The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)


Females select mates that are less related than expected among the Gombe chimpanzees

KARA K. SCHROEPFER-WALKER1, ANNE PUSEY1, REBECCA S. RUDICELL2, MIGUEL A. RAMIREZ3, BEATRICE H. HAHN3 and EMILY WROBLEWSKI4.

1Evolutionary Anthropology, Duke University, 2Vaccine Research Center, National Institutes of Health, 3Departments of Medicine and Microbiology, Perelman School of Medicine, University of Pennsylvania, 4Department of Structural Biology, Stanford University School of Medicine

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In chimpanzees, females typically disperse at adolescence and must integrate into a new group in unfamiliar surroundings, often facing substantial aggression from resident females, before reproducing. This unusual pattern for mammals likely occurs because male chimpanzees benefit in cooperating to defend a large territory, forcing female dispersal to prevent inbreeding. However in the Kasekela community in Gombe National Park, Tanzania half of all females remain in their natal group allowing for direct comparisons of inbreeding risk and avoidance between immigrant and natal females. We genotyped 129 chimpanzees at 8-11 microsatellite loci and calculated relatedness (R) between each dyad using Co-ancestry.

As expected, natal females were more related, on average, to the adult males in their community than were immigrant females, and thus faced a higher risk of inbreeding. However, among 41 conceptions over 24 years, natal females, overall, were not more related to the sires of their offspring than immigrant females, despite two instances of close inbreeding. Furthermore all females, on average, conceived with a sire that was significantly less related to them than non-sires. These results suggest that chimpanzees are capable of detecting relatedness, and thereby can decrease, though not completely eliminate, the risk of inbreeding. Whether inbreeding avoidance occurs through behavioral mechanisms or post-copulatory, cryptic female choice is not yet known.

Data collection supported by the Jane Goodall Institute. Construction of the longterm database was supported by grants from the NSF (DBS-9021946, SBR-9319909, BCS-0452315, IOS-LTREB-1052693), genetic analyses were supported by grants from the NIH (R01 AI50529, R01 AI58715, P30 AI 27767), and Wroblewski was supported by a Ruth L. Kirschstein National Research Service Award (NIH F32 AI085959-03).

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