Abstract
Inbreeding adversely affects fitness, whereas heterozygosity often augments it. Therefore, mechanisms to avoid inbreeding and increase genetic distance between mates should be advantageous in species where adult relatives reside together. Here we investigate mate choice for genetic dissimilarity in chimpanzees, a species in which many females avoid inbreeding through dispersal, but where promiscuous mating and sexual coercion can limit choice when related adults reside together. We take advantage of incomplete female dispersal in Gombe National Park, Tanzania to compare mate choice for genetic dissimilarity among immigrant and natal females in two communities using pairwise relatedness measures in 135 genotyped chimpanzees. As expected, natal females were more related to adult males in their community than were immigrant females. However, among 62 breeding events, natal females were not more related to the sires of their offspring than immigrant females, despite four instances of close inbreeding. Moreover, females were generally less related to the sires of their offspring than to non-sires. These results demonstrate that chimpanzees may be capable of detecting relatedness and selecting mates on the basis of genetic distance.
Highlights
Inbreeding depression, a reduction of fitness in the offspring of closely related mates, is a widely documented phenomenon thought to result largely from the homozygous expression of recessive deleterious alleles [1,2,3]
TT emigrated before her maternal brother was born and the conception occurred when she revisited her natal community after a sudden decrease in the adult male population in her transfer community [52]
As expected for a slowly reproducing species in which females invest heavily in each offspring and sometimes reside with close relatives, several mechanisms promote inbreeding avoidance and mate choice in chimpanzees
Summary
Inbreeding depression, a reduction of fitness in the offspring of closely related mates, is a widely documented phenomenon thought to result largely from the homozygous expression of recessive deleterious alleles [1,2,3]. Inbreeding can adversely affect fitness through numerous pathways, notably via early death or reproductive disadvantage [3]. Favour the evolution of mechanisms to 2 avoid inbreeding and promote mate selection of genetically different individuals, especially in species that live at high population densities or in social groups, and where the risk of encountering relatives is high [6,7]
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