Research article

Relatedness facilitates cooperation in the subsocial spider, Stegodyphus tentoriicola

Jasmin Ruch¹ , Lisa Heinrich¹ , Trine Bilde² and Jutta M Schneider¹

¹Zoological Institute and Museum, Biozentrum Grindel, University of Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany

²Department of Biological Sciences, Aarhus University, Ny Munkegade Building 540, 8000 Aarhus C, Denmark

author email corresponding author email

BMC Evolutionary Biology 2009, 9:257doi:10.1186/1471-2148-9-257

Published:	27 October 2009

Abstract

Background

Cooperative hunting and foraging in spiders is rare and prone to cheating such that the actions of selfish individuals negatively affect the whole group. The resulting social dilemma may be mitigated by kin selection since related individuals lose indirect fitness benefits by acting selfishly. Indeed, cooperation with genetic kin reduces the disadvantages of within-group competition in the subsocial spider Stegodyphus lineatus, supporting the hypothesis that high relatedness is an important pre-adaptation in the transition to sociality in spiders. In this study we examined the consequences of group size and relatedness on cooperative feeding in the subsocial spider S. tentoriicola, a species suggested to be at the transition to permanent sociality.

Results

We formed groups of 3 and 6 spiders that were either siblings or non-siblings. We found that increasing group size negatively affected feeding efficiency but that these negative effects were reduced in sib-groups. Sib groups were more likely to feed cooperatively and all group members grew more homogenously than groups of unrelated spiders. The measured differences did not translate into differential growth or mortality during the experimental period of 8 weeks.

Conclusion

The combination of our results with those from previous studies indicates that the conflict between individual interests and group interests may be reduced by nepotism and that the latter promote the maintenance of the social community.