Gene flow and genetic diversity of chimpanzees in Tanzanian habitats

Abstract

Tanzania is located at the southeastern end of the eastern chimpanzee (Pan troglodytes schweinfurthii) distribution. Except for two national parks, their habitats have been degraded due to human activities. To clarify the gene flow and genetic diversity of chimpanzees in Tanzania, we analyzed the mitochondrial sequences of chimpanzees in six sites (Lwazi, Wansisi, Mahale, Karobwa, Ugalla-Masito, and Gombe), some of which are now isolated. The southernmost habitat (Lwazi) was about 150 km away from the nearest habitat but, considering the geographic distance, the genetic distance of the chimpanzees between Lwazi and the other habitats was not high. In contrast, the genetic distance between the chimpanzees in the northernmost habitat (Gombe), and the other habitats was relatively high considering the geographic distance. The results suggest that the Malagarasi River, which runs between Gombe and the southern habitats, limits gene flow. The genetic difference analyses also suggest that the habitats of Wansisi, Mahale, Karobwa, and Ugalla-Masito can be regarded as one population ("Greater Mahale"). The genetic distance between Lwazi and Gombe was lower than that between Gombe and the Greater Mahale habitats. This result suggests that early chimpanzees came to the Greater Mahale habitats through the southern habitats around Lwazi. The nucleotide diversity was not different from that in other countries, probably due to the sequence variety. There were unique haplotypes in several habitats where the number of chimpanzees was estimated to be small, which implies that some haplotypes are probably be at risk of disappearing. These data will be useful for conservation planning.