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Jonathan N Pruitt - One of the best experts on this subject based on the ideXlab platform.
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physical and Social cues shape nest site preference and prey capture behavior in Social Spiders
Behavioral Ecology, 2020Co-Authors: Gabriella M Najm, Jonathan N Pruitt, Noa PinterwollmanAbstract:Animals often face conflicting demands when making movement decisions. To examine the decision process of Social animals, we evaluated nest-site preferences of the Social Spider Stegodyphus dumicola. Colonies engage in collective web building, constructing 3D nests and 2D capture webs on trees and fences. We examined how individuals and groups decide where to construct a nest based on habitat structure and conspecific presence. Individuals had a strong preference for 3D substrates and conspecific presence. Groups were then provided with conflicting options of 3D substrates versus 2D substrates with a conspecific. Groups preferred the 3D structures without presettled conspecifics over a 2D substrate with conspecifics. When a group fragmented and individuals settled on both substrates, the minority group eventually joined the majority. Before rejoining, the collective prey capture behavior of divided groups improved with the size of the majority fragment. The costs of slow responses to prey for split groups and weak conspecific attraction may explain why dispersal is rare in these Spiders.
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comparative genomics identifies putative signatures of Sociality in Spiders
Genome Biology and Evolution, 2020Co-Authors: Chao Tong, Gabriella M Najm, Noa Pinterwollman, Jonathan N Pruitt, Timothy A LinksvayerAbstract:Comparative genomics has begun to elucidate the genomic basis of Social life in insects, but insight into the genomic basis of Spider Sociality has lagged behind. To begin, to characterize genomic signatures associated with the evolution of Social life in Spiders, we performed one of the first Spider comparative genomics studies including five solitary species and two Social species, representing two independent origins of Sociality in the genus Stegodyphus. We found that the two Social Spider species had a large expansion of gene families associated with transport and metabolic processes and an elevated genome-wide rate of molecular evolution compared with the five solitary Spider species. Genes that were rapidly evolving in the two Social species relative to the five solitary species were enriched for transport, behavior, and immune functions, whereas genes that were rapidly evolving in the solitary species were enriched for energy metabolism processes. Most rapidly evolving genes in the Social species Stegodyphus dumicola were broadly expressed across four tissues and enriched for transport functions, but 12 rapidly evolving genes showed brain-specific expression and were enriched for Social behavioral processes. Altogether, our study identifies putative genomic signatures and potential candidate genes associated with Spider Sociality. These results indicate that future Spider comparative genomic studies, including broader sampling and additional independent origins of Sociality, can further clarify the genomic causes and consequences of Social life.
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comparative genomics identifies putative signatures of Sociality in Spiders
bioRxiv, 2019Co-Authors: Chao Tong, Gabriella M Najm, Noa Pinterwollman, Jonathan N Pruitt, Timothy A LinksvayerAbstract:Comparative genomics has begun to elucidate the genomic basis of Social life in insects but insight into the genomic basis of Spider Sociality has lagged behind. To begin to characterize genomic signatures associated with the evolution of Social life in Spiders, we performed one of the first Spider comparative genomics studies including five solitary species and two Social species, representing two independent origins of Sociality in the genus Stegodyphus. We found that the two Social Spider species had a large expansion of gene families associated with transport and metabolic processes and an elevated genome-wide rate of molecular evolution compared with the five solitary Spider species. Genes that were rapidly evolving in the two Social species relative to the five solitary species were enriched for transport, behavior, and immune functions, while genes that were rapidly evolving in the solitary species were enriched for energy metabolism processes. Most rapidly evolving genes in the Social species S. dumicola were broadly expressed across four tissues and enriched for transport functions, but 12 rapidly evolving genes showed brain-specific expression and were enriched for Social behavioral processes. Altogether, our study identifies putative genomic signatures and potential candidate genes associated with Spider Sociality. These results indicate that future Spider comparative genomic studies, including broader sampling and additional independent origins of Sociality, can further clarify the genomic causes and consequences of Social life.
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Experimental evidence of frequency-dependent selection on group behaviour
Nature ecology & evolution, 2019Co-Authors: Jonathan N Pruitt, Gabriella M Najm, Brendan L. Mcewen, Steven T. Cassidy, Noa Pinter-wollmanAbstract:Evolutionary ecologists often seek to identify the mechanisms maintaining intraspecific variation. In Social animals, whole groups can exhibit between-group differences in their collective traits. We examined whether negative frequency-dependent selection (that is, a rare-type advantage) could help to maintain between-group variation. We engineered neighbourhoods of Social Spider colonies bearing bold or shy foraging phenotypes and monitored their fecundity in situ. We found that bold colonies enjoyed a rare-type advantage that is lost as the frequency of bold colonies in a neighbourhood increases. The success of shy colonies was not frequency dependent. These dynamics seem to be driven by a foraging advantage of bold colonies that is lost in bold neighbourhoods because prey become scarce, and shy colonies perform better than bold colonies under low-resource conditions. Thus, to understand selection on collective traits, it is insufficient to examine groups in isolation. The phenotypic environment in which groups reside and compete must also be considered.
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participation in cooperative prey capture and the benefits gained from it are associated with individual personality
Current Zoology, 2016Co-Authors: James L L Lichtenstein, Noa Pinterwollman, Colin M. Wright, Lauren P Luscuskie, Graham A Montgomery, Jonathan N PruittAbstract:In animal societies, individuals’ behavioral idiosyncrasies often guide which tasks they perform. Such personality-specific task participation can increase individual task efficiency, thereby improving group performance. While several recent studies have documented group-level benefits of within-group behavioural (i.e., personality) diversity, how these benefits are realized at the individual level is unclear. Here we probe the individual-level benefits of personality-driven task participation in the Social Spider Stegodyphus dumicola . In S. dumicola the presence of at least one highly bold individual catalyzes foraging behaviour in shy colony members, and all group constituents heavily compete for prey. We assessed boldness by examining how quickly Spiders resumed normal movement after a simulated predator attack. We test here whether 1) participants in collective foraging gain more mass from prey items and 2) whether bold individuals are less resistant to starvation than shy Spiders, which would motivate the bold individuals to forage more. Next, we assembled colonies of shy Spiders with and without a bold individual, added one prey item, and then tracked the mass gain of each individual Spider after this single feeding event. We found that Spiders that participated in prey capture (whether bold or shy) gained more mass than non-participators, and colonies containing a single bold Spider gained more total mass than purely shy colonies. We also found that bold Spiders participated in more collective foraging events and were more susceptible to starvation than shy Spiders, suggesting that the aggressive foraging of bold individuals may represent a strategy to offset starvation risk. These findings add to the body of evidence that animal personality can shape Social organization, individual performance, and group success.
Noa Pinterwollman - One of the best experts on this subject based on the ideXlab platform.
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using multilayer network analysis to explore the temporal dynamics of collective behavior
Current Zoology, 2021Co-Authors: David N Fisher, Noa PinterwollmanAbstract:Social organisms often show collective behaviors such as group foraging or movement. Collective behaviors can emerge from interactions between group members and may depend on the behavior of key individuals. When Social interactions change over time, collective behaviors may change because these behaviors emerge from interactions among individuals. Despite the importance of, and growing interest in, the temporal dynamics of Social interactions, it is not clear how to quantify changes in interactions over time or measure their stability. Furthermore, the temporal scale at which we should observe changes in Social networks to detect biologically meaningful changes is not always apparent. Here we use multilayer network analysis to quantify temporal dynamics of Social networks of the Social Spider Stegodyphus dumicola and determine how these dynamics relate to individual and group behaviors. We found that Social interactions changed over time at a constant rate. Variation in both network structure and the identity of a keystone individual was not related to the mean or variance of the collective prey attack speed. Individuals that maintained a large and stable number of connections, despite changes in network structure, were the boldest individuals in the group. Therefore, Social interactions and boldness are linked across time, but group collective behavior is not influenced by the stability of the Social network. Our work demonstrates that dynamic Social networks can be modeled in a multilayer framework. This approach may reveal biologically important temporal changes to Social structure in other systems.
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physical and Social cues shape nest site preference and prey capture behavior in Social Spiders
Behavioral Ecology, 2020Co-Authors: Gabriella M Najm, Jonathan N Pruitt, Noa PinterwollmanAbstract:Animals often face conflicting demands when making movement decisions. To examine the decision process of Social animals, we evaluated nest-site preferences of the Social Spider Stegodyphus dumicola. Colonies engage in collective web building, constructing 3D nests and 2D capture webs on trees and fences. We examined how individuals and groups decide where to construct a nest based on habitat structure and conspecific presence. Individuals had a strong preference for 3D substrates and conspecific presence. Groups were then provided with conflicting options of 3D substrates versus 2D substrates with a conspecific. Groups preferred the 3D structures without presettled conspecifics over a 2D substrate with conspecifics. When a group fragmented and individuals settled on both substrates, the minority group eventually joined the majority. Before rejoining, the collective prey capture behavior of divided groups improved with the size of the majority fragment. The costs of slow responses to prey for split groups and weak conspecific attraction may explain why dispersal is rare in these Spiders.
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comparative genomics identifies putative signatures of Sociality in Spiders
Genome Biology and Evolution, 2020Co-Authors: Chao Tong, Gabriella M Najm, Noa Pinterwollman, Jonathan N Pruitt, Timothy A LinksvayerAbstract:Comparative genomics has begun to elucidate the genomic basis of Social life in insects, but insight into the genomic basis of Spider Sociality has lagged behind. To begin, to characterize genomic signatures associated with the evolution of Social life in Spiders, we performed one of the first Spider comparative genomics studies including five solitary species and two Social species, representing two independent origins of Sociality in the genus Stegodyphus. We found that the two Social Spider species had a large expansion of gene families associated with transport and metabolic processes and an elevated genome-wide rate of molecular evolution compared with the five solitary Spider species. Genes that were rapidly evolving in the two Social species relative to the five solitary species were enriched for transport, behavior, and immune functions, whereas genes that were rapidly evolving in the solitary species were enriched for energy metabolism processes. Most rapidly evolving genes in the Social species Stegodyphus dumicola were broadly expressed across four tissues and enriched for transport functions, but 12 rapidly evolving genes showed brain-specific expression and were enriched for Social behavioral processes. Altogether, our study identifies putative genomic signatures and potential candidate genes associated with Spider Sociality. These results indicate that future Spider comparative genomic studies, including broader sampling and additional independent origins of Sociality, can further clarify the genomic causes and consequences of Social life.
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comparative genomics identifies putative signatures of Sociality in Spiders
bioRxiv, 2019Co-Authors: Chao Tong, Gabriella M Najm, Noa Pinterwollman, Jonathan N Pruitt, Timothy A LinksvayerAbstract:Comparative genomics has begun to elucidate the genomic basis of Social life in insects but insight into the genomic basis of Spider Sociality has lagged behind. To begin to characterize genomic signatures associated with the evolution of Social life in Spiders, we performed one of the first Spider comparative genomics studies including five solitary species and two Social species, representing two independent origins of Sociality in the genus Stegodyphus. We found that the two Social Spider species had a large expansion of gene families associated with transport and metabolic processes and an elevated genome-wide rate of molecular evolution compared with the five solitary Spider species. Genes that were rapidly evolving in the two Social species relative to the five solitary species were enriched for transport, behavior, and immune functions, while genes that were rapidly evolving in the solitary species were enriched for energy metabolism processes. Most rapidly evolving genes in the Social species S. dumicola were broadly expressed across four tissues and enriched for transport functions, but 12 rapidly evolving genes showed brain-specific expression and were enriched for Social behavioral processes. Altogether, our study identifies putative genomic signatures and potential candidate genes associated with Spider Sociality. These results indicate that future Spider comparative genomic studies, including broader sampling and additional independent origins of Sociality, can further clarify the genomic causes and consequences of Social life.
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participation in cooperative prey capture and the benefits gained from it are associated with individual personality
Current Zoology, 2016Co-Authors: James L L Lichtenstein, Noa Pinterwollman, Colin M. Wright, Lauren P Luscuskie, Graham A Montgomery, Jonathan N PruittAbstract:In animal societies, individuals’ behavioral idiosyncrasies often guide which tasks they perform. Such personality-specific task participation can increase individual task efficiency, thereby improving group performance. While several recent studies have documented group-level benefits of within-group behavioural (i.e., personality) diversity, how these benefits are realized at the individual level is unclear. Here we probe the individual-level benefits of personality-driven task participation in the Social Spider Stegodyphus dumicola . In S. dumicola the presence of at least one highly bold individual catalyzes foraging behaviour in shy colony members, and all group constituents heavily compete for prey. We assessed boldness by examining how quickly Spiders resumed normal movement after a simulated predator attack. We test here whether 1) participants in collective foraging gain more mass from prey items and 2) whether bold individuals are less resistant to starvation than shy Spiders, which would motivate the bold individuals to forage more. Next, we assembled colonies of shy Spiders with and without a bold individual, added one prey item, and then tracked the mass gain of each individual Spider after this single feeding event. We found that Spiders that participated in prey capture (whether bold or shy) gained more mass than non-participators, and colonies containing a single bold Spider gained more total mass than purely shy colonies. We also found that bold Spiders participated in more collective foraging events and were more susceptible to starvation than shy Spiders, suggesting that the aggressive foraging of bold individuals may represent a strategy to offset starvation risk. These findings add to the body of evidence that animal personality can shape Social organization, individual performance, and group success.
Timothy A Linksvayer - One of the best experts on this subject based on the ideXlab platform.
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comparative genomics identifies putative signatures of Sociality in Spiders
Genome Biology and Evolution, 2020Co-Authors: Chao Tong, Gabriella M Najm, Noa Pinterwollman, Jonathan N Pruitt, Timothy A LinksvayerAbstract:Comparative genomics has begun to elucidate the genomic basis of Social life in insects, but insight into the genomic basis of Spider Sociality has lagged behind. To begin, to characterize genomic signatures associated with the evolution of Social life in Spiders, we performed one of the first Spider comparative genomics studies including five solitary species and two Social species, representing two independent origins of Sociality in the genus Stegodyphus. We found that the two Social Spider species had a large expansion of gene families associated with transport and metabolic processes and an elevated genome-wide rate of molecular evolution compared with the five solitary Spider species. Genes that were rapidly evolving in the two Social species relative to the five solitary species were enriched for transport, behavior, and immune functions, whereas genes that were rapidly evolving in the solitary species were enriched for energy metabolism processes. Most rapidly evolving genes in the Social species Stegodyphus dumicola were broadly expressed across four tissues and enriched for transport functions, but 12 rapidly evolving genes showed brain-specific expression and were enriched for Social behavioral processes. Altogether, our study identifies putative genomic signatures and potential candidate genes associated with Spider Sociality. These results indicate that future Spider comparative genomic studies, including broader sampling and additional independent origins of Sociality, can further clarify the genomic causes and consequences of Social life.
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comparative genomics identifies putative signatures of Sociality in Spiders
bioRxiv, 2019Co-Authors: Chao Tong, Gabriella M Najm, Noa Pinterwollman, Jonathan N Pruitt, Timothy A LinksvayerAbstract:Comparative genomics has begun to elucidate the genomic basis of Social life in insects but insight into the genomic basis of Spider Sociality has lagged behind. To begin to characterize genomic signatures associated with the evolution of Social life in Spiders, we performed one of the first Spider comparative genomics studies including five solitary species and two Social species, representing two independent origins of Sociality in the genus Stegodyphus. We found that the two Social Spider species had a large expansion of gene families associated with transport and metabolic processes and an elevated genome-wide rate of molecular evolution compared with the five solitary Spider species. Genes that were rapidly evolving in the two Social species relative to the five solitary species were enriched for transport, behavior, and immune functions, while genes that were rapidly evolving in the solitary species were enriched for energy metabolism processes. Most rapidly evolving genes in the Social species S. dumicola were broadly expressed across four tissues and enriched for transport functions, but 12 rapidly evolving genes showed brain-specific expression and were enriched for Social behavioral processes. Altogether, our study identifies putative genomic signatures and potential candidate genes associated with Spider Sociality. These results indicate that future Spider comparative genomic studies, including broader sampling and additional independent origins of Sociality, can further clarify the genomic causes and consequences of Social life.
Gabriella M Najm - One of the best experts on this subject based on the ideXlab platform.
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physical and Social cues shape nest site preference and prey capture behavior in Social Spiders
Behavioral Ecology, 2020Co-Authors: Gabriella M Najm, Jonathan N Pruitt, Noa PinterwollmanAbstract:Animals often face conflicting demands when making movement decisions. To examine the decision process of Social animals, we evaluated nest-site preferences of the Social Spider Stegodyphus dumicola. Colonies engage in collective web building, constructing 3D nests and 2D capture webs on trees and fences. We examined how individuals and groups decide where to construct a nest based on habitat structure and conspecific presence. Individuals had a strong preference for 3D substrates and conspecific presence. Groups were then provided with conflicting options of 3D substrates versus 2D substrates with a conspecific. Groups preferred the 3D structures without presettled conspecifics over a 2D substrate with conspecifics. When a group fragmented and individuals settled on both substrates, the minority group eventually joined the majority. Before rejoining, the collective prey capture behavior of divided groups improved with the size of the majority fragment. The costs of slow responses to prey for split groups and weak conspecific attraction may explain why dispersal is rare in these Spiders.
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comparative genomics identifies putative signatures of Sociality in Spiders
Genome Biology and Evolution, 2020Co-Authors: Chao Tong, Gabriella M Najm, Noa Pinterwollman, Jonathan N Pruitt, Timothy A LinksvayerAbstract:Comparative genomics has begun to elucidate the genomic basis of Social life in insects, but insight into the genomic basis of Spider Sociality has lagged behind. To begin, to characterize genomic signatures associated with the evolution of Social life in Spiders, we performed one of the first Spider comparative genomics studies including five solitary species and two Social species, representing two independent origins of Sociality in the genus Stegodyphus. We found that the two Social Spider species had a large expansion of gene families associated with transport and metabolic processes and an elevated genome-wide rate of molecular evolution compared with the five solitary Spider species. Genes that were rapidly evolving in the two Social species relative to the five solitary species were enriched for transport, behavior, and immune functions, whereas genes that were rapidly evolving in the solitary species were enriched for energy metabolism processes. Most rapidly evolving genes in the Social species Stegodyphus dumicola were broadly expressed across four tissues and enriched for transport functions, but 12 rapidly evolving genes showed brain-specific expression and were enriched for Social behavioral processes. Altogether, our study identifies putative genomic signatures and potential candidate genes associated with Spider Sociality. These results indicate that future Spider comparative genomic studies, including broader sampling and additional independent origins of Sociality, can further clarify the genomic causes and consequences of Social life.
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comparative genomics identifies putative signatures of Sociality in Spiders
bioRxiv, 2019Co-Authors: Chao Tong, Gabriella M Najm, Noa Pinterwollman, Jonathan N Pruitt, Timothy A LinksvayerAbstract:Comparative genomics has begun to elucidate the genomic basis of Social life in insects but insight into the genomic basis of Spider Sociality has lagged behind. To begin to characterize genomic signatures associated with the evolution of Social life in Spiders, we performed one of the first Spider comparative genomics studies including five solitary species and two Social species, representing two independent origins of Sociality in the genus Stegodyphus. We found that the two Social Spider species had a large expansion of gene families associated with transport and metabolic processes and an elevated genome-wide rate of molecular evolution compared with the five solitary Spider species. Genes that were rapidly evolving in the two Social species relative to the five solitary species were enriched for transport, behavior, and immune functions, while genes that were rapidly evolving in the solitary species were enriched for energy metabolism processes. Most rapidly evolving genes in the Social species S. dumicola were broadly expressed across four tissues and enriched for transport functions, but 12 rapidly evolving genes showed brain-specific expression and were enriched for Social behavioral processes. Altogether, our study identifies putative genomic signatures and potential candidate genes associated with Spider Sociality. These results indicate that future Spider comparative genomic studies, including broader sampling and additional independent origins of Sociality, can further clarify the genomic causes and consequences of Social life.
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Experimental evidence of frequency-dependent selection on group behaviour
Nature ecology & evolution, 2019Co-Authors: Jonathan N Pruitt, Gabriella M Najm, Brendan L. Mcewen, Steven T. Cassidy, Noa Pinter-wollmanAbstract:Evolutionary ecologists often seek to identify the mechanisms maintaining intraspecific variation. In Social animals, whole groups can exhibit between-group differences in their collective traits. We examined whether negative frequency-dependent selection (that is, a rare-type advantage) could help to maintain between-group variation. We engineered neighbourhoods of Social Spider colonies bearing bold or shy foraging phenotypes and monitored their fecundity in situ. We found that bold colonies enjoyed a rare-type advantage that is lost as the frequency of bold colonies in a neighbourhood increases. The success of shy colonies was not frequency dependent. These dynamics seem to be driven by a foraging advantage of bold colonies that is lost in bold neighbourhoods because prey become scarce, and shy colonies perform better than bold colonies under low-resource conditions. Thus, to understand selection on collective traits, it is insufficient to examine groups in isolation. The phenotypic environment in which groups reside and compete must also be considered.
Leticia Aviles - One of the best experts on this subject based on the ideXlab platform.
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trait overdispersion and the role of Sociality in the assembly of Social Spider communities across the americas
Proceedings of the National Academy of Sciences of the United States of America, 2018Co-Authors: Philippe Fernandezfournier, Jennifer Guevara, Catherine R Hoffman, Leticia AvilesAbstract:Among the factors that may lead to differences in resource use among closely related species, body size and morphology have been traditionally considered to play a role in community assembly. Here we argue that for animals that live and forage in groups, level of Sociality, reflecting differences in group size and cooperative tendencies, can be an additional and powerful dimension separating species in niche space. We compare 50+ communities of the Social Spider genus Anelosimus across the Americas against a null model that accounts for known effects of biotic and abiotic factors on the distribution of Social systems in the genus. We show that these communities are more overdispersed than expected by chance in either or both body size and level of Sociality, traits we have previously shown to be associated with differences in resource utilization (prey size, microhabitat, and phenology). We further show that the contribution of Sociality to differences in the size of the prey captured is two to three times greater than that of body size, suggesting that changes in group size and cooperative tendencies may be more effective than changes in body size at separating species in niche space.
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Prey size and scramble vs. contest competition in a Social Spider: implications for population dynamics.
The Journal of animal ecology, 2016Co-Authors: Ruth V. Sharpe, Leticia AvilesAbstract:There are many benefits of group living, but also substantial costs, one of which is competition for resources. How scarce food resources are distributed among different members of a population or Social group - whether via scramble or contest competition - can influence not only the variance in individual fitness, but also the stability and therefore survival of the group or population. Attributes of the food resources themselves, such as their size, may influence the type of intraspecific competition that occurs and therefore the intrinsic stability of a group or population. By experimentally manipulating the size of prey fed to artificial colonies of the Social Spider Anelosimus eximius, we investigated whether prey size could alter the degree of scramble vs. contest competition that takes place and, thus, potentially influence colony population dynamics. We found that large prey were shared more evenly than small prey and that individuals in poor condition were more likely to feed when prey were large than when prey were small. Additionally, we show that individuals participating in prey capture are also more likely to feed on the captured prey. We developed a simple mathematical model to explore the prey sizes that would be energetically worth defending, i.e. prey that are 'economically defendable'. The model shows that neither very small prey, nor prey above a certain size is worth monopolizing, with only intermediate size prey being 'economically defendable'. We therefore suggest the small and large prey in our experiment corresponds to our model's intermediate and large prey categories, respectively. As the size of prey captured by Social Spider colonies increases with colony size, our findings suggest that scramble competition may predominate in large colonies. Scramble competition, combined with the fact that prey biomass per capita declines as colonies grow beyond a certain size, would then explain why extremely large colonies of this Social Spider may suddenly go extinct. Our project thus illustrates the potential triple link between characteristics of the resources, individual behaviour and population dynamics, a link rarely considered in an empirical setting.
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reconstructing local population dynamics in noisy metapopulations the role of random catastrophes and allee effects
PLOS ONE, 2014Co-Authors: Edmund Hart, Leticia AvilesAbstract:Reconstructing the dynamics of populations is complicated by the different types of stochasticity experienced by populations, in particular if some forms of stochasticity introduce bias in parameter estimation in addition to error. Identification of systematic biases is critical when determining whether the intrinsic dynamics of populations are stable or unstable and whether or not populations exhibit an Allee effect, i.e., a minimum size below which deterministic extinction should follow. Using a simulation model that allows for Allee effects and a range of intrinsic dynamics, we investigated how three types of stochasticity--demographic, environmental, and random catastrophes--affect our ability to reconstruct the intrinsic dynamics of populations. Demographic stochasticity aside, which is only problematic in small populations, we find that environmental stochasticity--positive and negative environmental fluctuations--caused increased error in parameter estimation, but bias was rarely problematic, except at the highest levels of noise. Random catastrophes, events causing large-scale mortality and likely to be more common than usually recognized, caused immediate bias in parameter estimates, in particular when Allee effects were large. In the latter case, population stability was predicted when endogenous dynamics were actually unstable and the minimum viable population size was overestimated in populations with small or non-existent Allee effects. Catastrophes also generally increased extinction risk, in particular when endogenous Allee effects were large. We propose a method for identifying data points likely resulting from catastrophic events when such events have not been recorded. Using Social Spider colonies (Anelosimus spp.) as models for populations, we show that after known or suspected catastrophes are accounted for, reconstructed growth parameters are consistent with intrinsic dynamical instability and substantial Allee effects. Our results are applicable to metapopulation or time series data and are relevant for predicting extinction in conservation applications or the management of invasive species.
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sister clade comparisons reveal reduced maternal care behavior in Social cobweb Spiders
Behavioral Ecology, 2012Co-Authors: Kieran Samuk, Emily E Ledue, Leticia AvilesAbstract:Animals living in cooperative groups experience fundamentally different environments than their nonSocial relatives, potentially changing the strength of natural selection on some aspects of their behavior. Using a comparative approach, we examined a potential example of this phenomenon: an association between reduced levels of maternal care behavior and Sociality in cobweb Spiders. We compared 6 different measures of maternal care behavior between species from 2 independently derived Social clades and subSocial species from sister clades. In natural nests, we measured the mean distance between egg sacs and the nearest female and the proportion of egg sacs being attended. In the lab, we measured a female’s willingness to accept an egg sac, abandon her egg sac when disturbed, repair a damaged egg sac, and the speed at which a female reclaimed her egg sac when separated from it. Social species from both Social clades scored significantly lower than subSocial species from sister clades on 6 and 4 of 6 of these assays of maternal care, respectively. We discuss alternative explanations of this pattern, including the potential role of relaxed natural selection in a Social environment in permitting the evolution of a novel ‘‘low-parenting’’ phenotype. Key words: Anelosimus, cooperative breeding, evolution, maternal care, relaxed selection, Social Spider, Sociality. [Behav Ecol]
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cooperative capture of large prey solves scaling challenge faced by Spider societies
Proceedings of the National Academy of Sciences of the United States of America, 2008Co-Authors: Eric C Yip, Kimberly S Powers, Leticia AvilesAbstract:A decrease in the surface area per unit volume is a well known constraint setting limits to the size of organisms at both the cellular and whole-organismal levels. Similar constraints may apply to Social groups as they grow in size. The communal three-dimensional webs that Social Spiders build function ecologically as single units that intercept prey through their surface and should thus be subject to this constraint. Accordingly, we show that web prey capture area per Spider, and thus number of insects captured per capita, decreases with colony size in a neotropical Social Spider. Prey biomass intake per capita, however, peaks at intermediate colony sizes because the Spiders forage cooperatively and larger colonies capture increasingly large insects. A peaked prey biomass intake function would explain not only why these Spiders live in groups and cooperate but also why they disperse only at large colony sizes, thus addressing both Sociality and colony size range in this Social Spider. These findings may also explain the conspicuous absence of Social Spiders from higher latitudes and higher elevations, areas that we have previously shown to harbor considerably fewer insects of the largest size classes than the lowland tropical rainforests where Social Spiders thrive. Our findings thus illustrate the relevance of scaling laws to the size and functioning of levels of organization above the individual.