Abstract
Complex ecological pressures affect the social dynamics of many primatespecies, but it is unclear how they affect primate speciation. Molecular tools are oftenused to answer questions about the evolutionary histories and social systems ofprimates. Mitochondrial DNA (mtDNA), in particular, is frequently used to answermany of these questions, but because it is passed from mothers to offspring it revealsonly the histories of females. In many species, including chimpanzees, females gener-ally disperse from their natal groups while males are philopatric, and thus differences indispersal patterns likely leave different signatures in the genome. We previouslyanalyzed samples from 187 unrelated male and female chimpanzees in Nigeria andCameroon using 21 autosomal microsatellites and mtDNA sequences. Here, we examine the contributions of males and females in shaping the genetic history of thesechimpanzees by genotyping a subset of 56 males at 12 Y-chromosome microsatellites.We found that Y-chromosome population structure differed from the results of analysisof mtDNA haplotypes. The results also revealed that males in rainforest habitats(Guinean and Congolian rainforests) are more closely related to one another than thoseinhabiting the savanna-woodland mosaic ecotone in central Cameroon. In contrast, thepattern of female relatedness did not differ across habitats. We hypothesize that thesedifferences in population structure and patterns of relatedness among males in differenthabitat types may be due to differences in the community dynamics of chimpanzees inthe ecotone vs. rainforests, and that these factors contribute to making Cameroon anengine of diversification for chimpanzees. Broadly, these results demonstrate the importance of habitat variation in shaping social systems, population genetics, and primate speciation.