MBE Advance Access published online on June 3, 2008
Molecular Biology and Evolution, doi:10.1093/molbev/msn128
Gene Flow and Natural Selection in Oceanic Human Populations, Inferred from Genome-wide SNP Typing
Ryosuke Kimura1,*, Jun Ohashi2, Yasuhiro Matsumura3, Minato Nakazawa4, Tsukasa Inaoka5, Ryutaro Ohtsuka6, Motoki Osawa1 and Katsushi Tokunaga2
It is suggested that the major prehistoric human colonizations of Oceania occurred twice, namely, about 50,000 and 4,000 years ago. The first settlers are considered as ancestors of indigenous people in New Guinea and Australia. The second settlers are Austronesian-speaking people who dispersed by voyaging in the Pacific Ocean. In this study, we performed genome-wide SNP typing on an indigenous Melanesian (Papuan) population, Gidra, and a Polynesian population, Tongans, by using the Affymetrix 500K assay. The SNP data were analyzed together with the data of the HapMap samples provided by Affymetrix. In agreement with previous studies, our phylogenetic analysis indicated that indigenous Melanesians are genetically closer to Asians than to Africans and European Americans. Population structure analyses revealed that the Tongan population is genetically originated from Asians at 70% and indigenous Melanesians at 30%, which thus supports the so-called "Slow train" model. We also applied the SNP data to genome-wide scans for positive selection by examining haplotypic variation, and identified many candidates of locally selected genes. Providing a clue to understand human adaptation to environments, our approach based on evolutionary genetics must contribute to revealing unknown gene functions as well as functional differences between alleles. Conversely, this approach can also shed some light onto the invisible phenotypic differences between populations.
Key Words: adaptive evolution • gene flow • human genome • SNP • Oceania