Towards understanding the origin and dispersal of Austronesians in the Solomon Sea: HLA class II polymorphism in eight distinct populations of Asia-Oceania.

HLA class II nucleotide sequence polymorphisms were examined in eight ethnic groups of Asia-Oceania using DNA typing methods. Allele frequencies and characteristic DR/DQ haplotypes were determined and compared with those of other populations of Asia-Oceania. Genetic distances were measured to show the genetic relationship within the studied populations as well as between the studied populations and previously published populations. Phylogenetic trees were constructed based on HLA allele frequencies using the neighbour-joining method. The populations, mainly Trobriand Islanders, Roro, Tolai, Western Samoans and Taiwanese Aborigines, are characterized by a reduced diversity at the HLA loci examined, especially for DPB1. The high frequency of the 'Asian'-specific DPB1*0501 allele in Trobrianders and Roro, but also in Western Samoans and Taiwanese Aborigines, was the most striking result. The prevalence of DPB1*0501 and the short genetic distance from Trobriander and Roro to Taiwanese Aborigines provide evidence that the origin of the Austronesian odyssey is south-east Asia, and Taiwan could be an important part of it. The relatedness of Trobrianders to the Polynesian population from Western Samoa indicates a probable recent common ancestor. The observed lack of diversity may reflect bottleneck(s) and/or limited diversity of the founding population. Analysis of HLA class I antigens, together with mt-DNA and Y-chromosomal studies, will give us further information about the settlement of the Trobriand and other islands during the colonization of the Pacific.