Genetic Structure of a Primate Hybrid Zone

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Jolly/Disotell/Phillips-Conroy When two natural populations interbreed, they tend to become genetically homogenized. If, however, individuals of mixed ancestry are relatively unfit, a narrow, intervening hybrid zone may persist for generations, filtering gene-flow between the populations. Many such hybrid zones are known, but few involve primates, even though hybridization was probably important in human prehistory. Our study brings together investigators at New York University, Washington University in St. Louis, and Addis Ababa University, Ethiopia. It combines powerful, new techniques of genetic analysis with field observation to investigate hybridization between two baboon populations, strikingly different in both behavior and appearance, whose ranges meet in Ethiopia. We have already collected and stored DNA from about a thousand baboons, of four generations. In three more field seasons we shall complete this dataset, and clarify ecological influences on hybridization by mapping the hybrid zone more widely. Each animal will be typed for hypervariable DNA markers. Their distribution will show how social behavior affects the genetic structure of the populations, reveal patterns of inter-group migration, and indicate the darwinian fitness of cross-breeders and their offspring. The result will be a unique picture of the dynamics of natural hybridization and the genetics of evolutionary divergence.