ASN RSS https://amnat.org/ Latest press releases and announcements from the ASN en-us Fri, 12 Jul 2019 05:00:00 GMT 60 ASN Stand-Alone Meeting 2020 https://amnat.org/announcements/ASNAsilomar.html The American Society of Naturalists invites graduate students, postdocs, faculty and other professionals from ecology, evolution, behavior, genetics, physiology, and associated fields to a stand alone meeting at the Asilomar Conference Grounds on January 3-7, 2020. This meeting will celebrate the unique ability of ASN to unify broad conceptual themes across biology by integrating theory with data and by using new technological tools to address long-standing questions. In short, this conference will showcase what it means to be a naturalist and researcher in the 21st century. This conference is unique because it involves a small number of participants (200 people) interacting closely over meals, scientific talks, and casual conversations in a beautiful natural setting on the shore of the Monterey Peninsula. The scientific program will consist of posters, 15-minute talks, and 5-minute lightning talks, in addition to three symposia in the afternoons. Lightning talks are encouraged and will also include five minutes for questions, so are helpful for getting feedback and starting a conversation.&nbsp; Evening activities will include a presidential debate, a natural history trivia contest, and interactions around a bonfire. More information is available at www.amnat2020.com. Registration will open on August 15 and participants will be asked to submit abstracts (~200 words) and choose a presentation format (poster, talk, or lightning talk). Past meetings suggest that registration fills quite quickly, so prepare your abstracts soon so that you can register as soon as it opens. Registration will close after the first 200 people. Registration costs are not yet finalized, but for ASN members, are likely to be a little over $200 for students, a bit more for post-docs, and $400 for faculty. Participants are encouraged to stay at the Asilomar Conference Grounds, where three meals per day are included in the cost of your stay. More information about housing is available at the website. Each participant will need to register for housing at Asilomar individually, though you can indicate your preferred roommate(s). Room rates per night are: Single: $287 Double: $192 Triple: $164 Quad: $150 If you have any questions, concerns, or suggestions, please email Casey terHorst (casey.terhorst@csun.edu). Looking forward to seeing you in January! &nbsp;Planning for stand-alone meetings requires a two-year lead time.&nbsp; We had feedback from some attendees at the 2018 meeting that they would like the meeting to move around the country more.&nbsp; Unfortunately, the lead time was too short to change venues for the the 2020 meeting. We are actively looking NOW for organizers and venues in other parts of the country for the 2022 meetings. Please make suggestions! To recap: we need a venue that can accommodate 220 people, with approx. 7 smaller meeting rooms, one large room that can accommodate all present, joint eating facilities, and that ideally is located in a nice natural setting, in a place that is pleasant outside in January and not prohibitively expensive. These are harder criteria to meet than one might imagine. Anyone with suggestions for either organizer or venue, please contact&nbsp; Michael Whitlock (whitlock@zoology.ubc.ca) <p>The American Society of Naturalists invites graduate students, postdocs, faculty and other professionals from ecology, evolution, behavior, genetics, physiology, and associated fields to a stand alone meeting at the Asilomar Conference Grounds on January 3-7, 2020. This meeting will celebrate the unique ability of ASN to unify broad conceptual themes across biology by integrating theory with data and by using new technological tools to address long-standing questions. In short, this conference will showcase what it means to be a naturalist and researcher in the 21st century.</p> <p>This conference is unique because it involves a small number of participants (200 people) interacting closely over meals, scientific talks, and casual conversations in a beautiful natural setting on the shore of the Monterey Peninsula. The scientific program will consist of posters, 15-minute talks, and 5-minute lightning talks, in addition to three symposia in the afternoons. Lightning talks are encouraged and will also include five minutes for questions, so are helpful for getting feedback and starting a conversation.&nbsp; Evening activities will include a presidential debate, a natural history trivia contest, and interactions around a bonfire.</p> <p>More information is available at <a href="http://www.amnat2020.com">www.amnat2020.com</a>.</p> <p>Registration will open on August 15 and participants will be asked to submit abstracts (~200 words) and choose a presentation format (poster, talk, or lightning talk). Past meetings suggest that registration fills quite quickly, so prepare your abstracts soon so that you can register as soon as it opens. Registration will close after the first 200 people. Registration costs are not yet finalized, but for ASN members, are likely to be a little over $200 for students, a bit more for post-docs, and $400 for faculty.</p> <p>Participants are encouraged to stay at the Asilomar Conference Grounds, where three meals per day are included in the cost of your stay. More information about housing is available at the website. Each participant will need to register for housing at Asilomar individually, though you can indicate your preferred roommate(s). Room rates per night are:<br /> Single: $287<br /> Double: $192<br /> Triple: $164<br /> Quad: $150</p> <p>If you have any questions, concerns, or suggestions, please email Casey terHorst (<a href="mailto:casey.terhorst@csun.edu">casey.terhorst@csun.edu</a>). Looking forward to seeing you in January!</p> <p>&nbsp;</p><p>Planning for stand-alone meetings requires a two-year lead time.&nbsp; We had feedback from some attendees at the 2018 meeting that they would like the meeting to move around the country more.&nbsp; Unfortunately, the lead time was too short to change venues for the the 2020 meeting.</p> <p>We are actively looking NOW for organizers and venues in other parts of the country for the 2022 meetings. Please make suggestions!</p> <p>To recap: we need a venue that can accommodate 220 people, with approx. 7 smaller meeting rooms, one large room that can accommodate all present, joint eating facilities, and that ideally is located in a nice natural setting, in a place that is pleasant outside in January and not prohibitively expensive. These are harder criteria to meet than one might imagine.</p> <p>Anyone with suggestions for either organizer or venue, please contact&nbsp; Michael Whitlock (<a href="mailto:whitlock@zoology.ubc.ca?subject=Stand-Alone%20Meeting%20Location">whitlock@zoology.ubc.ca</a>)</p> Thu, 11 Jul 2019 05:00:00 GMT Call for ASN Graduate Student Representatives https://amnat.org/announcements/NomGCtoECRep.html The American Society of Naturalists Graduate Student Council invites applications for two to three new graduate student representatives to join us this year! The new application deadline is 7/31/2019. As a member of the Graduate Student Council you have the chance to participate in the workings of the society and interact with many of the great researchers who are members of the ASN. The ASN is committed to developing a variety of initiatives to provide more valuable services to its student members. Representatives take part in several committees that include choosing ASN-sponsored workshops, helping choose winners of the annual student research grant, organizing student events at conferences, participating in various committees, and running the website for grad student ASN members at http://asngrads.com/. Each year we seek new members to join for a 3-year term. We are also open to new roles or ideas for things you think the Grad Council could do to encourage student involvement and interaction among researchers. If you are interested in joining, please email Shengpei Wang (swang74@syr.edu) with the subject line “ASN GC application” and attach a single pdf document containing your CV and a short paragraph (less than 1 page) about what you hope to contribute and why you want to join the grad council. &nbsp;Kim Gilbert&nbsp;(GC rep 2014-2015): "Serving on the ASN grad council is a fantastic opportunity to not only meet faculty, post-docs, and students from a wide range of universities, but to become more involved in a great community of researchers in ecology and evolution. You learn about how journal societies run, as well as the ins and outs of organizing conference events. You also serve as an important representative for all graduate student members of the ASN to ensure the society is doing its best to meet student&#39;s needs at conferences or through other opportunities." Emily Weiss (GC rep 2013-2014): Serving on the Grad Council really was an incredibly enriching experience for me, and I hope that many other students will apply and get to have that experience too. Rafael Maia&nbsp;(GC rep 2013-2014): "I served the council for a couple years and strongly recommend it. Great society, exciting possibilities!" Courtney Fitzpatrick&nbsp;(founding GC rep): "Grad students: excellent opportunity to get involved, meet collaborators/mentors, and learn about your scientific society!" <p>The American Society of Naturalists Graduate Student Council invites applications for two to three new graduate student representatives to join us this year! The new application deadline is 7/31/2019.</p> <p>As a member of the Graduate Student Council you have the chance to participate in the workings of the society and interact with many of the great researchers who are members of the ASN. The ASN is committed to developing a variety of initiatives to provide more valuable services to its student members.</p> <p>Representatives take part in several committees that include choosing ASN-sponsored workshops, helping choose winners of the annual student research grant, organizing student events at conferences, participating in various committees, and running the website for grad student ASN members at <a href="http://asngrads.com/">http://asngrads.com/</a>.<br /> Each year we seek new members to join for a 3-year term. We are also open to new roles or ideas for things you think the Grad Council could do to encourage student involvement and interaction among researchers.</p> <p>If you are interested in joining, please email Shengpei Wang (<a href="mailto:swang74@syr.edu">swang74@syr.edu</a>) with the subject line &ldquo;ASN GC application&rdquo; and attach a single pdf document containing your CV and a short paragraph (less than 1 page) about what you hope to contribute and why you want to join the grad council.</p> <p>&nbsp;</p><p><strong>Kim Gilbert&nbsp;</strong>(GC rep 2014-2015):<br /> &quot;Serving on the ASN grad council is a fantastic opportunity to not only meet faculty, post-docs, and students from a wide range of universities, but to become more involved in a great community of researchers in ecology and evolution. You learn about how journal societies run, as well as the ins and outs of organizing conference events. You also serve as an important representative for all graduate student members of the ASN to ensure the society is doing its best to meet student&#39;s needs at conferences or through other opportunities.&quot;</p> <p><strong>Emily Weiss (</strong>GC rep 2013-2014):<br /> Serving on the Grad Council really was an incredibly enriching experience for me, and I hope that many other students will apply and get to have that experience too.</p> <p><strong>Rafael Maia&nbsp;</strong>(GC rep 2013-2014):<br /> &quot;I served the council for a couple years and strongly recommend it. Great society, exciting possibilities!&quot;</p> <p><strong>Courtney Fitzpatrick</strong>&nbsp;(founding GC rep):<br /> &quot;Grad students: excellent opportunity to get involved, meet collaborators/mentors, and learn about your scientific society!&quot;</p> Thu, 11 Jul 2019 05:00:00 GMT “False exclusion: A case to embed predator performance in classical population models” https://amnat.org/an/newpapers/Nov-Montagnes.html David J. S. Montagnes, Xuexia Zhu, Lei Gu, Yunfei Sun, Jun Wang, Rosie Horner, and Zhou Yang (Nov 2019) Read the Article (Just Accepted) Predator-prey dynamics are driven by insufficiently-explored predator behaviors that are inherently prey-dependent Ignorance is not bliss. Global health and, ultimately, our survival rely on strategic forward planning. Today, computer-driven simulations are the “crystal balls” by which we predict the future. But computers require valid instruction. If we “falsely exclude” – ignore – essential facts and concepts, then predictions will go disastrously wrong. Recently, through a UK-Chinese collaboration, researchers have re-evaluated and quantified three very basic, but essential, biological concepts: 1) when animals are fed less they are more likely to die; 2) an animal’s efficiency to use food changes with food availability (e.g., when food is abundant animals are wasteful); and 3) reproduction only occurs when there is sufficient quantities of food. Surprisingly, these “food-dependent” behaviors have been overlooked, or at least inadequately incorporated, in many models that predict population dynamics. The first step of this research produced a theoretical, mathematical framework that embraces these concepts. Then, essential experimental evidence, provided proof of concept. Only then could the experimental data and the computer model be used to reveal that including all three of these fundamental aspects of animal biology places into question our current evaluation of population dynamics. For instance, the revised approach predicts extinction when the old ones predicted survival. Now biologists can include these food-dependent behaviors, making more informed predictions of how predators respond in nature. Abstract We argue that predator-prey dynamics, a cornerstone of ecology, can be driven by insufficiently-explored aspects of predator performance that are inherently prey-dependent: i.e., these have been falsely excluded. Classical—Lotka-Volterra-based—models tend to only consider prey-dependent ingestion rate. We highlight three other prey-dependent responses and provide empirically-derived functions to describe them. These functions introduce neglected nonlinearities and threshold behaviors into dynamic models leading to unexpected outcomes: specifically, as prey abundance increases predators: 1) become less efficient at using prey; 2) initially allocate resources towards survival and then allocate resources towards reproduction; and 3) are less likely to die. Based on experiments using model-zooplankton, we explore consequences of including these functions in the classical structure and show they alter qualitative and quantitative dynamics of an empirically-informed, generic predator-prey model. Through bifurcation analysis, our revised structure predicts: 1) predator extinctions, where the classical structure allows persistence; 2) predator survival, where the classical structure drives predators towards extinction; and 3) greater stability through smaller amplitude of cycles, relative to the classical structure. Then, by exploring parameter space, we show how these responses alter predictions of predator-prey stability and competition between predators. Based on our results, we suggest that classical assumptions about predator responses to prey abundance should be re-evaluated. More forthcoming papers &raquo; <p>David J. S. Montagnes, Xuexia Zhu, Lei Gu, Yunfei Sun, Jun Wang, Rosie Horner, and Zhou Yang (Nov 2019) </p><p><i><a href="https://dx.doi.org/10.1086/705381">Read the Article</a></i> (Just Accepted)</p> <p><b>Predator-prey dynamics are driven by insufficiently-explored predator behaviors that are inherently prey-dependent </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>gnorance is not bliss. Global health and, ultimately, our survival rely on strategic forward planning. Today, computer-driven simulations are the “crystal balls” by which we predict the future. But computers require valid instruction. If we “falsely exclude” – ignore – essential facts and concepts, then predictions will go disastrously wrong. Recently, through a UK-Chinese collaboration, researchers have re-evaluated and quantified three very basic, but essential, biological concepts: 1) when animals are fed less they are more likely to die; 2) an animal’s efficiency to use food changes with food availability (e.g., when food is abundant animals are wasteful); and 3) reproduction only occurs when there is sufficient quantities of food. Surprisingly, these “food-dependent” behaviors have been overlooked, or at least inadequately incorporated, in many models that predict population dynamics. The first step of this research produced a theoretical, mathematical framework that embraces these concepts. Then, essential experimental evidence, provided proof of concept. Only then could the experimental data and the computer model be used to reveal that including all three of these fundamental aspects of animal biology places into question our current evaluation of population dynamics. For instance, the revised approach predicts extinction when the old ones predicted survival. Now biologists can include these food-dependent behaviors, making more informed predictions of how predators respond in nature. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">W</span>e argue that predator-prey dynamics, a cornerstone of ecology, can be driven by insufficiently-explored aspects of predator performance that are inherently prey-dependent: i.e., these have been falsely excluded. Classical—Lotka-Volterra-based—models tend to only consider prey-dependent ingestion rate. We highlight three other prey-dependent responses and provide empirically-derived functions to describe them. These functions introduce neglected nonlinearities and threshold behaviors into dynamic models leading to unexpected outcomes: specifically, as prey abundance increases predators: 1) become less efficient at using prey; 2) initially allocate resources towards survival and then allocate resources towards reproduction; and 3) are less likely to die. Based on experiments using model-zooplankton, we explore consequences of including these functions in the classical structure and show they alter qualitative and quantitative dynamics of an empirically-informed, generic predator-prey model. Through bifurcation analysis, our revised structure predicts: 1) predator extinctions, where the classical structure allows persistence; 2) predator survival, where the classical structure drives predators towards extinction; and 3) greater stability through smaller amplitude of cycles, relative to the classical structure. Then, by exploring parameter space, we show how these responses alter predictions of predator-prey stability and competition between predators. Based on our results, we suggest that classical assumptions about predator responses to prey abundance should be re-evaluated. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 10 Jul 2019 05:00:00 GMT “A spatial perspective on the phenological distribution of the spring woodland caterpillar peak” https://amnat.org/an/newpapers/Nov-Shutt.html Jack D. Shutt, Malcolm D. Burgess, and Albert B. Phillimore (Nov 2019) Read the Article (Just Accepted)In temperate regions, warmer springs cause a whole suite of ecological events to occur earlier, from trees coming into leaf to birds breeding. A cause for concern is whether species higher up the food chain are able to shift their timings forward by as much as those species below them. In deciduous forests there is a peak in moth caterpillar abundance during the spring, coinciding with the new leaves on the trees. It is well known that many bird species, including tits and flycatchers, rely heavily upon this spring food peak to raise their nestlings. However, little is known about how this caterpillar peak varies among the particular deciduous tree species involved, or geographically (e.g. by elevation or latitude), or which caterpillar species are most important in creating this food peak and whether their identity varies from one location or tree species to another. Drs.&nbsp;Shutt, Burgess, and Phillimore set about answering these questions by collecting caterpillars from 40 woodlands spread over 220&nbsp;km in Scotland. They identified 62 different caterpillar species based on DNA; however, just three species made up over half of all caterpillars collected, with the most common species (the winter moth) representing a third of the total, showing the importance of key species in the food chain. However, different tree species had different overall numbers of caterpillars, with oak and willow having the most, making these tree species of more value to the birds in spring. In addition, the timing of the peak in caterpillars was considerably later at higher elevations but didn’t change across latitude and was similar across the different tree species within a given area. These results are important as they show that poor breeding timing for the birds cannot be buffered by having a variety of tree species present. Abstract A&nbsp;classic system for studying trophic mismatch focuses on the timing of the spring caterpillar peak in relation to the breeding time and productivity of woodland passerine birds. Most work has been conducted in single-site oak woodlands and little is known about how insights generalize to other woodland types or across space. Here we present the results of a three-year study on the species composition and temporal distribution of the spring caterpillar peak on different tree taxa across 40 woodland sites spanning two degrees of latitude in Scotland. We used molecular barcoding to identify 62 caterpillar species, with winter moth (Operophtera brumata) the most abundant, comprising a third of the sample. Oak (Quercus sp.) and willow (Salix sp.) hosted significantly higher caterpillar abundances than other tree taxa, with winter moth exhibiting similar trends and invariantly proportionate across tree taxa. Caterpillar peak phenology was broadly similar between tree taxa. While latitude had little effect, increasing elevation increased the height of the caterpillar peak and retarded timing by 3.7 days/100&nbsp;m. These findings extend our understanding of how mismatch may play out spatially, with caterpillar peak date varying with elevation, and tree taxa varying in the caterpillar resource that they host. More forthcoming papers &raquo; <p>Jack D. Shutt, Malcolm D. Burgess, and Albert B. Phillimore (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705241">Read the Article</a></i> (Just Accepted)</p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n temperate regions, warmer springs cause a whole suite of ecological events to occur earlier, from trees coming into leaf to birds breeding. A cause for concern is whether species higher up the food chain are able to shift their timings forward by as much as those species below them. In deciduous forests there is a peak in moth caterpillar abundance during the spring, coinciding with the new leaves on the trees. It is well known that many bird species, including tits and flycatchers, rely heavily upon this spring food peak to raise their nestlings. However, little is known about how this caterpillar peak varies among the particular deciduous tree species involved, or geographically (e.g. by elevation or latitude), or which caterpillar species are most important in creating this food peak and whether their identity varies from one location or tree species to another. Drs.&nbsp;Shutt, Burgess, and Phillimore set about answering these questions by collecting caterpillars from 40 woodlands spread over 220&nbsp;km in Scotland. They identified 62 different caterpillar species based on DNA; however, just three species made up over half of all caterpillars collected, with the most common species (the winter moth) representing a third of the total, showing the importance of key species in the food chain. However, different tree species had different overall numbers of caterpillars, with oak and willow having the most, making these tree species of more value to the birds in spring. In addition, the timing of the peak in caterpillars was considerably later at higher elevations but didn’t change across latitude and was similar across the different tree species within a given area. These results are important as they show that poor breeding timing for the birds cannot be buffered by having a variety of tree species present.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>&nbsp;classic system for studying trophic mismatch focuses on the timing of the spring caterpillar peak in relation to the breeding time and productivity of woodland passerine birds. Most work has been conducted in single-site oak woodlands and little is known about how insights generalize to other woodland types or across space. Here we present the results of a three-year study on the species composition and temporal distribution of the spring caterpillar peak on different tree taxa across 40 woodland sites spanning two degrees of latitude in Scotland. We used molecular barcoding to identify 62 caterpillar species, with winter moth (<i>Operophtera brumata</i>) the most abundant, comprising a third of the sample. Oak (<i>Quercus</i> sp.) and willow (<i>Salix</i> sp.) hosted significantly higher caterpillar abundances than other tree taxa, with winter moth exhibiting similar trends and invariantly proportionate across tree taxa. Caterpillar peak phenology was broadly similar between tree taxa. While latitude had little effect, increasing elevation increased the height of the caterpillar peak and retarded timing by 3.7 days/100&nbsp;m. These findings extend our understanding of how mismatch may play out spatially, with caterpillar peak date varying with elevation, and tree taxa varying in the caterpillar resource that they host. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 10 Jul 2019 05:00:00 GMT “Eco-evolutionary feedbacks predict the time course of rapid life history evolution” https://amnat.org/an/newpapers/Nov-Reznick.html David N. Reznick, Ronald D. Bassar, Corey A. Handelsman, Cameron K. Ghalambor, Jeff Arendt, Tim Coulson, Tomos Potter, Emily W. Ruell, Julián Torres-Dowdall, Paul Bentzen, and Joseph Travis (Nov 2019) Read the Article (Just Accepted)Guppies, a perennial pet store favorite, have helped a UC Riverside scientist unlock a key question about evolution. Do animals evolve in response to the risk of being eaten, or to the environment that they create in the absence of predators? Turns out, it’s the latter. Riverside biology professor David Reznick explained that in the wild, guppies can migrate over waterfalls and rapids to places where most predators can’t follow them. Once they arrive in safer terrain, Reznick’s previous research shows they evolve rapidly, becoming genetically distinct from their ancestors. “We already knew that they evolved quickly, but what we didn’t yet understand was why,” Reznick said. In a paper appearing in The&nbsp;American Naturalist, Reznick and his co-authors explain the reason that the tiny fish evolve so quickly in safer waters. To answer their questions, the scientists traveled to Trinidad, guppies’ native habitat, and did an experiment. They moved guppies from areas in streams where predators were plentiful to areas where predators were mostly absent. Over the course of four years, they studied how the introduced guppies changed in comparison to ones from where they originated. “If guppies evolve because they aren’t at risk of becoming food for other fish, then evolution should be visible right away,” Reznick said. “However, if in the absence of predators, they become abundant and deplete the environment of food, then there will be a lag in detectable changes.” Guppies from all four streams were marked so they could be tracked over the course of four years. Specifically, in this paper, the scientists considered results for males, which tend to live about five months. They looked at the fishes’ age and size at maturity, which are key traits affecting population growth. They also tracked how the environment changed as the guppy populations expanded, focusing on the abundance of food such as algae and insects, as well as the presence of other non-predator fish. The finished product includes evidence from the four experimental populations in nature and from laboratory common garden studies of the grandchildren of wild caught fish, mathematical modeling, and quantitative genetic analyses of the one experimental population for which they had a pedigree. They found a two-to-three-year lag between when guppies were introduced and when males evolved, suggesting the second hypothesis was correct; guppies were first changing their new environments, and then as a result, they turned out to be changing themselves. “The speed of evolution makes it possible to study how it happens. The new news is that organisms can shape their own evolution by changing their environment,” Reznick said. One of Reznick’s current projects includes applying these concepts to questions about human evolution. “Unlike guppies and other organisms, human population density seems to increase without apparent limit, which increases our impact on our environment and on ourselves,” he said. Co-authors on this study included Ron Basser, a former PhD student at UC Riverside now assistant professor at Williams College, Joe Travis at Florida State University and Corey Handelsman, Cameron Ghalambor, Emily Ruell, and Julian Torres-Dowdall from Colorado State University, Tim Coulson and Tomos Potter of Oxford University, and Paul Bentzen of Dalhousie University. Abstract Organisms can change their environment and, in so doing, change the selection they experience and how they evolve. Population density is one potential mediator of such interactions because high population densities can impact the ecosystem and reduce resource availability. At present, such interactions are best known from theory and laboratory experiments. Here we quantify the importance of such interactions in nature by transplanting guppies from a stream where they co-occur with predators into tributaries that previously lacked both guppies and predators. If guppies evolve solely because of the immediate reduction in mortality rate, the strength of selection and rate of evolution should be greatest at the outset then decline as the population adapts to its new environment. If indirect effects caused by the increase in guppy population density in the absence of predation prevail, then there should be a lag in guppy evolution because time is required for them to modify their environment. The duration of this lag is predicted to be associated with the environmental modification caused by guppies. We observed a lag in life history evolution associated with increases in population density and altered ecology. How guppies evolved matched predictions derived from evolutionary theory that incorporates such density effects. More forthcoming papers &raquo; <p>David N. Reznick, Ronald D. Bassar, Corey A. Handelsman, Cameron K. Ghalambor, Jeff Arendt, Tim Coulson, Tomos Potter, Emily W. Ruell, Julián Torres-Dowdall, Paul Bentzen, and Joseph Travis (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705380">Read the Article</a></i> (Just Accepted)</p><p><span style="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>uppies, a perennial pet store favorite, have helped a UC Riverside scientist unlock a key question about evolution. Do animals evolve in response to the risk of being eaten, or to the environment that they create in the absence of predators? Turns out, it’s the latter. </p><p>Riverside biology professor David Reznick explained that in the wild, guppies can migrate over waterfalls and rapids to places where most predators can’t follow them. Once they arrive in safer terrain, Reznick’s previous research shows they evolve rapidly, becoming genetically distinct from their ancestors. “We already knew that they evolved quickly, but what we didn’t yet understand was why,” Reznick said. In a paper appearing in <i>The&nbsp;American Naturalist,</i> Reznick and his co-authors explain the reason that the tiny fish evolve so quickly in safer waters. </p><p>To answer their questions, the scientists traveled to Trinidad, guppies’ native habitat, and did an experiment. They moved guppies from areas in streams where predators were plentiful to areas where predators were mostly absent. Over the course of four years, they studied how the introduced guppies changed in comparison to ones from where they originated. “If guppies evolve because they aren’t at risk of becoming food for other fish, then evolution should be visible right away,” Reznick said. “However, if in the absence of predators, they become abundant and deplete the environment of food, then there will be a lag in detectable changes.” </p><p>Guppies from all four streams were marked so they could be tracked over the course of four years. Specifically, in this paper, the scientists considered results for males, which tend to live about five months. They looked at the fishes’ age and size at maturity, which are key traits affecting population growth. </p><p>They also tracked how the environment changed as the guppy populations expanded, focusing on the abundance of food such as algae and insects, as well as the presence of other non-predator fish. The finished product includes evidence from the four experimental populations in nature and from laboratory common garden studies of the grandchildren of wild caught fish, mathematical modeling, and quantitative genetic analyses of the one experimental population for which they had a pedigree. </p><p>They found a two-to-three-year lag between when guppies were introduced and when males evolved, suggesting the second hypothesis was correct; guppies were first changing their new environments, and then as a result, they turned out to be changing themselves. “The speed of evolution makes it possible to study how it happens. The new news is that organisms can shape their own evolution by changing their environment,” Reznick said. </p><p>One of Reznick’s current projects includes applying these concepts to questions about human evolution. “Unlike guppies and other organisms, human population density seems to increase without apparent limit, which increases our impact on our environment and on ourselves,” he said. </p><p>Co-authors on this study included Ron Basser, a former PhD student at UC Riverside now assistant professor at Williams College, Joe Travis at Florida State University and Corey Handelsman, Cameron Ghalambor, Emily Ruell, and Julian Torres-Dowdall from Colorado State University, Tim Coulson and Tomos Potter of Oxford University, and Paul Bentzen of Dalhousie University. </p> <hr /> <h3>Abstract</h3> <p><span style="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 can change their environment and, in so doing, change the selection they experience and how they evolve. Population density is one potential mediator of such interactions because high population densities can impact the ecosystem and reduce resource availability. At present, such interactions are best known from theory and laboratory experiments. Here we quantify the importance of such interactions in nature by transplanting guppies from a stream where they co-occur with predators into tributaries that previously lacked both guppies and predators. If guppies evolve solely because of the immediate reduction in mortality rate, the strength of selection and rate of evolution should be greatest at the outset then decline as the population adapts to its new environment. If indirect effects caused by the increase in guppy population density in the absence of predation prevail, then there should be a lag in guppy evolution because time is required for them to modify their environment. The duration of this lag is predicted to be associated with the environmental modification caused by guppies. We observed a lag in life history evolution associated with increases in population density and altered ecology. How guppies evolved matched predictions derived from evolutionary theory that incorporates such density effects. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 10 Jul 2019 05:00:00 GMT “Information about predators varies across an Amazonian rainforest as a result of sentinel species distribution” https://amnat.org/an/newpapers/Nov-Camerlenghi.html Ettore Camerlenghi, Paola Tellaroli, Matteo Griggio, and Ari E. Martínez (Nov 2019) Read the Article (Just Accepted) The distribution of different alarm calling species drives the patchiness of predator information in a rainforest Predation risk is considered one of the main drivers of the formation of mixed-species flocks of birds, in which different species aggregate, forage and move together in the forest. In many cases, certain species are exceptionally vigilant against predators and emit alarm calls upon detecting ambush predators. These species are considered a key element in allowing other flocking species to exploit otherwise “risky habitats”. The presence of these “sentinel species” allows other species to navigate a forested version of a landscape of fear.In the Amazon lowland rainforests of southeastern Peru, two different sentinel bird species occupy different types of habitats across tierra firme forest without overlapping. The Bluish-slate Antshrike specializes in patches of early successional stage, such as those gaps created by fallen trees. The Dusky-throated Antshrike occupies undisturbed areas of primary forest. Camerlenghi and colleagues showed that other flocking bird species (which can associate with either of these sentinel species) perceive the alarm calls given by the Bluish-slate as more reliable than those emitted by the Dusky-throated and react accordingly. Thus, not only do forest habitats inhabited by flocks differ structurally, but they may also differ in the quality of predator information provided by alarm calling species that inhabit them, with potential effects for the long-term survival of flock mates. Abstract Information about predation risk is of fundamental value in biological communities. As many prey species have shared predators, eavesdropping on other species’ alarms is a widely recognized mechanism underlying the formation of mixed-species groups. However, information transfer may vary both across and within groups because some species provide higher quality information about predators than others. We tested this phenomenon in Amazonian understory mixed-species flocks of birds in which two sentinel species, the Bluish-slate Antshrike (Thamnomanes schistogynus) and the Dusky-throated Antshrike (Thamnomanes ardesiacus) occupy different habitats and provide alarm calls that are used by eavesdropping flock mates. In a playback experiment, both associate species responded significantly more strongly to alarm calls from the same sentinel species, reflecting the greater reliability of information about predator threats that could affect survival and habitat choice. Our work provides evidence of a repeated asymmetry across space in the available information about threats. More forthcoming papers &raquo; <p>Ettore Camerlenghi, Paola Tellaroli, Matteo Griggio, and Ari E. Martínez (Nov 2019)</p> <p><i><a href="https://dx.doi.org/10.1086/705242">Read the Article</a></i> (Just Accepted)</p> <p><b>The distribution of different alarm calling species drives the patchiness of predator information in a rainforest </b></p><p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">P</span>redation risk is considered one of the main drivers of the formation of mixed-species flocks of birds, in which different species aggregate, forage and move together in the forest. In many cases, certain species are exceptionally vigilant against predators and emit alarm calls upon detecting ambush predators. These species are considered a key element in allowing other flocking species to exploit otherwise &ldquo;risky habitats&rdquo;. The presence of these &ldquo;sentinel species&rdquo; allows other species to navigate a forested version of a landscape of fear.</p><p>In the Amazon lowland rainforests of southeastern Peru, two different sentinel bird species occupy different types of habitats across tierra firme forest without overlapping. The Bluish-slate Antshrike specializes in patches of early successional stage, such as those gaps created by fallen trees. The Dusky-throated Antshrike occupies undisturbed areas of primary forest. Camerlenghi and colleagues showed that other flocking bird species (which can associate with either of these sentinel species) perceive the alarm calls given by the Bluish-slate as more reliable than those emitted by the Dusky-throated and react accordingly. Thus, not only do forest habitats inhabited by flocks differ structurally, but they may also differ in the quality of predator information provided by alarm calling species that inhabit them, with potential effects for the long-term survival of flock mates.</p> <hr /><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>nformation about predation risk is of fundamental value in biological communities. As many prey species have shared predators, eavesdropping on other species’ alarms is a widely recognized mechanism underlying the formation of mixed-species groups. However, information transfer may vary both across and within groups because some species provide higher quality information about predators than others. We tested this phenomenon in Amazonian understory mixed-species flocks of birds in which two sentinel species, the Bluish-slate Antshrike (<i>Thamnomanes schistogynus</i>) and the Dusky-throated Antshrike (<i>Thamnomanes ardesiacus</i>) occupy different habitats and provide alarm calls that are used by eavesdropping flock mates. In a playback experiment, both associate species responded significantly more strongly to alarm calls from the same sentinel species, reflecting the greater reliability of information about predator threats that could affect survival and habitat choice. Our work provides evidence of a repeated asymmetry across space in the available information about threats. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 10 Jul 2019 05:00:00 GMT “Understanding maladaptation by uniting ecological and evolutionary perspectives” https://amnat.org/an/newpapers/Oct-Brady-A.html Read the Article (Just Accepted) Abstract Evolutionary biologists have long trained their sights on adaptation, focusing on the power of natural selection to produce relative fitness advantages, while often ignoring changes in absolute fitness. Ecologists generally have taken a different tack, focusing on changes in abundance and ranges that reflect absolute fitness, while often ignoring relative fitness. We articulate the various causes of both forms of maladaptation and review numerous examples of their occurrence. This review indicates that maladaptation is reasonably common from both perspectives, yet often in contrasting ways. That is, maladaptation can appear strong from a relative fitness perspective and yet populations can be growing in abundance. Conversely, resident individuals can appear locally adapted (relative to non-resident individuals), and yet be declining in abundance. Understanding and interpreting these disconnects between relative and absolute maladaptation, as well as the cases of agreement, is increasingly critical in the face of accelerating human-mediated environmental change. We therefore present a framework for studying maladaptation, focusing in particular on the relationship between absolute and relative fitness, thereby drawing together evolutionary and ecological perspectives. The unification of these ecological and evolutionary perspectives has the potential to bring together previously disjunct research areas while addressing key conceptual issues and specific practical problems. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/705020">Read the Article</a></i> (Just Accepted) </p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>volutionary biologists have long trained their sights on adaptation, focusing on the power of natural selection to produce relative fitness advantages, while often ignoring changes in absolute fitness. Ecologists generally have taken a different tack, focusing on changes in abundance and ranges that reflect absolute fitness, while often ignoring relative fitness. We articulate the various causes of both forms of maladaptation and review numerous examples of their occurrence. This review indicates that maladaptation is reasonably common from both perspectives, yet often in contrasting ways. That is, maladaptation can appear strong from a relative fitness perspective and yet populations can be growing in abundance. Conversely, resident individuals can appear locally adapted (relative to non-resident individuals), and yet be declining in abundance. Understanding and interpreting these disconnects between relative and absolute maladaptation, as well as the cases of agreement, is increasingly critical in the face of accelerating human-mediated environmental change. We therefore present a framework for studying maladaptation, focusing in particular on the relationship between absolute and relative fitness, thereby drawing together evolutionary and ecological perspectives. The unification of these ecological and evolutionary perspectives has the potential to bring together previously disjunct research areas while addressing key conceptual issues and specific practical problems. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 27 Jun 2019 05:00:00 GMT “Between- and within-individual variation of maternal thyroid hormone deposition in wild great tits (<i>Parus major</i>)” https://amnat.org/an/newpapers/Oct-Hsu.html Bin-Yan Hsu, Irene Verhagen, Phillip Gienapp, Veerle M. Darras, Marcel E. Visser, and Suvi Ruuskanen (Oct 2019) Read the Article (Just Accepted)During breeding, some hormones are transferred from mothers to their offspring. These maternal hormones can influence the development, growth, physiology, and also behavior of the offspring. Evolutionary biologists have hypothesized that maternal hormones may be a “tool” for mothers to help their offspring adapt to the future environment after birth. To achieve this task, however, mothers must be able to adjust the amounts of hormone they transfer to their offspring. Can they do that? In this study, Hsu, Verhagen, Gienapp, Darras, Visser, and Ruuskanen chose the great tits (Parus major), a small passerine bird in Europe, as a model to study the flexibility of maternal hormone transfer. In birds, mothers transfer and store maternal hormones in the egg yolks. The authors analyzed the variation of maternal thyroid hormones in the eggs sampled from a Dutch population during 2013-2016. In all vertebrates, two thyroid hormones – triiodothyronine (T3) and thyroxine (T4) – are considered important to many physiological functions, such as development and metabolism. The analysis suggests that different females transfer different levels of T3 to the egg yolks on average. By contrast, each female bird is capable of adjusting T4 transfer differently for each clutch of eggs, thus potentially influencing the phenotype of the chicks and the degree of competition between the siblings hatching from these eggs. Because a previous study has shown that genetics has a moderate control over maternal T3 but not T4, this study shows that the two forms of maternal thyroid hormones exhibit different patterns of variation and flexibility, which may be linked to their respective functions. Abstract Maternal hormones are often considered a mediator of anticipatory maternal effects, namely mothers adjust maternal hormone transfer to prepare the offspring for the anticipated environment. The flexibility for mothers to adjust hormone transfer is therefore a prerequisite for such anticipatory maternal effects. Nevertheless, previous studies have only focused on the average differences of maternal hormone transfer between groups and neglected the substantial individual variation, despite that individual plasticity in maternal hormone transfer is actually the central assumption. In this study, we studied the between- and within-individual variation of maternal thyroid hormones (THs) in egg yolk of wild great tits (Parus major) and estimated the individual plasticity of maternal yolk THs across environmental temperature, clutch initiation dates and egg laying order using linear mixed-effects models. Interestingly, our models provide statistical evidence that the two main THs – the main biologically active hormone T3, and T4, which is mostly considered as a prohormone – exhibited different variation patterns. Yolk T3 showed significant between-individual variation on the average levels, in line with its previously reported moderate heritability. Yolk T4, however, showed significant between-clutch variation in the pattern over the laying sequence, suggesting a great within-individual plasticity. Our findings suggest that the role and function of the hormone within the endocrine axis likely influences its flexibility to respond to environmental change. Whether the flexibility of T4 deposition brings fitness advantage should be examined along with its potential effects on offspring, which remains to be further investigated. More forthcoming papers &raquo; <p>Bin-Yan Hsu, Irene Verhagen, Phillip Gienapp, Veerle M. Darras, Marcel E. Visser, and Suvi Ruuskanen (Oct 2019) </p><p><i><a href="https://dx.doi.org/10.1086/704738">Read the Article</a></i> (Just Accepted)</p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">D</span>uring breeding, some hormones are transferred from mothers to their offspring. These maternal hormones can influence the development, growth, physiology, and also behavior of the offspring. Evolutionary biologists have hypothesized that maternal hormones may be a “tool” for mothers to help their offspring adapt to the future environment after birth. To achieve this task, however, mothers must be able to adjust the amounts of hormone they transfer to their offspring. Can they do that?</p> <p>In this study, Hsu, Verhagen, Gienapp, Darras, Visser, and Ruuskanen chose the great tits (<i>Parus major</i>), a small passerine bird in Europe, as a model to study the flexibility of maternal hormone transfer. In birds, mothers transfer and store maternal hormones in the egg yolks. The authors analyzed the variation of maternal thyroid hormones in the eggs sampled from a Dutch population during 2013-2016. In all vertebrates, two thyroid hormones – triiodothyronine (T3) and thyroxine (T4) – are considered important to many physiological functions, such as development and metabolism. The analysis suggests that different females transfer different levels of T3 to the egg yolks on average. By contrast, each female bird is capable of adjusting T4 transfer differently for each clutch of eggs, thus potentially influencing the phenotype of the chicks and the degree of competition between the siblings hatching from these eggs. Because a previous study has shown that genetics has a moderate control over maternal T3 but not T4, this study shows that the two forms of maternal thyroid hormones exhibit different patterns of variation and flexibility, which may be linked to their respective functions.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>aternal hormones are often considered a mediator of anticipatory maternal effects, namely mothers adjust maternal hormone transfer to prepare the offspring for the anticipated environment. The flexibility for mothers to adjust hormone transfer is therefore a prerequisite for such anticipatory maternal effects. Nevertheless, previous studies have only focused on the average differences of maternal hormone transfer between groups and neglected the substantial individual variation, despite that individual plasticity in maternal hormone transfer is actually the central assumption. In this study, we studied the between- and within-individual variation of maternal thyroid hormones (THs) in egg yolk of wild great tits (<i>Parus major</i>) and estimated the individual plasticity of maternal yolk THs across environmental temperature, clutch initiation dates and egg laying order using linear mixed-effects models. Interestingly, our models provide statistical evidence that the two main THs – the main biologically active hormone T3, and T4, which is mostly considered as a prohormone – exhibited different variation patterns. Yolk T3 showed significant between-individual variation on the average levels, in line with its previously reported moderate heritability. Yolk T4, however, showed significant between-clutch variation in the pattern over the laying sequence, suggesting a great within-individual plasticity. Our findings suggest that the role and function of the hormone within the endocrine axis likely influences its flexibility to respond to environmental change. Whether the flexibility of T4 deposition brings fitness advantage should be examined along with its potential effects on offspring, which remains to be further investigated. </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, 12 Jun 2019 05:00:00 GMT “What determines the distinct morphology of species with a particular ecology? The roles of many-to-one mapping and trade-offs in the evolution of frog ecomorphology and performance” https://amnat.org/an/newpapers/Oct-Moen.html Daniel S. Moen (Oct 2019)Read the Article (Just Accepted) Many-to-one mapping leads to specialized ecomorphs without compromising performance in a shared behavior Ecologists and evolutionary biologists have long recognized that species that share a similar ecology (e.g. habitat use, diet) have similar body forms, or morphology. Yet the reasons why some body forms are related to ecology are often complicated by the fact that some organisms have many different behaviors associated with their ecology. For example, if an animal that lives mostly in the water has large leg muscles, it may have such muscles because those larger muscles help those species swim better than species that do not regularly swim. But such species may also move terrestrially (e.g. running or jumping), and it may be unclear whether the big muscles will aid or inhibit the terrestrial movement. A new article in The&nbsp;American Naturalist by Daniel Moen explores why certain frog body forms are associated with the microhabitats those species use by linking ecology, morphology, and functional performance. He looked at frogs and toads from three different continents and compared microhabitat (e.g. living in trees or water), leg morphology (leg length and muscle mass), and performance in two different behaviors (jumping and swimming). The results showed that frogs in different microhabitats were different in their leg morphology, and some of those differences were mirrored by swimming ability. However, all species – regardless of microhabitat – jumped equally well, as might be expected for organisms like frogs that use jumping as their primary terrestrial locomotion. The similar jumping ability despite differences in swimming ability and body form can be explained by a concept called many-to-one mapping, in which multiple anatomical traits affect functional performance, allowing species to specialize in body form for some behaviors but maintain similar performance in others. More generally, the study emphasizes the use of evolutionary analyses at large scales (temporally and geographically) for understanding the evolution of body form and its fit to ecology. Abstract Organisms inhabiting a specific environment often have distinct morphology, but the factors that affect this fit are unclear when multiple morphological traits affect performance in multiple behaviors. Does the realized morphology of a species reflect a compromise in performance among behaviors (i.e. trade-offs)? Or does many-to-one mapping result in morphological distinctness without compromising performance across behaviors? The importance of these principles in organismal design has rarely been compared at the macroevolutionary scale. Here, I study 191 species of frogs around the world that inhabit different microhabitats, using models of phenotypic evolution to examine how form-function relationships may explain the fit between ecology and morphology. I found three key results. First, despite being distinct in leg morphology, ecomorphs were similar in jumping performance. Second, ecomorphs that regularly swim showed higher swimming performance, which paralleled the higher leg muscle mass in these taxa. Third, many-to-one mapping of form onto function occurred at all but the highest levels of both jumping and swimming performance. The seemingly contradictory first two results were explained by the third: when one behavior occurs in all species while another is restricted to a subset, many-to-one mapping allows species with distinct ecologies to have distinct body forms that reflect their specialized behavior while maintaining similar performance in a more general, shared behavior. More forthcoming papers &raquo; <p>Daniel S. Moen (Oct 2019)</p><p><i><a href="https://dx.doi.org/10.1086/704736">Read the Article</a></i> (Just Accepted)</p> <p><b>Many-to-one mapping leads to specialized ecomorphs without compromising performance in a shared behavior </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">E</span>cologists and evolutionary biologists have long recognized that species that share a similar ecology (e.g. habitat use, diet) have similar body forms, or morphology. Yet the reasons why some body forms are related to ecology are often complicated by the fact that some organisms have many different behaviors associated with their ecology. For example, if an animal that lives mostly in the water has large leg muscles, it may have such muscles because those larger muscles help those species swim better than species that do not regularly swim. But such species may also move terrestrially (e.g. running or jumping), and it may be unclear whether the big muscles will aid or inhibit the terrestrial movement. A new article in <i>The&nbsp;American Naturalist</i> by Daniel Moen explores why certain frog body forms are associated with the microhabitats those species use by linking ecology, morphology, and functional performance. He looked at frogs and toads from three different continents and compared microhabitat (e.g. living in trees or water), leg morphology (leg length and muscle mass), and performance in two different behaviors (jumping and swimming). The results showed that frogs in different microhabitats were different in their leg morphology, and some of those differences were mirrored by swimming ability. However, all species – regardless of microhabitat – jumped equally well, as might be expected for organisms like frogs that use jumping as their primary terrestrial locomotion. The similar jumping ability despite differences in swimming ability and body form can be explained by a concept called many-to-one mapping, in which multiple anatomical traits affect functional performance, allowing species to specialize in body form for some behaviors but maintain similar performance in others. More generally, the study emphasizes the use of evolutionary analyses at large scales (temporally and geographically) for understanding the evolution of body form and its fit to ecology.</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>rganisms inhabiting a specific environment often have distinct morphology, but the factors that affect this fit are unclear when multiple morphological traits affect performance in multiple behaviors. Does the realized morphology of a species reflect a compromise in performance among behaviors (i.e. trade-offs)? Or does many-to-one mapping result in morphological distinctness without compromising performance across behaviors? The importance of these principles in organismal design has rarely been compared at the macroevolutionary scale. Here, I study 191 species of frogs around the world that inhabit different microhabitats, using models of phenotypic evolution to examine how form-function relationships may explain the fit between ecology and morphology. I found three key results. First, despite being distinct in leg morphology, ecomorphs were similar in jumping performance. Second, ecomorphs that regularly swim showed higher swimming performance, which paralleled the higher leg muscle mass in these taxa. Third, many-to-one mapping of form onto function occurred at all but the highest levels of both jumping and swimming performance. The seemingly contradictory first two results were explained by the third: when one behavior occurs in all species while another is restricted to a subset, many-to-one mapping allows species with distinct ecologies to have distinct body forms that reflect their specialized behavior while maintaining similar performance in a more general, shared behavior. </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, 11 Jun 2019 05:00:00 GMT “Early sibling conflict may ultimately benefit the family” https://amnat.org/an/newpapers/Oct-Smith.html Alyssa Laney Smith, Daniel Z. Atwater, and Ragan M. Callaway (Oct 2019) Read the Article (Just Accepted) Early sibling conflict via kin recognition may ultimately benefit the family for an invasive grass Seeds of goatgrass, a European plant that is invading California, have the ability to chemically inhibit the germination of their siblings more than non-siblings. At face value, this seems like strong conflict among relatives. However, in experiments with no chemical suppression of germination, goatgrass seedlings even more strongly suppressed their siblings through competition. Thus, by suppressing germination, goatgrass may allow their close kin to remain dormant for a time, and by doing so to avoid competition within the family later in life. Abstract Relatives often interact differently with each other than with non-relatives, and whether kin cooperate or compete has important consequences for the evolution of mating systems, seed size, dispersal, and competition. Previous research found that the larger of the size-dimorphic seeds produced by the annual plant, Aegilops triuncialis, suppressed germination of their smaller sibs by 25-60%. Here, we found evidence for kin-recognition and sibling rivalry later in life among Aegilops seedlings that places seed-seed interactions in a broader context. In experiments with size-dimorphic seeds, seedlings reduced the growth of sibling seedlings by ~40% but that of non-sibling seedlings by ~25%. These sequential antagonistic interactions between seeds and then seedlings provide insight into conflict and cooperation among kin. Kin-based conflict among seeds may maintain dormancy for some seeds until the coast is clear of more competitive siblings. If so, biotically induced seed dormancy may be a unique form of cooperation, which increases the inclusive fitness of maternal plants and offspring by minimizing competition among kin. More forthcoming papers &raquo; <p>Alyssa Laney Smith, Daniel Z. Atwater, and Ragan M. Callaway (Oct 2019) </p> <p><i><a href="https://dx.doi.org/10.1086/704773">Read the Article</a></i> (Just Accepted)</p> <p><b>Early sibling conflict via kin recognition may ultimately benefit the family for an invasive grass </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>eeds of goatgrass, a European plant that is invading California, have the ability to chemically inhibit the germination of their siblings more than non-siblings. At face value, this seems like strong conflict among relatives. However, in experiments with no chemical suppression of germination, goatgrass seedlings even more strongly suppressed their siblings through competition. Thus, by suppressing germination, goatgrass may allow their close kin to remain dormant for a time, and by doing so to avoid competition within the family later in life.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">R</span>elatives often interact differently with each other than with non-relatives, and whether kin cooperate or compete has important consequences for the evolution of mating systems, seed size, dispersal, and competition. Previous research found that the larger of the size-dimorphic seeds produced by the annual plant, <i>Aegilops triuncialis</i>, suppressed germination of their smaller sibs by 25-60%. Here, we found evidence for kin-recognition and sibling rivalry later in life among <i>Aegilops</i> seedlings that places seed-seed interactions in a broader context. In experiments with size-dimorphic seeds, seedlings reduced the growth of sibling seedlings by ~40% but that of non-sibling seedlings by ~25%. These sequential antagonistic interactions between seeds and then seedlings provide insight into conflict and cooperation among kin. Kin-based conflict among seeds may maintain dormancy for some seeds until the coast is clear of more competitive siblings. If so, biotically induced seed dormancy may be a unique form of cooperation, which increases the inclusive fitness of maternal plants and offspring by minimizing competition among kin. </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, 11 Jun 2019 05:00:00 GMT “Maladapted prey subsidize predators and facilitate range expansion” https://amnat.org/an/newpapers/Oct-Urban.html Mark C. Urban, Alice Scarpa, Justin M. J. Travis, and Greta Bocedi (Special Feature on Maladaptation)Read the Article (Just Accepted)Life is good when dinner is quick and easy. But prey usually make dinner difficult for predators by evolving defenses like thorns, shells, camouflage, and poison. Yet prey sometimes evolve to be less defended where predators are rare, like at the edge of a predator’s range. In these situations, prey are likely to become adapted to low-predator conditions, and maladapted to predators. How do these maladapted prey affect the predators that eat them? Scientists from the University of Connecticut and University of Aberdeen set out to answer this question using a combination of classic analytical theory and supercomputer-sized simulations. By providing a subsidy of easily captured resources, the authors find that maladapted prey can enhance predator abundances, persistence, and geographic range size. Simply put, maladaptation makes dinner easy for predators. Maladapted prey become even more important when predators are expanding their range, such as during climate change. As predators expand, they encounter less and less defended prey, speeding up the predator’s range expansion. These maladapted prey can even prevent the predator’s extinction during environmental change. These effects can be generalized to any enemy and victim system, ranging from plants and their herbivores to humans and our diseases. Overall, the work suggests the need to understand not just the adaptive dynamics of predator and prey, but their maladaptive dynamics as well. More generally, we need to work to spend more time considering how both adaptation and maladaptation affect species interactions to get a more complete view of biodiversity patterns, limits to species ranges, and responses to environmental change. Abstract Dispersal of prey from predator-free patches frequently supplies a trophic subsidy to predators by providing more prey than are produced locally. Prey arriving from predator-free patches might also have evolved weaker defenses against predators and thus enhance trophic subsidies by providing easily captured prey. Using local models assuming a linear or accelerating tradeoff between defense and population growth rate, we demonstrate that immigration of undefended prey increased predator abundances and decreased defended prey through eco-evolutionary apparent competition. In individual-based models with spatial structure, explicit genetics, and gene flow along an environmental gradient, prey became maladapted to predators at the predator’s range edge, and greater gene flow enhanced this maladaptation. The predator gained a subsidy from these easily captured prey, which enhanced its abundance, facilitated it's persistence in marginal habitats, extended its range extent, and enhanced range shifts during environmental changes, such as climate change. Once the predator expanded, prey adapted to it, and the advantage disappeared, resulting in an elastic predator range margin driven by eco-evolutionary dynamics. Overall, the results indicate a need to consider gene flow-induced maladaptation and species interactions as mutual forces that frequently determine ecological and evolutionary dynamics and patterns in nature. More forthcoming papers &raquo; <p>Mark C. Urban, Alice Scarpa, Justin M. J. Travis, and Greta Bocedi (Special Feature on Maladaptation)</p><p><i><a href="https://dx.doi.org/10.1086/704780">Read the Article</a></i> (Just Accepted)</p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">L</span>ife is good when dinner is quick and easy. But prey usually make dinner difficult for predators by evolving defenses like thorns, shells, camouflage, and poison. Yet prey sometimes evolve to be less defended where predators are rare, like at the edge of a predator’s range. In these situations, prey are likely to become adapted to low-predator conditions, and maladapted to predators. How do these maladapted prey affect the predators that eat them? </p><p>Scientists from the University of Connecticut and University of Aberdeen set out to answer this question using a combination of classic analytical theory and supercomputer-sized simulations. By providing a subsidy of easily captured resources, the authors find that maladapted prey can enhance predator abundances, persistence, and geographic range size. Simply put, maladaptation makes dinner easy for predators. </p><p>Maladapted prey become even more important when predators are expanding their range, such as during climate change. As predators expand, they encounter less and less defended prey, speeding up the predator’s range expansion. These maladapted prey can even prevent the predator’s extinction during environmental change. These effects can be generalized to any enemy and victim system, ranging from plants and their herbivores to humans and our diseases. </p><p>Overall, the work suggests the need to understand not just the adaptive dynamics of predator and prey, but their maladaptive dynamics as well. More generally, we need to work to spend more time considering how both adaptation and maladaptation affect species interactions to get a more complete view of biodiversity patterns, limits to species ranges, and responses to environmental change. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">D</span>ispersal of prey from predator-free patches frequently supplies a trophic subsidy to predators by providing more prey than are produced locally. Prey arriving from predator-free patches might also have evolved weaker defenses against predators and thus enhance trophic subsidies by providing easily captured prey. Using local models assuming a linear or accelerating tradeoff between defense and population growth rate, we demonstrate that immigration of undefended prey increased predator abundances and decreased defended prey through eco-evolutionary apparent competition. In individual-based models with spatial structure, explicit genetics, and gene flow along an environmental gradient, prey became maladapted to predators at the predator’s range edge, and greater gene flow enhanced this maladaptation. The predator gained a subsidy from these easily captured prey, which enhanced its abundance, facilitated it's persistence in marginal habitats, extended its range extent, and enhanced range shifts during environmental changes, such as climate change. Once the predator expanded, prey adapted to it, and the advantage disappeared, resulting in an elastic predator range margin driven by eco-evolutionary dynamics. Overall, the results indicate a need to consider gene flow-induced maladaptation and species interactions as mutual forces that frequently determine ecological and evolutionary dynamics and patterns in nature. </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, 11 Jun 2019 05:00:00 GMT “(In)exhaustible suppliers for evolution? Epistatic selection tunes the adaptive potential of non-genetic inheritance” https://amnat.org/an/newpapers/Oct-Rajon-A.html Etienne Rajon and Sylvain Charlat (Oct 2019) Read the Article (Just Accepted) Think non-genetic inheritance is important due to massive (epi)mutation rates? Not necessarily!Abstract Non-genetic inheritance media, from methyl-accepting cytosines to culture, tend to ‘mutate’ more frequently than DNA sequences. Whether or not this makes them inexhaustible suppliers for adaptive evolution will depend on the effect of non-genetic mutations (hereafter epimutations) on fitness-related traits. Here we investigate how these effects might themselves evolve, specifically whether natural selection may set boundaries to the adaptive potential of non-genetic inheritance media due to their higher mutability. In our model, the genetic and epigenetic contributions to a non-neutral phenotype are controlled by an epistatic modifier locus, which evolves under the combined effects of drift and selection. We show that a pure genetic control evolves when the environment is stable, provided that the population is large, such that the phenotype becomes robust to frequent epimutations. When the environment fluctuates, however, selection on the modifier locus also fluctuates and can overall produce a large non-genetic contribution to the phenotype, especially when the epimutation rate matches the rate of environmental variation. We further show that selection on the modifier locus is generally insensitive to recombination, meaning it is mostly direct, i.e. not relying on subsequent effects in future generations. These results suggest that unstable inheritance media might significantly contribute to fitness variation of traits subject to highly variable selective pressures, but little to traits responding to scarcely variable aspects of the environment. More generally, our study demonstrates that the rate of mutation and the adaptive potential of any inheritance media should not be seen as independent properties. Une source (in)tarissable pour l’évolution&nbsp;? Comment le potentiel adaptatif de l’hérédité non-génétique est modulé par la sélection épistatique Les supports de l’hérédité non-génétique, des cytosines méthylables à la culture, ont tendance à «&nbsp;muter&nbsp;» plus fréquemment que les séquences d’ADN. Ces supports ne peuvent néanmoins représenter une source intarissable de variation que si l’effet de ces mutations non-génétiques (ou épimutations) sur des traits liés à la fitness demeure élevé. Dans le cadre de ce projet, nous étudions comment ces effets peuvent évoluer, en particulier si la sélection naturelle peut limiter le potentiel adaptatif des épimutations du fait de leur forte mutabilité. Dans notre modèle, les contributions des supports génétiques et non-génétiques sont contrôlées par un locus «&nbsp;modificateur&nbsp;» agissant de manière épistatique, dont l’évolution dépend de l’action conjointe de la dérive et de la sélection. Nos résultats montrent qu’une forte contribution génétique devrait évoluer dans un environnement stable et pour une taille de population élevée, si bien qu’on peut s’attendre à ce que le phénotype dans ce contexte soit robuste aux épimutations. En revanche, lorsque l’environnement fluctue, la sélection sur le locus modificateur peut aussi fluctuer et aboutir à une contribution élevée du support non-génétique, en particulier lorsque le taux d’épimutation correspond au taux de changement environnemental. De plus, nous montrons que la sélection sur le locus modificateur est en général indépendante du taux de recombinaison, indiquant que cette sélection est directe et ne dépend pas des effets à venir dans les générations futures. Nos résultats indiquent que les supports instables de l’hérédité peuvent contribuer de façon importante à des variations de traits soumis à des pressions de sélection variables, mais peu à des traits liés à des caractéristiques de l’environnement stables dans le temps. De façon plus large, cette étude démontre que le taux d’occurrence et l’effet des mutations ne peuvent pas être considérés comme des propriétés indépendantes. More forthcoming papers &raquo; <p>Etienne Rajon and Sylvain Charlat (Oct 2019) </p><p><i><a href="https://dx.doi.org/10.1086/704772">Read the Article</a></i> (Just Accepted)</p> <p><b>Think non-genetic inheritance is important due to massive (epi)mutation rates? Not necessarily!</b></p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">N</span>on-genetic inheritance media, from methyl-accepting cytosines to culture, tend to ‘mutate’ more frequently than DNA sequences. Whether or not this makes them inexhaustible suppliers for adaptive evolution will depend on the effect of non-genetic mutations (hereafter epimutations) on fitness-related traits. Here we investigate how these effects might themselves evolve, specifically whether natural selection may set boundaries to the adaptive potential of non-genetic inheritance media due to their higher mutability. In our model, the genetic and epigenetic contributions to a non-neutral phenotype are controlled by an epistatic modifier locus, which evolves under the combined effects of drift and selection. We show that a pure genetic control evolves when the environment is stable, provided that the population is large, such that the phenotype becomes robust to frequent epimutations. When the environment fluctuates, however, selection on the modifier locus also fluctuates and can overall produce a large non-genetic contribution to the phenotype, especially when the epimutation rate matches the rate of environmental variation. We further show that selection on the modifier locus is generally insensitive to recombination, meaning it is mostly direct, i.e. not relying on subsequent effects in future generations. These results suggest that unstable inheritance media might significantly contribute to fitness variation of traits subject to highly variable selective pressures, but little to traits responding to scarcely variable aspects of the environment. More generally, our study demonstrates that the rate of mutation and the adaptive potential of any inheritance media should not be seen as independent properties. </p> <h4>Une source (in)tarissable pour l’évolution&nbsp;? Comment le potentiel adaptatif de l’hérédité non-génétique est modulé par la sélection épistatique</h4> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">L</span>es supports de l’hérédité non-génétique, des cytosines méthylables à la culture, ont tendance à «&nbsp;muter&nbsp;» plus fréquemment que les séquences d’ADN. Ces supports ne peuvent néanmoins représenter une source intarissable de variation que si l’effet de ces mutations non-génétiques (ou épimutations) sur des traits liés à la fitness demeure élevé. Dans le cadre de ce projet, nous étudions comment ces effets peuvent évoluer, en particulier si la sélection naturelle peut limiter le potentiel adaptatif des épimutations du fait de leur forte mutabilité. Dans notre modèle, les contributions des supports génétiques et non-génétiques sont contrôlées par un locus «&nbsp;modificateur&nbsp;» agissant de manière épistatique, dont l’évolution dépend de l’action conjointe de la dérive et de la sélection. Nos résultats montrent qu’une forte contribution génétique devrait évoluer dans un environnement stable et pour une taille de population élevée, si bien qu’on peut s’attendre à ce que le phénotype dans ce contexte soit robuste aux épimutations. En revanche, lorsque l’environnement fluctue, la sélection sur le locus modificateur peut aussi fluctuer et aboutir à une contribution élevée du support non-génétique, en particulier lorsque le taux d’épimutation correspond au taux de changement environnemental. De plus, nous montrons que la sélection sur le locus modificateur est en général indépendante du taux de recombinaison, indiquant que cette sélection est directe et ne dépend pas des effets à venir dans les générations futures. Nos résultats indiquent que les supports instables de l’hérédité peuvent contribuer de façon importante à des variations de traits soumis à des pressions de sélection variables, mais peu à des traits liés à des caractéristiques de l’environnement stables dans le temps. De façon plus large, cette étude démontre que le taux d’occurrence et l’effet des mutations ne peuvent pas être considérés comme des propriétés indépendantes. </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, 11 Jun 2019 05:00:00 GMT “Interspecific covariation in courtship displays, iridescent plumage, solar orientation, and their interactions in hummingbirds” https://amnat.org/an/newpapers/Oct-Simpson.html Richard K. Simpson and Kevin J. McGraw (Oct 2019) Read the Article (Just Accepted) The complex evolution of hummingbird visual courtship signals produced varied and unique signal interaction properties Animals exhibit a staggering array of exaggerated ornaments, such as peacock tails or deer antlers, and complex behavioral displays, like the elaborate dances of birds of paradise. Ornaments and behaviors are often used for courtship, and many animals use both ornaments and behaviors simultaneously, which prompts the questions of 1) why there is such a diversity of signaling traits, and 2) why animals use multiple signaling traits together. Previous work addressing these two questions has focused on understanding the information conveyed through animal signals, and how signals are transmitted and detected through the environment. However, Drs. Simpson and McGraw set out to tackle these questions from a different angle. Previously they found that male hummingbirds can alter the presentation of their iridescent throat feathers during courtship dances and that this signal interaction changes how males appear to females. For example, when a male is dancing for a female, he can manipulate how he orients his feathers relative to the female and sun to create a flashy, strobe-like color appearance. To tackle questions about signal evolution and diversity, Simpson and McGraw tested how signal interactions vary among multiple hummingbird species, and how signal interactions may be co-evolving with other signaling traits. They quantified the courtship dances, iridescent feathers, and signal interactions (male color appearance during courtship) of six hummingbird species in the American Southwest and found that signal interactions do vary among species, with some having very flashy color appearances during courtship and others having very consistently colored but brighter color appearances. Further, they found that species with more complex dances have flashier color appearances, while species with larger and more colorful feathers have brighter, more consistent color appearances, illustrating how these different signaling traits can co-evolve. This work demonstrates the need to incorporate signal interactions into future research on multiple signals so that biologists can better and more deeply understand the evolution and diversity of animal signals. Abstract Many animals communicate using multiple signals. Historically, most attention was paid to how these traits evolve and function in isolation, but recent work has focused on how signals may interact with one another and produce unique signal interaction properties. These interaction properties vary within species, but little is known about how they vary among species, especially with regards to how the expression of particular signals may drive different signal interaction mechanisms. We studied the evolutionary relationships between iridescent plumage, courtship (shuttle) displays, solar environment, and male color appearance during a display (i.e. the signal interaction property) among six species of North American “bee” hummingbirds. We found that color appearances co-vary with behavioral and plumage properties, which themselves negatively co-vary, such that species with more exaggerated displays appeared flashier during courtship, while species with more exaggerated plumage appeared brighter/more colorful with minimal color-changes. By understanding how signal interaction properties co-vary with signals, we were able to discover the complex, multi-layered evolutionary relationships underlying these traits and uncover new potential drivers of signal evolution. Our results highlight how studying the interaction properties between animal signals provides a richer understanding of how those traits evolved and diversified. More forthcoming papers &raquo; <p>Richard K. Simpson and Kevin J. McGraw (Oct 2019) </p><p><i><a href="https://dx.doi.org/10.1086/704774">Read the Article</a></i> (Just Accepted) </p> <p><b>The complex evolution of hummingbird visual courtship signals produced varied and unique signal interaction properties </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 exhibit a staggering array of exaggerated ornaments, such as peacock tails or deer antlers, and complex behavioral displays, like the elaborate dances of birds of paradise. Ornaments and behaviors are often used for courtship, and many animals use both ornaments and behaviors simultaneously, which prompts the questions of 1) why there is such a diversity of signaling traits, and 2) why animals use multiple signaling traits together. Previous work addressing these two questions has focused on understanding the information conveyed through animal signals, and how signals are transmitted and detected through the environment. However, Drs. Simpson and McGraw set out to tackle these questions from a different angle. Previously they found that male hummingbirds can alter the presentation of their iridescent throat feathers during courtship dances and that this signal interaction changes how males appear to females. For example, when a male is dancing for a female, he can manipulate how he orients his feathers relative to the female and sun to create a flashy, strobe-like color appearance. To tackle questions about signal evolution and diversity, Simpson and McGraw tested how signal interactions vary among multiple hummingbird species, and how signal interactions may be co-evolving with other signaling traits. They quantified the courtship dances, iridescent feathers, and signal interactions (male color appearance during courtship) of six hummingbird species in the American Southwest and found that signal interactions do vary among species, with some having very flashy color appearances during courtship and others having very consistently colored but brighter color appearances. Further, they found that species with more complex dances have flashier color appearances, while species with larger and more colorful feathers have brighter, more consistent color appearances, illustrating how these different signaling traits can co-evolve. This work demonstrates the need to incorporate signal interactions into future research on multiple signals so that biologists can better and more deeply understand the evolution and diversity of animal signals.</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>any animals communicate using multiple signals. Historically, most attention was paid to how these traits evolve and function in isolation, but recent work has focused on how signals may interact with one another and produce unique signal interaction properties. These interaction properties vary within species, but little is known about how they vary among species, especially with regards to how the expression of particular signals may drive different signal interaction mechanisms. We studied the evolutionary relationships between iridescent plumage, courtship (shuttle) displays, solar environment, and male color appearance during a display (i.e. the signal interaction property) among six species of North American &ldquo;bee&rdquo; hummingbirds. We found that color appearances co-vary with behavioral and plumage properties, which themselves negatively co-vary, such that species with more exaggerated displays appeared flashier during courtship, while species with more exaggerated plumage appeared brighter/more colorful with minimal color-changes. By understanding how signal interaction properties co-vary with signals, we were able to discover the complex, multi-layered evolutionary relationships underlying these traits and uncover new potential drivers of signal evolution. Our results highlight how studying the interaction properties between animal signals provides a richer understanding of how those traits evolved and diversified.</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, 11 Jun 2019 05:00:00 GMT “Soil microbiomes underlie population persistence of an endangered plant species” https://amnat.org/an/newpapers/Oct-David.html Read the Article (Just Accepted) Bioassays, long-term demographic data, and integral projection modeling show soil microbiomes boost plant populationsMicrobiomes can have profound effects on their hosts, yet we are still learning about their effects on higher-order processes. While recent research has considered how microbiomes alter processes at the community and ecosystem levels, lost in the shuffle has been the microbiome’s effect on host species’ populations, a knowledge gap that could have serious implications for plant and animal species listed as threatened and endangered. The origins of this study began 25 years ago with the first censuses of the endangered Hypericum cumulicola, a perennial herb endemic to the imperiled Florida scrub ecosystem. Using detailed demographic data collected annually from 15 populations at Archbold Biological Station, along with spatial and historical factors such as fire history, elevation, patch aggregation, and patch size, an integral projection model (IPM) was developed that quantified H.&nbsp;cumulicola population dynamics across the landscape (Quintana-Ascencio et al. 2018 Journal of Ecology). Because of the flexibility built into this original population model, it would serve as an ideal tool to quantify how other factors, namely the soil microbiome, could influence population growth of the plant, provided that the effects of the soil microbiome on individual plants could be quantified. In this new study, the authors set out to do just that by conducting bioassays that quantified the effect of microbes on two demographic rates critical to H.&nbsp;cumulicola populations – seed germination and first-year growth. By comparing the effects of live and sterilized soils on these demographic rates, they found that microbes substantially increased seed germination rates. Next, the authors incorporated the results of these bioassays into the IPM to quantify the population-level effects of the soil microbiome. The results were striking – in the absence of a soil microbiome, H.&nbsp;cumulicola populations would rarely experience population growth, leading to the conclusion that the soil microbiome plays a critical role in maintaining population persistence of its endangered host. Abstract Microbiomes can dramatically alter individual plant performance, yet how these effects influence higher order processes is not well resolved. In particular, little is known about how microbiome effects on individual plants alter plant population dynamics, a question critical to imperiled species conservation. Here, we integrate bioassays, multidecadal demographic data, and integral projection modeling to determine how the presence of the natural soil microbiome underlies plant population dynamics. Simulations indicated that the presence of soil microbiomes boosted population growth rates (&lambda;) of the endangered Hypericum cumulicola by 13% on average, the difference between population growth versus decline in 76% of patches. The greatest benefit (47% increase in &lambda;) occurred in low nutrient, high elevation habitats, suggesting that the soil microbiome may help expand H.&nbsp;cumulicola’s distribution to include these stressful habitats. Our results demonstrate that soil microbiomes can significantly affect plant population growth and persistence, and support the incorporation of soil microbiomes into conservation planning. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704684">Read the Article</a></i> (Just Accepted) </p> <p><b>Bioassays, long-term demographic data, and integral projection modeling show soil microbiomes boost plant populations</b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">M</span>icrobiomes can have profound effects on their hosts, yet we are still learning about their effects on higher-order processes. While recent research has considered how microbiomes alter processes at the community and ecosystem levels, lost in the shuffle has been the microbiome’s effect on host species’ <i>populations</i>, a knowledge gap that could have serious implications for plant and animal species listed as threatened and endangered. </p><p>The origins of this study began 25 years ago with the first censuses of the endangered <i>Hypericum cumulicola</i>, a perennial herb endemic to the imperiled Florida scrub ecosystem. Using detailed demographic data collected annually from 15 populations at Archbold Biological Station, along with spatial and historical factors such as fire history, elevation, patch aggregation, and patch size, an integral projection model (IPM) was developed that quantified <i>H.&nbsp;cumulicola</i> population dynamics across the landscape (Quintana-Ascencio et al. 2018 <i>Journal of Ecology</i>). Because of the flexibility built into this original population model, it would serve as an ideal tool to quantify how other factors, namely the soil microbiome, could influence population growth of the plant, provided that the effects of the soil microbiome on individual plants could be quantified. </p><p>In this new study, the authors set out to do just that by conducting bioassays that quantified the effect of microbes on two demographic rates critical to <i>H.&nbsp;cumulicola</i> populations – seed germination and first-year growth. By comparing the effects of live and sterilized soils on these demographic rates, they found that microbes substantially increased seed germination rates. Next, the authors incorporated the results of these bioassays into the IPM to quantify the population-level effects of the soil microbiome. The results were striking – in the absence of a soil microbiome, <i>H.&nbsp;cumulicola</i> populations would rarely experience population growth, leading to the conclusion that the soil microbiome plays a critical role in maintaining population persistence of its endangered host. </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>icrobiomes can dramatically alter individual plant performance, yet how these effects influence higher order processes is not well resolved. In particular, little is known about how microbiome effects on individual plants alter plant population dynamics, a question critical to imperiled species conservation. Here, we integrate bioassays, multidecadal demographic data, and integral projection modeling to determine how the presence of the natural soil microbiome underlies plant population dynamics. Simulations indicated that the presence of soil microbiomes boosted population growth rates (&lambda;) of the endangered <i>Hypericum cumulicola</i> by 13% on average, the difference between population growth versus decline in 76% of patches. The greatest benefit (47% increase in &lambda;) occurred in low nutrient, high elevation habitats, suggesting that the soil microbiome may help expand <i>H.&nbsp;cumulicola</i>&rsquo;s distribution to include these stressful habitats. Our results demonstrate that soil microbiomes can significantly affect plant population growth and persistence, and support the incorporation of soil microbiomes into conservation planning.</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, 06 Jun 2019 05:00:00 GMT “Pulsed immigration events can facilitate adaptation to harsh sink environments” https://amnat.org/an/newpapers/Sep-Peniston.html Read the Article (Just Accepted) The temporal spacing of immigration events can facilitate niche evolution in harsh sink environments The movement rate of organisms can vary a lot from year to year. For instance, more butterflies disperse among habitats in warmer years than colder ones, and the dispersal of many marine organisms depends on ocean conditions. Most ecological and evolutionary studies ignore this variation and assume that organisms have constant movement rates between habitats. However, in a recent paper, researchers at the University of Florida have shown that variation in dispersal rates may be important to understanding how species adapt to new environments. The researchers built mathematical models in which individuals of a species immigrated into a new environment to which the species was poorly adapted. They then evaluated how well the species could adapt to this environment. In different versions of the model, immigration could either happen every year or there could be years without immigration. They showed that adaptation to new environments was more likely when there were longer stretches of time between immigration events. This is because when maladapted immigrants mate with better adapted residents in the new environment, their genes get mixed together in their offspring. Therefore, any local adaptation that does occur may be lost when new immigrants arrive and mate. Longer gaps between immigration events allow the population to become better adapted before the next immigration event. Once the population becomes well-adapted, the population size will increase, and the relatively small number of new immigrants will no longer have a major effect on local adaptation. By investigating more realistic patterns of dispersal, this study offers new insights into how populations adapt to new environments. With increasing globalization, climate change, and habitat fragmentation, variation in migration rates between habitats are likely to change for many species. Therefore, the results of this study may have important implications for understanding how organisms will respond to the large-scale impacts humans are inflicting on our planet. Abstract In nature, rates of dispersal vary greatly over time, yet most theoretical explorations of ecological and evolutionary dynamics to date have assumed constant movement rates. Here, we examine how a particular pattern of temporal variation—periodic pulses of immigration—influences adaptation to a harsh environment, in which a species experiences conditions outside its niche requirements. Using both deterministic models and stochastic individual-based simulations, we show that for many ecological and genetic scenarios, temporally spacing out immigration events increases the probability that local adaptation is sufficient for persistence (i.e., niche evolution). When immigration events are too frequent, gene flow can hamper local adaptation in sexual species, but sufficiently infrequent pulses of immigration allow for repeated opportunities for adaptation with temporary escapes from gene flow during which local selection is unleashed. We develop versions of our models with and without density dependence for three different assumptions about the genetics underlying fitness (haploid, diploid, and quantitative genetic variation) so that our results may be applicable to a wide range of natural systems. Our study adds to a growing body of literature showing that temporal variation in migration rates can have significant effects on local adaptation, and is among the first to show how such variation affects niche evolution. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704608">Read the Article</a></i> (Just Accepted)</p> <p><b>The temporal spacing of immigration events can facilitate niche evolution in harsh sink environments </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 movement rate of organisms can vary a lot from year to year. For instance, more butterflies disperse among habitats in warmer years than colder ones, and the dispersal of many marine organisms depends on ocean conditions. Most ecological and evolutionary studies ignore this variation and assume that organisms have constant movement rates between habitats. However, in a recent paper, researchers at the University of Florida have shown that variation in dispersal rates may be important to understanding how species adapt to new environments.</p> <p>The researchers built mathematical models in which individuals of a species immigrated into a new environment to which the species was poorly adapted. They then evaluated how well the species could adapt to this environment. In different versions of the model, immigration could either happen every year or there could be years without immigration. They showed that adaptation to new environments was more likely when there were longer stretches of time between immigration events. This is because when maladapted immigrants mate with better adapted residents in the new environment, their genes get mixed together in their offspring. Therefore, any local adaptation that does occur may be lost when new immigrants arrive and mate. Longer gaps between immigration events allow the population to become better adapted before the next immigration event. Once the population becomes well-adapted, the population size will increase, and the relatively small number of new immigrants will no longer have a major effect on local adaptation.</p> <p>By investigating more realistic patterns of dispersal, this study offers new insights into how populations adapt to new environments. With increasing globalization, climate change, and habitat fragmentation, variation in migration rates between habitats are likely to change for many species. Therefore, the results of this study may have important implications for understanding how organisms will respond to the large-scale impacts humans are inflicting on our planet.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">I</span>n nature, rates of dispersal vary greatly over time, yet most theoretical explorations of ecological and evolutionary dynamics to date have assumed constant movement rates. Here, we examine how a particular pattern of temporal variation—periodic pulses of immigration—influences adaptation to a harsh environment, in which a species experiences conditions outside its niche requirements. Using both deterministic models and stochastic individual-based simulations, we show that for many ecological and genetic scenarios, temporally spacing out immigration events increases the probability that local adaptation is sufficient for persistence (i.e., niche evolution). When immigration events are too frequent, gene flow can hamper local adaptation in sexual species, but sufficiently infrequent pulses of immigration allow for repeated opportunities for adaptation with temporary escapes from gene flow during which local selection is unleashed. We develop versions of our models with and without density dependence for three different assumptions about the genetics underlying fitness (haploid, diploid, and quantitative genetic variation) so that our results may be applicable to a wide range of natural systems. Our study adds to a growing body of literature showing that temporal variation in migration rates can have significant effects on local adaptation, and is among the first to show how such variation affects niche evolution. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 30 May 2019 05:00:00 GMT “Evolution at the edge of expanding populations” https://amnat.org/an/newpapers/Sep-Deforet-A.html Read the Article (Just Accepted)Abstract Predicting evolution of expanding populations is critical to control biological threats such as invasive species and cancer metastasis. Expansion is primarily driven by reproduction and dispersal, but nature abounds with examples of evolution where organisms pay a reproductive cost to disperse faster. When does selection favor this ‘survival of the fastest?’ We searched for a simple rule, motivated by evolution experiments where swarming bacteria evolved into an hyperswarmer mutant which disperses ~100% faster but pays a growth cost of ~10% to make many copies of its flagellum. We analyzed a two-species model based on the Fisher equation to explain this observation: the population expansion rate (v) results from an interplay of growth (r) and dispersal (D) and is independent of the carrying capacity: v=2√rD. A mutant can take over the edge only if its expansion rate (v2) exceeds the expansion rate of the established species’ (v1); this simple condition (v2 > v1) determines the maximum cost in slower growth that a faster mutant can pay and still be able to take over. Numerical simulations and time-course experiments where we tracked evolution by imaging bacteria suggest that our findings are general: less favorable conditions delay but do not entirely prevent the success of the fastest. Thus, the expansion rate defines a traveling wave fitness, which could be combined with trade-offs to predict evolution of expanding populations. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704594">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>redicting evolution of expanding populations is critical to control biological threats such as invasive species and cancer metastasis. Expansion is primarily driven by reproduction and dispersal, but nature abounds with examples of evolution where organisms pay a reproductive cost to disperse faster. When does selection favor this ‘survival of the fastest?’ We searched for a simple rule, motivated by evolution experiments where swarming bacteria evolved into an hyperswarmer mutant which disperses ~100% faster but pays a growth cost of ~10% to make many copies of its flagellum. We analyzed a two-species model based on the Fisher equation to explain this observation: the population expansion rate (<i>v</i>) results from an interplay of growth (<i>r</i>) and dispersal (<i>D</i>) and is independent of the carrying capacity: <i>v</i>=2√<span style="text-decoration:overline;"><i>rD</i></span>. A mutant can take over the edge only if its expansion rate (<i>v</i><span style="font-size:70%; position:relative; bottom:-0.3em;">2</span>) exceeds the expansion rate of the established species’ (<i>v</i><span style="font-size:70%; position:relative; bottom:-0.3em;">1</span>); this simple condition (<i>v</i><span style="font-size:70%; position:relative; bottom:-0.3em;">2</span> &gt; <i>v</i><span style="font-size:70%; position:relative; bottom:-0.3em;">1</span>) determines the maximum cost in slower growth that a faster mutant can pay and still be able to take over. Numerical simulations and time-course experiments where we tracked evolution by imaging bacteria suggest that our findings are general: less favorable conditions delay but do not entirely prevent the success of the fastest. Thus, the expansion rate defines a traveling wave fitness, which could be combined with trade-offs to predict evolution of expanding populations. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Thu, 30 May 2019 05:00:00 GMT “Pollen on stigmas of herbarium specimens: a window into the impacts of a century of environmental disturbance on pollen transfer” https://amnat.org/an/newpapers/Sep-Johnson.html Read the Article (Just Accepted) A century of anthropogenic change in Hawaiʻi leaves a pollen ‘fingerprint’ on flower stigmas Biological collections provide a window into the past, and are the foundation of much of our knowledge about the diversity, range, and evolution of life. Billions of these specimens are preserved in natural history museums around the world. Recently, especially with the spread of new technologies such as genetic sequencing, mass digitization, and high resolution imaging, these collections are being revisited, and are yielding many exciting new insights into how global change is impacting life on earth. In this study, three University of Pittsburgh researchers, Anna Johnson, Maria Rebolleda-Gomez, and Tia-Lynn Ashman applied a novel method for gathering data from herbarium specimens to examine how pollination interactions have changed over longer ecological time scales than can usually be documented through long-term field studies. They collected pollen from herbarium specimen stigmas collected in the dry tropical forests of Hawaiʻi, an ecosystem that has experienced rapid habitat loss and disturbance over the last century. After counting and identifying the pollen grains to species, they compared the quantity and diversity of pollen which native dry forest plant species interacted with prior to 1950, and post 1950. They found that while the amount of pollen which these species received did not change dramatically, the identity of the pollen grains observed on herbarium stigmas was very different between the two time periods. This suggests that for plant species to survive in a rapidly changing world, they must be robust to shifts in species interactions, even for pollination, a key reproductive mutualism. The techniques demonstrated in this study hold promise for uncovering the history of pollination in other systems, especially those for which we currently lack an understanding of the types of interactions that species historically engaged in prior to widespread anthropogenic disturbances. Abstract Pollination is necessary for plant reproduction, but often highly susceptible to disruption, e.g., by habitat fragmentation and climate change. Here, we indirectly evaluated on a century time scale pollination interactions for species in one of the historically most disturbed habitats on earth—tropical dry forests of Hawaiʻi. We employed a novel method for acquiring a historical perspective on temporal change in pollination by characterizing pollen on stigmas of herbarium specimens from six remnant native species collected from 1909-2002. We determine whether temporal shifts occurred in 1) pollination quantity and quality, or 2) the composition of species interacting via pollen transfer. While pollen quantity remained constant, these remnant species interact with different species in modern times via pollen transfer than they did nearly 100 years ago. Species that are resilient to long-term environmental change may also be the ones subject to changes in pollination interactions. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704607">Read the Article</a></i> (Just Accepted)</p> <p><b>A century of anthropogenic change in Hawaiʻi leaves a pollen ‘fingerprint’ on flower stigmas </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>iological collections provide a window into the past, and are the foundation of much of our knowledge about the diversity, range, and evolution of life. Billions of these specimens are preserved in natural history museums around the world. Recently, especially with the spread of new technologies such as genetic sequencing, mass digitization, and high resolution imaging, these collections are being revisited, and are yielding many exciting new insights into how global change is impacting life on earth.</p> <p>In this study, three University of Pittsburgh researchers, Anna Johnson, Maria Rebolleda-Gomez, and Tia-Lynn Ashman applied a novel method for gathering data from herbarium specimens to examine how pollination interactions have changed over longer ecological time scales than can usually be documented through long-term field studies. They collected pollen from herbarium specimen stigmas collected in the dry tropical forests of Hawaiʻi, an ecosystem that has experienced rapid habitat loss and disturbance over the last century. After counting and identifying the pollen grains to species, they compared the quantity and diversity of pollen which native dry forest plant species interacted with prior to 1950, and post 1950. They found that while the amount of pollen which these species received did not change dramatically, the identity of the pollen grains observed on herbarium stigmas was very different between the two time periods. This suggests that for plant species to survive in a rapidly changing world, they must be robust to shifts in species interactions, even for pollination, a key reproductive mutualism. The techniques demonstrated in this study hold promise for uncovering the history of pollination in other systems, especially those for which we currently lack an understanding of the types of interactions that species historically engaged in prior to widespread anthropogenic disturbances.</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;">P</span>ollination is necessary for plant reproduction, but often highly susceptible to disruption, e.g., by habitat fragmentation and climate change. Here, we indirectly evaluated on a century time scale pollination interactions for species in one of the historically most disturbed habitats on earth&mdash;tropical dry forests of Hawaiʻi. We employed a novel method for acquiring a historical perspective on temporal change in pollination by characterizing pollen on stigmas of herbarium specimens from six remnant native species collected from 1909-2002. We determine whether temporal shifts occurred in 1) pollination quantity and quality, or 2) the composition of species interacting via pollen transfer. While pollen quantity remained constant, these remnant species interact with different species in modern times via pollen transfer than they did nearly 100 years ago. Species that are resilient to long-term environmental change may also be the ones subject to changes in pollination interactions.</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, 30 May 2019 05:00:00 GMT “Within-individual canalization contributes to age-related increases in trait repeatability: a longitudinal experiment in red knots” https://amnat.org/an/newpapers/Sep-Kok.html Read the Article (Just Accepted) Longitudinal lab experiment shows how canalization contributes to age-related changes in trait repeatability Individual variation is at the core of Darwin’s theory of evolution. Yet in ecology, variation between individuals was often considered as ‘noise’ or a nuisance. However, under changing environmental conditions, variation between individuals increases resilience for a population as a whole. Therefore, understanding what processes generate variation between individuals is important. This study focuses on individual variation and, in particular, what factors promote the development of variation between individuals. Researchers from the Royal Netherlands Institute for Sea Research (NL) and the University of Alberta (CA) looked at changes in bird ‘character’ with age, and if these changes are the unavoidable consequence of ageing or whether different experiences during life cause individuals to diverge. The scientists study the behavior of red knots—migratory shorebirds—exploring their surroundings in search of food. These birds differ in how they search (exploration behavior) and in the size of their stomachs (physiology). To investigate how these differences come about, 90 birds were brought into captivity either as juvenile or as adult, and then given identical experiences over the next two years. While the birds age, exploration behavior and stomach size are measured repeatedly to tease apart the effects of age, experience, and time in captivity on the amount of variation in both traits. If the birds’ individual experiences help maintain the differences between individuals, this variation should disappear during the course of the study because in these experiments, all birds have the same experience.Although it may seem easier to change one’s behavior than one’s physiology, these birds maintain their exploratory character while their stomach size changes. The next step is to follow the birds after their release back into the wild, to examine how the changes measured in the lab translate to real life. Abstract Age-related increases in the repeatable expression of labile phenotypic traits are often assumed to arise from an increase in among-individual variance due to differences in developmental plasticity or by means of state-behavior feedbacks. However, age-related increases in repeatability could also arise from a decrease in within-individual variance as a result of stabilizing trait expression, i.e. canalization. Here we describe age-related changes in within- and among-individual variance components in two correlated traits, gizzard mass and exploration behavior, in a medium-sized shorebird, the red knot (Calidris canutus). Increased repeatability of gizzard mass came about due to an increase in among-individual variance, unrelated to differences in developmental plasticity, together with decreases in within-individual variance, consistent with canalization. We also found canalization of exploration, but no age-related increase in overall repeatability, which suggests that showing predictable expression of exploration behavior may be advantageous from a very young age onward. Contrasts between juveniles and adults in the first year after their capture provide support for the idea that environmental conditions play a key role in generating among-individual variation in both gizzard mass and exploration behavior. Our study shows that stabilization of traits occurs under constant conditions: with increased exposure to predictable cues, individuals may become more certain in their assessment of the environment allowing traits to become canalized. De foarspelbere ûntwikkeling fan lichems- en gedrachseigenskippen: in eksperiment oer welhelberhyd fan eigenskippen by mientsen Alhoewol guon lichemseigenskippen fan jonge yndividuën hyltiten wer feroarje kinne, komme by it âlder wurden sokke eigenskippen ornaris dochs hyltiten mear fêst te lizzen. Soks kin komme troch it feroarjen fan yndividuele plastisiteit en troch weromkeppelingen tusken it gedrach en de steat fan sa’n bist. Yndividuele ferskillen yn it fêstlizzen fan eigenskippen fergrutsje de fariaasje tusken yndividuën. In technysk begrip om yndividuele fariaasje fan eigenskippen te kwantifisearjen is ‘repeatability’ (‘werhelberhyd’), mar it euvel is dat in taname fan dizze statistyske maat sawol komme kin troch in taname yn ‘e fariaasje tusken yndividuën en troch in ôfname fan de fariaasje binnen yndividuën; dit lêste neame wy ‘kanalisaasje’. Yn dit artikel beskriuwe wy hoe’t dizze twa boarnen fan fariaasje by it âlder wurden feroarje kinne by mientsen (Calidris canutus), en dat dogge wy oan ‘e hân fan twa besibbe eigenskippen: (1) it gewicht fan de spiermage, en (2) de wize werop mientsen yn in eksperimentele romte lytse stikjes waad ferkenne (der binne fûgels dy’t bot eksplorearje, en guon dy’t ôfwachtsje). It die bliken dat de werhelberhyd fan it magegewicht feroare troch tanimmende ferskillen tusken yndividuën en in ôfname fan de fariaasje binnen yndividuën, in kombinaasje fan plastisiteit en kanalisaasje dus. By eksploraasje-gedrach fûnen wy by it âlder wurden oanwizings foar kanalisaasje. Dat soe betsjutte kinne dat der foardielen binne om al op jonge leeftyd in bepaalde yndividuele wize fan eksploraasje oan te hâlden. Út in fergeliking tusken jonge en âlde fûgels (dy’t in ferskil yn ûntwikkeling yn it frije fjild wjerspegelje), blykte it bestean fan weromkeppelingen tusken de steat fan it lichem (magegewicht) en it gedrach (eksploraasje). Ús stúdzje lit lykwols foaral sjen dat eigenskippen, sels yn sitewaasjes dy’t net feroarje, fêst komme te lizzen. Miskien makket it fenomeen dat fûgels har omjouwing hyltiten better foarspelle kinne sokke kanalisaasje mooglik. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704593">Read the Article</a></i> (Just Accepted)</p> <p><b>Longitudinal lab experiment shows how canalization contributes to age-related changes in trait repeatability </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>ndividual variation is at the core of Darwin’s theory of evolution. Yet in ecology, variation between individuals was often considered as ‘noise’ or a nuisance. However, under changing environmental conditions, variation between individuals increases resilience for a population as a whole. Therefore, understanding what processes generate variation between individuals is important. </p><p>This study focuses on individual variation and, in particular, what factors promote the development of variation between individuals. Researchers from the Royal Netherlands Institute for Sea Research (NL) and the University of Alberta (CA) looked at changes in bird ‘character’ with age, and if these changes are the unavoidable consequence of ageing or whether different experiences during life cause individuals to diverge. </p><p>The scientists study the behavior of red knots—migratory shorebirds—exploring their surroundings in search of food. These birds differ in how they search (exploration behavior) and in the size of their stomachs (physiology). To investigate how these differences come about, 90 birds were brought into captivity either as juvenile or as adult, and then given identical experiences over the next two years. While the birds age, exploration behavior and stomach size are measured repeatedly to tease apart the effects of age, experience, and time in captivity on the amount of variation in both traits. If the birds’ individual experiences help maintain the differences between individuals, this variation should disappear during the course of the study because in these experiments, all birds have the same experience.</p><p>Although it may seem easier to change one’s behavior than one’s physiology, these birds maintain their exploratory character while their stomach size changes. The next step is to follow the birds after their release back into the wild, to examine how the changes measured in the lab translate to real life. </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>ge-related increases in the repeatable expression of labile phenotypic traits are often assumed to arise from an increase in among-individual variance due to differences in developmental plasticity or by means of state-behavior feedbacks. However, age-related increases in repeatability could also arise from a decrease in within-individual variance as a result of stabilizing trait expression, i.e. canalization. Here we describe age-related changes in within- and among-individual variance components in two correlated traits, gizzard mass and exploration behavior, in a medium-sized shorebird, the red knot (<i>Calidris canutus</i>). Increased repeatability of gizzard mass came about due to an increase in among-individual variance, unrelated to differences in developmental plasticity, together with decreases in within-individual variance, consistent with canalization. We also found canalization of exploration, but no age-related increase in overall repeatability, which suggests that showing predictable expression of exploration behavior may be advantageous from a very young age onward. Contrasts between juveniles and adults in the first year after their capture provide support for the idea that environmental conditions play a key role in generating among-individual variation in both gizzard mass and exploration behavior. Our study shows that stabilization of traits occurs under constant conditions: with increased exposure to predictable cues, individuals may become more certain in their assessment of the environment allowing traits to become canalized. </p><h4>De foarspelbere ûntwikkeling fan lichems- en gedrachseigenskippen: in eksperiment oer welhelberhyd fan eigenskippen by mientsen </h4> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>lhoewol guon lichemseigenskippen fan jonge yndividuën hyltiten wer feroarje kinne, komme by it âlder wurden sokke eigenskippen ornaris dochs hyltiten mear fêst te lizzen. Soks kin komme troch it feroarjen fan yndividuele plastisiteit en troch weromkeppelingen tusken it gedrach en de steat fan sa’n bist. Yndividuele ferskillen yn it fêstlizzen fan eigenskippen fergrutsje de fariaasje tusken yndividuën. In technysk begrip om yndividuele fariaasje fan eigenskippen te kwantifisearjen is ‘repeatability’ (‘werhelberhyd’), mar it euvel is dat in taname fan dizze statistyske maat sawol komme kin troch in taname yn ‘e fariaasje tusken yndividuën en troch in ôfname fan de fariaasje <i>binnen</i> yndividuën; dit lêste neame wy ‘kanalisaasje’. Yn dit artikel beskriuwe wy hoe’t dizze twa boarnen fan fariaasje by it âlder wurden feroarje kinne by mientsen (<i>Calidris canutus</i>), en dat dogge wy oan ‘e hân fan twa besibbe eigenskippen: (1) it gewicht fan de spiermage, en (2) de wize werop mientsen yn in eksperimentele romte lytse stikjes waad ferkenne (der binne fûgels dy’t bot eksplorearje, en guon dy’t ôfwachtsje). It die bliken dat de werhelberhyd fan it magegewicht feroare troch tanimmende ferskillen tusken yndividuën en in ôfname fan de fariaasje binnen yndividuën, in kombinaasje fan plastisiteit en kanalisaasje dus. By eksploraasje-gedrach fûnen wy by it âlder wurden oanwizings foar kanalisaasje. Dat soe betsjutte kinne dat der foardielen binne om al op jonge leeftyd in bepaalde yndividuele wize fan eksploraasje oan te hâlden. Út in fergeliking tusken jonge en âlde fûgels (dy’t in ferskil yn ûntwikkeling yn it frije fjild wjerspegelje), blykte it bestean fan weromkeppelingen tusken de steat fan it lichem (magegewicht) en it gedrach (eksploraasje). Ús stúdzje lit lykwols foaral sjen dat eigenskippen, sels yn sitewaasjes dy’t net feroarje, fêst komme te lizzen. Miskien makket it fenomeen dat fûgels har omjouwing hyltiten better foarspelle kinne sokke kanalisaasje mooglik. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 29 May 2019 05:00:00 GMT “Omnivory in bees: Elevated trophic positions among all major bee families” https://amnat.org/an/newpapers/Sep-Steffan.html Read the Article (Just Accepted) Bees are omnivores, mainly because as larvae, they eat lots of ‘microbial meat’Bees are widely thought to derive all protein directly from floral resources. Recent findings suggest this is largely untrue. It appears that larval bees feed extensively on pollen-borne prey, as well as on the pollen, itself. These prey are the microbes that are suffused throughout a fermenting pollen-provision. Because the microbes are actively consuming the pollen, these herbivorous organisms represent ‘microbial meat’ within the pollen-provision. When a larval bee consumes aged pollen, the bee is consuming both microbial and plant biomass, assimilating the amino acids of microbial prey as well as those of the plant material—analogous to eating bacon bits in a salad. The degree to which a bee assimilates microbe-derived amino acids can be measured empirically as the trophic position of the bee (the more meat consumed, the higher the trophic position). Importantly, gut microbiota do not elevate the hosting animal’s trophic position. To assess the pervasiveness of bee omnivory, the trophic positions of bees representing the six major bee families on Earth were examined. Adult bees were collected over the course of two years, from the cranberry marshlands of Wisconsin to the forests of New York. There was consistent, significant evidence of elevated trophic positions among all the bees in the study (54 specimens across 14 species, 12 genera), suggesting that most bees, if not all, are omnivorous. Such reliance on microbial nutrition also suggests that pollen-borne microbes represent true symbionts for bees; thus, to conserve bee fauna, their microbial symbionts will require attention, too. Abstract As pollen- and nectar-foragers, bees have long been considered strictly herbivorous. Their pollen-provisions, however, are host to abundant microbial communities, which feed on the pollen before/while it is consumed by bee larvae. In the process, microbes convert pollen into a complex of plant and microbial components. Since microbes are analogous to metazoan consumers within trophic hierarchies, the pollen-eating microbes are, functionally, herbivores. When bee larvae consume a microbe-rich pollen complex, they ingest proteins from plant and microbial sources, thus should register as omnivores on the trophic “ladder.” We tested this hypothesis by examining the isotopic compositions of amino acids extracted from native bees collected in North America over multiple years. We measured bee trophic position across the six major bee families. Our findings indicate that bee trophic identity was consistently and significantly higher than that of strict herbivores, providing the first evidence that omnivory is ubiquitous among bee fauna. Such omnivory suggests that pollen-borne microbes represent an important protein source for larval bees, which introduces new questions as to the link between floral fungicide residues and bee development. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704281">Read the Article</a></i> (Just Accepted)</p> <p><b>Bees are omnivores, mainly because as larvae, they eat lots of ‘microbial meat’</b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">B</span>ees are widely thought to derive all protein directly from floral resources. Recent findings suggest this is largely untrue. It appears that larval bees feed extensively on pollen-borne prey, as well as on the pollen, itself. These prey are the microbes that are suffused throughout a fermenting pollen-provision. Because the microbes are actively consuming the pollen, these herbivorous organisms represent ‘microbial meat’ within the pollen-provision. When a larval bee consumes aged pollen, the bee is consuming both microbial and plant biomass, assimilating the amino acids of microbial prey as well as those of the plant material—analogous to eating bacon bits in a salad. The degree to which a bee assimilates microbe-derived amino acids can be measured empirically as the trophic position of the bee (the more meat consumed, the higher the trophic position). Importantly, gut microbiota do not elevate the hosting animal’s trophic position. To assess the pervasiveness of bee omnivory, the trophic positions of bees representing the six major bee families on Earth were examined. Adult bees were collected over the course of two years, from the cranberry marshlands of Wisconsin to the forests of New York. There was consistent, significant evidence of elevated trophic positions among all the bees in the study (54 specimens across 14 species, 12 genera), suggesting that most bees, if not all, are omnivorous. Such reliance on microbial nutrition also suggests that pollen-borne microbes represent true symbionts for bees; thus, to conserve bee fauna, their microbial symbionts will require attention, too. </p> <hr /><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>s pollen- and nectar-foragers, bees have long been considered strictly herbivorous. Their pollen-provisions, however, are host to abundant microbial communities, which feed on the pollen before/while it is consumed by bee larvae. In the process, microbes convert pollen into a complex of plant and microbial components. Since microbes are analogous to metazoan consumers within trophic hierarchies, the pollen-eating microbes are, functionally, herbivores. When bee larvae consume a microbe-rich pollen complex, they ingest proteins from plant and microbial sources, thus should register as omnivores on the trophic “ladder.” We tested this hypothesis by examining the isotopic compositions of amino acids extracted from native bees collected in North America over multiple years. We measured bee trophic position across the six major bee families. Our findings indicate that bee trophic identity was consistently and significantly higher than that of strict herbivores, providing the first evidence that omnivory is ubiquitous among bee fauna. Such omnivory suggests that pollen-borne microbes represent an important protein source for larval bees, which introduces new questions as to the link between floral fungicide residues and bee development. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 May 2019 05:00:00 GMT “Decreasing predator density and activity explain declining predation of insect prey along elevational gradients” https://amnat.org/an/newpapers/Sep-Camacho-A.html Read the Article (Just Accepted)Abstract Predation, which is a fundamental force in ecosystems, has been found to decrease in intensity with elevation and latitude. The mechanisms behind this pattern, however, remain unaddressed. Using visual sampling of potential predators and live flies as baits, we assessed predation patterns along 4000-meter elevation transects on either side of the equatorial Andes. We found that at the lower elevations around eighty percent of predation events on our insect baits were due to ants. The decline in predation with elevation was mainly driven by a decline in the abundance of ants, whose importance relative to other predators also declined. We show that both predator density and activity (predation rate per individual predator) decreased with elevation, thus ascribing specific mechanisms to known predation patterns. We suggest that changes in these two mechanisms may reflect changes in primary productivity and metabolic rate with temperature, factors of potential relevance across latitudinal and other macroecological gradients, in particular for ectotherm predators and prey. La disminuci&oacute;n en la densidad y actividad de depredadores explican la reducci&oacute;n en la depredaci&oacute;n de insectos presas a lo largo de gradientes de elevaci&oacute;n La depredaci&oacute;n, una fuerza fundamental en los ecosistemas, se ha encontrado que decrece en intensidad con la elevaci&oacute;n y la latitud. Los mecanismos detr&aacute;s de este patr&oacute;n, sin embargo, no han sido estudiados. En este trabajo, usando muestreos visuales de potenciales depredadores y moscas vivas como cebos, evaluamos patrones de depredaci&oacute;n en transectos realizados con una variaci&oacute;n altitudinal de 4000 metros en las dos caras de los Andes ecuatoriales. Encontramos que, en altitudes bajas, alrededor del ochenta porciento de los eventos de depredaci&oacute;n en nuestros insectos cebo fueron causados por hormigas. El decrecimiento en depredaci&oacute;n asociado con la variaci&oacute;n altitudinal fue principalmente causado por una reducci&oacute;n en la abundancia de hormigas, cuya importancia relativa respecto a otros depredadores tambi&eacute;n disminuy&oacute;. Mostramos que tanto la densidad como la actividad de depredadores (tasa individual de depredaci&oacute;n por depredador) decrecieron con la altitud, atribuyendo mecanismos a patrones de depredaci&oacute;n ya conocidos. Sugerimos que cambios en estos dos mecanismos pueden reflejar cambios en la productividad primaria y en la tasa metab&oacute;lica relacionados con la temperatura, factores potencialmente relevantes a lo largo de gradientes de latitud y otros gradientes macroecol&oacute;gicos, particularmente para presas y depredadores ectotermos. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704279">Read the Article</a></i> (Just Accepted)</p><h3>Abstract</h3> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">P</span>redation, which is a fundamental force in ecosystems, has been found to decrease in intensity with elevation and latitude. The mechanisms behind this pattern, however, remain unaddressed. Using visual sampling of potential predators and live flies as baits, we assessed predation patterns along 4000-meter elevation transects on either side of the equatorial Andes. We found that at the lower elevations around eighty percent of predation events on our insect baits were due to ants. The decline in predation with elevation was mainly driven by a decline in the abundance of ants, whose importance relative to other predators also declined. We show that both predator density and activity (predation rate per individual predator) decreased with elevation, thus ascribing specific mechanisms to known predation patterns. We suggest that changes in these two mechanisms may reflect changes in primary productivity and metabolic rate with temperature, factors of potential relevance across latitudinal and other macroecological gradients, in particular for ectotherm predators and prey.</p> <h4>La disminuci&oacute;n en la densidad y actividad de depredadores explican la reducci&oacute;n en la depredaci&oacute;n de insectos presas a lo largo de gradientes de elevaci&oacute;n</h4> <p><span style="line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-size: 40px; font-weight: bold; float: left;">L</span>a depredaci&oacute;n, una fuerza fundamental en los ecosistemas, se ha encontrado que decrece en intensidad con la elevaci&oacute;n y la latitud. Los mecanismos detr&aacute;s de este patr&oacute;n, sin embargo, no han sido estudiados. En este trabajo, usando muestreos visuales de potenciales depredadores y moscas vivas como cebos, evaluamos patrones de depredaci&oacute;n en transectos realizados con una variaci&oacute;n altitudinal de 4000 metros en las dos caras de los Andes ecuatoriales. Encontramos que, en altitudes bajas, alrededor del ochenta porciento de los eventos de depredaci&oacute;n en nuestros insectos cebo fueron causados por hormigas. El decrecimiento en depredaci&oacute;n asociado con la variaci&oacute;n altitudinal fue principalmente causado por una reducci&oacute;n en la abundancia de hormigas, cuya importancia relativa respecto a otros depredadores tambi&eacute;n disminuy&oacute;. Mostramos que tanto la densidad como la actividad de depredadores (tasa individual de depredaci&oacute;n por depredador) decrecieron con la altitud, atribuyendo mecanismos a patrones de depredaci&oacute;n ya conocidos. Sugerimos que cambios en estos dos mecanismos pueden reflejar cambios en la productividad primaria y en la tasa metab&oacute;lica relacionados con la temperatura, factores potencialmente relevantes a lo largo de gradientes de latitud y otros gradientes macroecol&oacute;gicos, particularmente para presas y depredadores ectotermos.</p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"><span style="font-family: Georgia; font-size: large;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 May 2019 05:00:00 GMT “Destruction of spider webs and rescue of ensnared nestmates by a granivorous desert ant (<i>Veromessor pergandei</i>)” https://amnat.org/an/newpapers/Sep-Kwapich.html Read the Article (Just Accepted) Ants destroy spider webs and rescue trapped sisters that call for help Few prey species seek out and destroy the traps designed to capture them, and only a handful rescue group members in distress. That is why Kwapich and Hölldobler were surprised to discover that desert seed harvesting ants systematically dismantle spider webs constructed along their foraging routes, and retrieve sisters ensnared in spider silk. Animals that perform rescue behavior typically live in small groups with high-value individuals, but Veromessor pergandei form enormous societies that deploy up to 30,000 foragers each morning. To determine why colonies rescue seemingly disposable workers, the authors calculated the costs and benefits of web removal. They found that the seeds carried by foraging ants become tangled in undetected webs, reducing the total number of foraging trips individuals can take per day. By accounting for the length of a foraging career and number of trips per day, they estimated that unchecked spider predation could cost colonies 65,000 seeds per year. This is a high price to pay, because colonies need to gather enough resources to rear 600 new sisters each day. Many ant species clear debris from their foraging routes, but Kwapich and H&ouml;lldobler showed that V.&nbsp;pergandei foragers ignore novel objects, and even lack an innate ability to detect spider silk. Instead, ensnared ants release a chemical alarm signal, which stimulates a subset of large-bodied nestmates to remove surrounding webbing. Frozen ‘dummies’ marked with the same alarm compound were also rescued, and freed from their silk bindings. In essence, colonies only benefit from the removal of webs when workers are captured in them. Other seed harvesting ant species arrest foraging or change their foraging patterns in response to spiders. The authors propose that foraging on a single route during a limited temperature window, coupled with the necessary scale seed harvesting, led V.&nbsp;pergandei to its unusual defensive strategy. Abstract Prey species rarely seek-out and dismantle traps constructed by their predators. In the current study, we report an instance of targeted trap destruction by an invertebrate, and a novel context for rescue behavior. We found that foragers of the granivorous desert ant, Veromessor pergandei, identify and cooperatively dismantle spider webs (Araneae: Theridiidae, Steatoda spp. and Asagena sp.) During group foraging, workers ensnared in webs are recovered by sisters, who transport them to the nest and groom away their silk bindings. The presence of an ensnared nestmate and chemical alarm signal significantly increased the probability of web removal and nestmate retrieval. A subset of larger-bodied foragers participated in web removal, and 6.3% became tangled or were captured by spiders. Most animals that perform rescue behavior live in small groups, but V.&nbsp;pergandei colonies include tens of thousands of short-lived workers. To maintain their size, large colonies must collect enough seeds to produce 650 new ants each day. We hypothesize that the removal of spider webs allows for an unimpeded income of seeds on a single foraging path, during a brief daily temperature window. Despite the cost to individuals, webs are only recognized and removed when workers are captured in them. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704338">Read the Article</a></i> (Just Accepted) </p> <p><b>Ants destroy spider webs and rescue trapped sisters that call for help </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">F</span>ew prey species seek out and destroy the traps designed to capture them, and only a handful rescue group members in distress. That is why Kwapich and Hölldobler were surprised to discover that desert seed harvesting ants systematically dismantle spider webs constructed along their foraging routes, and retrieve sisters ensnared in spider silk. Animals that perform rescue behavior typically live in small groups with high-value individuals, but <i>Veromessor pergandei</i> form enormous societies that deploy up to 30,000 foragers each morning. </p><p>To determine why colonies rescue seemingly disposable workers, the authors calculated the costs and benefits of web removal. They found that the seeds carried by foraging ants become tangled in undetected webs, reducing the total number of foraging trips individuals can take per day. By accounting for the length of a foraging career and number of trips per day, they estimated that unchecked spider predation could cost colonies 65,000 seeds per year. This is a high price to pay, because colonies need to gather enough resources to rear 600 new sisters each day. </p><p>Many ant species clear debris from their foraging routes, but Kwapich and H&ouml;lldobler showed that <i>V.&nbsp;pergandei</i> foragers ignore novel objects, and even lack an innate ability to detect spider silk. Instead, ensnared ants release a chemical alarm signal, which stimulates a subset of large-bodied nestmates to remove surrounding webbing. Frozen &lsquo;dummies&rsquo; marked with the same alarm compound were also rescued, and freed from their silk bindings. In essence, colonies only benefit from the removal of webs when workers are captured in them. Other seed harvesting ant species arrest foraging or change their foraging patterns in response to spiders. The authors propose that foraging on a single route during a limited temperature window, coupled with the necessary scale seed harvesting, led <i>V.&nbsp;pergandei</i> to its unusual defensive strategy.</p> <hr/><h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>rey species rarely seek-out and dismantle traps constructed by their predators. In the current study, we report an instance of targeted trap destruction by an invertebrate, and a novel context for rescue behavior. We found that foragers of the granivorous desert ant, <i>Veromessor pergandei</i>, identify and cooperatively dismantle spider webs (Araneae: Theridiidae, <i>Steatoda</i> spp. and <i>Asagena</i> sp.) During group foraging, workers ensnared in webs are recovered by sisters, who transport them to the nest and groom away their silk bindings. The presence of an ensnared nestmate and chemical alarm signal significantly increased the probability of web removal and nestmate retrieval. A subset of larger-bodied foragers participated in web removal, and 6.3% became tangled or were captured by spiders. Most animals that perform rescue behavior live in small groups, but <i>V.&nbsp;pergandei</i> colonies include tens of thousands of short-lived workers. To maintain their size, large colonies must collect enough seeds to produce 650 new ants each day. We hypothesize that the removal of spider webs allows for an unimpeded income of seeds on a single foraging path, during a brief daily temperature window. Despite the cost to individuals, webs are only recognized and removed when workers are captured in them. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 May 2019 05:00:00 GMT “Intraspecific variation in worker body size makes North American bumble bees (<i>Bombus</i> spp.) less susceptible to decline” https://amnat.org/an/newpapers/Sep-Austin.html Read the Article Intraspecific variation in worker body size makes North American bumble bees less susceptible to population declines Population declines of bees are of broad interest, as bees are important pollinators of much of our wild and agricultural crops. While bee declines are likely caused by many factors, human-induced environmental changes are thought to be key culprits of these declines. A puzzle, however, is that not all bee species are declining – some are in fact thriving – which suggests differences between species in traits that enable responses to rapidly changed environments. In a new paper in The&nbsp;American Naturalist, M.&nbsp;W. Austin and A.&nbsp;S. Dunlap investigate traits in North American bumble bees (Bombus spp.) that may make certain species of bumble bees more susceptible to decline. They study two traits that may be particularly important for bees when encountering rapidly changed environments: 1) the amount of body size variation within a species (i.e. how close in size individual bees are) and 2) head size, a proxy for brain size and behavioral plasticity. High body size variation is likely adaptive within colonies; larger bees are more efficient workers, while smaller bees can withstand starvation for longer periods of time. Behavioral plasticity is thought to benefit species in changed environments, by allowing individuals to plastically change their behavior to novel environmental conditions. Using natural history collections from the Smithsonian, the American Museum of Natural History, the Field Museum, and the Illinois Natural History Survey, along with measures of bumble bee decline from the International Union for Conservation of Nature, the authors find that bumble bee species with low body size variation are more susceptible to decline, while species with higher body size variation are more likely to be thriving. Head size does not appear to affect a species’ likelihood of decline. These results suggest that high variation in body size enables bumble bees to successfully respond to environments altered by human activity, perhaps due to the benefits of body size variation within colonies. This study is part of Austin’s Ph.D. dissertation at the University of Missouri–St. Louis, where he became interested in this topic while considering why closely related species experience divergent population trends. Abstract Population declines have been documented in approximately one-third of bumble bee species. Certain drivers of these declines are known, however less is known about the interspecific trait differences that make certain species more susceptible to decline. Two traits, which have implications for responding to rapidly changed environments, may be particularly consequential for bumble bee populations: intraspecific body size variation and brain size. Bumble bee body size is highly variable and is likely adaptive at the colony level, and brain size correlates with cognitive traits (e.g. behavioral plasticity) in many groups. Trait variation and plasticity may buffer species against negative effects of rapidly changed environments. Using phylogenetically controlled analyses of 31 North American bumble bee species, we find higher intraspecific body size variation is associated with species having increased their relative abundance over time. However, this variation does not significantly interact with tongue length, another trait thought to influence bees’ decline susceptibility. Head size, a proxy for brain size, is not correlated with change in relative abundance. Our results support the hypothesis that variation in body size makes species less susceptible to decline in rapidly altered environments and suggests that this variation is important to the success of bumble bee populations. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704280">Read the Article</a></i></p> <p><b>Intraspecific variation in worker body size makes North American bumble bees less susceptible to population declines </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>opulation declines of bees are of broad interest, as bees are important pollinators of much of our wild and agricultural crops. While bee declines are likely caused by many factors, human-induced environmental changes are thought to be key culprits of these declines. A puzzle, however, is that not all bee species are declining – some are in fact thriving – which suggests differences between species in traits that enable responses to rapidly changed environments. </p><p>In a new paper in <i>The&nbsp;American Naturalist</i>, M.&nbsp;W. Austin and A.&nbsp;S. Dunlap investigate traits in North American bumble bees (<i>Bombus</i> spp.) that may make certain species of bumble bees more susceptible to decline. They study two traits that may be particularly important for bees when encountering rapidly changed environments: 1) the amount of body size variation within a species (i.e. how close in size individual bees are) and 2) head size, a proxy for brain size and behavioral plasticity. High body size variation is likely adaptive within colonies; larger bees are more efficient workers, while smaller bees can withstand starvation for longer periods of time. Behavioral plasticity is thought to benefit species in changed environments, by allowing individuals to plastically change their behavior to novel environmental conditions. </p><p>Using natural history collections from the Smithsonian, the American Museum of Natural History, the Field Museum, and the Illinois Natural History Survey, along with measures of bumble bee decline from the International Union for Conservation of Nature, the authors find that bumble bee species with low body size variation are more susceptible to decline, while species with higher body size variation are more likely to be thriving. Head size does not appear to affect a species’ likelihood of decline. These results suggest that high variation in body size enables bumble bees to successfully respond to environments altered by human activity, perhaps due to the benefits of body size variation within colonies. </p><p>This study is part of Austin’s Ph.D. dissertation at the University of Missouri–St. Louis, where he became interested in this topic while considering why closely related species experience divergent population trends.</p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">P</span>opulation declines have been documented in approximately one-third of bumble bee species. Certain drivers of these declines are known, however less is known about the interspecific trait differences that make certain species more susceptible to decline. Two traits, which have implications for responding to rapidly changed environments, may be particularly consequential for bumble bee populations: intraspecific body size variation and brain size. Bumble bee body size is highly variable and is likely adaptive at the colony level, and brain size correlates with cognitive traits (e.g. behavioral plasticity) in many groups. Trait variation and plasticity may buffer species against negative effects of rapidly changed environments. Using phylogenetically controlled analyses of 31 North American bumble bee species, we find higher intraspecific body size variation is associated with species having increased their relative abundance over time. However, this variation does not significantly interact with tongue length, another trait thought to influence bees’ decline susceptibility. Head size, a proxy for brain size, is not correlated with change in relative abundance. Our results support the hypothesis that variation in body size makes species less susceptible to decline in rapidly altered environments and suggests that this variation is important to the success of bumble bee populations. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 May 2019 05:00:00 GMT “Antagonistic responses of exposure to sublethal temperatures: Adaptive phenotypic plasticity coincides with a reduction in organismal performance” https://amnat.org/an/newpapers/Sep-Gilbert.html Read the Article Exposure to stressful temperatures induces adaptive plasticity but constrains ecological and organismal performance Anthropogenic climate change is exposing populations to new environmental pressures that can lead to a variety of physiological, genetic, or behavioral responses. When novel environmental conditions cause phenotypic shifts in the absence of genetic change (i.e. phenotypic plasticity), oftentimes researchers only consider quantifying how traits-of-interest shift, without considering that particularly stressful stimuli might lead to other unforeseen phenotypic outcomes. Because many species are now predisposed to higher incidences of heat waves within their environment, exposure to sublethal temperatures is considered to be a trigger of adaptive phenotypic plasticity, otherwise called ‘heat hardening’. Heat hardening occurs when an individual is exposed to sublethal temperatures, and as a result they can temporarily tolerate higher temperatures than they could prior to heat shock. However, because the trigger of heat hardening is a stressful increase in body temperatures close to upper thermal tolerance limits, organisms might exhibit unforeseen physiological consequences. In this study, Gilbert and Miles show that for tree lizards in the Sonoran Desert, when heat hardening is expressed, lizards prefer cooler temperatures when they thermoregulate, and exhibit reductions in locomotor performance (maximal speed) throughout the response. They also find that because of these physiological costs, tree lizards are not fully able to exploit the adaptive nature of a higher heat tolerance, thus weakening their reliance on phenotypic plasticity as a buffer from temperature extremes. This study demonstrates that even though plasticity can be adaptive and beneficial, when organisms are exposed to extreme environmental stimuli, these stimuli might induce maladaptive responses in other traits leading to antagonistic interactions between the phenotypic shifts triggered by new environments. Abstract A&nbsp;fitness benefit of phenotypic plasticity is the ability of an organism to survive short-term, deleterious environmental fluctuations. Yet, the influence of selection on plasticity in modulating shifts in phenotypic traits remains unclear. Short-term phenotypic plasticity in thermal tolerance traits is attained by exposure to sublethal hot or cold temperatures (i.e. the hardening response). Heat hardening is expected to buffer organisms from the unpredictability of extreme thermal fluctuations in the environment so as to minimize interruptions in activity and enhance survival. However, exposure to sublethal temperatures might entail other phenotypic costs that constrain or inhibit the prolonged use of hardening responses across longer timescales. Here, we estimated the onset of the heat hardening response, physiological and behavioral shifts during heat hardening, and geographic variation in heat hardening using tree lizards (Urosaurus ornatus). Peak heat hardening occurred 6h after exposure to sublethal temperatures. We found that both preferred body temperatures and locomotor performance diminished following exposure to sublethal temperatures, and performance levels did not approach pre-exposure levels until after the peak hardening response. We also found support for intraspecific variation in the hardening response along an environmental gradient, where populations in more thermally variable environments exhibited stronger plastic responses and populations with higher baseline heat tolerances exhibited weaker plastic responses. Sublethal temperature exposure might induce adaptive plasticity in thermal tolerance, however we find that these responses entail other phenotypic shifts that might curtail chronic reliance on plasticity in thermal traits as a mechanism of responding to changes in thermal environments induced by climate warming. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704208">Read the Article</a></i></p> <p><b>Exposure to stressful temperatures induces adaptive plasticity but constrains ecological and organismal performance </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>nthropogenic climate change is exposing populations to new environmental pressures that can lead to a variety of physiological, genetic, or behavioral responses. When novel environmental conditions cause phenotypic shifts in the absence of genetic change (i.e. phenotypic plasticity), oftentimes researchers only consider quantifying how traits-of-interest shift, without considering that particularly stressful stimuli might lead to other unforeseen phenotypic outcomes. Because many species are now predisposed to higher incidences of heat waves within their environment, exposure to sublethal temperatures is considered to be a trigger of adaptive phenotypic plasticity, otherwise called ‘heat hardening’. Heat hardening occurs when an individual is exposed to sublethal temperatures, and as a result they can temporarily tolerate higher temperatures than they could prior to heat shock. However, because the trigger of heat hardening is a stressful increase in body temperatures close to upper thermal tolerance limits, organisms might exhibit unforeseen physiological consequences. In this study, Gilbert and Miles show that for tree lizards in the Sonoran Desert, when heat hardening is expressed, lizards prefer cooler temperatures when they thermoregulate, and exhibit reductions in locomotor performance (maximal speed) throughout the response. They also find that because of these physiological costs, tree lizards are not fully able to exploit the adaptive nature of a higher heat tolerance, thus weakening their reliance on phenotypic plasticity as a buffer from temperature extremes. This study demonstrates that even though plasticity can be adaptive and beneficial, when organisms are exposed to extreme environmental stimuli, these stimuli might induce maladaptive responses in other traits leading to antagonistic interactions between the phenotypic shifts triggered by new environments. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">A</span>&nbsp;fitness benefit of phenotypic plasticity is the ability of an organism to survive short-term, deleterious environmental fluctuations. Yet, the influence of selection on plasticity in modulating shifts in phenotypic traits remains unclear. Short-term phenotypic plasticity in thermal tolerance traits is attained by exposure to sublethal hot or cold temperatures (i.e. the hardening response). Heat hardening is expected to buffer organisms from the unpredictability of extreme thermal fluctuations in the environment so as to minimize interruptions in activity and enhance survival. However, exposure to sublethal temperatures might entail other phenotypic costs that constrain or inhibit the prolonged use of hardening responses across longer timescales. Here, we estimated the onset of the heat hardening response, physiological and behavioral shifts during heat hardening, and geographic variation in heat hardening using tree lizards (<i>Urosaurus ornatus</i>). Peak heat hardening occurred 6h after exposure to sublethal temperatures. We found that both preferred body temperatures and locomotor performance diminished following exposure to sublethal temperatures, and performance levels did not approach pre-exposure levels until after the peak hardening response. We also found support for intraspecific variation in the hardening response along an environmental gradient, where populations in more thermally variable environments exhibited stronger plastic responses and populations with higher baseline heat tolerances exhibited weaker plastic responses. Sublethal temperature exposure might induce adaptive plasticity in thermal tolerance, however we find that these responses entail other phenotypic shifts that might curtail chronic reliance on plasticity in thermal traits as a mechanism of responding to changes in thermal environments induced by climate warming. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 May 2019 05:00:00 GMT “Plastic senescence in the honeybee and the disposable soma theory” https://amnat.org/an/newpapers/Sep-da-Silva.html Read the Article The lifespan differences between honeybee castes help distinguish between different evolutionary theories of ageing Honeybee workers have much shorter lifespans than the queen not simply because they live more dangerous lives, but because they age faster. This tells us that ageing evolves as a consequence of an organism’s life history being adapted to its environment. Designation of an individual as a worker or a queen is not based on different sets of genes but on nutrition – a larva that is fed a protein-rich diet develops into a queen, otherwise she develops into a worker. As a worker, a bee ages so rapidly that she typically lives for only one month. In contrast, a queen may live for two years. But why should workers age more rapidly? Evolutionary theories of ageing tell us that natural selection becomes weaker with age simply because any individual has a lower probability of surviving to an old age than to a young age for reasons unrelated to ageing, such as accidental death. As a result, natural selection is less efficient at removing mutations that reduce survival or fertility at older ages, which may explain ageing. It follows from this that species that live more dangerous lives should age more rapidly. This logic also applies to honeybee workers, who perform high-risk duties outside the hive. However, since the designation of a worker is not based on a genetic difference from the queen, its higher rate of ageing must be due to different genes being turned on. The genes that are turned on in a worker are thought to invest the energy in its food in maintaining the bee’s body just enough to keep it functioning for its expected short lifespan, and as a result the bee ages rapidly. Any greater investment in maintenance would be wasteful. These results support an evolutionary theory of ageing, known as the disposable soma theory, that explains ageing as the consequence of organisms evolving an optimal strategy of investment in maintaining their bodies. Abstract The demonstration of lifespan plasticity in natural populations would provide a powerful test of evolutionary theories of senescence. Plastic senescence is not easily explained by mutation accumulation or antagonistic pleiotropy but is a corollary of the disposable soma theory. The lifespan differences among castes of the eusocial Hymenoptera are potentially some of the most striking and extreme examples of lifespan plasticity. Although these differences are often assumed to be plastic, this has never been demonstrated conclusively because differences in lifespan may be caused by the proximate effects of different levels of environmental hazard experienced by castes. Here, age-dependent and age-independent components of instantaneous mortality rates of the honeybee (Apis mellifera) were estimated from published lifetables for natural and semi-natural populations to determine whether differences in lifespan between queens and workers and between different types workers are indeed plastic. These differences in lifespan were found to be due to differences in the rate of actuarial senescence, which correlate positively with the rate of extrinsic mortality, in accordance with the central prediction of evolutionary theories of senescence. Although all three evolutionary theories of senescence could, in principle, explain such plastic senescence, given differential gene expression between castes or life stages, only the disposable soma theory adequately explains the adaptive regulation of somatic maintenance in response to different environmental conditions that appears to underlie lifespan plasticity. More forthcoming papers &raquo; <p><i><a href="https://dx.doi.org/10.1086/704220">Read the Article</a></i></p> <p><b>The lifespan differences between honeybee castes help distinguish between different evolutionary theories of ageing </b></p><p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">H</span>oneybee workers have much shorter lifespans than the queen not simply because they live more dangerous lives, but because they age faster. This tells us that ageing evolves as a consequence of an organism’s life history being adapted to its environment. </p><p>Designation of an individual as a worker or a queen is not based on different sets of genes but on nutrition – a larva that is fed a protein-rich diet develops into a queen, otherwise she develops into a worker. As a worker, a bee ages so rapidly that she typically lives for only one month. In contrast, a queen may live for two years. But why should workers age more rapidly? Evolutionary theories of ageing tell us that natural selection becomes weaker with age simply because any individual has a lower probability of surviving to an old age than to a young age for reasons unrelated to ageing, such as accidental death. As a result, natural selection is less efficient at removing mutations that reduce survival or fertility at older ages, which may explain ageing. It follows from this that species that live more dangerous lives should age more rapidly. This logic also applies to honeybee workers, who perform high-risk duties outside the hive. However, since the designation of a worker is not based on a genetic difference from the queen, its higher rate of ageing must be due to different genes being turned on. The genes that are turned on in a worker are thought to invest the energy in its food in maintaining the bee’s body just enough to keep it functioning for its expected short lifespan, and as a result the bee ages rapidly. Any greater investment in maintenance would be wasteful. These results support an evolutionary theory of ageing, known as the disposable soma theory, that explains ageing as the consequence of organisms evolving an optimal strategy of investment in maintaining their bodies. </p> <hr /> <h3>Abstract</h3> <p><span style="float: left; font-size: 40px; line-height: 25px; padding-top: 4px; padding-right: 2px; padding-left: 2px; font-family: Garamond; font-weight: bold;">T</span>he demonstration of lifespan plasticity in natural populations would provide a powerful test of evolutionary theories of senescence. Plastic senescence is not easily explained by mutation accumulation or antagonistic pleiotropy but is a corollary of the disposable soma theory. The lifespan differences among castes of the eusocial Hymenoptera are potentially some of the most striking and extreme examples of lifespan plasticity. Although these differences are often assumed to be plastic, this has never been demonstrated conclusively because differences in lifespan may be caused by the proximate effects of different levels of environmental hazard experienced by castes. Here, age-dependent and age-independent components of instantaneous mortality rates of the honeybee (<i>Apis mellifera</i>) were estimated from published lifetables for natural and semi-natural populations to determine whether differences in lifespan between queens and workers and between different types workers are indeed plastic. These differences in lifespan were found to be due to differences in the rate of actuarial senescence, which correlate positively with the rate of extrinsic mortality, in accordance with the central prediction of evolutionary theories of senescence. Although all three evolutionary theories of senescence could, in principle, explain such plastic senescence, given differential gene expression between castes or life stages, only the disposable soma theory adequately explains the adaptive regulation of somatic maintenance in response to different environmental conditions that appears to underlie lifespan plasticity. </p> <div style="float: right;"><a href="http://www.amnat.org/an/newpapers.html"> <span style="font-size: large; font-family: Georgia;"><i>More forthcoming papers</i> &raquo;</span></a></div> Wed, 15 May 2019 05:00:00 GMT