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Anthony Di Fiore1,2 1Center for the Study of Human Origins, Department of Anthropology, New York University, 2New York Consortium in Evolutionary Primatology (NYCEP) Abstract Over the last few decades, field studies of atelin primates (woolly monkeys, spider monkeys, and muriquis) have revealed remarkable variation within and between genera in many aspects of social organization, including dispersal patterns and mating systems. Such variation is likely to influence the spatial structuring of kin relationships at both the social group and population level, with theoretical implications for the development and expression of intra- and intersexual social behavior and the pattern and degree of flexibility in associations among group members. With the development of noninvasive techniques for sampling individuals for genetic analysis, it has become possible to investigate some of these aspects of atelin social organization in more detail, both within and between taxa, using molecular data. Here, I report the results of a suite of molecular studies of two atelin primates, lowland woolly monkeys (Lagothrix poeppigii) and white-bellied spider monkeys (Ateles belzebuth), living in Amazonian Ecuador. For this study, a set of close to 200 tissue and/or fecal samples were collected from woolly monkeys and spider monkeys residing in various social groups in each of two local populations separated by ~35 km. These samples were then genotyped at between 7 and 15 highly variable microsatellite marker loci, and the genotype data then used to evaluate population genetic structure, paternity, and the spatial structuring of kin relationships within local populations of each taxon. For both taxa, molecular data confirm a high degree of female mobility, as expected based on long-term observational studies of other atelins. Analysis of pairwise relatedness values within groups revealed that animals of both sexes often resided as adults in social groups containing close kin, though not necessarily of the same sex. For at least some -- but not all -- social groups of each taxon, males were more closely related to one another on average than females, as would be predicted by a hypothesis of greater male than female philopatry among atelins. Additionally, for one well-studied community of spider monkeys, the pattern of spatial association among individuals (i.e., joint membership in subgroups) was not well predicted by genetic relatedness, and paternity analyses in two communities revealed that several different males were responsible for siring juveniles resident in those groups. Overall, these results highlight the contribution that molecular data can make to a more complete understanding of primate social organization than is possible from even the longest observational field studies. |