Effects of within-colony competition on body size asymmetries and reproductive skew in a social spider

Grinsted, L and Bilde, T (2013) Effects of within-colony competition on body size asymmetries and reproductive skew in a social spider. Journal of Evolutionary Biology, 26 (3). pp. 553-561. ISSN 1010-061X

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Reproductive partitioning is a key component of social organization in groups of cooperative organisms. In colonies of permanently social spiders of the genus Stegodyphus less than half of the females reproduce, while all females, including nonreproducers, perform suicidal allo-maternal care. Some theoretical models suggest that reproductive skew is a result of contest competition within colonies, leading to size hierarchies where only the largest females become reproducers. We investigated the effect of competition on within-group body size variation over six months in S. dumicola, by manipulating food level and colony size. We found no evidence that competition leads to increased size asymmetry within colonies, suggesting that contest competition may not be the proximate explanation for reproductive skew. Within-colony body size variation was high already in the juvenile stage, and did not increase over the course of the experiment, suggesting that body size variation is shaped at an early stage. This might facilitate task specialization within colonies and ensure colony-level reproductive output by early allocation of reproductive roles. We suggest that reproductive skew in social spiders may be an adaptation to sociality selected through inclusive fitness benefits of allo-maternal care as well as colony-level benefits maximizing colony survival and production.

Item Type: Article
Schools and Departments: School of Life Sciences > Biology and Environmental Science
Subjects: Q Science > QH Natural history > QH0301 Biology > QH0359 Evolution
Q Science > QL Zoology > QL0750 Animal behaviour
Depositing User: Lena Grinsted
Date Deposited: 11 Aug 2014 14:44
Last Modified: 07 Mar 2017 10:18
URI: http://srodev.sussex.ac.uk/id/eprint/49545

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