen limitation at the larval stage and the evolution of maternal investment per offspring in aquatic environments” http://amnat.org/an/newpapers/MayRollinson.html The DOI will be http://dx.doi.org/10.1086/696857 Maternal effects on body size are constrained in aquatic systems by O2 transport in larvae, not by the geometry of eggs In aquatic environments, a common observation is that mothers produce small eggs under warm conditions, a pattern that loosely comprises part of the well-known “temperature-size rule”. For decades, it was emphasized that oxygen limitation may drive this pattern in ectotherms: small eggs and embryos evolve in warm environments because metabolic rate of the embryo is high, and large eggs with low surface-area-to-volume ratios would become oxygen-limited. More recently, however, this idea has been turned on its head, as several studies have suggested that egg size per se does not influence the availability of oxygen to embryos, mainly because embryonic oxygen consumption increases with egg size more slowly than does the surface area of the egg that is available for gas exchange. Why then might egg size, and hence maternal investment per offspring, decrease as environmental temperature increases? Drawing from hundreds of amphibian species across two major clades, the authors use comparative methods to show that oxygen limitation at the larval stage, not the egg stage, helps explain variation in investment per offspring in aquatic environments. Large larvae may be oxygen limited because respiratory features, such as gills, are underdeveloped in early life, resulting in diffusive cutaneous oxygen uptake as a primary means of sustaining aerobic activity during a life stage where predation risk is high. This work helps extend the generality of temperature-dependent oxygen limitation as a mechanism driving the temperature-size rule in aquatic systems. Abstract Oxygen limitation and surface-area-to-volume relationships of the egg were long thought to constrain egg size in aquatic environments, but more recent evidence indicates that egg size per se does not influence oxygen availability to embryos. Here, we suggest that investment per offspring is nevertheless constrained in aquatic anamniotes, by virtue of oxygen transport in free-living larvae. Drawing on the well-supported assumption that oxygen limitation is relatively pronounced in aquatic vs terrestrial environments, and that oxygen limitation is particularly severe in warm aquatic environments, we employ comparative methods in the Amphibia to investigate this problem. Across hundreds of species and two major amphibian clades, the slope of species-mean egg diameter over habitat temperature is negative for species with aquatic larvae, but is positive or neutral for species featuring terrestrial eggs and no larvae. Yet, across species with aquatic larvae, the negative slope of egg diameter over temperature is similar whether eggs are laid terrestrially or aquatically, consistent with an oxygen constraint arising at the larval stage. Finally, egg size declines more strongly with temperature for species that cannot breathe aerially prior to metamorphosis, compared to those that can. Our results suggest oxygen transport in larvae, not eggs, constrains investment per offspring. This study further extends the generality of temperature-dependent oxygen limitation as a mechanism driving the temperature-size rule in aquatic systems. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696857 </i></p> <p><b>Maternal effects on body size are constrained in aquatic systems by O<span class="font-size:70%; position:relative; bottom:-0.3em;">2</span> transport in larvae, not by the geometry of eggs </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 aquatic environments, a common observation is that mothers produce small eggs under warm conditions, a pattern that loosely comprises part of the well-known “temperature-size rule”. For decades, it was emphasized that oxygen limitation may drive this pattern in ectotherms: small eggs and embryos evolve in warm environments because metabolic rate of the embryo is high, and large eggs with low surface-area-to-volume ratios would become oxygen-limited. More recently, however, this idea has been turned on its head, as several studies have suggested that egg size per se does not influence the availability of oxygen to embryos, mainly because embryonic oxygen consumption increases with egg size more slowly than does the surface area of the egg that is available for gas exchange. Why then might egg size, and hence maternal investment per offspring, decrease as environmental temperature increases? Drawing from hundreds of amphibian species across two major clades, the authors use comparative methods to show that oxygen limitation at the larval stage, not the egg stage, helps explain variation in investment per offspring in aquatic environments. Large larvae may be oxygen limited because respiratory features, such as gills, are underdeveloped in early life, resulting in diffusive cutaneous oxygen uptake as a primary means of sustaining aerobic activity during a life stage where predation risk is high. This work helps extend the generality of temperature-dependent oxygen limitation as a mechanism driving the temperature-size rule in aquatic 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;">O</span>xygen limitation and surface-area-to-volume relationships of the egg were long thought to constrain egg size in aquatic environments, but more recent evidence indicates that egg size per se does not influence oxygen availability to embryos. Here, we suggest that investment per offspring is nevertheless constrained in aquatic anamniotes, by virtue of oxygen transport in free-living larvae. Drawing on the well-supported assumption that oxygen limitation is relatively pronounced in aquatic vs terrestrial environments, and that oxygen limitation is particularly severe in warm aquatic environments, we employ comparative methods in the Amphibia to investigate this problem. Across hundreds of species and two major amphibian clades, the slope of species-mean egg diameter over habitat temperature is negative for species with aquatic larvae, but is positive or neutral for species featuring terrestrial eggs and no larvae. Yet, across species with aquatic larvae, the negative slope of egg diameter over temperature is similar whether eggs are laid terrestrially or aquatically, consistent with an oxygen constraint arising at the larval stage. Finally, egg size declines more strongly with temperature for species that cannot breathe aerially prior to metamorphosis, compared to those that can. Our results suggest oxygen transport in larvae, not eggs, constrains investment per offspring. This study further extends the generality of temperature-dependent oxygen limitation as a mechanism driving the temperature-size rule in aquatic systems. </p> <!-- <p><a href="http://dx.doi.org/10.1086/696857">Read&nbsp;the&nbsp;Article</a> </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, 02 Jan 2018 06:00:00 GMT “The consequences of polyandry for sibship structures, distributions of relationships and relatedness, and potential for inbreeding in a wild population” http://amnat.org/an/newpapers/MayGermain.html The DOI will be http://dx.doi.org/10.1086/696855 Female mating with multiple males reduces inbreeding potential among her offspring In many species, females produce broods or litters of offspring with multiple fathers, but the actual benefits of this behavior (known as ‘polyandry’) remain largely unknown. One potential benefit could be that producing offspring with several males changes the degree to which a female’s descendants are related and could potentially mate with a relative (‘inbreed’) in the future. Because inbreeding can have severely negative consequences for any resulting offspring, theory predicts that the overall risk of inbreeding within a population should be lower when females produce offspring with multiple males. However, to date, no study has determined the actual effects of this process in wild populations with complex reproductive systems, such as females producing multiple broods or litters with the same or different males over their lifetimes, or where males themselves mate with multiple females. In this study, researchers at the University of Aberdeen and the University of British Columbia used a long-term, island study population of Song Sparrows (Melospiza melodia) to determine the consequences of polyandry for inbreeding risk in future generations. Song sparrows form social pair-bonds where females and males cooperate to raise offspring, but DNA analysis reveals that about 28% of chicks in the population are fathered by a male other than their mother’s social mate. By comparing the actual genetic relatedness among all potential mates in the population with their relatedness had females only produced offspring with their social mate, this study finds that polyandry reduces the chances of inbreeding among close relatives (like full siblings) in future generations, but actually increases the chances of inbreeding among more distant relatives (like half-siblings). The overall conclusion of the study is that while polyandry can lead to some degree of reduced inbreeding in the future, thereby providing a benefit to this behavior, different aspects of mating systems in wild populations can substantially change this effect from what we would expect. Abstract The evolutionary benefits of simultaneous polyandry (female multiple mating within a single reproductive event) remain elusive. One potential benefit could arise if polyandry alters sibship structures and consequent relationships and relatedness among females’ descendants, and thereby intrinsically reduces future inbreeding risk (the ‘indirect inbreeding avoidance hypothesis’). However such effects have not been quantified in naturally complex mating systems that also encompass iteroparity, overlapping generations, sequential polyandry, and polygyny. We used long-term social and genetic pedigree data from song sparrows (Melospiza melodia) to quantify cross-generational consequences of simultaneous polyandry for offspring sibship structures and distributions of relationships and relatedness among possible mates. Simultaneous polyandry decreased full-sibships and increased half-sibships on average, but such effects varied among females and were smaller than would occur in the absence of sequential polyandry or polygyny. Further, while simultaneous polyandry decreased the overall frequencies of possible matings among adult full-sibs, it increased the frequencies of possible matings among adult half-sibs and more distant relatives. These results imply that the intrinsic consequences of simultaneous polyandry for inbreeding risk could cause weak indirect selection on polyandry, but the magnitude and direction of such effects will depend on complex interactions with other mating system components and the form of inbreeding depression. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696855 </i> </p> <p><b>Female mating with multiple males reduces inbreeding potential among her offspring </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 many species, females produce broods or litters of offspring with multiple fathers, but the actual benefits of this behavior (known as ‘polyandry’) remain largely unknown. One potential benefit could be that producing offspring with several males changes the degree to which a female’s descendants are related and could potentially mate with a relative (‘inbreed’) in the future. Because inbreeding can have severely negative consequences for any resulting offspring, theory predicts that the overall risk of inbreeding within a population should be lower when females produce offspring with multiple males. However, to date, no study has determined the actual effects of this process in wild populations with complex reproductive systems, such as females producing multiple broods or litters with the same or different males over their lifetimes, or where males themselves mate with multiple females. </p><p>In this study, researchers at the University of Aberdeen and the University of British Columbia used a long-term, island study population of Song Sparrows (<i>Melospiza melodia</i>) to determine the consequences of polyandry for inbreeding risk in future generations. Song sparrows form social pair-bonds where females and males cooperate to raise offspring, but DNA analysis reveals that about 28% of chicks in the population are fathered by a male other than their mother’s social mate. By comparing the actual genetic relatedness among all potential mates in the population with their relatedness had females only produced offspring with their social mate, this study finds that polyandry reduces the chances of inbreeding among close relatives (like full siblings) in future generations, but actually increases the chances of inbreeding among more distant relatives (like half-siblings). The overall conclusion of the study is that while polyandry can lead to some degree of reduced inbreeding in the future, thereby providing a benefit to this behavior, different aspects of mating systems in wild populations can substantially change this effect from what we would expect. </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 evolutionary benefits of simultaneous polyandry (female multiple mating within a single reproductive event) remain elusive. One potential benefit could arise if polyandry alters sibship structures and consequent relationships and relatedness among females’ descendants, and thereby intrinsically reduces future inbreeding risk (the ‘indirect inbreeding avoidance hypothesis’). However such effects have not been quantified in naturally complex mating systems that also encompass iteroparity, overlapping generations, sequential polyandry, and polygyny. We used long-term social and genetic pedigree data from song sparrows (<i>Melospiza melodia</i>) to quantify cross-generational consequences of simultaneous polyandry for offspring sibship structures and distributions of relationships and relatedness among possible mates. Simultaneous polyandry decreased full-sibships and increased half-sibships on average, but such effects varied among females and were smaller than would occur in the absence of sequential polyandry or polygyny. Further, while simultaneous polyandry decreased the overall frequencies of possible matings among adult full-sibs, it increased the frequencies of possible matings among adult half-sibs and more distant relatives. These results imply that the intrinsic consequences of simultaneous polyandry for inbreeding risk could cause weak indirect selection on polyandry, but the magnitude and direction of such effects will depend on complex interactions with other mating system components and the form of inbreeding depression. </p> <!-- <p><a href="http://dx.doi.org/10.1086/696855">Read&nbsp;the&nbsp;Article</a> </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, 02 Jan 2018 06:00:00 GMT “Selfing can facilitate transitions between pollination syndromes” http://amnat.org/an/newpapers/MayWessinger-A.html The DOI will be http://dx.doi.org/10.1086/696856 A population genetic model suggests delayed selfing can facilitate transitions to hummingbird pollination Abstract Pollinator-mediated selection on plants can favor transitions to a new pollinator depending on the relative abundances and efficiencies of pollinators present in the community. A frequently observed example is the transition from bee pollination to hummingbird pollination. We present a population genetic model that examines whether the ability to inbreed can influence evolutionary change in traits that underlie pollinator attraction. We find that a transition to a more efficient, but less abundant pollinator is favored under a broadened set of ecological conditions if plants are capable of delayed selfing rather than obligately outcrossing. Delayed selfing allows plants carrying an allele that attracts the novel pollinator to reproduce even when this pollinator is rare, providing reproductive assurance. In addition, delayed selfing weakens the effects of Haldane's sieve by increasing the fixation probability for recessive alleles that confer adaptation to the new pollinator. Our model provides novel insight into the paradoxical abundance of recessive mutations in adaptation to hummingbird attraction. It further predicts that transitions to efficient but less abundant pollinators (such as hummingbirds in certain communities) should disproportionately occur in self-compatible lineages. Currently available mating system datasets are consistent with this prediction and we suggest future areas of research that will enable a rigorous test of this theory. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696856 </i> </p> <p><b>A population genetic model suggests delayed selfing can facilitate transitions to hummingbird pollination </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;">P</span>ollinator-mediated selection on plants can favor transitions to a new pollinator depending on the relative abundances and efficiencies of pollinators present in the community. A frequently observed example is the transition from bee pollination to hummingbird pollination. We present a population genetic model that examines whether the ability to inbreed can influence evolutionary change in traits that underlie pollinator attraction. We find that a transition to a more efficient, but less abundant pollinator is favored under a broadened set of ecological conditions if plants are capable of delayed selfing rather than obligately outcrossing. Delayed selfing allows plants carrying an allele that attracts the novel pollinator to reproduce even when this pollinator is rare, providing reproductive assurance. In addition, delayed selfing weakens the effects of Haldane's sieve by increasing the fixation probability for recessive alleles that confer adaptation to the new pollinator. Our model provides novel insight into the paradoxical abundance of recessive mutations in adaptation to hummingbird attraction. It further predicts that transitions to efficient but less abundant pollinators (such as hummingbirds in certain communities) should disproportionately occur in self-compatible lineages. Currently available mating system datasets are consistent with this prediction and we suggest future areas of research that will enable a rigorous test of this theory. </p> <!-- <p><a href="http://dx.doi.org/10.1086/696856">Read&nbsp;the&nbsp;Article</a> </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, 02 Jan 2018 06:00:00 GMT “Maternal effects in a wild songbird are environmentally plastic but only marginally alter the rate of adaptation” http://amnat.org/an/newpapers/MayRamakers.html The DOI will be http://dx.doi.org/10.1086/696847 Bridging the gap between theory and data: Plastic maternal effect in wild bird has limited potential to affect adaptation Genes are not the only source of resemblance between you and your parents. Imagine, for example, how the amount of care that a mother provides influences the condition of her offspring or, more indirectly, how the number of offspring within the brood influences this condition through sibling competition. If the size of a brood negatively influences the condition of each individual offspring, this may create the odd situation where offspring that inherit genes for producing many offspring may actually produce few offspring; this is because they are in a poor condition, as a direct result from growing up with many siblings. We call this a negative maternal effect (NME). Ramakers and colleagues (2018) wondered: if the environment worsens, making raising many offspring difficult, can a population respond by producing fewer offspring, or is it inhibited in doing so because of NMEs? Looking at clutch size in a small woodland bird, the great tit (Parus major), in the Netherlands, they used long-term field observations, experiments, and predictive modelling to predict how populations would respond in case of an environmental change—for the better or the worse—and how NMEs may facilitate or hamper this response. They showed that NMEs indeed exist in the great tit but that in the long run, according to the predictive model, their effect is too small to make a difference in how rapidly a population can respond to new environments. Their work emphasizes that predictive models are important in understanding evolutionary processes, but they need to be backed up by data from actual populations to keep them realistic. Abstract Despite ample evidence for the presence of maternal effects (MEs) in a variety of traits, and strong theoretical indications for their evolutionary consequences, empirical evidence to what extent MEs can influence evolutionary responses to selection remains ambiguous. We tested the degree to which MEs can alter the rate of adaptation of a key life-history trait, clutch size, using an individual-based model approach parameterized with experimental data from a long-term study of great tits (Parus major). We modelled two types of MEs: (i) an environmentally plastic ME, in which the relationship between maternal and offspring clutch size depended on the maternal environment via offspring condition, and (ii) a ‘fixed’ ME, in which this relationship was constant. Although both types of ME affected the rate of adaptation following an abrupt environmental shift, the overall effects were small. We conclude that evolutionary consequences of MEs are modest at best in our study system, at least for the trait and the particular type of ME we considered here. A closer link between theoretical and empirical work on MEs would hence be useful to obtain accurate predictions about the evolutionary consequences of MEs more generally. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696847 </i> </p> <p><b>Bridging the gap between theory and data: Plastic maternal effect in wild bird has limited potential to affect adaptation </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;">G</span>enes are not the only source of resemblance between you and your parents. Imagine, for example, how the amount of care that a mother provides influences the condition of her offspring or, more indirectly, how the number of offspring within the brood influences this condition through sibling competition. If the size of a brood negatively influences the condition of each individual offspring, this may create the odd situation where offspring that inherit genes for producing many offspring may actually produce few offspring; this is because they are in a poor condition, as a direct result from growing up with many siblings. We call this a negative maternal effect (NME). Ramakers and colleagues (2018) wondered: if the environment worsens, making raising many offspring difficult, can a population respond by producing fewer offspring, or is it inhibited in doing so because of NMEs? Looking at clutch size in a small woodland bird, the great tit (<i>Parus major</i>), in the Netherlands, they used long-term field observations, experiments, and predictive modelling to predict how populations would respond in case of an environmental change—for the better or the worse—and how NMEs may facilitate or hamper this response. They showed that NMEs indeed exist in the great tit but that in the long run, according to the predictive model, their effect is too small to make a difference in how rapidly a population can respond to new environments. Their work emphasizes that predictive models are important in understanding evolutionary processes, but they need to be backed up by data from actual populations to keep them realistic.</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 ample evidence for the presence of maternal effects (MEs) in a variety of traits, and strong theoretical indications for their evolutionary consequences, empirical evidence to what extent MEs can influence evolutionary responses to selection remains ambiguous. We tested the degree to which MEs can alter the rate of adaptation of a key life-history trait, clutch size, using an individual-based model approach parameterized with experimental data from a long-term study of great tits (<i>Parus major</i>). We modelled two types of MEs: (i) an environmentally plastic ME, in which the relationship between maternal and offspring clutch size depended on the maternal environment via offspring condition, and (ii) a ‘fixed’ ME, in which this relationship was constant. Although both types of ME affected the rate of adaptation following an abrupt environmental shift, the overall effects were small. We conclude that evolutionary consequences of MEs are modest at best in our study system, at least for the trait and the particular type of ME we considered here. A closer link between theoretical and empirical work on MEs would hence be useful to obtain accurate predictions about the evolutionary consequences of MEs more generally. </p> <!-- <p><a href="http://dx.doi.org/10.1086/696847">Read&nbsp;the&nbsp;Article</a> </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, 02 Jan 2018 06:00:00 GMT “Host traits drive viral life histories across phytoplankton viruses” http://amnat.org/an/newpapers/MayEdwards-A.html The DOI will be http://dx.doi.org/10.1086/696849 Burst size and latent period across diverse phytoplankton viruses can be explained in terms of life history evolution Abstract Viruses are integral to ecological and evolutionary processes, but we have a poor understanding of what drives variation in key traits across diverse viruses. For lytic viruses, burst size, latent period, and genome size are primary characteristics controlling host-virus dynamics. Here we synthesize data on these traits for 75 strains of phytoplankton viruses, which play an important role in global biogeochemistry. We find that primary traits of the host (genome size, growth rate) explain 40-50% of variation in burst size and latent period. Specifically, burst size and latent period both exhibit saturating relationships vs. the host:virus genome size ratio, with both traits increasing at low genome size ratios while showing no relationship at high size ratios. In addition, latent period declines as host growth rate increases. We analyze a model of latent period evolution to explore mechanisms that could cause these patterns. The model predicts that burst size may often be set by the host genomic resources available for viral construction, while latent period evolves to permit this maximal burst size, modulated by host metabolic rate. These results suggest that general mechanisms may underlie the evolution of diverse viruses. Future extensions of this work could help explain viral regulation of host populations, viral influence on community structure and diversity, and viral roles in biogeochemical cycles. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696849 </i></p> <p><b>Burst size and latent period across diverse phytoplankton viruses can be explained in terms of life history evolution </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;">V</span>iruses are integral to ecological and evolutionary processes, but we have a poor understanding of what drives variation in key traits across diverse viruses. For lytic viruses, burst size, latent period, and genome size are primary characteristics controlling host-virus dynamics. Here we synthesize data on these traits for 75 strains of phytoplankton viruses, which play an important role in global biogeochemistry. We find that primary traits of the host (genome size, growth rate) explain 40-50% of variation in burst size and latent period. Specifically, burst size and latent period both exhibit saturating relationships vs. the host:virus genome size ratio, with both traits increasing at low genome size ratios while showing no relationship at high size ratios. In addition, latent period declines as host growth rate increases. We analyze a model of latent period evolution to explore mechanisms that could cause these patterns. The model predicts that burst size may often be set by the host genomic resources available for viral construction, while latent period evolves to permit this maximal burst size, modulated by host metabolic rate. These results suggest that general mechanisms may underlie the evolution of diverse viruses. Future extensions of this work could help explain viral regulation of host populations, viral influence on community structure and diversity, and viral roles in biogeochemical cycles. </p> <!-- <p><a href="http://dx.doi.org/10.1086/696849">Read&nbsp;the&nbsp;Article</a> </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, 02 Jan 2018 06:00:00 GMT “Overdispersed spatial patterning of dominant bunchgrasses in southeastern pine savannas” http://amnat.org/an/newpapers/MayHovanes-A.html The DOI will be http://dx.doi.org/10.1086/696834 Bunchgrasses are spatially overdispersed in pine savannas; this may affect population, community, and ecosystem dynamics Abstract Spatial patterning is a key natural history attribute of sessile organisms that frequently emerges from and dictates potential for interactions among organisms. We tested whether bunchgrasses, the dominant plant functional group in longleaf pine savanna groundcover communities, are non-randomly patterned by characterizing the spatial dispersion of three bunchgrass species across six sites in Louisiana and Florida. We mapped bunchgrass tussocks > 5.0-cm basal diameter in three 3×3-m plots in each site. We modeled tussocks as two-dimensional objects to analyze their spatial relationships while preserving sizes and shapes of individual tussocks. Tussocks were overdispersed (more regularly spaced than random) for all species and sites at the local interaction scale (<&nbsp;0.3&nbsp;m). This general pattern likely arises from a tussock-centered, distance-dependent mechanism e.g., inter-tussock competition. Non-random spatial patterns of dominant species have implications for community assembly and ecosystem function in tussock-dominated grasslands and savannas, including those characterized by extreme biodiversity. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696834 </i></p> <p><b>Bunchgrasses are spatially overdispersed in pine savannas; this may affect population, community, and ecosystem dynamics </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;">S</span>patial patterning is a key natural history attribute of sessile organisms that frequently emerges from and dictates potential for interactions among organisms. We tested whether bunchgrasses, the dominant plant functional group in longleaf pine savanna groundcover communities, are non-randomly patterned by characterizing the spatial dispersion of three bunchgrass species across six sites in Louisiana and Florida. We mapped bunchgrass tussocks > 5.0-cm basal diameter in three 3×3-m plots in each site. We modeled tussocks as two-dimensional objects to analyze their spatial relationships while preserving sizes and shapes of individual tussocks. Tussocks were overdispersed (more regularly spaced than random) for all species and sites at the local interaction scale (<&nbsp;0.3&nbsp;m). This general pattern likely arises from a tussock-centered, distance-dependent mechanism e.g., inter-tussock competition. Non-random spatial patterns of dominant species have implications for community assembly and ecosystem function in tussock-dominated grasslands and savannas, including those characterized by extreme biodiversity. </p> <!-- <p><a href="http://dx.doi.org/10.1086/696834">Read&nbsp;the&nbsp;Article</a> </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, 02 Jan 2018 06:00:00 GMT “Intraspecific variation in learning: worker wasps are less able to learn and remember individual conspecific faces than queen wasps” http://amnat.org/an/newpapers/MayTibbetts-A.html The DOI will be http://dx.doi.org/10.1086/696848 Worker paper wasps have lower individual recognition ability than queens, even though castes are flexible Abstract Research on individual recognition often focuses on species-typical recognition abilities rather than assessing intraspecific variation in recognition. As individual recognition is cognitively costly, the capacity for recognition may vary within species. We test how individual face recognition differs between nest-founding queens (foundresses) and workers in Polistes fuscatus paper wasps. Individual recognition mediates dominance interactions among foundresses. Three previously published experiments have shown that foundresses (1) benefit by advertising their identity with distinctive facial patterns that facilitate recognition, (2) have robust memories of individuals, and 3)rapidly learn to distinguish between face images. Like foundresses, workers have variable facial patterns and are capable of individual recognition. However, worker dominance interactions are muted. Therefore, individual recognition may be less important for workers than foundresses. We find: (1) workers with unique faces receive similar amounts of aggression as workers with common faces, indicating that wasps do not benefit from advertising their individual identity with a unique appearance, (2) workers lack robust memories for individuals, as they cannot remember unique conspecifics after a six-day separation and (3) workers learn to distinguish between facial images more slowly than foundresses during training. The recognition differences between foundresses and workers are notable because Polistes lack discrete castes; foundresses and workers are morphologically similar and workers can take over as queens. Overall, social benefits and receiver capacity for individual recognition are surprisingly plastic. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696848 </i> </p> <p><b>Worker paper wasps have lower individual recognition ability than queens, even though castes are flexible </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;">R</span>esearch on individual recognition often focuses on species-typical recognition abilities rather than assessing intraspecific variation in recognition. As individual recognition is cognitively costly, the capacity for recognition may vary within species. We test how individual face recognition differs between nest-founding queens (foundresses) and workers in <i>Polistes fuscatus</i> paper wasps. Individual recognition mediates dominance interactions among foundresses. Three previously published experiments have shown that foundresses (1) benefit by advertising their identity with distinctive facial patterns that facilitate recognition, (2) have robust memories of individuals, and 3)rapidly learn to distinguish between face images. Like foundresses, workers have variable facial patterns and are capable of individual recognition. However, worker dominance interactions are muted. Therefore, individual recognition may be less important for workers than foundresses. We find: (1) workers with unique faces receive similar amounts of aggression as workers with common faces, indicating that wasps do not benefit from advertising their individual identity with a unique appearance, (2) workers lack robust memories for individuals, as they cannot remember unique conspecifics after a six-day separation and (3) workers learn to distinguish between facial images more slowly than foundresses during training. The recognition differences between foundresses and workers are notable because <i>Polistes</i> lack discrete castes; foundresses and workers are morphologically similar and workers can take over as queens. Overall, social benefits and receiver capacity for individual recognition are surprisingly plastic. </p> <!-- <p> <a href="http://dx.doi.org/10.1086/696848">Read&nbsp;the&nbsp;Article</a> </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, 02 Jan 2018 06:00:00 GMT “Model adequacy and microevolutionary explanations for stasis in the fossil record” http://amnat.org/an/newpapers/AprVoje-A.html The DOI will be http://dx.doi.org/10.1086/696265 Tests of microevolutionary explanations for stasis in the fossil record using adequacy tests Abstract Long-term phenotypic stasis is frequently observed in the fossil record, but not readily predicted from microevolutionary theory. To test competing explanations for stasis on macroevolutionary time scales we need reliably estimated parameters from appropriate evolutionary models that adequately describe the evolutionary trait dynamics. Here, we develop tests to assess the adequacy of the most commonly used stasis model in evolutionary biology and apply them to time series of phenotypic traits from fossil lineages. Of the 572 fossil time series we analyzed from the literature, 263 times series showed a better fit to the stasis model relative to alternative models, but only 172 of those fitted the stasis model both in relative and absolute terms. The estimated trait variances from these 172 time series do not correlate with rough proxies of effective population size. Our preliminary investigation of the fixed-optimum hypothesis hence fails to give empirical support to the idea that genetic drift around a constant trait optimum is an explanation for stasis in the fossil record. We argue that optima following stationary processes on the adaptive landscape is a viable hypothesis for stasis that needs further investigation. We end by discussing how investigations of model adequacy can be a valuable approach for increasing our understanding of the dynamics of the adaptive landscape on macroevolutionary time scales. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696265 </i></p> <p><b>Tests of microevolutionary explanations for stasis in the fossil record using adequacy tests </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;">L</span>ong-term phenotypic stasis is frequently observed in the fossil record, but not readily predicted from microevolutionary theory. To test competing explanations for stasis on macroevolutionary time scales we need reliably estimated parameters from appropriate evolutionary models that adequately describe the evolutionary trait dynamics. Here, we develop tests to assess the adequacy of the most commonly used stasis model in evolutionary biology and apply them to time series of phenotypic traits from fossil lineages. Of the 572 fossil time series we analyzed from the literature, 263 times series showed a better fit to the stasis model relative to alternative models, but only 172 of those fitted the stasis model both in relative and absolute terms. The estimated trait variances from these 172 time series do not correlate with rough proxies of effective population size. Our preliminary investigation of the fixed-optimum hypothesis hence fails to give empirical support to the idea that genetic drift around a constant trait optimum is an explanation for stasis in the fossil record. We argue that optima following stationary processes on the adaptive landscape is a viable hypothesis for stasis that needs further investigation. We end by discussing how investigations of model adequacy can be a valuable approach for increasing our understanding of the dynamics of the adaptive landscape on macroevolutionary time scales. </p> <!-- <p><a href="http://dx.doi.org/10.1086/696265">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 05 Dec 2017 06:00:00 GMT “Inferring causalities in landscape genetics: An extension of Wright’s causal modeling to distance matrices” http://amnat.org/an/newpapers/AprFourtune-A.html The DOI will be http://dx.doi.org/10.1086/696233 Researchers present new methods extending causal modeling (path analysis and the d-sep test) to distance matrices Abstract Identifying landscape features that affect functional connectivity among populations is a major challenge in fundamental and applied sciences. Landscape genetics combines landscape and genetic data to address this issue, with the main objective of disentangling direct and indirect relationships among an intricate set of variables. Causal modeling has strong potential to address the complex nature of landscape genetic datasets. However, this statistical approach was not initially developed to address the pairwise distance matrices commonly used in landscape genetics. Here, we aimed to extend the applicability of two causal modeling methods, i.e., maximum-likelihood path analysis and the directional-separation test, by developing statistical approaches aimed at handling distance matrices and improving functional connectivity inference. Using simulations, we showed that these approaches greatly improved the robustness of the absolute (using a frequentist approach) and relative (using an information-theoretic approach) fit of the tested models. We used an empirical dataset combining genetic information on a freshwater fish species (Gobio occitaniae) and detailed landscape descriptors to demonstrate the usefulness of causal modeling to identify functional connectivity in wild populations. Specifically, we demonstrated how direct and indirect relationships involving altitude, temperature and oxygen concentration influenced within- and between-population genetic diversity of G.&nbsp;occitaniae. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696233 </i></p> <p><b>Researchers present new methods extending causal modeling (path analysis and the d-sep test) to distance matrices </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>dentifying landscape features that affect functional connectivity among populations is a major challenge in fundamental and applied sciences. Landscape genetics combines landscape and genetic data to address this issue, with the main objective of disentangling direct and indirect relationships among an intricate set of variables. Causal modeling has strong potential to address the complex nature of landscape genetic datasets. However, this statistical approach was not initially developed to address the pairwise distance matrices commonly used in landscape genetics. Here, we aimed to extend the applicability of two causal modeling methods, i.e., maximum-likelihood path analysis and the directional-separation test, by developing statistical approaches aimed at handling distance matrices and improving functional connectivity inference. Using simulations, we showed that these approaches greatly improved the robustness of the absolute (using a frequentist approach) and relative (using an information-theoretic approach) fit of the tested models. We used an empirical dataset combining genetic information on a freshwater fish species (<i>Gobio occitaniae</i>) and detailed landscape descriptors to demonstrate the usefulness of causal modeling to identify functional connectivity in wild populations. Specifically, we demonstrated how direct and indirect relationships involving altitude, temperature and oxygen concentration influenced within- and between-population genetic diversity of <i>G.&nbsp;occitaniae</i>. </p> <!-- <p><a href="http://dx.doi.org/10.1086/696233">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 05 Dec 2017 06:00:00 GMT “Temperature drives epidemics in a zooplankton-fungus disease system: a trait-driven approach points to transmission via host foraging” http://amnat.org/an/newpapers/AprShocket-A.html The DOI will be http://dx.doi.org/10.1086/696096 Warmer temperatures increase transmission rate (via host foraging) & drive bigger fungal epidemics in zooplankton Abstract Climatic warming will likely have idiosyncratic impacts on infectious diseases, causing some to increase while others decrease or shift geographically. A mechanistic framework could better predict these different temperature-disease outcomes. However, such a framework remains challenging to develop, due to the non-linear and (sometimes) opposing thermal responses of different host and parasite traits, and due to the difficulty of validating model predictions with observations and experiments. We address these challenges in a zooplankton-fungus (Daphnia dentifera–Metschnikowia bicuspidata) system. We test the hypothesis that warmer temperatures promote disease spread and produce larger epidemics. In lakes, epidemics that start earlier and warmer in autumn grow much larger. In a mesocosm experiment, warmer temperatures produced larger epidemics. A mechanistic model parameterized with trait assays revealed that this pattern arose primarily from the temperature-dependence of transmission rate (β), governed by the increasing foraging (and hence parasite exposure) rate of hosts (f). In the trait assays, parasite production seemed sufficiently responsive to shape epidemics as well; however, this trait proved too thermally insensitive in the mesocosm experiment and lake survey to matter much. Thus, in warmer environments, increased foraging of hosts raised transmission rate, yielding bigger epidemics through a potentially general, exposure-based mechanism for ectotherms. This mechanistic approach highlights how a trait-based framework will enhance predictive insight into responses of infectious disease to a warmer world. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696096 </i> </p> <p><b>Warmer temperatures increase transmission rate (via host foraging) & drive bigger fungal epidemics in zooplankton </b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">C</span>limatic warming will likely have idiosyncratic impacts on infectious diseases, causing some to increase while others decrease or shift geographically. A mechanistic framework could better predict these different temperature-disease outcomes. However, such a framework remains challenging to develop, due to the non-linear and (sometimes) opposing thermal responses of different host and parasite traits, and due to the difficulty of validating model predictions with observations and experiments. We address these challenges in a zooplankton-fungus (<i>Daphnia dentifera&ndash;Metschnikowia bicuspidata</i>) system. We test the hypothesis that warmer temperatures promote disease spread and produce larger epidemics. In lakes, epidemics that start earlier and warmer in autumn grow much larger. In a mesocosm experiment, warmer temperatures produced larger epidemics. A mechanistic model parameterized with trait assays revealed that this pattern arose primarily from the temperature-dependence of transmission rate (<i>β</i>), governed by the increasing foraging (and hence parasite exposure) rate of hosts (<i>f</i>). In the trait assays, parasite production seemed sufficiently responsive to shape epidemics as well; however, this trait proved too thermally insensitive in the mesocosm experiment and lake survey to matter much. Thus, in warmer environments, increased foraging of hosts raised transmission rate, yielding bigger epidemics through a potentially general, exposure-based mechanism for ectotherms. This mechanistic approach highlights how a trait-based framework will enhance predictive insight into responses of infectious disease to a warmer world. </p> <!-- <p> <a href="http://dx.doi.org/10.1086/696096">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 05 Dec 2017 06:00:00 GMT “Neglected patterns of variation in phenotypic plasticity: Age- and sex-specific antipredator plasticity in a cichlid fish” http://amnat.org/an/newpapers/AprMeuthen.html The DOI will be http://dx.doi.org/10.1086/696264 This study indicates sex- and age-specific phenotypic plasticity whose patterns correspond to theoretical predictions Organisms are to some extent able to flexibly adjust their morphology, physiology, and behavior to current environmental conditions. This so-called “phenotypic plasticity” is beneficial because the environment often fluctuates and so does the presence of predators. However, long-term effects of developing and living in the presence of predator cues are largely unexplored. Denis Meuthen, Timo Thünken, and colleagues from the Theo Bakker lab at the University of Bonn, Germany, aimed to fill this gap by conducting a comprehensive experiment on Pelvicachromis taeniatus, an African cichlid fish with bright coloration in both sexes. Over more than two years, they investigated morphological and color development of fish that were regularly exposed to conspecific alarm cues – which signal the presence of predators. Based on photographs taken at six developmental stages from juveniles to reproductively active adults, the researchers show that predator effects are present, but neither consistently nor uniformly expressed across sexes and life stages. In an early juvenile stage, alarm-cue exposed fish developed beneficial morphological responses such as increased body size, longer dorsal spines and increased eye diameters, all of which are adaptations to reduce predation risk. In an early adult stage, alarm-cue exposed males showed delayed expression of nuptial body coloration, but invested in body size. In males of other developmental stages as well as in adult females, the researchers did not find any significant effects. These results suggest that phenotypic plasticity optimizes predator-defense traits during vulnerable developmental stages such as during early life and shortly prior to reproduction. This study is part of Denis Meuthen’s PhD thesis focusing on intragenerational antipredator phenotypic plasticity. As postdoc he is currently studying transgenerational phenotypic plasticity in fathead minnows at the University of Saskatchewan, Canada. The senior author Timo Thünken is interested in how variation in the developmental environment affects animals’ behavior and also in sexual selection, focusing on adaptive inbreeding in P.&nbsp;taeniatus. Abstract The ability of organisms to plastically respond to changing environments is well studied. However, variation in phenotypic plasticity during ontogeny is less well understood despite its relevance of being an important source of phenotypic variation in nature. Here, we comprehensively study ontogenetic variation in morphological antipredator plasticity across multiple traits in Pelvicachromis taeniatus, a Western African cichlid fish with sexually dimorphic ornamentation. In a split-clutch design, fish were raised under different levels of perceived predation risk (conspecific alarm cues or distilled water). Morphological plasticity varied substantially across ontogeny: it was first observable at an early juvenile stage where alarm cue-exposed fish grew faster. Subsequently, significant plasticity was absent until the onset of sexual maturity. Here, alarm-cue-exposed males were bigger than control males, which led to deeper bodies, longer dorsal spines, bigger caudal peduncles and increased eye diameters. Sexual ornamentation emerged delayed in alarm cue-exposed males. In later adulthood, the plastic responses receded. Despite small effect sizes, these responses represent putative adaptive plasticity as they are likely to reduce predation risk. In females, we did not observe any plasticity. In accordance with theory, these results suggest fine-tuned expression of plasticity that potentially increases defenses during vulnerable developmental stages and reproductive output. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696264 </i></p> <p><b>This study indicates sex- and age-specific phenotypic plasticity whose patterns correspond to theoretical predictions </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>rganisms are to some extent able to flexibly adjust their morphology, physiology, and behavior to current environmental conditions. This so-called “phenotypic plasticity” is beneficial because the environment often fluctuates and so does the presence of predators. However, long-term effects of developing and living in the presence of predator cues are largely unexplored. Denis Meuthen, Timo Thünken, and colleagues from the Theo Bakker lab at the University of Bonn, Germany, aimed to fill this gap by conducting a comprehensive experiment on <i>Pelvicachromis taeniatus</i>, an African cichlid fish with bright coloration in both sexes. Over more than two years, they investigated morphological and color development of fish that were regularly exposed to conspecific alarm cues – which signal the presence of predators. Based on photographs taken at six developmental stages from juveniles to reproductively active adults, the researchers show that predator effects are present, but neither consistently nor uniformly expressed across sexes and life stages. In an early juvenile stage, alarm-cue exposed fish developed beneficial morphological responses such as increased body size, longer dorsal spines and increased eye diameters, all of which are adaptations to reduce predation risk. In an early adult stage, alarm-cue exposed males showed delayed expression of nuptial body coloration, but invested in body size. In males of other developmental stages as well as in adult females, the researchers did not find any significant effects. These results suggest that phenotypic plasticity optimizes predator-defense traits during vulnerable developmental stages such as during early life and shortly prior to reproduction. </p> <p>This study is part of Denis Meuthen’s PhD thesis focusing on intragenerational antipredator phenotypic plasticity. As postdoc he is currently studying transgenerational phenotypic plasticity in fathead minnows at the University of Saskatchewan, Canada. The senior author Timo Thünken is interested in how variation in the developmental environment affects animals’ behavior and also in sexual selection, focusing on adaptive inbreeding in <i>P.&nbsp;taeniatus</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>he ability of organisms to plastically respond to changing environments is well studied. However, variation in phenotypic plasticity during ontogeny is less well understood despite its relevance of being an important source of phenotypic variation in nature. Here, we comprehensively study ontogenetic variation in morphological antipredator plasticity across multiple traits in <i>Pelvicachromis taeniatus</i>, a Western African cichlid fish with sexually dimorphic ornamentation. In a split-clutch design, fish were raised under different levels of perceived predation risk (conspecific alarm cues or distilled water). Morphological plasticity varied substantially across ontogeny: it was first observable at an early juvenile stage where alarm cue-exposed fish grew faster. Subsequently, significant plasticity was absent until the onset of sexual maturity. Here, alarm-cue-exposed males were bigger than control males, which led to deeper bodies, longer dorsal spines, bigger caudal peduncles and increased eye diameters. Sexual ornamentation emerged delayed in alarm cue-exposed males. In later adulthood, the plastic responses receded. Despite small effect sizes, these responses represent putative adaptive plasticity as they are likely to reduce predation risk. In females, we did not observe any plasticity. In accordance with theory, these results suggest fine-tuned expression of plasticity that potentially increases defenses during vulnerable developmental stages and reproductive output. <!-- <a href="http://dx.doi.org/10.1086/696264">Read&nbsp;the&nbsp;Article</a> --></p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 05 Dec 2017 06:00:00 GMT “Calculating competitive intransitivity: Computational challenges” http://amnat.org/an/newpapers/AprLaird.html The DOI will be http://dx.doi.org/10.1086/696266 Intransitivity indices based on competitive reversals can only be computed exactly for species-poor systems In ‘intransitive’ competition within a group of species, species cannot be listed in a strict hierarchy in which those higher on the list outcompete those lower on the list but never vice versa; rather, in intransitive competition, species form loops, where, for example, species A outcompetes species B, and B outcompetes C, but C outcompetes A. Thus, intransitive competition can be likened to the familiar game of rock-paper-scissors (‘RPS’). Intransitive competition is found in numerous natural systems, such as in plant communities, in lizard populations, in bacterial films, and in coral reefs. Moreover, it is important in community ecology because it may promote species coexistence through the phenomenon of indirect facilitation (i.e., ‘the enemy of my enemy is my friend’). Real communities usually have more than three species, leading to many more possible competitive interrelationships that the simple ‘hierarchy versus RPS’ scenario. Measuring competitive intransitivity in species-rich communities is therefore an important task. In such systems, one way of measuring intransitivity is to consider the minimum number of hypothetical reversals (i.e., converting ‘A outcompetes B’ to ‘B outcompetes A’) that would need to be applied to an assemblage to make it a perfect hierarchy—systems that require more reversals are relatively more intransitive than those that require fewer. While such an approach is intuitively appealing, Robert Laird (University of Lethbridge) and Brandon Schamp (Algoma University) demonstrate that a previous attempt at creating such an index had incorrect formulas. More broadly, by connecting this ‘reversal-based method’ with an equivalent problem from graph theory, Laird and Schamp show that there is no feasible way to compute an exact number of reversals for anything but species-poor communities. For this reason, they emphasize other intransitivity indices, based on the proportion of three-species subsets that engage in rock-paper-scissors competition, as viable (and computable) alternatives. Abstract Intransitive, or ‘rock-paper-scissors’ competition is compelling because it promotes species coexistence and because recent work suggests it may be common in natural systems. One class of intransitivity indices works by considering s, the minimum number of competitive reversals to convert a given competitive community (i.e., a ‘tournament’) to a hierarchy. The most straightforward example of such ‘reversal-based’ indices is Petraitis’ index, t = 1 − s/M, where M is the maximum s across all possible n-species tournaments. Using exhaustive searches, we prove that Petraitis’ formula for M (and, therefore, t) does not hold for n ≥ 7. Furthermore, the determination of s for even moderate values of n may prove difficult, as the equivalent graph-theoretical problem is NP-hard; there is no known computationally feasible way to compute an exact answer for anything but small values of n, let alone a closed-form solution. Petraitis’ t is a valuable index of intransitivity; however, at present its use is limited to relatively species-poor systems. More broadly, reversal-based indices, while intuitive, may be problematic because of this computability issue. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696266 </i></p> <p><b>Intransitivity indices based on competitive reversals can only be computed exactly for species-poor systems </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 ‘intransitive’ competition within a group of species, species cannot be listed in a strict hierarchy in which those higher on the list outcompete those lower on the list but never vice versa; rather, in intransitive competition, species form loops, where, for example, species A outcompetes species B, and B outcompetes C, but C outcompetes A. Thus, intransitive competition can be likened to the familiar game of rock-paper-scissors (‘RPS’). Intransitive competition is found in numerous natural systems, such as in plant communities, in lizard populations, in bacterial films, and in coral reefs. Moreover, it is important in community ecology because it may promote species coexistence through the phenomenon of indirect facilitation (i.e., ‘the enemy of my enemy is my friend’). Real communities usually have more than three species, leading to many more possible competitive interrelationships that the simple ‘hierarchy versus RPS’ scenario. Measuring competitive intransitivity in species-rich communities is therefore an important task. In such systems, one way of measuring intransitivity is to consider the minimum number of hypothetical reversals (i.e., converting ‘A outcompetes B’ to ‘B outcompetes A’) that would need to be applied to an assemblage to make it a perfect hierarchy—systems that require more reversals are relatively more intransitive than those that require fewer. While such an approach is intuitively appealing, Robert Laird (University of Lethbridge) and Brandon Schamp (Algoma University) demonstrate that a previous attempt at creating such an index had incorrect formulas. More broadly, by connecting this ‘reversal-based method’ with an equivalent problem from graph theory, Laird and Schamp show that there is no feasible way to compute an exact number of reversals for anything but species-poor communities. For this reason, they emphasize other intransitivity indices, based on the proportion of three-species subsets that engage in rock-paper-scissors competition, as viable (and computable) alternatives. </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>ntransitive, or ‘rock-paper-scissors’ competition is compelling because it promotes species coexistence and because recent work suggests it may be common in natural systems. One class of intransitivity indices works by considering s, the minimum number of competitive reversals to convert a given competitive community (i.e., a ‘tournament’) to a hierarchy. The most straightforward example of such ‘reversal-based’ indices is Petraitis’ index, <i>t</i> = 1 − <i>s/M</i>, where <i>M</i> is the maximum <i>s</i> across all possible <i>n</i>-species tournaments. Using exhaustive searches, we prove that Petraitis’ formula for <i>M</i> (and, therefore, <i>t</i>) does not hold for <i>n</i> ≥ 7. Furthermore, the determination of <i>s</i> for even moderate values of <i>n</i> may prove difficult, as the equivalent graph-theoretical problem is NP-hard; there is no known computationally feasible way to compute an exact answer for anything but small values of <i>n</i>, let alone a closed-form solution. Petraitis’ <i>t</i> is a valuable index of intransitivity; however, at present its use is limited to relatively species-poor systems. More broadly, reversal-based indices, while intuitive, may be problematic because of this computability issue. </p> <!-- <p><a href="http://dx.doi.org/10.1086/696266">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 05 Dec 2017 06:00:00 GMT “Constraints imposed by a natural landscape override offspring fitness effects to shape oviposition decisions in wild forked fungus beetles” http://amnat.org/an/newpapers/AprWood-A.html The DOI will be http://dx.doi.org/10.1086/696218 Genetic mark-recapture reveals that wild fungus beetles do not avoid oviposition sites with high offspring mortality Abstract Oviposition site decisions often maximize offspring fitness, but costs constraining choice can cause females to oviposit in poor developmental environments. It is unclear whether these constraints cumulatively outweigh offspring fitness to determine oviposition decisions in wild populations. Understanding how constraints shape oviposition in natural landscapes is a critical step toward revealing how maternal behavior influences fundamental phenomena like the evolution of specialization and the use of “sink” environments. Here, we used a genetic capture-recapture technique to reconstruct the oviposition decisions of individual females in a natural metapopulation of a beetle (Bolitotherus cornutus) that oviposits on three fungus species. We measured larval fitness-related traits (mass, development time, survival) on each fungus, and compared the oviposition preferences of females in laboratory versus field tests. Larval fitness differed substantially among fungi, and females preferred a high-quality (high larval fitness) fungus in laboratory trials. However, females frequently laid eggs on the lowest-quality fungus in the wild. They preferred high-quality fungi when moving between oviposition sites, but this preference disappeared as the distance between sites increased and was inconsistent between study plots. Our results suggest constraints on oviposition preferences in natural landscapes are sufficiently large to drive oviposition in poor developmental environments even when offspring fitness consequences are severe. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696218 </i></p> <p><b>Genetic mark-recapture reveals that wild fungus beetles do not avoid oviposition sites with high offspring mortality </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;">O</span>viposition site decisions often maximize offspring fitness, but costs constraining choice can cause females to oviposit in poor developmental environments. It is unclear whether these constraints cumulatively outweigh offspring fitness to determine oviposition decisions in wild populations. Understanding how constraints shape oviposition in natural landscapes is a critical step toward revealing how maternal behavior influences fundamental phenomena like the evolution of specialization and the use of “sink” environments. Here, we used a genetic capture-recapture technique to reconstruct the oviposition decisions of individual females in a natural metapopulation of a beetle (<i>Bolitotherus cornutus</i>) that oviposits on three fungus species. We measured larval fitness-related traits (mass, development time, survival) on each fungus, and compared the oviposition preferences of females in laboratory versus field tests. Larval fitness differed substantially among fungi, and females preferred a high-quality (high larval fitness) fungus in laboratory trials. However, females frequently laid eggs on the lowest-quality fungus in the wild. They preferred high-quality fungi when moving between oviposition sites, but this preference disappeared as the distance between sites increased and was inconsistent between study plots. Our results suggest constraints on oviposition preferences in natural landscapes are sufficiently large to drive oviposition in poor developmental environments even when offspring fitness consequences are severe.</p> <!-- <p> <a href="http://dx.doi.org/10.1086/696218">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 01 Dec 2017 06:00:00 GMT “Neutral community dynamics and the evolution of species interactions” http://amnat.org/an/newpapers/AprCoelho.html The DOI will be http://dx.doi.org/10.1086/696216 The study integrates neutral community dynamics with species interactions The mutual beneficial (mutualistic) interactions between species have sparked the interest of many naturalists over the centuries. Those interactions frequently involve dozens, or even hundreds of species, forming a complex network of interdependences. Ecologists have described recurrent natural features in the structure of these networks. For example, (i) few species interact with many species, while most species interact only with few species; (ii) specialist species interact only with small subgroup of species; (iii) the number of realized interactions is low compared to the total number of potential interactions; and, (iv) closely related species tend to interact with the same subgroup of partners. Although the features of mutualistic networks are well known, ecologists still do not fully understand why these patterns exist. Marco Túlio P. Coelho and Thiago F. Rangel from the Universidade Federal de Goiás, Brazil, have developed a computer simulation model to study the causes of patterns in mutualistic networks. In their highly simplified virtual world, all individuals are identical, regardless of their species, and interact with one another by chance alone. Surprisingly, the four most recurring features of mutualistic networks emerge even in such a highly simplified virtual world. By studying the properties and rules that govern their virtual world, the researchers show that features of mutualistic networks are an emergent consequence of where the individuals are located and how they disperse over space, but not of their species identity. Abstract A&nbsp;contemporary goal in ecology is to determine the ecological and evolutionary processes that generate recurring structural patterns in mutualistic networks. One of the great challenges is testing the capacity of neutral processes to replicate observed patterns in ecological networks, since the original formulation of the neutral theory lacks trophic interactions. Here, we developed a stochastic simulation neutral model adding trophic interactions to the neutral theory of biodiversity. Without invoking ecological differences among individuals of different species, and assuming that ecological interactions emerge randomly, here we demonstrated that a spatially explicit multitrophic neutral model is able to capture the recurrent structural patterns of mutualistic networks (i.e., degree distribution, connectance, nestedness and phylogenetic signal of species interactions). Non-random species distribution, caused by probabilistic events of migration and speciation, create non-random network patterns. These findings have broad implications for the interpretation of niche-based processes as drivers of ecological networks, as well as the integration of network structures with demographic stochasticity. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696216 </i> </p> <p><b>The study integrates neutral community dynamics with species interactions </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 mutual beneficial (mutualistic) interactions between species have sparked the interest of many naturalists over the centuries. Those interactions frequently involve dozens, or even hundreds of species, forming a complex network of interdependences. Ecologists have described recurrent natural features in the structure of these networks. For example, (i) few species interact with many species, while most species interact only with few species; (ii) specialist species interact only with small subgroup of species; (iii) the number of realized interactions is low compared to the total number of potential interactions; and, (iv) closely related species tend to interact with the same subgroup of partners. Although the features of mutualistic networks are well known, ecologists still do not fully understand why these patterns exist. </p><p>Marco Túlio P. Coelho and Thiago F. Rangel from the Universidade Federal de Goiás, Brazil, have developed a computer simulation model to study the causes of patterns in mutualistic networks. In their highly simplified virtual world, all individuals are identical, regardless of their species, and interact with one another by chance alone. Surprisingly, the four most recurring features of mutualistic networks emerge even in such a highly simplified virtual world. By studying the properties and rules that govern their virtual world, the researchers show that features of mutualistic networks are an emergent consequence of where the individuals are located and how they disperse over space, but not of their species identity. </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;contemporary goal in ecology is to determine the ecological and evolutionary processes that generate recurring structural patterns in mutualistic networks. One of the great challenges is testing the capacity of neutral processes to replicate observed patterns in ecological networks, since the original formulation of the neutral theory lacks trophic interactions. Here, we developed a stochastic simulation neutral model adding trophic interactions to the neutral theory of biodiversity. Without invoking ecological differences among individuals of different species, and assuming that ecological interactions emerge randomly, here we demonstrated that a spatially explicit multitrophic neutral model is able to capture the recurrent structural patterns of mutualistic networks (i.e., degree distribution, connectance, nestedness and phylogenetic signal of species interactions). Non-random species distribution, caused by probabilistic events of migration and speciation, create non-random network patterns. These findings have broad implications for the interpretation of niche-based processes as drivers of ecological networks, as well as the integration of network structures with demographic stochasticity.</p> <!-- <p> <a href="http://dx.doi.org/10.1086/696216">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Fri, 01 Dec 2017 06:00:00 GMT “Evolution of genetic variance during adaptive radiation” http://amnat.org/an/newpapers/AprWalter.html The DOI will be http://dx.doi.org/10.1086/696123 Natural selection increases genetic variance in the direction of natural selection to facilitate adaptive radiation Adaptive radiation occurs when new forms adapt rapidly to novel environments. Natural selection can favor certain combinations of traits, but not all trait combinations are possible. For example, the genes controlling plant height can also determine plant width and create a strong genetic correlation where wider plants are also taller, while short wide plants are never observed. Natural selection should then occur in directions determined by the availability of genetic variance, along the genetic correlation. However, if natural selection favors a trait combination that is not accessible because it lies away from this genetic correlation (i.e., short, wide plant shapes), adaptation towards this optimal phenotype would be difficult. Genetic correlations between traits are therefore expected to restrict the rate of adaptation because they are not expected to align with the optimal phenotype after the colonization of a novel habitat, making it difficult to understand how adaptive radiation occurs. Walter et al. estimated genetic correlations between ten morphological traits for four contrasting ecotypes of an Australian wildflower that displays strong morphological divergence. The authors show that genetic correlations among traits are different in each ecotype, suggesting that genetic correlations are malleable during the early stages of adaptive radiation. Divergence in genetic correlations was associated with divergence in traits, indicating that in each environment adaptation occurred along trait combinations that possessed the greatest genetic variance. One possibility is that radiations proceed because natural selection strengthens beneficial genetic correlations at the expense of other trait combinations. Alternatively, rare alleles present in the ancestral population may become beneficial in a novel environment and rapidly rise in frequency. Both scenarios could align genetic correlations with the optimal phenotype, ultimately suggesting that during the early stages of adaptive radiation, natural selection can focus genetic variation in the direction of selection and promote rapid adaptive divergence. Abstract Genetic correlations between traits can concentrate genetic variance into fewer phenotypic dimensions that can bias evolutionary trajectories along the axis of greatest genetic variance and away from optimal phenotypes, constraining the rate of evolution. If genetic correlations limit adaptation, rapid adaptive divergence between multiple contrasting environments may be difficult. However, if natural selection increases the frequency of rare alleles after colonization of new environments, an increase in genetic variance in the direction of selection can accelerate adaptive divergence. Here, we explored adaptive divergence of an Australian native wildflower by examining the alignment between divergence in phenotype mean and divergence in genetic variance among four contrasting ecotypes. We found divergence in mean multivariate phenotype along two major axes represented by different combinations of plant architecture and leaf traits. Ecotypes also showed divergence in the level of genetic variance in individual traits, and the multivariate distribution of genetic variance among traits. Divergence in multivariate phenotypic mean aligned with divergence in genetic variance, with much of the divergence in phenotype among ecotypes associated with changes in trait combinations containing substantial levels of genetic variance. Overall, our results suggest that natural selection can alter the distribution of genetic variance underlying phenotypic traits, increasing the amount of genetic variance in the direction of natural selection and potentially facilitating rapid adaptive divergence during an adaptive radiation. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696123 </i></p> <p><b>Natural selection increases genetic variance in the direction of natural selection to facilitate adaptive radiation </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;">A</span>daptive radiation occurs when new forms adapt rapidly to novel environments. Natural selection can favor certain combinations of traits, but not all trait combinations are possible. For example, the genes controlling plant height can also determine plant width and create a strong genetic correlation where wider plants are also taller, while short wide plants are never observed. Natural selection should then occur in directions determined by the availability of genetic variance, along the genetic correlation. However, if natural selection favors a trait combination that is not accessible because it lies away from this genetic correlation (i.e., short, wide plant shapes), adaptation towards this optimal phenotype would be difficult. Genetic correlations between traits are therefore expected to restrict the rate of adaptation because they are not expected to align with the optimal phenotype after the colonization of a novel habitat, making it difficult to understand how adaptive radiation occurs.</p> <p>Walter et al. estimated genetic correlations between ten morphological traits for four contrasting ecotypes of an Australian wildflower that displays strong morphological divergence. The authors show that genetic correlations among traits are different in each ecotype, suggesting that genetic correlations are malleable during the early stages of adaptive radiation. Divergence in genetic correlations was associated with divergence in traits, indicating that in each environment adaptation occurred along trait combinations that possessed the greatest genetic variance. One possibility is that radiations proceed because natural selection strengthens beneficial genetic correlations at the expense of other trait combinations. Alternatively, rare alleles present in the ancestral population may become beneficial in a novel environment and rapidly rise in frequency. Both scenarios could align genetic correlations with the optimal phenotype, ultimately suggesting that during the early stages of adaptive radiation, natural selection can focus genetic variation in the direction of selection and promote rapid adaptive divergence.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">G</span>enetic correlations between traits can concentrate genetic variance into fewer phenotypic dimensions that can bias evolutionary trajectories along the axis of greatest genetic variance and away from optimal phenotypes, constraining the rate of evolution. If genetic correlations limit adaptation, rapid adaptive divergence between multiple contrasting environments may be difficult. However, if natural selection increases the frequency of rare alleles after colonization of new environments, an increase in genetic variance in the direction of selection can accelerate adaptive divergence. Here, we explored adaptive divergence of an Australian native wildflower by examining the alignment between divergence in phenotype mean and divergence in genetic variance among four contrasting ecotypes. We found divergence in mean multivariate phenotype along two major axes represented by different combinations of plant architecture and leaf traits. Ecotypes also showed divergence in the level of genetic variance in individual traits, and the multivariate distribution of genetic variance among traits. Divergence in multivariate phenotypic mean aligned with divergence in genetic variance, with much of the divergence in phenotype among ecotypes associated with changes in trait combinations containing substantial levels of genetic variance. Overall, our results suggest that natural selection can alter the distribution of genetic variance underlying phenotypic traits, increasing the amount of genetic variance in the direction of natural selection and potentially facilitating rapid adaptive divergence during an adaptive radiation.</p> <!-- <p> <a href="http://dx.doi.org/10.1086/696123">Read&nbsp;the&nbsp;Article</a> </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, 29 Nov 2017 06:00:00 GMT “The geometry of nutrient-space based life-history trade-offs: Sex-specific effects of macronutrient intake on the trade-off between encapsulation ability and reproductive effort in decorated crickets” http://amnat.org/an/newpapers/AprRapkin.html The DOI will be http://dx.doi.org/10.1086/696147 An analytical approach to measure nutrient based life-history trade-offs Life-history theory assumes that trade-offs result from traits competing for limited resources, with the resource most commonly studied being the quantity and/or quality of diet. Recent studies have started using artificial diets that vary both the ratio of protein to carbohydrate and the overall nutritional value of the diet to create a multi-dimensional nutritional space, using a method called the geometric framework of nutrition. These studies have suggested that life-history trade-offs are often regulated by the intake of specific nutrients; however, a formal approach to identify and quantify the strength of such trade-offs is lacking. In their article appearing in The American Naturalist, Rapkin et al. present an analytical approach for quantifying nutrient based life-history trade-offs using the geometric framework. They suggest that trade-offs occur whenever life-history traits of interest are maximized in different regions of nutritional space and that the strength of any trade-offs can be quantified using both the angle and the distance between nutritional optima. Rapkin et al. then test their proposed analytical approach, examining the effect of protein and carbohydrate intake on the trade-off between reproduction and aspects of immune function in male and female decorated crickets (Gryllodes sigillatus). They show that female encapsulation ability and egg laying increased with the intake of both protein and carbohydrate, whereas male encapsulation ability increased with protein intake but male calling effort increased with carbohydrate intake. The trade-offs between traits were therefore shown to be larger in males than females with significant negative correlations between the traits in males, non-overlapping regions of nutritional optima, and larger estimates of the angle and distance between these nutritional optima. A greater consideration of specific nutrient effects on life-history trade-offs will, therefore, be important for future studies. Abstract Life-history theory assumes that traits compete for limited resources resulting in trade-offs. The most commonly manipulated resource in empirical studies is the quantity or quality of diet. Recent studies using the Geometric Framework for nutrition, however, suggest that trade-offs are often regulated by the intake of specific nutrients but a formal approach to identify and quantify the strength of such trade-offs is lacking. We posit that trade-offs occur whenever life-history traits are maximized in different regions of nutrient space, as evidenced by non-overlapping 95% confidence regions of the global maximum for each trait, and large angles (θ) between linear nutritional vectors and Euclidean distances (d) between global maxima. We then examined the effects of protein and carbohydrate intake on the trade-off between reproduction and aspects of immune function in male and female Gryllodes sigillatus. Female encapsulation ability and egg production increased with the intake of both nutrients, whereas male encapsulation ability increased with protein intake but calling effort increased with carbohydrate intake. The trade-offs between traits was therefore larger in males than females, as demonstrated by significant negative correlations between the traits in males, non-overlapping 95% confidence regions and larger estimates of θ and d. Under dietary choice, the sexes had similar regulated intakes but neither optimally regulated nutrient intake for maximal trait expression. We highlight that greater consideration of specific nutrient intake is needed when examining nutrient-space based trade-offs. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696147 </i></p> <p><b>An analytical approach to measure nutrient based life-history trade-offs </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;">L</span>ife-history theory assumes that trade-offs result from traits competing for limited resources, with the resource most commonly studied being the quantity and/or quality of diet. Recent studies have started using artificial diets that vary both the ratio of protein to carbohydrate and the overall nutritional value of the diet to create a multi-dimensional nutritional space, using a method called the geometric framework of nutrition. These studies have suggested that life-history trade-offs are often regulated by the intake of specific nutrients; however, a formal approach to identify and quantify the strength of such trade-offs is lacking. </p> <p>In their article appearing in <i>The American Naturalist</i>, Rapkin et al. present an analytical approach for quantifying nutrient based life-history trade-offs using the geometric framework. They suggest that trade-offs occur whenever life-history traits of interest are maximized in different regions of nutritional space and that the strength of any trade-offs can be quantified using both the angle and the distance between nutritional optima. </p> <p>Rapkin et al. then test their proposed analytical approach, examining the effect of protein and carbohydrate intake on the trade-off between reproduction and aspects of immune function in male and female decorated crickets (<i>Gryllodes sigillatus</i>). They show that female encapsulation ability and egg laying increased with the intake of both protein and carbohydrate, whereas male encapsulation ability increased with protein intake but male calling effort increased with carbohydrate intake. The trade-offs between traits were therefore shown to be larger in males than females with significant negative correlations between the traits in males, non-overlapping regions of nutritional optima, and larger estimates of the angle and distance between these nutritional optima. A greater consideration of specific nutrient effects on life-history trade-offs will, therefore, be important for future studies. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">L</span>ife-history theory assumes that traits compete for limited resources resulting in trade-offs. The most commonly manipulated resource in empirical studies is the quantity or quality of diet. Recent studies using the Geometric Framework for nutrition, however, suggest that trade-offs are often regulated by the intake of specific nutrients but a formal approach to identify and quantify the strength of such trade-offs is lacking. We posit that trade-offs occur whenever life-history traits are maximized in different regions of nutrient space, as evidenced by non-overlapping 95% confidence regions of the global maximum for each trait, and large angles (<b><i>θ</i></b>) between linear nutritional vectors and Euclidean distances (<b><i>d</i></b>) between global maxima. We then examined the effects of protein and carbohydrate intake on the trade-off between reproduction and aspects of immune function in male and female <i>Gryllodes sigillatus</i>. Female encapsulation ability and egg production increased with the intake of both nutrients, whereas male encapsulation ability increased with protein intake but calling effort increased with carbohydrate intake. The trade-offs between traits was therefore larger in males than females, as demonstrated by significant negative correlations between the traits in males, non-overlapping 95% confidence regions and larger estimates of <b><i>θ</i></b> and <b><i>d</i></b>. Under dietary choice, the sexes had similar regulated intakes but neither optimally regulated nutrient intake for maximal trait expression. We highlight that greater consideration of specific nutrient intake is needed when examining nutrient-space based trade-offs. <!-- <a href="http://dx.doi.org/10.1086/696147">Read&nbsp;the&nbsp;Article</a> --> </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, 29 Nov 2017 06:00:00 GMT “Female density-dependent chemical warfare underlies fitness effects of group sex ratio in flour beetles” http://amnat.org/an/newpapers/MarKhan-A.html Read the Article Females (not males) drive fitness effects of biased sex ratio via secreted toxins for resource (not sexual) competition Abstract In animals, skewed sex ratios can affect individual fitness either via sexual (e.g. intersexual conflict or intrasexual mate competition) or non-sexual interactions (e.g. sex-specific resource competition). Because most analyses of sex ratio focus on sexual interactions, the relative importance of sexual vs. non-sexual mechanisms remains unclear. We tested both mechanisms in the flour beetle Tribolium castaneum, where male-biased sex ratios increase female fitness relative to unbiased or female-biased groups. Although flour beetles show both sexual and non-sexual (resource) competition, we found that sexual interactions did not explain female fitness. Instead, female fecundity was dramatically reduced even after a brief exposure to flour conditioned by other females. Earlier studies suggested that secreted toxins might mediate density-dependent population growth in flour beetles. We identified ethyl- and methyl-benzoquinone (EBQ and MBQ; “quinones”), as components of adult stink glands that regulate female fecundity. In female-biased groups (i.e. at high female density), females upregulated quinones and suppressed each other’s reproduction. In male-biased groups, low female density and associated low quinone levels maximized fecundity. Thus, females appear to use quinones as weapons for female-specific, density-dependent interference competition. Our results underscore the importance of non-sexual interference competition that may often underlie the fitness consequences of skewed sex ratios. More forthcoming papers &raquo; <p><strong><a href="http://dx.doi.org/10.1086/695806"><i>Read the Article</i></a></strong></p> <p><b>Females (not males) drive fitness effects of biased sex ratio via secreted toxins for resource (not sexual) competition </b></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;">I</span>n animals, skewed sex ratios can affect individual fitness either via sexual (e.g. intersexual conflict or intrasexual mate competition) or non-sexual interactions (e.g. sex-specific resource competition). Because most analyses of sex ratio focus on sexual interactions, the relative importance of sexual vs. non-sexual mechanisms remains unclear. We tested both mechanisms in the flour beetle <i>Tribolium castaneum</i>, where male-biased sex ratios increase female fitness relative to unbiased or female-biased groups. Although flour beetles show both sexual and non-sexual (resource) competition, we found that sexual interactions did not explain female fitness. Instead, female fecundity was dramatically reduced even after a brief exposure to flour conditioned by other females. Earlier studies suggested that secreted toxins might mediate density-dependent population growth in flour beetles. We identified ethyl- and methyl-benzoquinone (EBQ and MBQ; &ldquo;quinones&rdquo;), as components of adult stink glands that regulate female fecundity. In female-biased groups (i.e. at high female density), females upregulated quinones and suppressed each other&rsquo;s reproduction. In male-biased groups, low female density and associated low quinone levels maximized fecundity. Thus, females appear to use quinones as weapons for female-specific, density-dependent interference competition. Our results underscore the importance of non-sexual interference competition that may often underlie the fitness consequences of skewed sex ratios. <!-- <p><a href="http://dx.doi.org/10.1086/695806">Read&nbsp;the&nbsp;Article</a> </p> --></p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 28 Nov 2017 06:00:00 GMT Letter to the US Congress on Proposed Tax Cuts and Jobs Act http://amnat.org/announcements/LTRTuitionTax.html Text of the letter: We are writing as President of the Society for the Study of Evolution (2,674 members), the President of the American Society of Naturalists (1,323 members) and the President of the Society of Systematic Biologists (700 members) to express significant concerns regarding the proposed Tax Cuts and Jobs Act. If the deduction for qualified tuition and related expenses is repealed, taxes will greatly increase for many graduate students, such that pursuing a doctoral degree in the United States may no longer be financially feasible. As you may know, most PhD students in the United States receive a small stipend, which is taxed as income, to cover living expenses while conducting research. Many also receive a tuition waiver in exchange for working as a teaching assistant or research assistant. If the Tax Cuts and Jobs Act is passed, and students’ tuition is taxed, graduate students’ tax burden will increase by roughly 30 to 60 percent for students at public universities, and 200 to 400 percent for students at private universities, where tuition is typically much higher1. This tax burden would be more than a third of a student’s salary at a private university. Such a change would make pursuing a doctoral degree prohibitively expensive for many students. Graduate students are invaluable players in the field of scientific research. Taxing tuition will prevent many from finishing their work, leaving their programs without a degree. Many more will be prevented from entering into a doctoral program. These changes would decimate advanced education in the United States. If we instead facilitate higher education, not only in biology and STEM but across fields, then we train an innovative, competitive workforce that will maintain this country’s position at the forefront of science and technology. To ensure the continuation of valuable research by graduate students across the country, please preserve the deduction for qualified tuition and related expenses. Sincerely, Sally Otto, Society for the Study of Evolution Kathleen Donohue, American Society of Naturalists Luke Harmon, Society of Systematic Biologists <p>Text of the letter:</p> <p>We are writing as President of the Society for the Study of Evolution (2,674 members), the President of the American Society of Naturalists (1,323 members) and the President of the Society of Systematic Biologists (700 members) to express significant concerns regarding the proposed Tax Cuts and Jobs Act. If the deduction for qualified tuition and related expenses is repealed, taxes will greatly increase for many graduate students, such that pursuing a doctoral degree in the United States may no longer be financially feasible.</p> <p>As you may know, most PhD students in the United States receive a small stipend, which is taxed as income, to cover living expenses while conducting research. Many also receive a tuition waiver in exchange for working as a teaching assistant or research assistant.</p> <p>If the Tax Cuts and Jobs Act is passed, and students&rsquo; tuition is taxed, graduate students&rsquo; tax burden will increase by roughly 30 to 60 percent for students at public universities, and 200 to 400 percent for students at private universities, where tuition is typically much higher1. This tax burden would be more than a third of a student&rsquo;s salary at a private university. Such a change would make pursuing a doctoral degree prohibitively expensive for many students.</p> <p>Graduate students are invaluable players in the field of scientific research. Taxing tuition will prevent many from finishing their work, leaving their programs without a degree. Many more will be prevented from entering into a doctoral program. These changes would decimate advanced education in the United States. If we instead facilitate higher education, not only in biology and STEM but across fields, then we train an innovative, competitive workforce that will maintain this country&rsquo;s position at the forefront of science and technology.</p> <p>To ensure the continuation of valuable research by graduate students across the country, please preserve the deduction for qualified tuition and related expenses.</p> <p>Sincerely,</p> <p>Sally Otto, Society for the Study of Evolution</p> <p>Kathleen Donohue, American Society of Naturalists</p> <p>Luke Harmon, Society of Systematic Biologists</p> Mon, 27 Nov 2017 06:00:00 GMT “Venus flytrap rarely traps its pollinators” http://amnat.org/an/newpapers/AprYngstdt.html The DOI will be http://dx.doi.org/10.1086/696124 Venus flytrap pollinators now documented: Bees, beetles are key flower visitors. They stay clear of the snap-traps Carnivorous plants are best known for their ability to digest insects and other prey as a source of nutrients. Like their more mundane cousins, however, these plants also often rely on insects as pollinators. Plants that eat their own pollinators would appear to be at a reproductive disadvantage, but the identity of pollinators and the extent of pollinator-prey overlap is unknown for most of the world’s 600 carnivorous plants. Now, thanks to a collaborative effort involving researchers from North Carolina State University, the North Carolina Botanical Garden, and the U.S. Fish and Wildlife Service, this key piece of natural history has been revealed for the Venus flytrap, the only terrestrial carnivorous plant with an active snap trap. The new study shows that more than 98 species of insects and spiders visit Venus flytrap flowers in their native North Carolina. The most important of these—as determined by their abundance and the amount of flytrap pollen on their bodies—included a green sweat bee and two kinds of beetles. To see if the flytraps ever eat their pollinators, the researchers also gently pried open snap-traps of about 200 plants and removed their partly digested prey, primarily spiders and ants. The most important pollinators never appeared in traps, and few species were shared between flowers and traps. Those flower visitor species that were trapped turned out to be poor pollinators; examples include fire ants and buckeye butterflies, which were consumed as caterpillars but visited flowers as adults (and carried little pollen). These results indicate that the Venus flytrap largely avoids pollinator-prey overlap, balancing its needs for prey and pollination. Future work will examine which plant traits are important for keeping these interactions separate; for example, the placement of flowers on tall stalks, or the different colors of flowers and traps, may help the plant recruit different invertebrates for different functions. The new study provides a foundation for examining how tradeoffs between potentially conflicting interactions have shaped the evolution of carnivorous plants. Abstract Because carnivorous plants rely on arthropods as pollinators and prey, they risk consuming would-be mutualists. We examined this potential conflict in the Venus flytrap (Dionaea muscipula)), whose pollinators were previously unknown. Diverse arthropods from two classes and nine orders visited flowers; 56% of visitors carried D.&nbsp;muscipula pollen, often mixed with pollen of co-flowering species. Within this diverse, generalized community, certain bee and beetle species appear to be the most important pollinators, based on their abundance, pollen load size, and pollen fidelity. D.&nbsp;muscipula prey spanned four invertebrate classes and eleven orders; spiders, beetles, and ants were most common. At the family and species levels, few taxa were shared between traps and flowers, yielding a near-zero value of niche overlap for these potentially competing structures. Spatial separation of traps and flowers may contribute to partitioning the invertebrate community between nutritional and reproductive functions in D.&nbsp;muscipula. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696124 </i> </p> <p><b>Venus flytrap pollinators now documented: Bees, beetles are key flower visitors. They stay clear of the snap-traps </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>arnivorous plants are best known for their ability to digest insects and other prey as a source of nutrients. Like their more mundane cousins, however, these plants also often rely on insects as pollinators. Plants that eat their own pollinators would appear to be at a reproductive disadvantage, but the identity of pollinators and the extent of pollinator-prey overlap is unknown for most of the world’s 600 carnivorous plants. Now, thanks to a collaborative effort involving researchers from North Carolina State University, the North Carolina Botanical Garden, and the U.S. Fish and Wildlife Service, this key piece of natural history has been revealed for the Venus flytrap, the only terrestrial carnivorous plant with an active snap trap. </p><p>The new study shows that more than 98 species of insects and spiders visit Venus flytrap flowers in their native North Carolina. The most important of these—as determined by their abundance and the amount of flytrap pollen on their bodies—included a green sweat bee and two kinds of beetles. To see if the flytraps ever eat their pollinators, the researchers also gently pried open snap-traps of about 200 plants and removed their partly digested prey, primarily spiders and ants. The most important pollinators never appeared in traps, and few species were shared between flowers and traps. Those flower visitor species that were trapped turned out to be poor pollinators; examples include fire ants and buckeye butterflies, which were consumed as caterpillars but visited flowers as adults (and carried little pollen). </p> <p>These results indicate that the Venus flytrap largely avoids pollinator-prey overlap, balancing its needs for prey and pollination. Future work will examine which plant traits are important for keeping these interactions separate; for example, the placement of flowers on tall stalks, or the different colors of flowers and traps, may help the plant recruit different invertebrates for different functions. The new study provides a foundation for examining how tradeoffs between potentially conflicting interactions have shaped the evolution of carnivorous plants. </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">B</span>ecause carnivorous plants rely on arthropods as pollinators and prey, they risk consuming would-be mutualists. We examined this potential conflict in the Venus flytrap (<i>Dionaea muscipula</i>)), whose pollinators were previously unknown. Diverse arthropods from two classes and nine orders visited flowers; 56% of visitors carried <i>D.&nbsp;muscipula</i> pollen, often mixed with pollen of co-flowering species. Within this diverse, generalized community, certain bee and beetle species appear to be the most important pollinators, based on their abundance, pollen load size, and pollen fidelity. <i>D.&nbsp;muscipula</i> prey spanned four invertebrate classes and eleven orders; spiders, beetles, and ants were most common. At the family and species levels, few taxa were shared between traps and flowers, yielding a near-zero value of niche overlap for these potentially competing structures. Spatial separation of traps and flowers may contribute to partitioning the invertebrate community between nutritional and reproductive functions in <i>D.&nbsp;muscipula</i>. </p> <!-- <p> <a href="http://dx.doi.org/10.1086/696124">Read&nbsp;the&nbsp;Article</a> </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, 21 Nov 2017 06:00:00 GMT “Pluck or luck: does trait variation or chance drive variation in lifetime reproductive success?” http://amnat.org/an/newpapers/AprSnyder.html The DOI will be http://dx.doi.org/10.1086/696125 Lifetime reproductive success is determined largely by luck, not fitness-enhancing traits What makes highly successful individuals (those living a long time or producing many offspring over their lives) successful? How much of it is due to being special (having traits associated with high fitness) and how much of it is due to being lucky? Similarly, if we observe a highly successful individual, what can we conclude about their likely traits and with what confidence? Snyder and Ellner show how to define and answer these questions mathematically and apply their analyses to a series of case studies and models of varying complexity. For reasonable parameter choices, they find that most of success is about luck, not having high-fitness traits. Along the same line, having high-fitness traits is often necessary but not sufficient for being highly successful—an individual also needs to be lucky. These findings leave evolutionary dynamics intact—beneficial traits will spread by natural selection in populations large enough for luck to average out. However, when population-level ecological outcomes (such as birth rate or prey capture rate) are dominated by luck, within-population trait variation may be difficult to detect and may not contribute much to explaining ecological patterns. Abstract While there has been extensive interest in how intraspecific trait variation affects ecological processes, outcomes are highly variable even when individuals are identical: some are lucky while others are not. Trait variation is therefore only important if it adds substantially to the variability produced by luck. We ask when trait variation has a substantial effect on variability in lifetime reproductive success (LRS), using two approaches: 1) we partition the variation in LRS into contributions from luck and trait variation; 2) we ask what can be inferred about an individual&#39;s traits, and with what certainty, given their observed LRS. In theoretical stage- and size-structured models, and two empirical case studies, we find that luck usually dominates the variance of LRS. Even when individuals differ substantially in ways that affect expected LRS, unless the effects of luck are substantially reduced (e.g. low variability in reproductive lifespan or in annual fecundity), most variance in lifetime outcomes is due to luck, implying that departures from “null” models omitting trait variation will be hard to detect. Luck also obscures the relationship between realized LRS and individual traits. While trait variation may influence the fate of populations, luck often governs the lives of individuals. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/696125 </i> </p> <p><b>Lifetime reproductive success is determined largely by luck, not fitness-enhancing traits </b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">W</span>hat makes highly successful individuals (those living a long time or producing many offspring over their lives) successful? How much of it is due to being special (having traits associated with high fitness) and how much of it is due to being lucky? Similarly, if we observe a highly successful individual, what can we conclude about their likely traits and with what confidence? Snyder and Ellner show how to define and answer these questions mathematically and apply their analyses to a series of case studies and models of varying complexity. For reasonable parameter choices, they find that most of success is about luck, not having high-fitness traits. Along the same line, having high-fitness traits is often necessary but not sufficient for being highly successful&mdash;an individual also needs to be lucky. These findings leave evolutionary dynamics intact&mdash;beneficial traits will spread by natural selection in populations large enough for luck to average out. However, when population-level ecological outcomes (such as birth rate or prey capture rate) are dominated by luck, within-population trait variation may be difficult to detect and may not contribute much to explaining ecological patterns.</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;">W</span>hile there has been extensive interest in how intraspecific trait variation affects ecological processes, outcomes are highly variable even when individuals are identical: some are lucky while others are not. Trait variation is therefore only important if it adds substantially to the variability produced by luck. We ask when trait variation has a substantial effect on variability in lifetime reproductive success (LRS), using two approaches: 1) we partition the variation in LRS into contributions from luck and trait variation; 2) we ask what can be inferred about an individual&#39;s traits, and with what certainty, given their observed LRS. In theoretical stage- and size-structured models, and two empirical case studies, we find that luck usually dominates the variance of LRS. Even when individuals differ substantially in ways that affect expected LRS, unless the effects of luck are substantially reduced (e.g. low variability in reproductive lifespan or in annual fecundity), most variance in lifetime outcomes is due to luck, implying that departures from &ldquo;null&rdquo; models omitting trait variation will be hard to detect. Luck also obscures the relationship between realized LRS and individual traits. While trait variation may influence the fate of populations, luck often governs the lives of individuals.</p> <!-- <p> <a href="http://dx.doi.org/10.1086/696125">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Tue, 21 Nov 2017 06:00:00 GMT “Life history traits evolved jointly with climatic niche and disturbance regime in the genus Leucadendron (Proteaceae)” http://amnat.org/an/newpapers/FebTonnabel-A.html The DOI is http://dx.doi.org/10.1086/695283 Abstract Organisms have evolved a diversity of life history strategies to cope with variation in their environment. Persistence as adults and/or seeds across recruitment events allows species to dampen the effects of environmental fluctuations. The evolution of life cycles with overlapping generations should thus permit the colonization of environments with uncertain recruitment. We tested this hypothesis in Leucadendron (Proteaceae), a genus with high functional diversity native to fire-prone habitats in the South African fynbos. We analyzed the joint evolution of life history traits (adult survival and seed bank strategies) and ecological niches (climate and fire regime) using comparative methods and accounting for various sources of uncertainty. In the fynbos, species with canopy seed banks that are unable to survive fire as adults display non-overlapping generations. In contrast, resprouters with an underground seed bank may be less threatened by extreme climatic events and fire intervals given their iteroparity and long-lasting seed bank. Life cycles with non-overlapping generations indeed jointly evolved with niches with less exposure to frost, but not with less exposure to drought. Canopy seed banks jointly evolved with niches with more predictable fire return, compared to underground seed banks. The evolution of extraordinary functional diversity among fynbos plants thus reflects, at least in part, the diversity of both climates and fire regimes in this region. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><i>The DOI is http://dx.doi.org/10.1086/695283 </i></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;">O</span>rganisms have evolved a diversity of life history strategies to cope with variation in their environment. Persistence as adults and/or seeds across recruitment events allows species to dampen the effects of environmental fluctuations. The evolution of life cycles with overlapping generations should thus permit the colonization of environments with uncertain recruitment. We tested this hypothesis in <i>Leucadendron</i> (Proteaceae), a genus with high functional diversity native to fire-prone habitats in the South African fynbos. We analyzed the joint evolution of life history traits (adult survival and seed bank strategies) and ecological niches (climate and fire regime) using comparative methods and accounting for various sources of uncertainty. In the fynbos, species with canopy seed banks that are unable to survive fire as adults display non-overlapping generations. In contrast, resprouters with an underground seed bank may be less threatened by extreme climatic events and fire intervals given their iteroparity and long-lasting seed bank. Life cycles with non-overlapping generations indeed jointly evolved with niches with less exposure to frost, but not with less exposure to drought. Canopy seed banks jointly evolved with niches with more predictable fire return, compared to underground seed banks. The evolution of extraordinary functional diversity among fynbos plants thus reflects, at least in part, the diversity of both climates and fire regimes in this region. <a href="http://dx.doi.org/10.1086/695283">Read&nbsp;the&nbsp;Article</a> </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 16 Nov 2017 06:00:00 GMT “Collective dispersal leads to variance in fitness and maintains offspring size variation within marine populations” http://amnat.org/an/newpapers/MarBurgess.html Read the Article &nbsp; Collective dispersal selects for risk avoidance life histories, which consequently maintains variation in offspring size Larval dispersal in coastal environments is influenced by turbulent eddies that are several kilometers wide and last several weeks. These eddies can collect the larvae of benthic marine species (such as lobsters, sea urchins, reef fish) into dense groups that travel as coherent ‘packets’. Such collective dispersal means that sibling larvae released within a few days of each other would succeed (return to the coast and settle) or fail (are lost offshore) in groups. Therefore, turbulent dispersal generates unpredictable variation in fitness because some groups of offspring are lucky and others are not. How do marine life histories evolve in this turbulent and unpredictable setting to avoid occasional recruitment failures? Is it better to increase mean fitness, which also increases variability in fitness, or is it better to reduce variability even at the cost of a lower mean? By analogy with financial investment strategies, reducing variation at the expense of the mean is known as “bet hedging.” Scott Burgess, Robin Snyder, and Barry Rountree develop a mathematical model that predicts how turbulent dispersal influences the evolution of offspring size and spawning duration. They find that evolution favors offspring sizes that maximize fitness, even though this also increases the unpredictability of recruitment—there is no bet hedging. However, it can take a very long time for offspring sizes to evolve to the optimum, which means that types that differ in the size of offspring they produce can coexist for long periods. In nature, variation in offspring size within the same population is quite common. In the past, it’s been thought that this is the result of good and bad years or locations favoring different sizes. This paper shows that this kind of environmental variation is unnecessary to explain variation in size seen in nature: multiple offspring sizes can, in theory, coexist even in a uniform environment if larval dispersal is risky and the fates of larvae are correlated. Abstract Variance in fitness is well known to influence the outcome of evolution but is rarely considered in the theory of marine reproductive strategies. In coastal environments, turbulent mesoscale eddies can collect larvae into ‘packets’ resulting in collective dispersal. Larvae in packets return to the coast or are lost offshore in groups, producing variance in fitness. Using a Markov process to calculate fixation probabilities for competing phenotypes, we examine the evolution of offspring size and spawning duration in species with benthic adults and pelagic offspring. The offspring size that provides mothers with the highest mean fitness also generates the greatest variance in fitness, but pairwise invasion plots show that bet-hedging strategies are not evolutionarily stable: maximizing expected fitness correctly predicts the unique evolutionarily stable strategy. Nonetheless, fixation can take a long time. We find that selection to increase spawning duration as a risk-avoidance strategy to reduce the negative impacts of stochastic recruitment success can allow multiple offspring sizes to coexist in a population for extended periods. This has two important consequences for offspring size: 1) coexistence occurs over a broader range of sizes and is longer when spawning duration is longer, because longer spawning durations reduce variation in fitness and increase the time to fixation, and 2) longer spawning durations can compensate for having a non-optimal size and even allow less optimal sizes to reach fixation. Collective dispersal and longer spawning durations could effectively maintain offspring size variation even in the absence of good and bad years or locations. Empirical comparisons of offspring size would, therefore, not always reflect environment-specific differences in the optimal size. More forthcoming papers &raquo; <p><a href="http://dx.doi.org/10.1086/695879"><strong>Read the Article</strong></a></p> <p>&nbsp; <p><b>Collective dispersal selects for risk avoidance life histories, which consequently maintains variation in offspring size </b></p> </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;">L</span>arval dispersal in coastal environments is influenced by turbulent eddies that are several kilometers wide and last several weeks. These eddies can collect the larvae of benthic marine species (such as lobsters, sea urchins, reef fish) into dense groups that travel as coherent &lsquo;packets&rsquo;. Such collective dispersal means that sibling larvae released within a few days of each other would succeed (return to the coast and settle) or fail (are lost offshore) in groups. Therefore, turbulent dispersal generates unpredictable variation in fitness because some groups of offspring are lucky and others are not. How do marine life histories evolve in this turbulent and unpredictable setting to avoid occasional recruitment failures? Is it better to increase mean fitness, which also increases variability in fitness, or is it better to reduce variability even at the cost of a lower mean? By analogy with financial investment strategies, reducing variation at the expense of the mean is known as &ldquo;bet hedging.&rdquo;</p> <p>Scott Burgess, Robin Snyder, and Barry Rountree develop a mathematical model that predicts how turbulent dispersal influences the evolution of offspring size and spawning duration. They find that evolution favors offspring sizes that maximize fitness, even though this also increases the unpredictability of recruitment&mdash;there is no bet hedging. However, it can take a very long time for offspring sizes to evolve to the optimum, which means that types that differ in the size of offspring they produce can coexist for long periods. In nature, variation in offspring size within the same population is quite common. In the past, it&rsquo;s been thought that this is the result of good and bad years or locations favoring different sizes. This paper shows that this kind of environmental variation is unnecessary to explain variation in size seen in nature: multiple offspring sizes can, in theory, coexist even in a uniform environment if larval dispersal is risky and the fates of larvae are correlated.</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;">V</span>ariance in fitness is well known to influence the outcome of evolution but is rarely considered in the theory of marine reproductive strategies. In coastal environments, turbulent mesoscale eddies can collect larvae into &lsquo;packets&rsquo; resulting in collective dispersal. Larvae in packets return to the coast or are lost offshore in groups, producing variance in fitness. Using a Markov process to calculate fixation probabilities for competing phenotypes, we examine the evolution of offspring size and spawning duration in species with benthic adults and pelagic offspring. The offspring size that provides mothers with the highest mean fitness also generates the greatest variance in fitness, but pairwise invasion plots show that bet-hedging strategies are not evolutionarily stable: maximizing expected fitness correctly predicts the unique evolutionarily stable strategy. Nonetheless, fixation can take a long time. We find that selection to increase spawning duration as a risk-avoidance strategy to reduce the negative impacts of stochastic recruitment success can allow multiple offspring sizes to coexist in a population for extended periods. This has two important consequences for offspring size: 1) coexistence occurs over a broader range of sizes and is longer when spawning duration is longer, because longer spawning durations reduce variation in fitness and increase the time to fixation, and 2) longer spawning durations can compensate for having a non-optimal size and even allow less optimal sizes to reach fixation. Collective dispersal and longer spawning durations could effectively maintain offspring size variation even in the absence of good and bad years or locations. Empirical comparisons of offspring size would, therefore, not always reflect environment-specific differences in the optimal size.</p> <!-- <p> <a href="http://dx.doi.org/10.1086/695879">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 16 Nov 2017 06:00:00 GMT “Southern Ocean mesopelagic fish comply with Bergmann’s rule” http://amnat.org/an/newpapers/MarSaunders.html Read the ArticleA&nbsp;new study from the British Antarctic Survey shows how lanternfish, small bioluminescent fish from the ocean’s twilight zone, are likely to respond to the warming of the Southern Ocean. These fish are one of the most abundant groups of organisms in the oceans and inhabit the twilight zone where they feed on small crustaceans. Their large collective biomass feeds a multitude of Southern Ocean predators, including penguins and seals. Changes in their distribution can have a devastating impact on these predators. The team studied patterns in body size of lanternfish in relation to temperature and latitude across the Scotia-Weddell sector of the Southern Ocean. By examining net samples and in situ temperature measurements from recent research surveys (2006-2009), it was found that lanternfish body size increases with decreasing temperature and increasing latitude. Furthermore, the team revealed that attaining a greater body size is vital for these organisms to survive in colder regions further south. If ocean warming trends continue, many smaller sub-Antarctic species will also be able to reach the far south, possibly displacing the larger Antarctic species presently there. Such small fish will be less energy rich than their larger counterparts, which will have ramifications for the penguins and seals that depend on them. Lead author Dr. Ryan Saunders says, “Understanding how lanternfish are governed by their environment is an important step to being able to predict how the Southern Ocean ecosystem will respond to future change.” The work was carried out as part of the Ecosystems program at the British Antarctic Survey, which examines the operation of Southern Ocean food-webs and their sensitivity to climatic variability and change. Lanternfish remain relatively understudied in the Southern Ocean, but are increasingly being recognized as an important alternative food source to Antarctic krill for many Southern Ocean predators. At present there is no developed fishery for lanternfish although they are receiving increasing international interest as a potential source of fishmeal. Abstract The applicability of macroecological rules to patterns in body size varies between taxa. One of the most examined is Bergmann’s rule, which states that body size increases with decreasing temperature and increasing latitude, although the rule is not universal and the proposed mechanisms underpinning it are multifarious and lack congruence. This study considers the degree to which Bergmann’s rule applies to the Southern Ocean mesopelagic fish community. We studied patterns in body size, temperature and latitude across a 12&deg; latitudinal gradient within the Scotia-Weddell sector. Intra-specific Bergmann’s rule was found to apply to 8 out of the 11 biomass-dominant species in the family Myctophidae. The rule was also apparent at an inter-specific level. Our study suggests that greater attainable body size in this community is a necessary attribute to reach colder regions further south. The adherence of these taxa to Bergmann’s rule enables such species to act as sentinels for identifying the drivers and consequences of ocean warming on the Southern Ocean ecosystem. More forthcoming papers &raquo; <p><a href="http://dx.doi.org/10.1086/695767"><strong><i>Read the Article</i></strong></a></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>&nbsp;new study from the British Antarctic Survey shows how lanternfish, small bioluminescent fish from the ocean&rsquo;s twilight zone, are likely to respond to the warming of the Southern Ocean. These fish are one of the most abundant groups of organisms in the oceans and inhabit the twilight zone where they feed on small crustaceans. Their large collective biomass feeds a multitude of Southern Ocean predators, including penguins and seals. Changes in their distribution can have a devastating impact on these predators.</p> <p>The team studied patterns in body size of lanternfish in relation to temperature and latitude across the Scotia-Weddell sector of the Southern Ocean. By examining net samples and in situ temperature measurements from recent research surveys (2006-2009), it was found that lanternfish body size increases with decreasing temperature and increasing latitude. Furthermore, the team revealed that attaining a greater body size is vital for these organisms to survive in colder regions further south.</p> <p>If ocean warming trends continue, many smaller sub-Antarctic species will also be able to reach the far south, possibly displacing the larger Antarctic species presently there. Such small fish will be less energy rich than their larger counterparts, which will have ramifications for the penguins and seals that depend on them.</p> <p>Lead author Dr. Ryan Saunders says, &ldquo;Understanding how lanternfish are governed by their environment is an important step to being able to predict how the Southern Ocean ecosystem will respond to future change.&rdquo; The work was carried out as part of the Ecosystems program at the British Antarctic Survey, which examines the operation of Southern Ocean food-webs and their sensitivity to climatic variability and change. Lanternfish remain relatively understudied in the Southern Ocean, but are increasingly being recognized as an important alternative food source to Antarctic krill for many Southern Ocean predators. At present there is no developed fishery for lanternfish although they are receiving increasing international interest as a potential source of fishmeal.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">T</span>he applicability of macroecological rules to patterns in body size varies between taxa. One of the most examined is Bergmann&rsquo;s rule, which states that body size increases with decreasing temperature and increasing latitude, although the rule is not universal and the proposed mechanisms underpinning it are multifarious and lack congruence. This study considers the degree to which Bergmann&rsquo;s rule applies to the Southern Ocean mesopelagic fish community. We studied patterns in body size, temperature and latitude across a 12&deg; latitudinal gradient within the Scotia-Weddell sector. Intra-specific Bergmann&rsquo;s rule was found to apply to 8 out of the 11 biomass-dominant species in the family Myctophidae. The rule was also apparent at an inter-specific level. Our study suggests that greater attainable body size in this community is a necessary attribute to reach colder regions further south. The adherence of these taxa to Bergmann&rsquo;s rule enables such species to act as sentinels for identifying the drivers and consequences of ocean warming on the Southern Ocean ecosystem.</p> <!-- <p><a href="http://dx.doi.org/10.1086/695767">Read&nbsp;the&nbsp;Article</a> </p> --> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 16 Nov 2017 06:00:00 GMT “Keystone individuals alter ecological and evolutionary consumer-resource dynamics” http://amnat.org/an/newpapers/FebStart.html The DOI is http://dx.doi.org/10.1086/695322 A single individual with extreme traits changes populations, communities, and evolution Variation among organisms’ characteristics (traits), whether among species, populations, or individuals, forms a central pillar of both ecology and evolution. Recently, work in community ecology has suggested that differences among individuals and populations can have enormous consequences for where species are found, their abundances, and how they interact with other species in the community. However, these studies have invariably considered differences in traits among populations (mean difference) or variation within a population (variance difference). As a result, we lack an ecological or evolutionary answer to the idiom ‘can one person really make a difference?’. Put otherwise, can the addition or removal of one specific individual from a population have large and irreplaceable effects on the ecology and evolution of the system? Here, Denon Start (University of Toronto, ON, Canada) extends the keystone individual concept from behavioral ecology to encompass ecology and evolutionary biology. Applied to ecology and evolution, he defines the keystone individual concept as the idea that certain individuals, usually with extreme (unusual) trait values, have important consequences, and that replacing an extreme individual with a ‘normal’ individual would fundamentally change the ecological or evolutionary dynamics of the system. He then explores this concept at the Koffler Scientific Reserve in southern Ontario, using a gall-maker and its natural enemies. He shows that the presence of a single individual with an extreme predator-attracting phenotype increases mortality, changes the composition of predator communities, and increases selection for anti-predator traits in the surrounding gall-maker population. In short, the presence of a single individual with an extreme phenotype fundamentally changes the way the rest of the population interacts with other species, and the consequences of those interactions for selection. Given the massive variation among individuals, and the importance of individuals for communities, keystone individuals are likely to be common in systems as diverse as insect herbivores and human infectious diseases. Abstract Intraspecific variation is central to our understanding of evolution and ecology, but these fields generally consider either the mean trait value or its variance. Alternatively, the keystone individual concept from behavioral ecology posits that a single individual with an extreme phenotype can have disproportionate and irreplaceable effects on group dynamics. Here, I generalize this concept to include non-behavioral traits and broader ecological and evolutionary dynamics. I test for the effects of individuals with extreme phenotypes on the ecology and evolution of a gall-forming fly and its natural enemies that select for opposite gall sizes. Specifically I introduce a putatively keystone predator-attracting individual gall-maker, hypothesizing that the presence of such an individual should (i) increase gall-maker population-level mortality, (ii) cause consumer communities to be dominated by species that are most attracted to the keystone individual, (iii) increase selection for traits conferring defense against the most common consumer, and (iv) weaken patterns of stabilizing selection. I find support for both the ecological and evolutionary consequences of single individuals with extreme phenotypes, suggesting that they can be considered keystone individuals. I discuss the generality of the keystone individual concept, suggesting likely consequences for ecology and evolution. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><i>The DOI is http://dx.doi.org/10.1086/695322 </i></p> <p><b>A single individual with extreme traits changes populations, communities, and evolution </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;">V</span>ariation among organisms&rsquo; characteristics (traits), whether among species, populations, or individuals, forms a central pillar of both ecology and evolution. Recently, work in community ecology has suggested that differences among individuals and populations can have enormous consequences for where species are found, their abundances, and how they interact with other species in the community. However, these studies have invariably considered differences in traits among populations (mean difference) or variation within a population (variance difference). As a result, we lack an ecological or evolutionary answer to the idiom &lsquo;can one person really make a difference?&rsquo;. Put otherwise, can the addition or removal of one specific individual from a population have large and irreplaceable effects on the ecology and evolution of the system?</p> <p>Here, Denon Start (University of Toronto, ON, Canada) extends the keystone individual concept from behavioral ecology to encompass ecology and evolutionary biology. Applied to ecology and evolution, he defines the keystone individual concept as the idea that certain individuals, usually with extreme (unusual) trait values, have important consequences, and that replacing an extreme individual with a &lsquo;normal&rsquo; individual would fundamentally change the ecological or evolutionary dynamics of the system.</p> <p>He then explores this concept at the Koffler Scientific Reserve in southern Ontario, using a gall-maker and its natural enemies. He shows that the presence of a single individual with an extreme predator-attracting phenotype increases mortality, changes the composition of predator communities, and increases selection for anti-predator traits in the surrounding gall-maker population. In short, the presence of a single individual with an extreme phenotype fundamentally changes the way the rest of the population interacts with other species, and the consequences of those interactions for selection. Given the massive variation among individuals, and the importance of individuals for communities, keystone individuals are likely to be common in systems as diverse as insect herbivores and human infectious diseases.</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;">I</span>ntraspecific variation is central to our understanding of evolution and ecology, but these fields generally consider either the mean trait value or its variance. Alternatively, the keystone individual concept from behavioral ecology posits that a single individual with an extreme phenotype can have disproportionate and irreplaceable effects on group dynamics. Here, I generalize this concept to include non-behavioral traits and broader ecological and evolutionary dynamics. I test for the effects of individuals with extreme phenotypes on the ecology and evolution of a gall-forming fly and its natural enemies that select for opposite gall sizes. Specifically I introduce a putatively keystone predator-attracting individual gall-maker, hypothesizing that the presence of such an individual should (i) increase gall-maker population-level mortality, (ii) cause consumer communities to be dominated by species that are most attracted to the keystone individual, (iii) increase selection for traits conferring defense against the most common consumer, and (iv) weaken patterns of stabilizing selection. I find support for both the ecological and evolutionary consequences of single individuals with extreme phenotypes, suggesting that they can be considered keystone individuals. I discuss the generality of the keystone individual concept, suggesting likely consequences for ecology and evolution.</p> <p><a href="http://dx.doi.org/10.1086/695322">Read&nbsp;the&nbsp;Article</a></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 Nov 2017 06:00:00 GMT “Mechanisms of assortative mating in speciation with gene flow: connecting theory and empirical research” http://amnat.org/an/newpapers/JanKopp-A.html READ THE PAPER Abstract The large body of theory on speciation with gene flow has brought to light fundamental differences in the effects of two types of mating rules on speciation: preference/trait rules, in which divergence in both (female) preferences and (male) mating traits is necessary for assortment, and matching rules, in which individuals mate with like individuals based on the presence of traits or alleles that they have in common. These rules can emerge from a variety of behavioral or other mechanisms in ways that are not always obvious. We discuss the theoretical properties of both types of rules and explain why speciation is generally thought to be more likely under matching rather than preference/trait rules. We furthermore discuss whether specific assortative mating mechanisms fall under a preference/trait or matching rule, present empirical evidence for these mechanisms, and propose empirical tests that could distinguish between them. The synthesis of the theoretical literature on these assortative mating rules with empirical studies of the mechanisms by which they act can provide important insights into the occurrence of speciation with gene flow. Finally, by providing a clear framework we hope to inspire greater alignment in the ways that both theoreticians and empiricists study mating rules and how these rules affect speciation through maintaining or eroding barriers to gene flow among closely related species or populations. More forthcoming papers &raquo; <p><a href="http://dx.doi.org/10.1086/694889"><i>READ THE PAPER</i></a></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;">T</span>he large body of theory on speciation with gene flow has brought to light fundamental differences in the effects of two types of mating rules on speciation: preference/trait rules, in which divergence in both (female) preferences and (male) mating traits is necessary for assortment, and matching rules, in which individuals mate with like individuals based on the presence of traits or alleles that they have in common. These rules can emerge from a variety of behavioral or other mechanisms in ways that are not always obvious. We discuss the theoretical properties of both types of rules and explain why speciation is generally thought to be more likely under matching rather than preference/trait rules. We furthermore discuss whether specific assortative mating mechanisms fall under a preference/trait or matching rule, present empirical evidence for these mechanisms, and propose empirical tests that could distinguish between them. The synthesis of the theoretical literature on these assortative mating rules with empirical studies of the mechanisms by which they act can provide important insights into the occurrence of speciation with gene flow. Finally, by providing a clear framework we hope to inspire greater alignment in the ways that both theoreticians and empiricists study mating rules and how these rules affect speciation through maintaining or eroding barriers to gene flow among closely related species or populations. <!-- <a href="http://dx.doi.org/10.1086/694889">Read&nbsp;the&nbsp;Article</a> --></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 Nov 2017 06:00:00 GMT “Learning to cooperate: The evolution of social rewards in repeated interactions” http://amnat.org/an/newpapers/JanDridi.html READ THE PAPER Biologists Slimane Dridi and Erol Ak&ccedil;ay at the University of Pennsylvania demonstrate in a new mathematical model that evolution may shape the learning system of biological organisms to have preferences for increasing the chances of survival of others. The authors base their theoretical work on previous experimental discoveries made by other scientists, indicating that humans as well as other species find cooperation rewarding. An action is rewarding if the brain region specialized in processing rewards (the same region that is activated when we expect to eat sweet or salted foods) is activated when performing this action. Starting from this observation, the authors explored the possibility that natural selection could favor individuals who would be rewarded by the mere action of cooperating with a social partner. Combining the theories of reinforcement learning and natural selection, they investigate the situation where individuals in a population engage in social interactions that offer the possibility to cooperate or defect. These capture many of the interactions that occur in society and nature, such as the current problem of investing efforts to protect the climate, or the work performed by soldiers in ant colonies. The authors show that two main types of individuals are likely to take over an evolving population: individuals who the authors call “conditionally other-regarding”, meaning that they find mutual cooperation rewarding but are averse to exploitation (i.e., the situation where they cooperate but their partner defects), and selfish individuals who are only rewarded by defecting, which is the optimal action from a materialistic standpoint. Purely altruistic individuals who completely sacrifice their material gain to help others are generally not favored by natural selection. However, they can coexist with conditionally other-regarding individuals. This research helps us better understand the psychological motives behind the learning dynamics of helping behaviors in society and nature. More forthcoming papers &raquo; <p><strong><a href="http://dx.doi.org/10.1086/694822"><i>READ THE PAPER</i></a></strong></p> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">B</span>iologists Slimane Dridi and Erol Ak&ccedil;ay at the University of Pennsylvania demonstrate in a new mathematical model that evolution may shape the learning system of biological organisms to have preferences for increasing the chances of survival of others. The authors base their theoretical work on previous experimental discoveries made by other scientists, indicating that humans as well as other species find cooperation rewarding. An action is rewarding if the brain region specialized in processing rewards (the same region that is activated when we expect to eat sweet or salted foods) is activated when performing this action.</p> <p>Starting from this observation, the authors explored the possibility that natural selection could favor individuals who would be rewarded by the mere action of cooperating with a social partner. Combining the theories of reinforcement learning and natural selection, they investigate the situation where individuals in a population engage in social interactions that offer the possibility to cooperate or defect. These capture many of the interactions that occur in society and nature, such as the current problem of investing efforts to protect the climate, or the work performed by soldiers in ant colonies.</p> <p>The authors show that two main types of individuals are likely to take over an evolving population: individuals who the authors call &ldquo;conditionally other-regarding&rdquo;, meaning that they find mutual cooperation rewarding but are averse to exploitation (i.e., the situation where they cooperate but their partner defects), and selfish individuals who are only rewarded by defecting, which is the optimal action from a materialistic standpoint. Purely altruistic individuals who completely sacrifice their material gain to help others are generally not favored by natural selection. However, they can coexist with conditionally other-regarding individuals. This research helps us better understand the psychological motives behind the learning dynamics of helping behaviors in society and nature. <!-- <a href="http://dx.doi.org/10.1086/694822">Read&nbsp;the&nbsp;Article</a> --></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 Nov 2017 06:00:00 GMT “Seasonal food scarcity prompts long-distance foraging by a wild social bee” http://amnat.org/an/newpapers/JanPope.html Read the Paper Seasonal food scarcity prompts long-distance foraging by a wild social bee Across the globe, pollinating insects are essential for the persistence of plant communities and provide services that are critical for the production of many crops, worth an estimated $200 billion globally in enhanced yields each year. Bees—a large and diverse group of insects that primarily depend on pollen and nectar from flowering plants—are some of the most widespread and effective pollinators. Despite their ubiquity and importance to humans, little is known about the spatial range at which wild bees forage for food, or how they alter their behavior in landscapes where flowering plant density shifts across the year. This is due, in part, to the difficulties of tracking the movements of flying insects in the wild. In this study, graduate student Nathaniel Pope and Dr. Shalene Jha from the University of Texas at Austin collected wild bumble bees and used genetic markers to identify sister bees as they foraged across multiple landscapes in the chaparral of central California. Using the bees’ genetic information, Pope and Jha mapped out the foraging patterns of each colony across different time periods. They found that bumble bees are more sophisticated foragers than previously expected; bumble bees choose to fly longer distances to reach higher density patches of flowers, but only in the summer months when flowering resources are more limited. Overall, the results from the study suggest that potential alterations to plant flowering due to global change could dramatically alter bumble bee movement and pollination services. Further, the research suggests that current pollinator conservation efforts should consider targeting late-season floral resources, when bees may be most stressed by long-distance foraging. More forthcoming papers &raquo; <p><a href="http://dx.doi.org/10.1086/694843"><i>Read the Paper </i></a></p> <p><b>Seasonal food scarcity prompts long-distance foraging by a wild social bee </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;">A</span>cross the globe, pollinating insects are essential for the persistence of plant communities and provide services that are critical for the production of many crops, worth an estimated $200 billion globally in enhanced yields each year. Bees&mdash;a large and diverse group of insects that primarily depend on pollen and nectar from flowering plants&mdash;are some of the most widespread and effective pollinators. Despite their ubiquity and importance to humans, little is known about the spatial range at which wild bees forage for food, or how they alter their behavior in landscapes where flowering plant density shifts across the year. This is due, in part, to the difficulties of tracking the movements of flying insects in the wild.</p> <p>In this study, graduate student Nathaniel Pope and Dr. Shalene Jha from the University of Texas at Austin collected wild bumble bees and used genetic markers to identify sister bees as they foraged across multiple landscapes in the chaparral of central California. Using the bees&rsquo; genetic information, Pope and Jha mapped out the foraging patterns of each colony across different time periods. They found that bumble bees are more sophisticated foragers than previously expected; bumble bees choose to fly longer distances to reach higher density patches of flowers, but only in the summer months when flowering resources are more limited. Overall, the results from the study suggest that potential alterations to plant flowering due to global change could dramatically alter bumble bee movement and pollination services. Further, the research suggests that current pollinator conservation efforts should consider targeting late-season floral resources, when bees may be most stressed by long-distance foraging.<!-- <a href="http://dx.doi.org/10.1086/694843">Read&nbsp;the&nbsp;Article</a> --> </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 Nov 2017 06:00:00 GMT “Sex-specific heterogeneity in fixed morphological traits influences individual fitness in a monogamous bird population” http://amnat.org/an/newpapers/JanPlard.html Read the Paper Population dynamics of a monogamous bird is driven by sex-specific life-history strategies Individuals differ in sex and intrinsic quality and their body condition changes over the course of the year—all of which results in individual differences in survival and reproductive abilities. Despite this fact, we lack empirical knowledge about how individual heterogeneity influences individual demographic performance and how it affects population dynamics, because models of population dynamics typically focus on average demographic rates, excluding possible differences in survival and reproductive performance among individuals. In this study, researchers from the Swiss Ornithological Institute, in collaboration with researchers from the Universities of Bern and of Bristol, study the influence of individual intrinsic quality and annual condition on the dynamics of a population of hoopoes. The hoopoe is a medium-sized monogamous bird species. The study population is located in the Swiss Alps, where hoopoes breed in nestboxes installed in vineyards and fruit-tree plantations. Results show that males and females contribute differently to population growth, with high-quality males contributing much more than females and low-quality males. High-quality males are characterized by large morphological size and high survival compared to low-quality males and females. Although females live shorter lives, they have a strong impact on annual reproductive success. Taking account of partner quality and availability, this study shows that annual reproductive success is influenced by the condition and the quality of both sexes. While individual condition influences the timing of breeding, which strongly affects clutch size, female quality and to a lesser extent male quality shape the number of fledglings produced by a pair. Thus, the study provides evidence that even in a monogamous bird species with biparental care, individuals’ contribution to the population can vary between males and females and is linked to individual traits. The study also suggests that population dynamics are more strongly driven by high-quality individuals, which has consequences for the management and conservation of wild populations. More forthcoming papers &raquo; <p><a href="http://dx.doi.org/10.1086/694823"><i>Read the Paper</i></a></p> <p><b>Population dynamics of a monogamous bird is driven by sex-specific life-history strategies </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>ndividuals differ in sex and intrinsic quality and their body condition changes over the course of the year—all of which results in individual differences in survival and reproductive abilities. Despite this fact, we lack empirical knowledge about how individual heterogeneity influences individual demographic performance and how it affects population dynamics, because models of population dynamics typically focus on average demographic rates, excluding possible differences in survival and reproductive performance among individuals. In this study, researchers from the Swiss Ornithological Institute, in collaboration with researchers from the Universities of Bern and of Bristol, study the influence of individual intrinsic quality and annual condition on the dynamics of a population of hoopoes. </p><p>The hoopoe is a medium-sized monogamous bird species. The study population is located in the Swiss Alps, where hoopoes breed in nestboxes installed in vineyards and fruit-tree plantations. Results show that males and females contribute differently to population growth, with high-quality males contributing much more than females and low-quality males. High-quality males are characterized by large morphological size and high survival compared to low-quality males and females. Although females live shorter lives, they have a strong impact on annual reproductive success. Taking account of partner quality and availability, this study shows that annual reproductive success is influenced by the condition and the quality of both sexes. </p><p>While individual condition influences the timing of breeding, which strongly affects clutch size, female quality and to a lesser extent male quality shape the number of fledglings produced by a pair. Thus, the study provides evidence that even in a monogamous bird species with biparental care, individuals&rsquo; contribution to the population can vary between males and females and is linked to individual traits. The study also suggests that population dynamics are more strongly driven by high-quality individuals, which has consequences for the management and conservation of wild populations. <!-- <a href="http://dx.doi.org/10.1086/694823">Read&nbsp;the&nbsp;Article</a> --> </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 Nov 2017 06:00:00 GMT “Using human vision to detect variation in avian coloration: How bad is it?” http://amnat.org/an/newpapers/FebBergeron.html Read the Paper Human vision detects most of the variation in animal color in the visible range Biologists have long known that animals differ in their visual systems. Species often differ in the number and types of cone cells in their eyes. These differences in visual systems have led to the conclusion that human vision can never be used to assess variation in animal coloration. This idea stands in contrast with the fact that many productive research programs on color pattern evolution have relied on human vision. Are humans missing the majority of color variation in nature and, instead, only investigating a narrow subset of variation? Admittedly, humans cannot detect ultraviolet, far-red or polarized signals. However, the question remains as to whether humans are failing to detect the bulk of color variation in the visible range. Bergeron and Fuller addressed this question by using a methodology that should be flawed by human subjectivity and comparing it to a methodology that is free of human perceptual biases. They compared the coloration of bird specimens from a museum with the coloration of bird images from a field guide (see image at right). They found that field guide images detected the vast majority of the variation in coloration that was present in the museum specimens. This means that human vision detects the major patterns in coloration in the visible range. Human vision cannot be used to say which color patterns are more or less conspicuous to another species, but it can be used to detect major patterns in animal coloration in the visible spectrum in nature. Abstract Assessing variation in animal coloration is difficult as animals differ in their visual system properties. This has led some to propose that human vision can never be used to evaluate coloration, yet many studies have a long history of relying on human vision. To reconcile these views, we compared the reflectance spectra of preserved avian plumage elements with two measures that are humans biased: RGB values from digital photographs and the corresponding reflectance spectra from a field guide. We measured 73 plumage elements across 14 bird species. The field guide reflectance spectra were drastically different from that of the actual birds, particularly for blue elements. However, principal components analyses on all three data sets indicated remarkably similar data structure. We conclude that human vision can detect much of the variation in coloration in the visible range, providing fodder for subsequent studies in ecology, evolution, behavior, and visual ecology. More forthcoming papers &raquo; <p><a href="http://dx.doi.org/10.1086/695282"><i>Read the Paper</i></a></p> <p><b>Human vision detects most of the variation in animal color in the visible range </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;">B</span>iologists have long known that animals differ in their visual systems. Species often differ in the number and types of cone cells in their eyes. These differences in visual systems have led to the conclusion that human vision can never be used to assess variation in animal coloration. This idea stands in contrast with the fact that many productive research programs on color pattern evolution have relied on human vision. Are humans missing the majority of color variation in nature and, instead, only investigating a narrow subset of variation? Admittedly, humans cannot detect ultraviolet, far-red or polarized signals. However, the question remains as to whether humans are failing to detect the bulk of color variation in the visible range.</p> <p>Bergeron and Fuller addressed this question by using a methodology that should be flawed by human subjectivity and comparing it to a methodology that is free of human perceptual biases. They compared the coloration of bird specimens from a museum with the coloration of bird images from a field guide (see image at right). They found that field guide images detected the vast majority of the variation in coloration that was present in the museum specimens. This means that human vision detects the major patterns in coloration in the visible range. Human vision cannot be used to say which color patterns are more or less conspicuous to another species, but it can be used to detect major patterns in animal coloration in the visible spectrum in nature. </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>ssessing variation in animal coloration is difficult as animals differ in their visual system properties. This has led some to propose that human vision can never be used to evaluate coloration, yet many studies have a long history of relying on human vision. To reconcile these views, we compared the reflectance spectra of preserved avian plumage elements with two measures that are humans biased: RGB values from digital photographs and the corresponding reflectance spectra from a field guide. We measured 73 plumage elements across 14 bird species. The field guide reflectance spectra were drastically different from that of the actual birds, particularly for blue elements. However, principal components analyses on all three data sets indicated remarkably similar data structure. We conclude that human vision can detect much of the variation in coloration in the visible range, providing fodder for subsequent studies in ecology, evolution, behavior, and visual ecology. </p> <!-- <p><a href="http://dx.doi.org/10.1086/695282">Read&nbsp;the&nbsp;Article</a></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 Nov 2017 06:00:00 GMT “A migratory divide in the Painted Bunting (Passerina ciris)” http://amnat.org/an/newpapers/FebBattey.html The DOI is http://dx.doi.org/10.1086/695439 Genomic data maps migration in a songbird and confirms a 66-yr-old hypothesis of trans-gulf migration Every spring, temperate North America welcomes the arrival of one of the continent’s most striking songbirds, the Painted Bunting, to their breeding grounds in northern Mexico and the Southeastern US. What we haven’t known, until recently, is exactly where they’re coming from. Now researchers at the University of Washington and Burke Museum of Natural History have used genetic data to map the annual migration of the species, and discovered an unexpected difference in the flight paths of populations in Texas and Louisiana. The team, working in the lab of Burke Museum Curator of Ornithology John Klicka, sequenced DNA and took measurements of the size and shape of Painted Buntings caught both while breeding and while overwintering. With these data, they used mathematical models to identify groups of individuals that share a recent common ancestor, drawing links between different parts of the species’ two seasonal ranges. The researchers found that breeding birds in Louisiana are closely related to wintering birds from the Yucat&aacute;n Peninsula; meanwhile, breeding populations in Texas, Kansas, and Oklahoma match wintering samples from western and central Mexico. Breeding birds from the Atlantic Coast, meanwhile, appear to winter only in Florida, the Bahamas, and Cuba, and rarely interbreed with other populations. The data provides the first evidence that Painted Buntings using different migratory routes are also genetically differentiated, thus shedding light on how seasonal migration shapes the evolution of songbirds. Additionally, they show that declining populations along the Atlantic Coast and in the Mississippi River Valley are unique in both their genes and their life history, and should be treated as independent units by conservationists looking to preserve this iconic species. Abstract In the Painted Bunting (Passerina ciris), a North American songbird, populations on the Atlantic coast and interior southern United States are known to be allopatric during the breeding season, but efforts to map connectivity with wintering ranges have been largely inconclusive. Using genomic and morphological data from museum specimens and banded birds, we found evidence of three genetically differentiated Painted Bunting populations with distinct wintering ranges and molt-migration phenologies. In addition to confirming that the Atlantic coast population remains allopatric throughout the annual cycle, we identified an unexpected migratory divide within the interior breeding range. Populations breeding in Louisiana winter on the Yucat&aacute;n Peninsula, and are parapatric with other interior populations that winter in mainland Mexico and Central America. Across the interior breeding range, genetic ancestry is also associated with variation in wing length, suggesting that selection may be promoting morphological divergence in populations with different migration strategies. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><i>The DOI is http://dx.doi.org/10.1086/695439 </i></p> <p><b>Genomic data maps migration in a songbird and confirms a 66-yr-old hypothesis of trans-gulf migration </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;">E</span>very spring, temperate North America welcomes the arrival of one of the continent&rsquo;s most striking songbirds, the Painted Bunting, to their breeding grounds in northern Mexico and the Southeastern US. What we haven&rsquo;t known, until recently, is exactly where they&rsquo;re coming from. Now researchers at the University of Washington and Burke Museum of Natural History have used genetic data to map the annual migration of the species, and discovered an unexpected difference in the flight paths of populations in Texas and Louisiana. The team, working in the lab of Burke Museum Curator of Ornithology John Klicka, sequenced DNA and took measurements of the size and shape of Painted Buntings caught both while breeding and while overwintering. With these data, they used mathematical models to identify groups of individuals that share a recent common ancestor, drawing links between different parts of the species&rsquo; two seasonal ranges. The researchers found that breeding birds in Louisiana are closely related to wintering birds from the Yucat&aacute;n Peninsula; meanwhile, breeding populations in Texas, Kansas, and Oklahoma match wintering samples from western and central Mexico. Breeding birds from the Atlantic Coast, meanwhile, appear to winter only in Florida, the Bahamas, and Cuba, and rarely interbreed with other populations. The data provides the first evidence that Painted Buntings using different migratory routes are also genetically differentiated, thus shedding light on how seasonal migration shapes the evolution of songbirds. Additionally, they show that declining populations along the Atlantic Coast and in the Mississippi River Valley are unique in both their genes and their life history, and should be treated as independent units by conservationists looking to preserve this iconic species.</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;">I</span>n the Painted Bunting (<i>Passerina ciris</i>), a North American songbird, populations on the Atlantic coast and interior southern United States are known to be allopatric during the breeding season, but efforts to map connectivity with wintering ranges have been largely inconclusive. Using genomic and morphological data from museum specimens and banded birds, we found evidence of three genetically differentiated Painted Bunting populations with distinct wintering ranges and molt-migration phenologies. In addition to confirming that the Atlantic coast population remains allopatric throughout the annual cycle, we identified an unexpected migratory divide within the interior breeding range. Populations breeding in Louisiana winter on the Yucat&aacute;n Peninsula, and are parapatric with other interior populations that winter in mainland Mexico and Central America. Across the interior breeding range, genetic ancestry is also associated with variation in wing length, suggesting that selection may be promoting morphological divergence in populations with different migration strategies.</p> <p><a href="http://dx.doi.org/10.1086/695439">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT “Rising variability, not slowing down, as a leading indicator of a stochastically driven abrupt transition in a dryland ecosystem” http://amnat.org/an/newpapers/JanChen.html The DOI is http://dx.doi.org/10.1086/694821 Leading indicators distinguish critical transition from stochastic transition, a long-term study in a dryland ecosystem Complex real ecosystems may abruptly shift from one alternative state to another near a critical point, which is characterized by a phenomenon called critical slowing down (CSD). In this study, the authors investigate whether the leading indicators of CSD will proceed to the impending transition. Empirical tests on leading indicators on ecological systems have largely been limited to studies employing microcosms and aquatic ecosystems, but not in field systems where stochasticity can play a significant role in driving transitions. This study presents the first empirical analysis of the temporal indicators of state transition in a dryland ecosystem. Combining empirical data and a simple modeling framework, prior to the transition the system showed no (or weak) signatures of CSD, but exhibited expected increasing trends in the variability, quantified by variance and skewness. These surprising results are consistent with the theoretical expectation of stochastically driven abrupt transitions that occur away from critical points; indeed, a driver of vegetation – annual rainfall – showed rising variance prior to the transition. The study suggests that rising variability can potentially serve as a leading indicator of stochastically driven transitions in real world ecosystems. Overall, the changing pattern of an ecosystem between alternative states sometimes may be not determinate, but just stochastic. The authors still find some evidence to forecast it. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><i>The DOI is http://dx.doi.org/10.1086/694821 </i></p> <p><b>Leading indicators distinguish critical transition from stochastic transition, a long-term study in a dryland ecosystem </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>omplex real ecosystems may abruptly shift from one alternative state to another near a critical point, which is characterized by a phenomenon called critical slowing down (CSD). In this study, the authors investigate whether the leading indicators of CSD will proceed to the impending transition. Empirical tests on leading indicators on ecological systems have largely been limited to studies employing microcosms and aquatic ecosystems, but not in field systems where stochasticity can play a significant role in driving transitions. This study presents the first empirical analysis of the temporal indicators of state transition in a dryland ecosystem.</p> <p>Combining empirical data and a simple modeling framework, prior to the transition the system showed no (or weak) signatures of CSD, but exhibited expected increasing trends in the variability, quantified by variance and skewness. These surprising results are consistent with the theoretical expectation of stochastically driven abrupt transitions that occur away from critical points; indeed, a driver of vegetation &ndash; annual rainfall &ndash; showed rising variance prior to the transition. The study suggests that rising variability can potentially serve as a leading indicator of stochastically driven transitions in real world ecosystems.</p> <p>Overall, the changing pattern of an ecosystem between alternative states sometimes may be not determinate, but just stochastic. The authors still find some evidence to forecast it. <a href="http://dx.doi.org/10.1086/694821">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT “Patterns of local community composition are linked to large-scale diversification and dispersal of clades” http://amnat.org/an/newpapers/FebWiens.html Read the Article Local communities are dominated by clades with rapid rates of global-scale diversification and dispersal What determines which groups of organisms will have the most species at any location on Earth? Few studies, if any, have addressed this fundamental question. A new study suggests there is a simple explanation for these patterns of diversity. A new paper in The&nbsp;American Naturalist addresses the question of which groups dominate local communities, by analyzing data from snakes. The study used data from 166 local sites around the world and an evolutionary tree of 1,262 snake species. The results reveal that those groups that evolve new species most rapidly and spread most quickly are those that dominate most local communities around the world. On the other hand, groups that are present in a region longer than others rarely dominate local communities, despite having more time to build up species diversity. The results also reveal that most snake communities around the world are surprisingly similar to each other. Specifically, most communities are dominated by members of one family (Colubridae), which includes garter snakes and kingsnakes. Most communities also have dangerously venomous species from the viper family and the cobra family. Remarkably, these venomous groups have spread around the world almost as much as the highly successful Colubridae have, but generally have few species in local communities. The results suggest that these dangerously venomous snakes may be weaker competitors relative to species of the mostly harmless Colubridae. The tendency for local communities to be dominated by a few groups that proliferate and spread rapidly may apply to many other organisms besides snakes. For example, plants, frogs, mammals, and birds are each dominated by a rapidly proliferating group that has spread around the world. The new study proposes that there may be simple explanation for patterns of local species diversity across organisms and around the world. Abstract At any location, a group of organisms may be represented by several clades. What determines which clades will dominate local communities in terms of their species richness? Here, this relatively neglected question is addressed by analyzing 166 local assemblages of snakes distributed globally. For most regions, local assemblages are dominated by clades with higher global-scale diversification rates and more frequent dispersal into each region, and not by clades that have been present in that region longer. This result contrasts with many other studies of local richness (in other organisms), which show strong impacts of regional colonization time on overall local species richness of clades. Furthermore, even though local assemblages are assembled independently on different continents, most regions have converged on similar patterns of proportional richness. Specifically, a few rapidly diversifying clades dominate most communities around the world. The high diversification rates of these clades are then linked to their high dispersal rates. Similar patterns may occur in many groups, such as plants, frogs, salamanders, birds, and mammals. More forthcoming papers &raquo; <p><a href="http://dx.doi.org/10.1086/695495"><strong><i>Read the Article</i></strong></a></p> <p><b>Local communities are dominated by clades with rapid rates of global-scale diversification and dispersal </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>hat determines which groups of organisms will have the most species at any location on Earth? Few studies, if any, have addressed this fundamental question. A new study suggests there is a simple explanation for these patterns of diversity. </p><p>A new paper in <i>The&nbsp;American Naturalist</i> addresses the question of which groups dominate local communities, by analyzing data from snakes. The study used data from 166 local sites around the world and an evolutionary tree of 1,262 snake species. The results reveal that those groups that evolve new species most rapidly and spread most quickly are those that dominate most local communities around the world. On the other hand, groups that are present in a region longer than others rarely dominate local communities, despite having more time to build up species diversity. </p><p>The results also reveal that most snake communities around the world are surprisingly similar to each other. Specifically, most communities are dominated by members of one family (Colubridae), which includes garter snakes and kingsnakes. Most communities also have dangerously venomous species from the viper family and the cobra family. Remarkably, these venomous groups have spread around the world almost as much as the highly successful Colubridae have, but generally have few species in local communities. The results suggest that these dangerously venomous snakes may be weaker competitors relative to species of the mostly harmless Colubridae. </p><p>The tendency for local communities to be dominated by a few groups that proliferate and spread rapidly may apply to many other organisms besides snakes. For example, plants, frogs, mammals, and birds are each dominated by a rapidly proliferating group that has spread around the world. The new study proposes that there may be simple explanation for patterns of local species diversity across organisms and around the world.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>t any location, a group of organisms may be represented by several clades. What determines which clades will dominate local communities in terms of their species richness? Here, this relatively neglected question is addressed by analyzing 166 local assemblages of snakes distributed globally. For most regions, local assemblages are dominated by clades with higher global-scale diversification rates and more frequent dispersal into each region, and not by clades that have been present in that region longer. This result contrasts with many other studies of local richness (in other organisms), which show strong impacts of regional colonization time on overall local species richness of clades. Furthermore, even though local assemblages are assembled independently on different continents, most regions have converged on similar patterns of proportional richness. Specifically, a few rapidly diversifying clades dominate most communities around the world. The high diversification rates of these clades are then linked to their high dispersal rates. Similar patterns may occur in many groups, such as plants, frogs, salamanders, birds, and mammals.</p> <!-- <p> <a href="http://dx.doi.org/10.1086/695495">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT “Temperature-dependent species interactions shape priority effects and the persistence of unequal competitors” http://amnat.org/an/newpapers/FebGrainger.html Read the Article Temperature-dependent trophic interactions strengthen priority effects and shift competitive outcomes ‘Priority effects’ occur when an early arriving species alters the long-term make-up of an ecological community. Although common in nature, scientists are only beginning to understand the conditions under which priority effects arise. Tess Grainger and colleagues at the University of Toronto hypothesized that priority effects should be stronger at high temperatures, as warming speeds up growth rates and feeding, allowing early arrivers to more rapidly impact a shared environment. They tackled this prediction using an experiment with two competing aphid species and a shared milkweed host, and demonstrated that warming strengthens priority effects by simultaneously causing a more rapid induction of milkweed defenses and a faster depletion of the plant resource. These changes were matched with a shift in dispersal rates at higher temperature that are likely to influence the timing of species’ arrival at a local plant. This experiment tests emerging theory on the temperature-dependence of trophic interactions, and presents and tests new hypotheses that link temperature, priority effects and dispersal across spatial and temporal scales. Abstract The order of species arrival at a site can determine the outcome of competitive interactions when early arrivers alter the environment or deplete shared resources. These priority effects are predicted to be stronger at high temperatures, as higher vital rates caused by warming allows early arrivers to more rapidly impact a shared environment. We tested this prediction using a pair of congeneric aphid species that specialize on milkweed plants. We manipulated temperature and arrival order of the two aphid species, and measured aphid population dynamics and milkweed survival and defensive traits. We found that warming increased the impact of aphids on the quantity and quality of milkweed, which amplified the importance of priority effects by increasing the competitive exclusion of the inferior competitor when it arrived late. Warming also enhanced interspecific differences in dispersal, which could alter relative arrival times at a regional scale. Our experiment provides a first link between temperature-dependent trophic interactions, priority effects and dispersal. This study suggests that the indirect and cascading effects of temperature observed here may be important determinants of diversity in the temporally and spatially complex landscapes that characterize ecological communities. More forthcoming papers &raquo; <p><strong><a href="http://dx.doi.org/10.1086/695688"><i>Read the Article</i></a></strong></p> <p><b>Temperature-dependent trophic interactions strengthen priority effects and shift competitive outcomes </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;">&lsquo;P</span>riority effects&rsquo; occur when an early arriving species alters the long-term make-up of an ecological community. Although common in nature, scientists are only beginning to understand the conditions under which priority effects arise. Tess Grainger and colleagues at the University of Toronto hypothesized that priority effects should be stronger at high temperatures, as warming speeds up growth rates and feeding, allowing early arrivers to more rapidly impact a shared environment. They tackled this prediction using an experiment with two competing aphid species and a shared milkweed host, and demonstrated that warming strengthens priority effects by simultaneously causing a more rapid induction of milkweed defenses and a faster depletion of the plant resource. These changes were matched with a shift in dispersal rates at higher temperature that are likely to influence the timing of species&rsquo; arrival at a local plant. This experiment tests emerging theory on the temperature-dependence of trophic interactions, and presents and tests new hypotheses that link temperature, priority effects and dispersal across spatial and temporal 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;">T</span>he order of species arrival at a site can determine the outcome of competitive interactions when early arrivers alter the environment or deplete shared resources. These priority effects are predicted to be stronger at high temperatures, as higher vital rates caused by warming allows early arrivers to more rapidly impact a shared environment. We tested this prediction using a pair of congeneric aphid species that specialize on milkweed plants. We manipulated temperature and arrival order of the two aphid species, and measured aphid population dynamics and milkweed survival and defensive traits. We found that warming increased the impact of aphids on the quantity and quality of milkweed, which amplified the importance of priority effects by increasing the competitive exclusion of the inferior competitor when it arrived late. Warming also enhanced interspecific differences in dispersal, which could alter relative arrival times at a regional scale. Our experiment provides a first link between temperature-dependent trophic interactions, priority effects and dispersal. This study suggests that the indirect and cascading effects of temperature observed here may be important determinants of diversity in the temporally and spatially complex landscapes that characterize ecological communities. </p> <p><!-- <a href="http://dx.doi.org/10.1086/695688">Read&nbsp;the&nbsp;Article</a> --></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 Nov 2017 06:00:00 GMT “Multilevel selection in the filamentous ascomycete Neurospora tetrasperma” http://amnat.org/an/newpapers/MarMeunier.html Read the Article This paper experimentally shows an ongoing transition in individuality in a fungus An individual defines a single, separate organism distinguished from others of the same kind. Throughout the evolution of life, there have been transitions in individuality when autonomous entities have grouped together to form new, higher-level individuals. Examples of such transitions are when genes grouped to form genomes, cells to form bodies, and organisms to form societies. Theoretical expectations during transitions in individuality are well defined. Most importantly, grouping has to yield benefits, arising e.g. from cooperation amongst lower levels of the group. At the same time, conflicts between members of the group may arise and should be minimized, e.g. in ensuring genetic homogeneity inside of the group. Divergence from the inside would mean that selfish variants, deleterious to the group-level could invade and take over, which is what happens, for example, in cancers. The researchers, all female scientists from Uppsala University in Sweden, investigated pros and cons of a transition in individuality in Fungi, a group where individuality has been a long-standing issue. They postulated that their model, Neurospora tetrasperma, is undergoing a transition in individuality. In this species, two different levels of individuals exist: the nucleus and the mycelium. Cooperation and/or conflicts may be expected among differing nuclei that could benefit or harm the mycelium, respectively. The researchers investigated how the nuclear ratio between the two types varied in different conditions, and how fitness was impacted by changes in nuclear ratios. The nuclei had complementary traits, consistent with cooperation and division of labor. However, they also verified the existence of conflicts at the nuclear level: in one lineage, one type of nucleus replicated and transmitted better, yet had a negative impact on the mycelium fitness. Heterokaryosis in N.&nbsp;tetrasperma thus exemplifies a genetic system where transition in individuality seems at the same time advantageous and incomplete. Abstract The history of life has been driven by evolutionary transitions in individuality, i.e., the aggregation of autonomous individuals to form a new, higher-level individual. The fungus Neurospora tetrasperma has recently undergone an evolutionary transition in individuality from homokaryosis (one single type of nuclei in the same cytoplasm) to heterokaryosis (two genetically divergent and free-ranging nuclear types). In this species, selection can act at different levels: while nuclei can compete in their replication and transmission into short-lived asexual spores, at the level of the heterokaryotic individual cooperation between nuclear types is required to produce the long-lived sexual spores. Conflicts can arise between these two levels of selection if the coevolution between nuclear types is disrupted. Here, we investigated the extent of multilevel selection in three strains of N.&nbsp;tetrasperma. We assessed the ratio between nuclear types under different conditions, and measured fitness traits of homo- and heterokaryotic mycelia with varying nuclear ratios. We show that the two nuclei have complementary traits, consistent with division of labor and cooperation. In one strain, for which a recent chromosomal introgression was detected, we observed the occurrence of selfish nuclei, enjoying better replication and transmission than sister nuclei at the same time as being detrimental to the heterokaryon. We hypothesize that introgression has disrupted the coevolution between nuclear types in this strain. More forthcoming papers &raquo; <p><a href="http://dx.doi.org/10.1086/695803"><strong><i>Read the Article</i></strong></a></p> <p><b>This paper experimentally shows an ongoing transition in individuality in a fungus </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>n individual defines a single, separate organism distinguished from others of the same kind. Throughout the evolution of life, there have been transitions in individuality when autonomous entities have grouped together to form new, higher-level individuals. Examples of such transitions are when genes grouped to form genomes, cells to form bodies, and organisms to form societies. Theoretical expectations during transitions in individuality are well defined. Most importantly, grouping has to yield benefits, arising e.g. from cooperation amongst lower levels of the group. At the same time, conflicts between members of the group may arise and should be minimized, e.g. in ensuring genetic homogeneity inside of the group. Divergence from the inside would mean that selfish variants, deleterious to the group-level could invade and take over, which is what happens, for example, in cancers. The researchers, all female scientists from Uppsala University in Sweden, investigated pros and cons of a transition in individuality in Fungi, a group where individuality has been a long-standing issue. They postulated that their model, <i>Neurospora tetrasperma</i>, is undergoing a transition in individuality. In this species, two different levels of individuals exist: the nucleus and the mycelium. Cooperation and/or conflicts may be expected among differing nuclei that could benefit or harm the mycelium, respectively. The researchers investigated how the nuclear ratio between the two types varied in different conditions, and how fitness was impacted by changes in nuclear ratios. The nuclei had complementary traits, consistent with cooperation and division of labor. However, they also verified the existence of conflicts at the nuclear level: in one lineage, one type of nucleus replicated and transmitted better, yet had a negative impact on the mycelium fitness. Heterokaryosis in <i>N.&nbsp;tetrasperma</i> thus exemplifies a genetic system where transition in individuality seems at the same time advantageous and incomplete. </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he history of life has been driven by evolutionary transitions in individuality, i.e., the aggregation of autonomous individuals to form a new, higher-level individual. The fungus <i>Neurospora tetrasperma </i>has recently undergone an evolutionary transition in individuality from homokaryosis (one single type of nuclei in the same cytoplasm) to heterokaryosis (two genetically divergent and free-ranging nuclear types). In this species, selection can act at different levels: while nuclei can compete in their replication and transmission into short-lived asexual spores, at the level of the heterokaryotic individual cooperation between nuclear types is required to produce the long-lived sexual spores. Conflicts can arise between these two levels of selection if the coevolution between nuclear types is disrupted. Here, we investigated the extent of multilevel selection in three strains of <i>N.&nbsp;tetrasperma</i>. We assessed the ratio between nuclear types under different conditions, and measured fitness traits of homo- and heterokaryotic mycelia with varying nuclear ratios. We show that the two nuclei have complementary traits, consistent with division of labor and cooperation. In one strain, for which a recent chromosomal introgression was detected, we observed the occurrence of selfish nuclei, enjoying better replication and transmission than sister nuclei at the same time as being detrimental to the heterokaryon. We hypothesize that introgression has disrupted the coevolution between nuclear types in this strain. </p> <!-- <p><a href="http://dx.doi.org/10.1086/695803">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT “Extreme climate-induced life-history plasticity in an amphibian” http://amnat.org/an/newpapers/FebBecker.html Read the Article Rainfall determines key life history decisions in a frog Blue whales live for more than 100 years, while adult mayflies may come and go in a day. Our own lifespan has increased by nearly 10 years over the past generation. We are used to a world where the life expectancy of animals is expected to vary by a few years, but what if your lifespan was linked to the weather? Researchers from University of Cape Town, South African National Biodiversity Institute, and Stellenbosch University have discovered a frog whose likelihood of survival appears to be linked to the amount of winter rainfall in South Africa’s biodiverse fynbos biome. Rose’s mountain toadlet comes out every winter to breed, but the amount of time the males spend waiting in puddles for females to arrive influences life-expectancy of these tiny toadlets. At only 20-30 mm long, these voiceless toadlets are easily overlooked, but the researchers, Francois Becker, John Measey, Krystal Tolley, and Res Altwegg, undertook a mark-recapture study over 7 years, to reach the finding that whether toadlets live long (4+ years), or just one year, depends on the weather. Surprisingly, ‘good weather’ for frogs (wet winters) was found to reduce survival as animals are thought to spend more time out in the open, while ‘bad weather’ (drier winters) means they abandon the breeding site quicker, resulting in these toadlets living to try again another winter. The correlation between survival and winter rainfall is truly remarkable, but the exact mechanism determining survival needs more work, and time is running out. The latest IUCN assessment is that this species is Critically Endangered and with climate in the area changing, it could be that changes in the winter rainfall regime could add to existing threats for this special species. While this is the first known example of a vertebrate with extreme changes survival that appear to be weather dependent, it may simply be due to a lack of sufficient research on the world’s smaller animal species. The researchers suggest that this kind of weather induced longevity change may be far more common than we are aware of, prompting more concern about how changes to the climate may affect wildlife. Abstract Age specific survival and reproduction are closely linked to fitness and therefore subject to strong selection that typically limits their variability within species. Furthermore, adult survival rate in vertebrate populations is typically less variable over time than other life history traits, such as fecundity or recruitment. Hence, adult survival is often conserved within a population over time, compared to the variation in survival found across taxa. In stark contrast to this general pattern, we report evidence of extreme short-term variation of adult survival in Rose’s Mountain Toadlet (Capensibufo rosei), which is apparently climate-induced. Over seven years, annual survival rate varied between 0.04 and 0.92, and 94% of this variation was explained by variation in breeding-season rainfall. Preliminary results suggest that this variation reflects adaptive life-history plasticity to a degree thus far unrecorded for any vertebrate, rather than direct rainfall induced mortality. In wet years, these toads appeared to achieve increased reproduction at the expense of their own survival whereas in dry years, their survival increased at the expense of reproduction. Such environmentally induced plasticity may reflect a diversity of life-history strategies not previously appreciated among vertebrates. More forthcoming papers &raquo; <p><strong><a href="http://dx.doi.org/10.1086/695315"><i>Read the Article</i></a></strong></p> <p><b>Rainfall determines key life history decisions in a frog </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;">B</span>lue whales live for more than 100 years, while adult mayflies may come and go in a day. Our own lifespan has increased by nearly 10 years over the past generation. We are used to a world where the life expectancy of animals is expected to vary by a few years, but what if your lifespan was linked to the weather? Researchers from University of Cape Town, South African National Biodiversity Institute, and Stellenbosch University have discovered a frog whose likelihood of survival appears to be linked to the amount of winter rainfall in South Africa&rsquo;s biodiverse fynbos biome.</p> <p>Rose&rsquo;s mountain toadlet comes out every winter to breed, but the amount of time the males spend waiting in puddles for females to arrive influences life-expectancy of these tiny toadlets. At only 20-30 mm long, these voiceless toadlets are easily overlooked, but the researchers, Francois Becker, John Measey, Krystal Tolley, and Res Altwegg, undertook a mark-recapture study over 7 years, to reach the finding that whether toadlets live long (4+ years), or just one year, depends on the weather. Surprisingly, &lsquo;good weather&rsquo; for frogs (wet winters) was found to reduce survival as animals are thought to spend more time out in the open, while &lsquo;bad weather&rsquo; (drier winters) means they abandon the breeding site quicker, resulting in these toadlets living to try again another winter.</p> <p>The correlation between survival and winter rainfall is truly remarkable, but the exact mechanism determining survival needs more work, and time is running out. The latest IUCN assessment is that this species is Critically Endangered and with climate in the area changing, it could be that changes in the winter rainfall regime could add to existing threats for this special species.</p> <p>While this is the first known example of a vertebrate with extreme changes survival that appear to be weather dependent, it may simply be due to a lack of sufficient research on the world&rsquo;s smaller animal species. The researchers suggest that this kind of weather induced longevity change may be far more common than we are aware of, prompting more concern about how changes to the climate may affect wildlife.</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>ge specific survival and reproduction are closely linked to fitness and therefore subject to strong selection that typically limits their variability within species. Furthermore, adult survival rate in vertebrate populations is typically less variable over time than other life history traits, such as fecundity or recruitment. Hence, adult survival is often conserved within a population over time, compared to the variation in survival found across taxa. In stark contrast to this general pattern, we report evidence of extreme short-term variation of adult survival in Rose&rsquo;s Mountain Toadlet (<i>Capensibufo rosei</i>), which is apparently climate-induced. Over seven years, annual survival rate varied between 0.04 and 0.92, and 94% of this variation was explained by variation in breeding-season rainfall. Preliminary results suggest that this variation reflects adaptive life-history plasticity to a degree thus far unrecorded for any vertebrate, rather than direct rainfall induced mortality. In wet years, these toads appeared to achieve increased reproduction at the expense of their own survival whereas in dry years, their survival increased at the expense of reproduction. Such environmentally induced plasticity may reflect a diversity of life-history strategies not previously appreciated among vertebrates.</p> <!-- <p><a href="http://dx.doi.org/10.1086/695315">Read&nbsp;the&nbsp;Article</a></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 Nov 2017 06:00:00 GMT “Coupling, reinforcement and speciation” http://amnat.org/an/newpapers/FebButlin-A.html Read the Article Species are isolated by many barriers to gene flow working together. We ask how this coupling of barriers can evolveAbstract During the process of speciation, populations may diverge for traits, and at their underlying loci, that contribute barriers to gene flow. These barrier traits and barrier loci underlie individual barrier effects, by which we mean the contribution that a barrier locus or trait, or some combination of barrier loci or traits makes to overall isolation. The evolution of strong reproductive isolation typically requires the origin of multiple barrier effects. Critically, it also requires the coincidence of barrier effects: for example, two barrier effects, one due to assortative mating and the other due to hybrid inviability, create a stronger overall barrier to gene flow if they coincide than if they distinguish independent pairs of populations. Here, we define ‘coupling’ as any process that generates coincidence of barrier effects, resulting in a stronger overall barrier to gene flow. We argue that speciation research, both empirical and theoretical, needs to consider both the origin of barrier effects and the ways in which they are coupled. Coincidence of barrier effects can occur either as a by-product of selection on individual barrier effects or of population processes, or as an adaptive response to indirect selection. Adaptive coupling may be accompanied by further evolution that enhances individual barrier effects. Reinforcement, classically viewed as the evolution of pre-zygotic barriers to gene flow in response to costs of hybridization, is an example of this type of process. However, we argue for an extended view of reinforcement that includes coupling processes involving enhancement of any type of additional barrier effect as a result of an existing barrier. This view of coupling and reinforcement may help to guide development of both theoretical and empirical research on the process of speciation. More forthcoming papers &raquo; <p><strong><a href="http://dx.doi.org/10.1086/695136"><i>Read the Article</i></a></strong></p> <p><b>Species are isolated by many barriers to gene flow working together. We ask how this coupling of barriers can evolve</b></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;">D</span>uring the process of speciation, populations may diverge for traits, and at their underlying loci, that contribute barriers to gene flow. These barrier traits and barrier loci underlie individual barrier effects, by which we mean the contribution that a barrier locus or trait, or some combination of barrier loci or traits makes to overall isolation. The evolution of strong reproductive isolation typically requires the origin of multiple barrier effects. Critically, it also requires the coincidence of barrier effects: for example, two barrier effects, one due to assortative mating and the other due to hybrid inviability, create a stronger overall barrier to gene flow if they coincide than if they distinguish independent pairs of populations. Here, we define &lsquo;coupling&rsquo; as any process that generates coincidence of barrier effects, resulting in a stronger overall barrier to gene flow. We argue that speciation research, both empirical and theoretical, needs to consider both the origin of barrier effects and the ways in which they are coupled. Coincidence of barrier effects can occur either as a by-product of selection on individual barrier effects or of population processes, or as an adaptive response to indirect selection. Adaptive coupling may be accompanied by further evolution that enhances individual barrier effects. Reinforcement, classically viewed as the evolution of pre-zygotic barriers to gene flow in response to costs of hybridization, is an example of this type of process. However, we argue for an extended view of reinforcement that includes coupling processes involving enhancement of <i>any type</i> of additional barrier effect as a result of an existing barrier. This view of coupling and reinforcement may help to guide development of both theoretical and empirical research on the process of speciation. <!-- <a href="http://dx.doi.org/10.1086/695136">Read&nbsp;the&nbsp;Article</a> --></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 Nov 2017 06:00:00 GMT “A dynamic state model of migratory behavior and physiology to assess the consequences of environmental variation and anthropogenic disturbance on marine vertebrates” http://amnat.org/an/newpapers/FebPirotta.html The DOI is https://dx.doi.org/10.1086/695135 Dynamic state modeling offers new insights into the migratory behavior and physiology of baleen whales Animals that migrate between their feeding and breeding grounds are subject to intense physiological pressure. On the feeding grounds, they must acquire a large portion of the energy they need to cover their travel and reproductive costs, before returning to the breeding grounds where they may exhaust the accumulated resources. This paper explores the mechanisms underlying this complex trade-off and suggests hypotheses on the processes driving migratory behavior, with blue whales as an example. Researchers at Washington State University, in collaboration with colleagues from the University of California Santa Cruz, Oregon State University, and Stanford University, have combined their expertise and available data on the ecology, feeding behavior, movements, energetics, and reproduction of migrating blue whales to develop a model describing a female’s optimal behavior over time. They find that migration emerges from the animals tracking the seasonal variability of prey in their range, while having to return to the breeding grounds. The results also show that female blue whales must feed on the breeding grounds to sustain the large costs of lactation, while pregnancy is energetically less costly. The authors then use the model to demonstrate how environmental changes could disproportionately affect reproductive success depending on how whales react and adjust to a perturbed environment. They also predict that the impact of localized, acute disturbance from human activities depends on how whales change their behavior, while chronic, but weaker, disturbances are expected to have limited short-term effects on reproduction. Blue whale migration appears to balance access to sufficient food resources with the constraints of reproduction. The proposed approach could be applied to other migratory species to disentangle similar trade-offs. Abstract Integrating behavior and physiology is critical to formulating new hypotheses on the evolution of animal life-history strategies. Migratory capital breeders acquire most of the energy they need to sustain migration, gestation and lactation before parturition. Therefore, when predicting the impact of environmental variation on such species, a mechanistic understanding of the physiology of their migratory behavior is required. Using baleen whales as a model system, we developed a dynamic state variable model that captures the interplay among behavioral decisions, energy, reproductive needs and the environment. We applied the framework to blue whales (Balaenoptera musculus) in the Eastern North Pacific Ocean, and explored the effects of environmental and anthropogenic perturbations on female reproductive success. We demonstrate the emergence of migration to track prey resources, enabling us to quantify the trade-offs among capital breeding, body condition, and metabolic expenses. We predict that periodic climatic oscillations affect reproductive success less than unprecedented environmental changes do. The effect of localized, acute anthropogenic impacts depended on whales’ behavioral response to the disturbance; chronic, but weaker, disturbances had little effect on reproductive success. Because we link behavior and vital rates by modeling individuals’ energetic budgets, we provide a general framework to investigate the ecology of migration and assess the population consequences of disturbance, while identifying critical knowledge gaps. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><i>The DOI is https://dx.doi.org/10.1086/695135 </i></p> <p><b>Dynamic state modeling offers new insights into the migratory behavior and physiology of baleen whales </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;">A</span>nimals that migrate between their feeding and breeding grounds are subject to intense physiological pressure. On the feeding grounds, they must acquire a large portion of the energy they need to cover their travel and reproductive costs, before returning to the breeding grounds where they may exhaust the accumulated resources. This paper explores the mechanisms underlying this complex trade-off and suggests hypotheses on the processes driving migratory behavior, with blue whales as an example.</p> <p>Researchers at Washington State University, in collaboration with colleagues from the University of California Santa Cruz, Oregon State University, and Stanford University, have combined their expertise and available data on the ecology, feeding behavior, movements, energetics, and reproduction of migrating blue whales to develop a model describing a female&rsquo;s optimal behavior over time. They find that migration emerges from the animals tracking the seasonal variability of prey in their range, while having to return to the breeding grounds. The results also show that female blue whales must feed on the breeding grounds to sustain the large costs of lactation, while pregnancy is energetically less costly.</p> <p>The authors then use the model to demonstrate how environmental changes could disproportionately affect reproductive success depending on how whales react and adjust to a perturbed environment. They also predict that the impact of localized, acute disturbance from human activities depends on how whales change their behavior, while chronic, but weaker, disturbances are expected to have limited short-term effects on reproduction. Blue whale migration appears to balance access to sufficient food resources with the constraints of reproduction. The proposed approach could be applied to other migratory species to disentangle similar trade-offs.</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;">I</span>ntegrating behavior and physiology is critical to formulating new hypotheses on the evolution of animal life-history strategies. Migratory capital breeders acquire most of the energy they need to sustain migration, gestation and lactation before parturition. Therefore, when predicting the impact of environmental variation on such species, a mechanistic understanding of the physiology of their migratory behavior is required. Using baleen whales as a model system, we developed a dynamic state variable model that captures the interplay among behavioral decisions, energy, reproductive needs and the environment. We applied the framework to blue whales (<i>Balaenoptera musculus</i>) in the Eastern North Pacific Ocean, and explored the effects of environmental and anthropogenic perturbations on female reproductive success. We demonstrate the emergence of migration to track prey resources, enabling us to quantify the trade-offs among capital breeding, body condition, and metabolic expenses. We predict that periodic climatic oscillations affect reproductive success less than unprecedented environmental changes do. The effect of localized, acute anthropogenic impacts depended on whales&rsquo; behavioral response to the disturbance; chronic, but weaker, disturbances had little effect on reproductive success. Because we link behavior and vital rates by modeling individuals&rsquo; energetic budgets, we provide a general framework to investigate the ecology of migration and assess the population consequences of disturbance, while identifying critical knowledge gaps.</p> <p> <a href="https://dx.doi.org/10.1086/695135">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT “Leaf form evolution in Viburnum parallels variation within individual plants” http://amnat.org/an/newpapers/FebSpriggs-A.html The DOI is http://dx.doi.org/10.1086/695337 Abstract Few studies have critically evaluated how morphological variation within individual organisms corresponds to variation within and among species. Sub-individual variation in plants facilitates such studies because their indeterminate, modular growth generates multiple serially homologous structures along growing axes. Focusing on leaf form, we evaluate how sub-individual trait variation relates to leaf evolution across Viburnum, a clade of woody angiosperms. In Viburnum we infer multiple independent origins of wide/lobed leaves with toothed margins from ancestors with elliptical, smooth-margined leaves. We document leaf variation along the branches of individual plants of 28 species and among populations across the wide range of V.&nbsp;dentatum. We conclude that when novel leaf forms evolved in Viburnum, they were intercalated at the beginning of the seasonal leaf sequence, which then generated a repeated spectrum of leaf forms along each branch (seasonal heteroblasty). We hypothesize that the existence of such a spectrum then facilitated additional evolutionary shifts, including reversions to more ancestral forms. We argue that the recurrent production of alternative phenotypes provides opportunities to canalize the production of particular forms, and that this phenomenon has played an important role in generating macro-scale patterns. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><i>The DOI is http://dx.doi.org/10.1086/695337 </i></p> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">F</span>ew studies have critically evaluated how morphological variation within individual organisms corresponds to variation within and among species. Sub-individual variation in plants facilitates such studies because their indeterminate, modular growth generates multiple serially homologous structures along growing axes. Focusing on leaf form, we evaluate how sub-individual trait variation relates to leaf evolution across <i>Viburnum</i>, a clade of woody angiosperms. In <i>Viburnum</i> we infer multiple independent origins of wide/lobed leaves with toothed margins from ancestors with elliptical, smooth-margined leaves. We document leaf variation along the branches of individual plants of 28 species and among populations across the wide range of <i>V.&nbsp;dentatum</i>. We conclude that when novel leaf forms evolved in <i>Viburnum</i>, they were intercalated at the beginning of the seasonal leaf sequence, which then generated a repeated spectrum of leaf forms along each branch (seasonal heteroblasty). We hypothesize that the existence of such a spectrum then facilitated additional evolutionary shifts, including reversions to more ancestral forms. We argue that the recurrent production of alternative phenotypes provides opportunities to canalize the production of particular forms, and that this phenomenon has played an important role in generating macro-scale patterns. <a href="http://dx.doi.org/10.1086/695337">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT “Coinfection timing drives host population dynamics through changes in virulence” http://amnat.org/an/newpapers/FebMarchetto-A.html The DOI is http://dx.doi.org/10.1086/695316 Explicitly tracking coinfection timing can be important in a number of systems, such as when parasites share a vector Abstract Infections of one host by multiple parasites are common, and several studies have found that the order of parasite invasion can affect both within-host competition and disease severity. However, it is unclear to what extent coinfection timing might be important to consider when modeling parasite impacts on host populations. Using a model system of two viruses infecting barley, we found that simultaneous infections of the two viruses were significantly more damaging to hosts than sequential coinfections. While priority effects were evident in within-host concentrations of sequential coinfections, priority did not influence any parameters, such as virulence or transmission rate, that affect host population dynamics. We built a susceptible-infected model to examine whether the observed difference in coinfection virulence could impact host population dynamics under a range of scenarios. We found that coinfection timing can have an important, but context dependent, effect on projected host population dynamics. Studies that examine only simultaneous coinfections could inflate disease impact predictions. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><i>The DOI is http://dx.doi.org/10.1086/695316 </i></p> <p><b>Explicitly tracking coinfection timing can be important in a number of systems, such as when parasites share a vector </b></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;">I</span>nfections of one host by multiple parasites are common, and several studies have found that the order of parasite invasion can affect both within-host competition and disease severity. However, it is unclear to what extent coinfection timing might be important to consider when modeling parasite impacts on host populations. Using a model system of two viruses infecting barley, we found that simultaneous infections of the two viruses were significantly more damaging to hosts than sequential coinfections. While priority effects were evident in within-host concentrations of sequential coinfections, priority did not influence any parameters, such as virulence or transmission rate, that affect host population dynamics. We built a susceptible-infected model to examine whether the observed difference in coinfection virulence could impact host population dynamics under a range of scenarios. We found that coinfection timing can have an important, but context dependent, effect on projected host population dynamics. Studies that examine only simultaneous coinfections could inflate disease impact predictions. <a href="https://dx.doi.org/10.1086/695316">Read&nbsp;the&nbsp;Article</a></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 Nov 2017 06:00:00 GMT “Offspring size and reproductive allocation in harvester ants” http://amnat.org/an/newpapers/JanWiernasz.html READ THE PAPER: http://dx.doi.org/10.1086/694903 Taking the Trivers-Willard hypothesis beyond mammals, researchers find that ant colonies invest differently in queens and males When organisms reproduce, they must distribute resources among their offspring. How many offspring should be produced? How big should they be? Should the number of females be the same as the number of males? Should similar amounts of resources be invested in females and males or should one sex receive preferential investment? Diane Wiernasz and Blaine Cole (University of Houston, Houston, TX) address these questions in Western Harvester Ants, using information from an experiment on more than 200 ant colonies, part of their long-term study population near Grand Junction, CO. Harvester ants collect and store the seeds of local plants to use as food. Both male and female offspring are more successful when they are larger, but small size has greater negative effects on daughters. In a field experiment, when colonies are given additional food that they can store, they make more of both male and females; colonies benefit the most from producing more offspring of both sexes. However, colonies given extra food that cannot be stored make larger males but not larger females. Colonies appear to have an "invest in females first" strategy, and always make females that are relatively large. When food is limited, resources are used preferentially to make large daughters and what is left is invested in sons. The mathematical model developed in this study successfully extends the classic work of Trivers and Willard to show how parents that produce multiple offspring should invest in females vs. males based not only on parental resources but on the benefits that increased investment will provide to offspring of each sex. More forthcoming papers &raquo; <p style="text-align: right;"><i>READ THE PAPER: <a href="http://dx.doi.org/10.1086/694903">http://dx.doi.org/10.1086/694903 </a></i></p> <p><b>Taking the Trivers-Willard hypothesis beyond mammals, researchers find that ant colonies invest differently in queens and males </b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">W</span>hen organisms reproduce, they must distribute resources among their offspring. How many offspring should be produced? How big should they be? Should the number of females be the same as the number of males? Should similar amounts of resources be invested in females and males or should one sex receive preferential investment? Diane Wiernasz and Blaine Cole (University of Houston, Houston, TX) address these questions in Western Harvester Ants, using information from an experiment on more than 200 ant colonies, part of their long-term study population near Grand Junction, CO. Harvester ants collect and store the seeds of local plants to use as food.</p> <p>Both male and female offspring are more successful when they are larger, but small size has greater negative effects on daughters. In a field experiment, when colonies are given additional food that they can store, they make more of both male and females; colonies benefit the most from producing more offspring of both sexes. However, colonies given extra food that cannot be stored make larger males but not larger females. Colonies appear to have an &quot;invest in females first&quot; strategy, and always make females that are relatively large. When food is limited, resources are used preferentially to make large daughters and what is left is invested in sons. The mathematical model developed in this study successfully extends the classic work of Trivers and Willard to show how parents that produce multiple offspring should invest in females vs. males based not only on parental resources but on the benefits that increased investment will provide to offspring of each sex. <!-- <a href="http://dx.doi.org/10.1086/694903">Read&nbsp;the&nbsp;Article</a> --> </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 Nov 2017 06:00:00 GMT “Testing range-limit hypotheses using range-wide habitat suitability and occupancy for the scarlet monkeyflower (Erythranthe cardinalis)” http://amnat.org/an/newpapers/MarAngert-A.html The DOI will be http://dx.doi.org/10.1086/695984 Abstract Determining the causes of geographic range limits is a fundamental problem in ecology, evolution, and conservation biology. Range limits arise due to fitness and dispersal limitation, which yield contrasting predictions about habitat suitability and occupancy of suitable habitat across geographic ranges. If a range edge is limited primarily by fitness, occupancy of suitable habitat should be high, habitat suitability should decline towards the edge, and no suitable habitat should exist beyond it. In contrast, a range edge limited primarily by dispersal should have unoccupied but suitable habitat at and beyond the edge. We built ecological niche models relating occurrence records for the scarlet monkeyflower (Erythranthe cardinalis) to climatic variables, and applied these models to independent data from systematic, range-wide surveys of presence and absence to estimate the availability and occupancy of climatically suitable habitat. We found that fitness limitation predominated over dispersal limitation, but dispersal limitation also played a role at the poleward edge. These results are consistent with the hypothesis that dispersal limitation is more important along shallow environmental gradients and also suggest that synergy between dispersal and fitness limitation can contribute to colonization failure. The framework used here is validated by independent data and could be readily applied to inferring causes of range limits in many other species. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695984 </i></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;">D</span>etermining the causes of geographic range limits is a fundamental problem in ecology, evolution, and conservation biology. Range limits arise due to fitness and dispersal limitation, which yield contrasting predictions about habitat suitability and occupancy of suitable habitat across geographic ranges. If a range edge is limited primarily by fitness, occupancy of suitable habitat should be high, habitat suitability should decline towards the edge, and no suitable habitat should exist beyond it. In contrast, a range edge limited primarily by dispersal should have unoccupied but suitable habitat at and beyond the edge. We built ecological niche models relating occurrence records for the scarlet monkeyflower (<i>Erythranthe cardinalis</i>) to climatic variables, and applied these models to independent data from systematic, range-wide surveys of presence and absence to estimate the availability and occupancy of climatically suitable habitat. We found that fitness limitation predominated over dispersal limitation, but dispersal limitation also played a role at the poleward edge. These results are consistent with the hypothesis that dispersal limitation is more important along shallow environmental gradients and also suggest that synergy between dispersal and fitness limitation can contribute to colonization failure. The framework used here is validated by independent data and could be readily applied to inferring causes of range limits in many other species.</p> <!-- <p><a href="http://dx.doi.org/10.1086/695984">Read&nbsp;the&nbsp;Article</a></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 Nov 2017 06:00:00 GMT “Partitioning the effects of eco-evolutionary feedbacks on community stability” http://amnat.org/an/newpapers/MarPatel.html The DOI will be http://dx.doi.org/10.1086/695834 Natural communities are perpetually subject to disturbances in their environment. Do communities recover from these perturbations or might species be lost? Communities may respond to disturbances in two ways: through an ecological response (species densities may change) and through an evolutionary response (species may adapt to new conditions). Swati Patel, from Tulane University, and co-authors Michael Cortez and Sebastian Schreiber explore how these two responses, in some cases, work together to maintain stable communities, and in others, drive instability that may lead to the loss of species. Using mathematical models, they develop a simple and general formula that predicts whether a community is able to recover or not following an environmental disturbance. Importantly, they find that this depends on how quickly species can evolve relative to how quickly their densities change. Surprisingly, faster evolution does not necessarily imply more stable communities; communities with more rapidly evolving species can actually be more prone to species loss! Abstract A&nbsp;fundamental challenge in ecology continues to be identifying mechanisms that stabilize community dynamics. By altering the interactions within a community, eco-evolutionary feedbacks may play a role in community stability. Indeed, recent empirical and theoretical studies demonstrate that these feedbacks can stabilize or destabilize communities, and moreover, that this sometimes depends on the relative rate of ecological to evolutionary processes. So far, theory on how eco-evolutionary feedbacks impact stability exists only for a few special cases. In our work, we develop a general theory for determining the effects of eco-evolutionary feedbacks on stability in communities with an arbitrary number of interacting species and evolving traits for when evolution is slow and fast. We characterize how eco-evolutionary feedbacks lead to stable communities that would otherwise be unstable, and vice versa. Additionally, we show how one can identify the roles of direct and indirect feedbacks between ecological and evolutionary processes on stability, and how the effects of those feedbacks depend on the rate of evolution relative to the ecological time scales. Applying our methods to models of competing species and food chains, we demonstrate how the functional form of trade offs, genetic correlations between traits, and the rate of evolution determine whether eco-evolutionary feedbacks stabilize or destabilize communities. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695834 </i></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;">N</span>atural communities are perpetually subject to disturbances in their environment. Do communities recover from these perturbations or might species be lost? Communities may respond to disturbances in two ways: through an ecological response (species densities may change) and through an evolutionary response (species may adapt to new conditions). Swati Patel, from Tulane University, and co-authors Michael Cortez and Sebastian Schreiber explore how these two responses, in some cases, work together to maintain stable communities, and in others, drive instability that may lead to the loss of species. Using mathematical models, they develop a simple and general formula that predicts whether a community is able to recover or not following an environmental disturbance. Importantly, they find that this depends on how quickly species can evolve relative to how quickly their densities change. Surprisingly, faster evolution does not necessarily imply more stable communities; communities with more rapidly evolving species can actually be more prone to species loss!</p> <hr /> <h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">A</span>&nbsp;fundamental challenge in ecology continues to be identifying mechanisms that stabilize community dynamics. By altering the interactions within a community, eco-evolutionary feedbacks may play a role in community stability. Indeed, recent empirical and theoretical studies demonstrate that these feedbacks can stabilize or destabilize communities, and moreover, that this sometimes depends on the relative rate of ecological to evolutionary processes. So far, theory on how eco-evolutionary feedbacks impact stability exists only for a few special cases. In our work, we develop a general theory for determining the effects of eco-evolutionary feedbacks on stability in communities with an arbitrary number of interacting species and evolving traits for when evolution is slow and fast. We characterize how eco-evolutionary feedbacks lead to stable communities that would otherwise be unstable, and vice versa. Additionally, we show how one can identify the roles of direct and indirect feedbacks between ecological and evolutionary processes on stability, and how the effects of those feedbacks depend on the rate of evolution relative to the ecological time scales. Applying our methods to models of competing species and food chains, we demonstrate how the functional form of trade offs, genetic correlations between traits, and the rate of evolution determine whether eco-evolutionary feedbacks stabilize or destabilize communities.</p> <!-- <p><a href="http://dx.doi.org/10.1086/695834">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT “Towards a mechanistic understanding of thermal niche partitioning” http://amnat.org/an/newpapers/MarSmith-A.html The DOI will be http://dx.doi.org/10.1086/695805 Abstract We develop a theoretical framework to elucidate the mechanistic basis of thermal niche partitioning in ectotherms. Using a food web module of two consumers competing for a biotic resource, we investigate how temperature effects on species&#39; attack and mortality rates scale up to population-level outcomes of coexistence and exclusion. We find that differences between species in their competitive effects ultimately arise from asymmetries generated by the non-linear nature of the temperature response of mortality: cold-adapted species, and thermal specialists, limit themselves more strongly than they limit their warm-adapted, and generalist, competitors. These asymmetries become greater as seasonal temperature fluctuations increase, generating latitudinal variation in coexistence patterns and priority effects. Characterizing species&#39; thermal niches in terms of mechanistic descriptions of trait responses to temperature allows us to make testable predictions about the population-level outcomes of competition based solely on three fundamental, and easily measurable, quantities: attack rate optima, response breadths and temperature sensitivity of mortality. We validate our framework by testing its predictions with data from an insect host-parasitoid community. Simply by quantifying the three basic quantities we predict that priority effects cannot occur in this system, which is borne out by population-level experiments showing that the outcome of competition does not depend on initial conditions. More broadly, our framework can predict the conditions under which exotic invasive species can exclude, or coexist with, native biota, and the effects of climate warming on competitive communities across latitudinal gradients. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695805 </i></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;">W</span>e develop a theoretical framework to elucidate the mechanistic basis of thermal niche partitioning in ectotherms. Using a food web module of two consumers competing for a biotic resource, we investigate how temperature effects on species&#39; attack and mortality rates scale up to population-level outcomes of coexistence and exclusion. We find that differences between species in their competitive effects ultimately arise from asymmetries generated by the non-linear nature of the temperature response of mortality: cold-adapted species, and thermal specialists, limit themselves more strongly than they limit their warm-adapted, and generalist, competitors. These asymmetries become greater as seasonal temperature fluctuations increase, generating latitudinal variation in coexistence patterns and priority effects. Characterizing species&#39; thermal niches in terms of mechanistic descriptions of trait responses to temperature allows us to make testable predictions about the population-level outcomes of competition based solely on three fundamental, and easily measurable, quantities: attack rate optima, response breadths and temperature sensitivity of mortality. We validate our framework by testing its predictions with data from an insect host-parasitoid community. Simply by quantifying the three basic quantities we predict that priority effects cannot occur in this system, which is borne out by population-level experiments showing that the outcome of competition does not depend on initial conditions. More broadly, our framework can predict the conditions under which exotic invasive species can exclude, or coexist with, native biota, and the effects of climate warming on competitive communities across latitudinal gradients.</p> <!-- <p> <a href="http://dx.doi.org/10.1086/695805">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT “Evolution as a coexistence mechanism: Does genetic architecture matter?” http://amnat.org/an/newpapers/MarSchreiber.html The DOI will be http://dx.doi.org/10.1086/695832 Synergistic pleitropy and dominance in defensive alleles promote polymorphic prey and predator coexistence A&nbsp;fundamental principle in ecology is the competitive exclusion principle. Like two gladiatorial combatants in the Colosseum, this principle asserts that when two species compete for a single resource, one species will be driven extinct (the loser) and one will persist (the winner). Competition for resources, whether that be pathogens competing for hosts, herbivores competing for plants, or predators competing for prey, is ubiquitous in nature. Yet many of these competing species coexist. How can this be? Using mathematical models, Sebastian Schreiber, a Professor of Evolution and Ecology at the University of California, Davis, and his co-authors show that evolution of defenses by the exploited species provides one possible answer. This new coexistence mechanism requires that genotypes defended against one of the competitors are poorly defended against the other competitor. This trade-off can lead to a complicated rock-paper-scissor dynamic, in which no resource genotype or competitor ever has the upper hand against everybody else. Namely, when one competitor is more abundant in the system, the genotype best defended against this competitor becomes abundant. Unable to exploit this well defended genotype, this competitor species decreases in abundance as the other competitor becomes more common. Thus, the cycle continues as the genotype best defended against this other competitor becomes more abundant. Whether this mechanism is effective for enabling coexistence, however, depends on the details of the genetics underlying the defensive trait. In light of recent empirical evidence that evolution can occur quickly, the work of Schreiber and colleagues raises the tantalizing possibility that species may coexist due to the evolution of others rather than evolution of their own traits. Abstract Species sharing a prey or a predator species may go extinct due to exploitative or apparent competition. We examine whether evolution of the shared species acts as a coexistence mechanism and to what extent the answer depends on the genetic architecture underlying trait evolution. In our models of exploitative and apparent competition, the shared species evolves its defense or prey use. Evolving species are either haploid or diploid. A single locus pleiotropically determines prey nutritional quality and predator attack rates. When pleiotropy is sufficiently antagonistic (e.g. nutritional prey are harder to capture), eco-evolutionary assembly culminates in one of two stable states supporting only two species. When pleiotropy is weakly antagonistic or synergistic, assembly is intransitive: species-genotype pairs are cyclically displaced by rare invasions of the missing genotypes or species. This intransitivity allows for coexistence if, along its equilibria, the geometric mean of recovery rates exceeds the geometric mean of loss rates of the rare genotypes or species. By affecting these rates, synergistic pleiotropy can mediate coexistence, while antagonistic pleiotropy does not. For diploid populations experiencing weak antagonistic pleiotropy, superadditive allelic contributions to fitness can mitigate coexistence via an eco-evolutionary storage effect. Density-dependence and mutations also promote coexistence. These results highlight how the efficacy of evolution as a coexistence mechanism may depend on the underlying genetic architecture. More forthcoming papers &raquo; <p><i>The DOI will be http://dx.doi.org/10.1086/695832 </i></p> <p><b>Synergistic pleitropy and dominance in defensive alleles promote polymorphic prey and predator coexistence </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;fundamental principle in ecology is the competitive exclusion principle. Like two gladiatorial combatants in the Colosseum, this principle asserts that when two species compete for a single resource, one species will be driven extinct (the loser) and one will persist (the winner). Competition for resources, whether that be pathogens competing for hosts, herbivores competing for plants, or predators competing for prey, is ubiquitous in nature. Yet many of these competing species coexist. How can this be? Using mathematical models, Sebastian Schreiber, a Professor of Evolution and Ecology at the University of California, Davis, and his co-authors show that evolution of defenses by the exploited species provides one possible answer. This new coexistence mechanism requires that genotypes defended against one of the competitors are poorly defended against the other competitor. This trade-off can lead to a complicated rock-paper-scissor dynamic, in which no resource genotype or competitor ever has the upper hand against everybody else. Namely, when one competitor is more abundant in the system, the genotype best defended against this competitor becomes abundant. Unable to exploit this well defended genotype, this competitor species decreases in abundance as the other competitor becomes more common. Thus, the cycle continues as the genotype best defended against this other competitor becomes more abundant. Whether this mechanism is effective for enabling coexistence, however, depends on the details of the genetics underlying the defensive trait. In light of recent empirical evidence that evolution can occur quickly, the work of Schreiber and colleagues raises the tantalizing possibility that species may coexist due to the evolution of others rather than evolution of their own traits.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">S</span>pecies sharing a prey or a predator species may go extinct due to exploitative or apparent competition. We examine whether evolution of the shared species acts as a coexistence mechanism and to what extent the answer depends on the genetic architecture underlying trait evolution. In our models of exploitative and apparent competition, the shared species evolves its defense or prey use. Evolving species are either haploid or diploid. A single locus pleiotropically determines prey nutritional quality and predator attack rates. When pleiotropy is sufficiently antagonistic (e.g. nutritional prey are harder to capture), eco-evolutionary assembly culminates in one of two stable states supporting only two species. When pleiotropy is weakly antagonistic or synergistic, assembly is intransitive: species-genotype pairs are cyclically displaced by rare invasions of the missing genotypes or species. This intransitivity allows for coexistence if, along its equilibria, the geometric mean of recovery rates exceeds the geometric mean of loss rates of the rare genotypes or species. By affecting these rates, synergistic pleiotropy can mediate coexistence, while antagonistic pleiotropy does not. For diploid populations experiencing weak antagonistic pleiotropy, superadditive allelic contributions to fitness can mitigate coexistence via an eco-evolutionary storage effect. Density-dependence and mutations also promote coexistence. These results highlight how the efficacy of evolution as a coexistence mechanism may depend on the underlying genetic architecture. </p> <!-- <p><a href="http://dx.doi.org/10.1086/695832">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT “Multivariate climate change can favor large herbivore body size in food webs” http://amnat.org/an/newpapers/MarSmthRmsh.html Read the Article Climate change may drive shifts towards larger herbivore body size Scientists have generally expected animals to get smaller as the planet warms, based on relationships between animal growth and development and temperature. However, global climate change means more than just warmer temperatures: other climate factors such as atmospheric carbon dioxide and rainfall patterns are also expected to change. Smith-Ramesh et al. have constructed a model based on food web interactions amongst old-field plants, grasshoppers, and spiders exposed to multiple changing climate variables. They find that under certain predicted future scenarios, climate change could actually result in larger animal body sizes. These results challenge past assumptions that climate change will result in smaller animals across the board. Abstract Climate change is expected to favor smaller-bodied organisms through effects of temperature on physiological performance and food-web interactions, so much so that smaller body size has been touted as a universal response to global warming alongside range-shifts and changing phenology. However, climate change involves more than warming. It is multivariate, and the interplay between climate variables may result in less straightforward predictions. We present a model that considers the simultaneous effect of multiple variables (temperature, CO2, and moisture) on herbivore body sizes within a tri-trophic food web comprised of vegetation, herbivores, and a shared predator. The model accounts for climate effects on animal behavior, plant and animal metabolism, and plant quality to explore emergent effects on herbivore body size. Our analysis reveals that some common multivariate climate change scenarios may favor larger-bodied herbivores, challenging previous findings of shifts toward small-bodied herbivores in the face of rising temperatures. More forthcoming papers &raquo; <p><strong><a href="http://dx.doi.org/10.1086/695768"><i>Read the Article</i></a></strong></p> <p><b>Climate change may drive shifts towards larger herbivore body size </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>cientists have generally expected animals to get smaller as the planet warms, based on relationships between animal growth and development and temperature. However, global climate change means more than just warmer temperatures: other climate factors such as atmospheric carbon dioxide and rainfall patterns are also expected to change. Smith-Ramesh et al. have constructed a model based on food web interactions amongst old-field plants, grasshoppers, and spiders exposed to multiple changing climate variables. They find that under certain predicted future scenarios, climate change could actually result in larger animal body sizes. These results challenge past assumptions that climate change will result in smaller animals across the board.</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>limate change is expected to favor smaller-bodied organisms through effects of temperature on physiological performance and food-web interactions, so much so that smaller body size has been touted as a universal response to global warming alongside range-shifts and changing phenology. However, climate change involves more than warming. It is multivariate, and the interplay between climate variables may result in less straightforward predictions. We present a model that considers the simultaneous effect of multiple variables (temperature, CO<span style="font-size:70%; position:relative; bottom:-0.3em;">2</span>, and moisture) on herbivore body sizes within a tri-trophic food web comprised of vegetation, herbivores, and a shared predator. The model accounts for climate effects on animal behavior, plant and animal metabolism, and plant quality to explore emergent effects on herbivore body size. Our analysis reveals that some common multivariate climate change scenarios may favor larger-bodied herbivores, challenging previous findings of shifts toward small-bodied herbivores in the face of rising temperatures. </p> <!-- <p><a href="http://dx.doi.org/10.1086/695768">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT “Temperature dependent growth and fission rate plasticity drive seasonal and geographic changes in body size in a clonal sea anemone” http://amnat.org/an/newpapers/FebRyan.html Read the Article Fission rate plasticity allows clonal animals to track rapid changes in optimal body size through time and space Phenotypic plasticity, or the ability of individuals to continuously refine their morphology in response to changing conditions, presents a major challenge when predicting the ecological and evolutionary effects of environmental change. The “temperature-size rule” is a commonly observed pattern in animals where individuals grow to be smaller as adults when conditions are warmer. In aquatic animals, this pattern may reflect an increasing risk of oxygen limitation as water warms, favoring smaller bodied animals with a higher surface area to volume ratio. Clonal animals may be able to change size throughout their lives by adjusting the rate at which they grow versus divide. This flexibility may allow them to track a changing optimal body size as the environment changes, but can also influence patterns of investment in asexual and sexual reproduction. Using lab experiments and field observations, Will H. Ryan demonstrated that changes in the fission rate and average body size of the clonal sea anemone, Diadumene lineata, follow seasonal temperature changes. He grew anemones collected from across the species’ US Atlantic range (Florida, Georgia, and Massachusetts) in chambers mimicking seasonal temperature patterns found at these sites. The year-long experiment showed that annual patterns of growth, size, and clonal investment are highly dependent on local temperature patterns, leading to a gradient in the degree of asexuality expressed across the species range. Northern populations stay large and divide infrequently, whereas southern sites stay small and divide all year. Intermediate sites alternate between phases of individual growth and clonal proliferation. Variation in the response among individuals from different sites suggests that natural selection may be able to shape these patterns. For organisms with complex life cycles, like these sea anemones, environmental variation not only alters the speed of growth and development, but can also change the timing and nature of major life history events, such as fission. Abstract The temperature-size rule (TSR) is a commonly observed pattern where adult body size is negatively correlated with developmental temperature. In part, this may occur as a consequence of allometric scaling, where changes in the ratio of surface area to mass limit oxygen diffusion as body size increases. As oxygen demand increases with temperature, a smaller body should be favored as temperature increases. For clonal animals, small changes in growth and/or fission rate can rapidly alter the average body size of clonal descendants. Here I test the hypothesis that the clonal sea anemone Diadumene lineata is able to track an optimal body size through seasonal temperature changes using fission rate plasticity. Individuals from three regions (Florida, Georgia and Massachusetts) across the species’ latitudinal range were grown in a year-long reciprocal common garden experiment mimicking seasonal temperature changes at three sites. Average body size was found to be smaller and fission rates higher in warmer conditions, consistent with the TSR pattern. However, seasonal size and fission patterns reflect a complex interaction between region-specific thermal reaction norms and the local temperature regime. These details provide insight into both the range of conditions required for oxygen limitation to contribute to a negative correlation between body size and temperature and the role that fission rate plasticity can play in tracking a rapidly changing optimal phenotype. More forthcoming papers &raquo; <p><strong><a href="http://dx.doi.org/10.1086/695496"><i>Read the Article</i></a></strong></p> <p><b>Fission rate plasticity allows clonal animals to track rapid changes in optimal body size through time and space </b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">P</span>henotypic plasticity, or the ability of individuals to continuously refine their morphology in response to changing conditions, presents a major challenge when predicting the ecological and evolutionary effects of environmental change. The &ldquo;temperature-size rule&rdquo; is a commonly observed pattern in animals where individuals grow to be smaller as adults when conditions are warmer. In aquatic animals, this pattern may reflect an increasing risk of oxygen limitation as water warms, favoring smaller bodied animals with a higher surface area to volume ratio. Clonal animals may be able to change size throughout their lives by adjusting the rate at which they grow versus divide. This flexibility may allow them to track a changing optimal body size as the environment changes, but can also influence patterns of investment in asexual and sexual reproduction.</p> <p>Using lab experiments and field observations, Will H. Ryan demonstrated that changes in the fission rate and average body size of the clonal sea anemone, <i>Diadumene lineata</i>, follow seasonal temperature changes. He grew anemones collected from across the species&rsquo; US Atlantic range (Florida, Georgia, and Massachusetts) in chambers mimicking seasonal temperature patterns found at these sites. The year-long experiment showed that annual patterns of growth, size, and clonal investment are highly dependent on local temperature patterns, leading to a gradient in the degree of asexuality expressed across the species range. Northern populations stay large and divide infrequently, whereas southern sites stay small and divide all year. Intermediate sites alternate between phases of individual growth and clonal proliferation. Variation in the response among individuals from different sites suggests that natural selection may be able to shape these patterns.</p> <p>For organisms with complex life cycles, like these sea anemones, environmental variation not only alters the speed of growth and development, but can also change the timing and nature of major life history events, such as fission. </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 temperature-size rule (TSR) is a commonly observed pattern where adult body size is negatively correlated with developmental temperature. In part, this may occur as a consequence of allometric scaling, where changes in the ratio of surface area to mass limit oxygen diffusion as body size increases. As oxygen demand increases with temperature, a smaller body should be favored as temperature increases. For clonal animals, small changes in growth and/or fission rate can rapidly alter the average body size of clonal descendants. Here I test the hypothesis that the clonal sea anemone <i>Diadumene lineata </i>is able to track an optimal body size through seasonal temperature changes using fission rate plasticity. Individuals from three regions (Florida, Georgia and Massachusetts) across the species’ latitudinal range were grown in a year-long reciprocal common garden experiment mimicking seasonal temperature changes at three sites. Average body size was found to be smaller and fission rates higher in warmer conditions, consistent with the TSR pattern. However, seasonal size and fission patterns reflect a complex interaction between region-specific thermal reaction norms and the local temperature regime. These details provide insight into both the range of conditions required for oxygen limitation to contribute to a negative correlation between body size and temperature and the role that fission rate plasticity can play in tracking a rapidly changing optimal phenotype. </p> <!-- <p><a href="http://dx.doi.org/10.1086/695496">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT “The behavior and reproductive physiology of a solitary progressive provisioning vespid wasp: Evidence for a solitary-cycle origin of reproductive castes” http://amnat.org/an/newpapers/FebKelstrup-A.html The DOI is https://dx.doi.org/10.1086/695336 Abstract The emergence of queens and workers from solitary antecedents mark a major evolutionary transition in the history of life. The solitary progressive provisioning wasp Synagris cornuta, a member of the subfamily basal to eusocial vespid wasps (Eumeninae), alternates between behavioral states characterized as queen-like and worker-like. Akin to a queen in eusocial wasps, a S.&nbsp;cornuta female initiates construction of a cell into which she oviposits, and then, similar to a worker, she cares for the brood as it develops. The Ovarian Groundplan (OGP) hypothesis for caste origins predicts that these behavioral states are associated with cyclical changes in ovarian status, where females performing queen-like tasks have eggs and those performing worker-like tasks possess only small oocytes. Our findings show strong support for the OGP hypothesis: the ovaries of S.&nbsp;cornuta females undergo differential oogenesis depending on the behavioral phase: the largest oocyte in the ovaries of females building a cell progress faster compared to that of females attending brood. Yet contrary to the OGP hypothesis, neither juvenile hormone nor ecdysteroids are associated with the reproductive cycle. Finally, the cuticular hydrocarbon profile showed no link with ovarian status, suggesting that fertility signals evolved subsequent to the emergence of group living. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><i>The DOI is https://dx.doi.org/10.1086/695336 </i></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;">T</span>he emergence of queens and workers from solitary antecedents mark a major evolutionary transition in the history of life. The solitary progressive provisioning wasp <i>Synagris cornuta</i>, a member of the subfamily basal to eusocial vespid wasps (Eumeninae), alternates between behavioral states characterized as queen-like and worker-like. Akin to a queen in eusocial wasps, a <i>S.&nbsp;cornuta</i> female initiates construction of a cell into which she oviposits, and then, similar to a worker, she cares for the brood as it develops. The Ovarian Groundplan (OGP) hypothesis for caste origins predicts that these behavioral states are associated with cyclical changes in ovarian status, where females performing queen-like tasks have eggs and those performing worker-like tasks possess only small oocytes. Our findings show strong support for the OGP hypothesis: the ovaries of <i>S.&nbsp;cornuta</i> females undergo differential oogenesis depending on the behavioral phase: the largest oocyte in the ovaries of females building a cell progress faster compared to that of females attending brood. Yet contrary to the OGP hypothesis, neither juvenile hormone nor ecdysteroids are associated with the reproductive cycle. Finally, the cuticular hydrocarbon profile showed no link with ovarian status, suggesting that fertility signals evolved subsequent to the emergence of group living. <a href="https://dx.doi.org/10.1086/695336">Read&nbsp;the&nbsp;Article</a></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 Nov 2017 06:00:00 GMT “Shared genes but not shared genetic variation: legume colonization by two belowground symbionts” http://amnat.org/an/newpapers/MarOssler.html The DOI is https://dx.doi.org/10.1086/695829 Mutualisms are widely established interactions in nature. More often than not, hosts rely simultaneously on multiple symbionts—for example, humans and the microorganisms that make up the human microbiome, or economically important crops (such as soy beans) and their root symbionts. Hosts that rely on multiple symbionts often regulate them through shared genetic pathways. We can think of these genetic pathways as telephone party lines that help hosts regulate the density and exchange of resource interactions with multiple symbionts. However, it is still unclear if these shared pathways constrain the interactions between hosts and their symbionts, and what impacts these pathways could have on the evolution of populations.To address this question, Julia Ossler and Katy Heath examine the complex multiplayer mutualism among Chamaecrista fasciculata (partridge pea) and its two belowground symbionts (phosphorous acquiring arbuscular mycorrhizal fungi (AMF) and nitrogen fixing rhizobia). In a greenhouse experiment, they examine the response of 75 families of partridge pea to phosphorus fertilizer, specifically examining if changes in symbionts’ colonization on host roots are connected among families due to shared genetic pathways (“telephone party lines”). Understanding if shared genetic pathways generate limited multiplayer mutualism can help us understand how symbioses (co-)evolve in the context of complex natural communities. Despite the known existence of shared genetic pathways in the mutualism between partridge pea, AMF, and nitrogen fixing rhizobia, the researchers find that hosts retain the ability to interact and evolve independently with each symbiont, speaking to the potentially vast amount of genetic variation that may lie outside of shared genetic pathways, and the important role this plays in natural selection of mutualisms. Abstract Mutualisms between hosts and multiple symbionts can generate diffuse coevolution if genetic covariance exists between host traits governing multiple interactions. Rhizobia and arbuscular mycorrhizal fungi (AMF) both interact with legume hosts, providing complementary nutrients (nitrogen and phosphorous). Molecular approaches have revealed extensive pleiotropy in the plant genetic pathways required for colonization of both symbionts; however, a quantitative genetic approach is required to understand whether this pleiotropy shapes evolution in natural populations. In a greenhouse experiment with 75 families of Chamaecrista fasciculata grown in two phosphorous environments (fertilized and unfertilized), positive covariance between nodule number and plant aboveground biomass within and across environments indicates selection for increased colonization by rhizobia. Genetic variation for host restriction of AMF colonization in response to P suggests that this aspect of context-dependency can evolve in host populations, and that selection in this mutualism varies with P. Despite the existence of gene-level pleiotropy during rhizobium and AMF infection, we find no evidence for genetic covariance in symbiont colonization or its response to phosphorous – suggesting that genetic variation at other, non-pleiotropic loci govern variation in colonization and thus that these traits likely evolve independently in plant populations. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><i>The DOI is https://dx.doi.org/10.1086/695829 </i></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;">M</span>utualisms are widely established interactions in nature. More often than not, hosts rely simultaneously on multiple symbionts&mdash;for example, humans and the microorganisms that make up the human microbiome, or economically important crops (such as soy beans) and their root symbionts. Hosts that rely on multiple symbionts often regulate them through shared genetic pathways. We can think of these genetic pathways as telephone party lines that help hosts regulate the density and exchange of resource interactions with multiple symbionts. However, it is still unclear if these shared pathways constrain the interactions between hosts and their symbionts, and what impacts these pathways could have on the evolution of populations.</p><p>To address this question, Julia Ossler and Katy Heath examine the complex multiplayer mutualism among <i>Chamaecrista fasciculata</i> (partridge pea) and its two belowground symbionts (phosphorous acquiring arbuscular mycorrhizal fungi (AMF) and nitrogen fixing rhizobia). In a greenhouse experiment, they examine the response of 75 families of partridge pea to phosphorus fertilizer, specifically examining if changes in symbionts’ colonization on host roots are connected among families due to shared genetic pathways (“telephone party lines”). </p><p>Understanding if shared genetic pathways generate limited multiplayer mutualism can help us understand how symbioses (co-)evolve in the context of complex natural communities. Despite the known existence of shared genetic pathways in the mutualism between partridge pea, AMF, and nitrogen fixing rhizobia, the researchers find that hosts retain the ability to interact and evolve independently with each symbiont, speaking to the potentially vast amount of genetic variation that may lie outside of shared genetic pathways, and the important role this plays in natural selection of mutualisms. </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;">M</span>utualisms between hosts and multiple symbionts can generate diffuse coevolution if genetic covariance exists between host traits governing multiple interactions. Rhizobia and arbuscular mycorrhizal fungi (AMF) both interact with legume hosts, providing complementary nutrients (nitrogen and phosphorous). Molecular approaches have revealed extensive pleiotropy in the plant genetic pathways required for colonization of both symbionts; however, a quantitative genetic approach is required to understand whether this pleiotropy shapes evolution in natural populations. In a greenhouse experiment with 75 families of <i>Chamaecrista fasciculata </i>grown in two phosphorous environments (fertilized and unfertilized), positive covariance between nodule number and plant aboveground biomass within and across environments indicates selection for increased colonization by rhizobia. Genetic variation for host restriction of AMF colonization in response to P suggests that this aspect of context-dependency can evolve in host populations, and that selection in this mutualism varies with P. Despite the existence of gene-level pleiotropy during rhizobium and AMF infection, we find no evidence for genetic covariance in symbiont colonization or its response to phosphorous &ndash; suggesting that genetic variation at other, non-pleiotropic loci govern variation in colonization and thus that these traits likely evolve independently in plant populations.</p> <p><a href="https://dx.doi.org/10.1086/695829">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT “Evolution in a community context: trait responses to multiple species interactions” http://amnat.org/an/newpapers/Mar-terHorst.html The DOI is https://dx.doi.org/10.1086/695835 Evolution in a community context limits adaptation to any single species, but results in adaptation to communities Imagine if somebody tried to describe your personality based only on your interactions with one person. It would be nearly impossible because you interact with many different people, each in a different way. Moreover, you might interact with your parent differently when your partner is present, or when your whole family is present. Much of our mechanistic understanding of how species evolve is based on controlled observations and experiments involving one species evolving in response to one another. Yet, species live in a world of complex interactions with many other species: predators, prey, competitors, herbivores, pollinators, and many more. To understand how species evolve in natural environments, we need to better understand how evolution in response to many species differs from evolution in response to just one other species. A recent review by Casey terHorst of California State University, Northridge, and colleagues highlights a number of reasons why it is important to consider so-called “evolution in a community context”. “Evolution becomes more difficult to predict when we start thinking about many species,” terHorst says, “because we have to think about all the indirect ways that they interact with each other.” Imagine trying to play rock-paper-scissors; there is no winning strategy. It gets even more complicated if you use a version popularized on The&nbsp;Big Bang Theory: rock-paper-scissor-lizard-Spock. We have to think about how genes are linked. For example, natural selection might favor plants with versions of genes that make flowers with more nectar, but that gene may be negatively linked to another one that produces chemicals to defend against herbivores and another that affects competitive ability. As terHorst says, “It’s certainly not simple to think about, but we’re starting with baby steps to understand what happens with just a little more complexity, with the hope of building up to more complex models.” Abstract Species that coexist in diverse natural communities interact in complex ways that alter each other’s abundances and affect selection on each other’s traits. Consequently, predicting trait evolution in natural communities may require understanding ecological and evolutionary dynamics involving a number of species. In August 2016, the American Society of Naturalists sponsored a symposium to explore evolution in a community context, focusing on microevolutionary processes. Here we provide an introduction to our perspectives on this topic by defining the context and describing some examples of when and how microevolutionary responses to multiple species may differ from evolution in isolation or in two-species communities. We find that indirect ecological and evolutionary effects can result in non-additive selection and evolution that cannot be predicted from pairwise interactions. Genetic correlations of ecological traits in one species can alter trait evolution and adaptation, as well as the abundances of other species. In general, evolution in multispecies communities can change ecological interactions, which then feed back to future evolutionary changes in ways that depend on these indirect effects. We suggest avenues for future research in this field, including determining the circumstances under which pairwise evolution does not adequately describe evolutionary trajectories. Read&nbsp;the&nbsp;Article More forthcoming papers &raquo; <p><i>The DOI is https://dx.doi.org/10.1086/695835 </i></p> <p><b>Evolution in a community context limits adaptation to any single species, but results in adaptation to communities </b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">I</span>magine if somebody tried to describe your personality based only on your interactions with one person. It would be nearly impossible because you interact with many different people, each in a different way. Moreover, you might interact with your parent differently when your partner is present, or when your whole family is present. Much of our mechanistic understanding of how species evolve is based on controlled observations and experiments involving one species evolving in response to one another. Yet, species live in a world of complex interactions with many other species: predators, prey, competitors, herbivores, pollinators, and many more. To understand how species evolve in natural environments, we need to better understand how evolution in response to many species differs from evolution in response to just one other species. A recent review by Casey terHorst of California State University, Northridge, and colleagues highlights a number of reasons why it is important to consider so-called &ldquo;evolution in a community context&rdquo;. &ldquo;Evolution becomes more difficult to predict when we start thinking about many species,&rdquo; terHorst says, &ldquo;because we have to think about all the indirect ways that they interact with each other.&rdquo; Imagine trying to play rock-paper-scissors; there is no winning strategy. It gets even more complicated if you use a version popularized on <i>The&nbsp;Big Bang Theory</i>: rock-paper-scissor-lizard-Spock. We have to think about how genes are linked. For example, natural selection might favor plants with versions of genes that make flowers with more nectar, but that gene may be negatively linked to another one that produces chemicals to defend against herbivores and another that affects competitive ability. As terHorst says, &ldquo;It&rsquo;s certainly not simple to think about, but we&rsquo;re starting with baby steps to understand what happens with just a little more complexity, with the hope of building up to more complex models.&rdquo;</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;">S</span>pecies that coexist in diverse natural communities interact in complex ways that alter each other&rsquo;s abundances and affect selection on each other&rsquo;s traits. Consequently, predicting trait evolution in natural communities may require understanding ecological and evolutionary dynamics involving a number of species. In August 2016, the American Society of Naturalists sponsored a symposium to explore evolution in a community context, focusing on microevolutionary processes. Here we provide an introduction to our perspectives on this topic by defining the context and describing some examples of when and how microevolutionary responses to multiple species may differ from evolution in isolation or in two-species communities. We find that indirect ecological and evolutionary effects can result in non-additive selection and evolution that cannot be predicted from pairwise interactions. Genetic correlations of ecological traits in one species can alter trait evolution and adaptation, as well as the abundances of other species. In general, evolution in multispecies communities can change ecological interactions, which then feed back to future evolutionary changes in ways that depend on these indirect effects. We suggest avenues for future research in this field, including determining the circumstances under which pairwise evolution does not adequately describe evolutionary trajectories.</p> <p><a href="https://dx.doi.org/10.1086/695835">Read&nbsp;the&nbsp;Article</a> </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 Nov 2017 06:00:00 GMT Nominations for the 2018 Edward O. Wilson Naturalist Award, Due January 1 http://amnat.org/announcements/NomEOWilson.html The Edward O. Wilson Naturalist Award is given to an active investigator in mid-career who has made significant contributions to the knowledge of a particular ecosystem or group of organisms. Individuals whose research and writing illuminate principles of evolutionary biology and an enhanced aesthetic appreciation of natural history will merit special consideration. The recipient need not be a member of the Society. The award will consist of an especially appropriate work of art and a prize of $2,000. The ASN strongly encourages its members to submit nominations of deserving people. The names of former recipients can be found here&nbsp;http://www.amnat.org/awards.html#Wilson Nominations will be held over for two years. The application packet should in the form of a single PDF consisting of a letter of nominations, curriculum vitae of the candidate including a publication list, and three key publications to be send electronically by January 1, 2018, to David Skelly. david.skelly@yale.edu Please indicate "E. O. Wilson Award" in the subject line.&nbsp; <p>The Edward O. Wilson Naturalist Award is given to an active investigator in mid-career who has made significant contributions to the knowledge of a particular ecosystem or group of organisms. Individuals whose research and writing illuminate principles of evolutionary biology and an enhanced aesthetic appreciation of natural history will merit special consideration. <em>The recipient need not be a member of the Society</em>. The award will consist of an especially appropriate work of art and a prize of $2,000.</p> <p>The ASN strongly encourages its members to submit nominations of deserving people. The names of former recipients can be found here&nbsp;<a href="http://www.amnat.org/awards.html#Wilson">http://www.amnat.org/awards.html#Wilson</a></p> <p>Nominations will be held over for two years.</p> <p>The application packet should in the form of a single PDF consisting of a letter of nominations, curriculum vitae of the candidate including a publication list, and three key publications to be send electronically by January 1, 2018, to David Skelly. <a href="mailto:david.skelly@yale.edu">david.skelly@yale.edu</a> Please indicate &quot;E. O. Wilson Award&quot; in the subject line.&nbsp;</p> Mon, 13 Nov 2017 06:00:00 GMT Hurricane Relief http://amnat.org/announcements/Relief.html The American Society of Naturalists will be giving small grants to researchers and students affected by the recent hurricanes in the Caribbean. We have allocated $8,000 to this effort from our existing funds, to be distributed as grants of up to $2000. We would like to distribute more funds using your donations. If you would like to donate to this effort, please visit the following link for “ASN Funds for Hurricane Recovery.” https://subfill.uchicago.edu/JournalPubs/Donation.aspx?webpub=ANXThe American Society of Naturalists will be giving small grants to researchers and students affected by the recent hurricanes in the Caribbean, up to $2000. If you would like to apply, please send an application with the following information: 1.&nbsp;&nbsp; &nbsp;Your name, E-mail, Professional mailing address, Preferred mailing address, if different 2.&nbsp;&nbsp; &nbsp;Your Institution, Department, and Position 3.&nbsp;&nbsp; &nbsp;Are you and ASN member? Is your mentor and ASN member? 4.&nbsp;&nbsp; &nbsp;Brief description of the loss experienced because of the hurricanes and how an award from ASN would be used Please send application materials to Manuel Leal, at: lealm@missouri.edu <p>The American Society of Naturalists will be giving small grants to researchers and students affected by the recent hurricanes in the Caribbean. We have allocated $8,000 to this effort from our existing funds, to be distributed as grants of up to $2000. We would like to distribute more funds using your donations. If you would like to donate to this effort, please visit the following link for &ldquo;ASN Funds for Hurricane Recovery.&rdquo;<br /> <a href="https://subfill.uchicago.edu/JournalPubs/Donation.aspx?webpub=ANX">https://subfill.uchicago.edu/JournalPubs/Donation.aspx?webpub=ANX</a></p><p>The American Society of Naturalists will be giving small grants to researchers and students affected by the recent hurricanes in the Caribbean, up to $2000. If you would like to apply, please send an application with the following information:<br /> 1.&nbsp;&nbsp; &nbsp;Your name, E-mail, Professional mailing address, Preferred mailing address, if different<br /> 2.&nbsp;&nbsp; &nbsp;Your Institution, Department, and Position<br /> 3.&nbsp;&nbsp; &nbsp;Are you and ASN member? Is your mentor and ASN member?<br /> 4.&nbsp;&nbsp; &nbsp;Brief description of the loss experienced because of the hurricanes and how an award from ASN would be used<br /> Please send application materials to Manuel Leal, at: <a href="mailto:lealm@missouri.edu">lealm@missouri.edu</a></p> Mon, 13 Nov 2017 06:00:00 GMT Applications for the 2018 ASN Student Research Awards, due January 31 http://amnat.org/announcements/StudentResearchAward.html The ASN Student Research Awards: The ASN Student Research Awards support research by student members that advances the goals of the society: the conceptual unification of ecology, evolution, or behavior. Each award consists of a $2,000 check to the candidate. An applicant must 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 Ph.D. Projects in all types of research (i.e., laboratory, field, theory) are encouraged. A total of ten proposals will receive awards. Proposals will be judged on originality, strength, and significance of the questions being addressed, prospects for significant results, and the match between the proposed research and the ASN mission. Applications include four elements: 1) A two-page proposal describing the research project for which support is requested; 2) A budget with justification (one page); 3) a short curriculum vitae (two pages); 4) a statement from the Ph.D. supervisor that verifies that the applicant meets the eligibility requirements, and confirms the supervisor’s support for the proposed project (one page). Detailed Instructions: The two-page proposal should describe a specific research project for which support is requested.&nbsp; While some background and context is appropriate, the proposal should not be a general overview of the applicant’s complete dissertation.&nbsp; The proposal should have a title at the top of the first page.&nbsp; The proposal should be single-spaced, have 1-inch (2.5cm) margins all around, and be written in an 11- or 12-point standard font on 8.5 x 11 inch pages.&nbsp; A list of references should follow, but is not included in the 2-page limit. The budget and budget justification should clearly support the specific proposed project.&nbsp; If total costs of the project exceed $2000, some indication of how the applicant intends to find support for remaining costs should be given. The CV should meet the same formatting requirements as the project description. All materials should be compiled into one PDF.&nbsp; The .pdf filename should be in the format Lastname_Firstname_SRA (example:&nbsp; Wright_Sewall_RSA.pdf). Send your application via e-mail to Dr. Jeff Dudycha at AmNatSRA@gmail.com with “ASN Student Research Award” in the subject line. Deadline for submission of all materials is January 31, 2018. Judging: Applications will be reviewed by a committee of six persons: three faculty-level researchers and three graduate students. Senior-level appointments are made by the President-Elect. Members each serve for three years; the longest-serving faculty-level committee member serves as chair in her/his final year on the committee. Graduate student appointments are made from the Graduate Council, in consultation with the President-Elect. <p><strong>The ASN Student Research Awards:</strong></p> <p>The ASN Student Research Awards support research by student members that advances the goals of the society: the conceptual unification of ecology, evolution, or behavior. Each award consists of a $2,000 check to the candidate. An applicant must 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 Ph.D. Projects in all types of research (i.e., laboratory, field, theory) are encouraged. A total of ten proposals will receive awards. Proposals will be judged on originality, strength, and significance of the questions being addressed, prospects for significant results, and the match between the proposed research and the ASN mission.</p> <p>Applications include four elements: 1) A two-page proposal describing the research project for which support is requested; 2) A budget with justification (one page); 3) a short curriculum vitae (two pages); 4) a statement from the Ph.D. supervisor that verifies that the applicant meets the eligibility requirements, and confirms the supervisor&rsquo;s support for the proposed project (one page).</p> <p><strong>Detailed Instructions:</strong></p> <ol> <li>The two-page proposal should describe a specific research project for which support is requested.&nbsp; While some background and context is appropriate, the proposal should not be a general overview of the applicant&rsquo;s complete dissertation.&nbsp; The proposal should have a title at the top of the first page.&nbsp; The proposal should be single-spaced, have 1-inch (2.5cm) margins all around, and be written in an 11- or 12-point standard font on 8.5 x 11 inch pages.&nbsp; A list of references should follow, but is not included in the 2-page limit.</li> <li>The budget and budget justification should clearly support the specific proposed project.&nbsp; If total costs of the project exceed $2000, some indication of how the applicant intends to find support for remaining costs should be given.</li> <li>The CV should meet the same formatting requirements as the project description.</li> <li><strong>All materials should be compiled into one PDF.&nbsp; The .pdf filename should be in the format Lastname_Firstname_SRA (example:&nbsp; Wright_Sewall_RSA.pdf).</strong></li> <li>Send your application via e-mail to Dr. Jeff Dudycha at <a href="http://AmNatSRA@gmail.com">AmNatSRA@gmail.com</a> with &ldquo;ASN Student Research Award&rdquo; in the subject line.</li> <li>Deadline for submission of all materials is January 31, 2018.</li> </ol> <p><strong>Judging:</strong></p> <p>Applications will be reviewed by a committee of six persons: three faculty-level researchers and three graduate students. Senior-level appointments are made by the President-Elect. Members each serve for three years; the longest-serving faculty-level committee member serves as chair in her/his final year on the committee. Graduate student appointments are made from the Graduate Council, in consultation with the President-Elect.</p> Mon, 13 Nov 2017 06:00:00 GMT Nominations for the 2018 Sewall Wright Award, Due January 1 http://amnat.org/announcements/NomWright.html The American Society of Naturalists invites nominations for the 2018 Sewall Wright Award. The Sewall Wright Award was established in 1991 for a senior but highly active investigator, who is making fundamental contributions to the Society’s goals in promoting the conceptual unification of the natural biological sciences. The winner of the 2018 Sewall Wright Award President will be announced by the President during the annual meeting prior to the Presidential address.&nbsp; The recipient will be invited to write a paper for publication in a special section of the journal and will receive an honorarium of $1000. The recipient need not be a member of the Society. The ASN strongly encourages its members to submit nominations of deserving people, preferentially scientists in their prime period as active and influential researcher rather than nearing retirement, who have been successful at conceptually unifying the biological sciences in some way. Ideally, all area’s of ecology, evolution, behavioral ecology, and genetics are represented among the nominees. Nominations will be held over for two years. The names of former recipients can be found here: http://www.amnat.org/awards.html#Wright For the 2018 Sewall Wright Award, the prize committee encourages nominations from the membership. A nomination should consist of a letter with a brief description of why the nominee is deserving of the award. Please send all nominations by January 1, 2018, via e-mail to Andr&eacute; M. de Roos (A.M.deRoos@uva.nl). Please indicate “Sewall Wright Award” in the subject line and let the filename of the nomination letter indicate the name of the nominee. <p>The American Society of Naturalists invites nominations for the 2018 Sewall Wright Award. The Sewall Wright Award was established in 1991 for a senior but highly active investigator, who is making fundamental contributions to the Society&rsquo;s goals in promoting the conceptual unification of the natural biological sciences. The winner of the 2018 Sewall Wright Award President will be announced by the President during the annual meeting prior to the Presidential address.&nbsp; The recipient will be invited to write a paper for publication in a special section of the journal and will receive an honorarium of $1000. The recipient need not be a member of the Society.</p> <p>The ASN strongly encourages its members to submit nominations of deserving people, preferentially scientists in their prime period as active and influential researcher rather than nearing retirement, who have been successful at conceptually unifying the biological sciences in some way. Ideally, all area&rsquo;s of ecology, evolution, behavioral ecology, and genetics are represented among the nominees. Nominations will be held over for two years.</p> <p>The names of former recipients can be found here:<br /> <a href="http://www.amnat.org/awards.html#Wright">http://www.amnat.org/awards.html#Wright</a></p> <p>For the 2018 Sewall Wright Award, the prize committee encourages nominations from the membership. A nomination should consist of a letter with a brief description of why the nominee is deserving of the award. Please send all nominations by January 1, 2018, via e-mail to Andr&eacute; M. de Roos (<a href="mailto:A.M.deRoos@uva.nl">A.M.deRoos@uva.nl</a>). Please indicate &ldquo;Sewall Wright Award&rdquo; in the subject line and let the filename of the nomination letter indicate the name of the nominee.</p> Thu, 09 Nov 2017 06:00:00 GMT