Mitochondrial DNA Analyses of Cercopithecus Monkeys Reveal a Localized Hybrid Origin for C. mitis doggetti in Gombe National Park, Tanzania

Abstract

In recent years, hybridization has gained recognition as an important creative force in primate evolution. The exchange of genetic material between species provides genetic novelty on which evolutionary forces, such as natural selection, may act. The guenon radiation (Tribe Cercopithecini) is known for numerous cases of contemporary hybridization—in the wild and captivity—between broadly sympatric species. Interspecific hybrids are viable, and field studies report fertile hybrid females. Despite being a well-documented phenomenon, hybridization among wild guenons is relatively rare and sporadic. An exception is the long-standing hybridization between Cercopithecus mitis doggetti and C. ascanius schmidti in Gombe National Park, Tanzania, where hybrids comprise a significant proportion of the breeding population. Here, I used mitochondrial loci to conduct a genetic survey of the Gombe population and examine the extent and direction of gene flow between the parental species. I extracted DNA from noninvasive fecal samples of unhabituated individuals (N = 144 individuals) with known phenotype and provenance. All parental phenotypes and hybrid individuals were identified in the field based on species specific pelage colors and patterns. Phylogenetic analyses of DNA sequences from inside and outside the hybrid zone show Gombe’s population of C. mitis doggetti is distinct from neighboring conspecific populations in having mitochondrial DNA of C. ascanius schmidti. All animals surveyed from the hybrid zone have one of two haplotypes of C. ascanius schmidti unique to Gombe. These results provide evidence of asymmetric introgressive hybridization between sympatric guenon species, a likely consequence of colonization patterns of the parental species during range expansions. The spatial distribution patterns of the two haplotypes imply that Gombe is a site of both historic and contemporary hybridization between sympatric guenons. The discovery of gene flow and ongoing hybridization between clearly defined species, ecologically distinct enough to coexist in broad sympatry, provides an ideal system to investigate speciation mechanisms in primate adaptive radiations.