Tree-dwelling populations of the skink egernia striolata aggregate in groups of close kin

It has been proposed that limits on habitat availability and the risk of dispersal may have been a driver for the evolution of social behavior in the Egernia group of lizards. To test this hypothesis we sampled 46 individual Egernia striolata from trees in the Pilliga National Park, Australia, where retreat sites appeared abundant and often unoccupied. We collected genetic data at seven microsatellite loci from each individual and show that individuals within the same aggregation were highly related to each other, and that this was significantly different from random (mean 0.208 ± 0.400 SD, P = 0.002). From the geographic distribution of relatedness and parentage analysis we infer that adults can show high levels of site fidelity, and their offspring delayed dispersal from their natal tree. We have therefore provided evidence for kin-based sociality in habitat with abundant retreat sites, thus indicating that limitations on habitat availability are not necessary for social aggregations in this species.