1Department of Anthropology, New York University, 2New York Consortium in Evolutionary Primatology, (NYCEP), 3Department of Anthropology, University of Texas at Austin
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Observational studies of squirrel monkeys (Saimiri) have documented instances of intragroup transfer for both males and females, depending on the species and the local ecology. Measurements of genetic relatedness among individuals are useful for testing predictions regarding the evolution of kin-biased social behaviors, sex-biased dispersal patterns and various fitness outcomes for adult group members following reproductive behaviors. Still, little genetic information is available to support hypotheses surrounding the ecological and social parameters that may affect the population structure and dispersal outcomes within such variable social systems of Saimiri. Here, we use genetic data to assess kin structure within social groups among a wild population of Saimiri sciureus at the Tiputini Biodiversity Station in eastern Ecuador; we also use these data to infer dispersal patterns and evaluate possible sex biases in dispersal. If there is greater male dispersal, then average pairwise relatedness, FST values, and intragroup mean corrected assignment indices among adult females should be greater than those among adult males. Adult females should also have a greater number of close kin members that are of the same age class and sex. Genomic template was extracted from fecal samples and fourteen loci were amplified for 62 unique individuals. Not only were the two social groups genetically distinct, as estimated by FST measurements, but average pairwise relatedness values and mean corrected assignment indices were greater for females than males. This suggests that much of the gene flow is due to male dispersal and that females are the philopatric sex.
This research was supported by a dissertation improvement grant from NSF (DIG #06-22481), a dissertation fieldwork grant from the Wenner-Gren Foundation (DFGA Gr. #7803), and by a NSF IGERT grant (0333415) to NYCEP.