Doctoral Dissertation Improvement: Phylogenetic Relationships and Gene Flow Among Southern African Baboons

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Common baboons (Papio) comprise a series of geographically distinct forms or 'semi-species' that, while recognizably different from one another in appearance and behavior, are known to hybridize in the wild where their ranges meet. Papio is particularly useful in the study of the processes of divergence and reticulation that affect the evolution of closely-related, hybridizing species because baboons are the only primates for which we have detailed behavioral, genetic, and morphological data as well as long-term research in the dynamics of hybridization. In addition to this, studies of Papio can provide more direct insight into the evolution species, like early Homo, that occupy similar econiches. Baboons, like early Homo, are terrestrial, ecologically generalist primates that evolved in the savannas and woodlands of Pleistocene Africa. The climate-driven changes in these environments that affected the evolution of Papio may well have impacted Homo. However, baboons retain the genetic signature of the timing and geographic placement of these events that more recently evolved modern humans have lost.Current knowledge of the evolution of Papio largely comes from studies of eastern African baboons. However, it is unclear if these eastern African baboons are representative of Papio as a whole. This study, therefore, will focus on the evolutionary relationships and patterns of gene flow among southern African forms, the yellow and chacma baboons, which come into physical contact with one another in central Zambia. The evolutionary relationships among populations of these two forms will be inferred from mitochondrial DNA sequence data, while genetic exchange between populations will be discerned using both mitochondrial DNA and an array of nuclear genomic microsatellite markers. Questions addressed by this research include: what are the relationships among populations of southern African baboons? Do these two forms hybridize, and if so, what pattern does the resulting gene flow take? Is this genetic exchange driven by the dispersal of males from their natal groups into other nearby groups, as in eastern Africa? Answers to these questions will help clarify the taxonomy of Papio, improve our understanding of the relationships among baboon species and the factors that have affected their evolution, and provide insight into how such processes may impact the evolution of similar primate species.Baboons are commonly used in biomedical, behavioral, and genetic research. An accurate understanding of the evolutionary relationships among these important model organisms is necessary for such studies. This project will provide scientific training opportunities for the co-PI and undergraduate students. It will also promote professional contact and collaboration between scientists in the United States and Zambia, which has not been a traditional geographical focus of research by biological anthropologists.