Detection of gene flow between subspecies
We used the statistical model implemented in TreeMix to infer patterns of population splits and mixtures among subspecies (Pickrell & Pritchard, 2012). As revealed from the FSTstatistic above, some populations are genetically similar, indicating panmixia within a relative wide geographic range, e.g. Andaman Sea on the west of Malay Peninsula, South China Sea (Gulf of Thailand and Hainan Island). Hence, one representing population from each region was used in this analysis. The eleven populations were related to the common ancestor through a graph of ancestral populations, which was inferred by allele frequency and a Gaussian approximation to genetic drift (Pickrell & Pritchard, 2012). Gene flow events were inferred by adding admixtures onto the Maximum Likelihood population splitting topology.