Evidence for kin-structured group founding and limited juvenile dispersal in the sub-social spider Stegodyphus lineatus (Araneae, Eresidae)

In sub-social spiders, restricted dispersal of young (i.e., natal philopatry) and the potential for inbreeding could contribute to within-population subdivision, thus resulting in a population structure similar to that found in social congeners. In this context, we analyzed the origin and mode of individual distribution patterns and their contribution to within-population structure in juveniles of the sub-social spider Stegodyphus lineatus. We investigated the distribution of juveniles for four months after leaving the maternal nest using allozyme genetic markers. We found that isolated groups of juveniles consisted predominantly of siblings, whereas larger aggregations of individuals showed mixing of different juvenile sibling groups. However, even within such aggregations, sibling groups could be identified. Within the population at large, a heterozygote deficit and an uneven distribution of alleles were found. This was caused by limited movement of juveniles and males away from the natal site. Thus, the within-population (intrademic) structure could be partitioned into two components, resulting from kin-groups and population subdivision into demes. We compare this type of population structure with that found in non-social and social species, and discuss whether it provides conditions that could favor the evolution of sociality.