also, from the conclusion:
Genetic structure—inferred by both genetic relatedness coefficients and pedigree relationships—coincided with ‘social communities’, an intermediate tier of the social network that closely corresponds to spatial relationships among individuals. This finding supports the idea that kin structure can arise as an emergent property of limited dispersal alone and need not imply any targeted, beneficial interactions among kin. These results are consistent with many studies showing that philopatry is a powerful mechanism by which genetic structure can accumulate as a by-product...Kin in space: social viscosity in a spatially and genetically substructured network
Jochen B.W. Wolf, Fritz Trillmich
Proceedings of the Royal Society London B Early online
Abstract: Population substructuring is a fundamental aspect of animal societies. A growing number of theoretical studies recognize that who-meets-whom is not random, but rather determined by spatial relationships or illustrated by social networks. Structural properties of large highly dynamic social systems are notoriously difficult to unravel. Network approaches provide powerful ways to analyse the intricate relationships between social behaviour, dispersal strategies and genetic structure. Applying network analytical tools to a colony of the highly gregarious Galápagos sea lion (Zalophus wollebaeki), we find several genetic clusters that correspond to spatially determined ‘network communities’. Overall relatedness was low, and genetic structure in the network can be interpreted as an emergent property of philopatry and seems not to be primarily driven by targeted interactions among highly related individuals in family groups. Nevertheless, social relationships between directly adjacent individuals in the network were stronger among genetically more similar individuals. Taken together, these results suggest that even small differences in the degree of relatedness can influence behavioural decisions. This raises the fascinating prospect that kin selection may also apply to low levels of relatedness within densely packed animal groups where less obvious co-operative interactions such as increased tolerance and stress reduction are important.