Molecular phylogenetics and historical biogeography of east African chimpanzees

Two hundred and sixty eight DNA sequences (hypervariable region 1 of the mitochondrial control region) were obtained from chimpanzees (Pun hugh4tes) in 19 natural populations within the range of the easternmost subspecies, II t. schwein&rthi. Methods of phylogenetic reconstruction were applied at both the haplotype and population levels. Chimpanzee haplotypes do not sort into location-specific clades on any haplotype trees, indicating that the subspecies is free of major phylogeographic subdivkioning. Trees of populations in which geographic structure was imposed on the data lacked phylogenetic resolution in that interpopulational relationships were poorly supported statistically. These results indicate either a near simultaneous origin for the chimpanzee populations sampled, or an obscuring of interpopulational phylogenetic relationships by gene flow. In contrast, area dadograms of the forests from which chimpanzees were sampled (constructed using lists of endemic taxa) were robust and statistically well-supported. Chimpanzee population history is apparently decoupled from the history of the forests which the populations inhabit. Eastern chimpanzee data are also used to draw phylogenetic and molecular evolutionary comparisons to humans.