In our recent survey, the transparent small Lacustrine goby, Gobiopterus lacustris had reported as the endemic species of Luzon, Philippines, was identified as an abundant species in mangroves of Leizhou Peninsula, China. Here, high diversity and significant differentiation of five sites of samples representing the west and east populations were revealed by mitochondrial DNA sequences. Five haplotypes of 56 cytochrome oxidase subunit I (Cox1) with the lengths of 623 base pairs (bp) have the high pairwise identity (>98.8%). Moreover, a total of 31 haplotypes for 129 partial D-loop regions were clustered into two clades corresponding to the east and west sampling sites. The strong population structure was confirmed (ΦST = 0.43017, p < .0001) with high haplotype diversity (h = 0.880 ± 0.017) and low nucleotide diversity (p=.00484). Moreover, both the mismatch distribution analysis and neutral test of D-loop revealed that the west group might experience a recent demographic expansion. Lastly, the isolation-with-migration analysis supported the expansion and indicated that the east-west split happened at approximately 7.1 kyr ago. Given the distribution and diversity, G. lacustris could be a good model for the study of the sea-level fluctuations and coast evolution of the South China Sea.
Keywords: Cox1 barcodes; South China Sea; Zhanjiang Mangrove; control region.