November 05, 2013

Population structure in Thailand

PLoS ONE 8(11): e79522. doi:10.1371/journal.pone.0079522

Insight into the Peopling of Mainland Southeast Asia from Thai Population Genetic Structure

Pongsakorn Wangkumhang et al.

There is considerable ethno-linguistic and genetic variation among human populations in Asia, although tracing the origins of this diversity is complicated by migration events. Thailand is at the center of Mainland Southeast Asia (MSEA), a region within Asia that has not been extensively studied. Genetic substructure may exist in the Thai population, since waves of migration from southern China throughout its recent history may have contributed to substantial gene flow. Autosomal SNP data were collated for 438,503 markers from 992 Thai individuals. Using the available self-reported regional origin, four Thai subpopulations genetically distinct from each other and from other Asian populations were resolved by Neighbor-Joining analysis using a 41,569 marker subset. Using an independent Principal Components-based unsupervised clustering approach, four major MSEA subpopulations were resolved in which regional bias was apparent. A major ancestry component was common to these MSEA subpopulations and distinguishes them from other Asian subpopulations. On the other hand, these MSEA subpopulations were admixed with other ancestries, in particular one shared with Chinese. Subpopulation clustering using only Thai individuals and the complete marker set resolved four subpopulations, which are distributed differently across Thailand. A Sino-Thai subpopulation was concentrated in the Central region of Thailand, although this constituted a minority in an otherwise diverse region. Among the most highly differentiated markers which distinguish the Thai subpopulations, several map to regions known to affect phenotypic traits such as skin pigmentation and susceptibility to common diseases. The subpopulation patterns elucidated have important implications for evolutionary and medical genetics. The subpopulation structure within Thailand may reflect the contributions of different migrants throughout the history of MSEA. The information will also be important for genetic association studies to account for population-structure confounding effects.



terryt said...

This is actually a very interesting paper.

"The subpopulation structure within Thailand may reflect the contributions of different migrants throughout the history of MSEA".

Certainly. For those who haven't followed the link: What the authors found was a basic shared substructure overlain by later immigrant populations. The latest appears to have been a general 'Chinese' population (SPD-dark red) found mostly in the Central region but present also in both Vietnam and Cambodia aswell as in China. Of the others SPA-dark blue was found in Cambodia as well as in south Thailand especially and belongs genetically more widely to South and Central Asia. I'm sure I remember something about Indian Y-DNA being found in both Thailand and Cambodia. SPB-light blue was also found in Cambodia as well as in northeast Thailand and probably indicates the close relationship between the two countries genetically. SPC-yellow, on the other hand, was found in Vietnam and presumably indicates an immigration from that country into northern Thailand over the mountains.

Garvan said...

Does anybody know if the data will be published? I would love to look at this data set myself.

It is correct to say the Northern Thai came from Vietnam. As recently as 200 years ago the largest group in the North called themselves Thai-Vietnamese. Ultimately all Thai's must have migrated south via Vietnam and Lao and sometimes Burma.