Chimpanzee molecular ecology: Kinship, behavior, and dispersal

Chimpanzees are one of the few species where males consistently remain in and females typically disperse from the natal group. This makes them ideal study subjects to address two major issues: (1) the effect of kinship on behavior and (2) the effect of sex-biased dispersal on patterns of variation in uniparentally-inherited genetic markers. In this thesis, I investigate these topics through a systematic study of wild chimpanzees in Uganda.; Kin selection has frequently been proposed to explain why male chimpanzees frequently affiliate and cooperate and females are relatively asocial. Results of my research on the Ngogo community of chimpanzees of Kibale National Park are not entirely consistent with this hypothesis. While males clearly preferred to affiliate and cooperate with their maternal brothers in several behavioral contexts, the overall impact of kinship on male social relationships was limited. Paternal brothers did not selectively interact, and the majority of highly affiliative and cooperative dyads were not closely related. Additional analyses revealed that females in two spatially defined neighborhoods located on the peripheries of the Ngogo territory had significantly elevated average genetic relatedness, association frequency, and spatial cohesion. These results suggest that females in these two neighborhoods may be composed of related females who dispersed from the same, neighboring communities.; A large body of theoretical work suggests that analyses of variation at the maternally inherited mtDNA and the paternally inherited Y-chromosome are a potentially powerful way to reveal the differing migratory histories of men and women across human societies. However, the few empirical studies where both mtDNA and Y-chromosome variation and patterns of sex-biased migration are known from ethnographic observation have produced conflicting results. I review some methodological reasons for these inconsistencies, and take them into account to provide an unbiased characterization of mtDNA and Y-chromosome variation in four chimpanzee communities. I found that patterns of mtDNA and Y-chromosome variation were more strongly contrasting in chimpanzees than patrilocal human societies, even when taking into account factors other than differences in the extent of female-biased dispersal that would reduce within-group variation of the Y-chromosome more strongly in chimpanzees than in patrilocal humans.