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

TY - JOUR

T1 - Prey to predator body size ratio in the evolution of cooperative hunting—a social spider test case

AU - Grinsted, Lena

AU - Schou, Mads F.

AU - Settepani, Virginia

AU - Holm, Christina

AU - Bird, Tharina L.

AU - Bilde, Trine

PY - 2020/3

Y1 - 2020/3

N2 - 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.

AB - 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.

KW - Dietary niche

KW - Group living

KW - Phenotypic plasticity

KW - Predator-prey interactions

KW - Social evolution

UR - http://www.scopus.com/inward/record.url?scp=85076224997&partnerID=8YFLogxK

U2 - 10.1007/s00427-019-00640-w

DO - 10.1007/s00427-019-00640-w

M3 - Journal article

C2 - 31768622

AN - SCOPUS:85076224997

SN - 0949-944X

VL - 230

SP - 173

EP - 184

JO - Development Genes and Evolution

JF - Development Genes and Evolution

IS - 2

ER -