Prey to predator body size ratio in the evolution of cooperative hunting—a social spider test case

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  • Lena Grinsted, Royal Holloway University of London
  • ,
  • Mads F. Schou, Lunds Universitet
  • ,
  • Virginia Settepani
  • Christina Holm
  • ,
  • Tharina L. Bird, Department of Biological Sciences and Biotechnology, Botswana International University of Science and Technology
  • ,
  • Trine Bilde

One of the benefits of cooperative hunting may be that predators can subdue larger prey. In spiders, cooperative, social species can capture prey many times larger than an individual predator. However, we propose that cooperative prey capture does not have to be associated with larger caught prey per se, but with an increase in the ratio of prey to predator body size. This can be achieved either by catching larger prey while keeping predator body size constant, or by evolving a smaller predator body size while maintaining capture of large prey. We show that within a genus of relatively large spiders, Stegodyphus, subsocial spiders representing the ancestral state of social species are capable of catching the largest prey available in the environment. Hence, within this genus, the evolution of cooperation would not provide access to otherwise inaccessible, large prey. Instead, we show that social Stegodyphus spiders are smaller than their subsocial counterparts, while catching similar sized prey, leading to the predicted increase in prey-predator size ratio with sociality. We further show that in a genus of small spiders, Anelosimus, the level of sociality is associated with an increased size of prey caught while predator size is unaffected by sociality, leading to a similar, predicted increase in prey-predator size ratio. In summary, we find support for our proposed ‘prey to predator size ratio hypothesis’ and discuss how relaxed selection on large body size in the evolution of social, cooperative living may provide adaptive benefits for ancestrally relatively large predators.

OriginalsprogEngelsk
TidsskriftDevelopment Genes and Evolution
Vol/bind230
Nummer2
Sider (fra-til)173-184
Antal sider12
ISSN0949-944X
DOI
StatusUdgivet - 2020

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