Genetic variation and phylogeography of Micronoemacheilus pulcher populations among drainage systems between western South China and Hainan Island

Genetic variation and phylogeographic patterns of Micronemacheilus pulcher populations from 12 drainage systems between western South China and Hainan Island were investigated, based on nucleotide sequences of the mtDNA cytochrome b (Cyt b) gene, with 108 individuals. There were 138 variable nucleotide sites among 1140 base pairs of the Cyt b gene (12.11% of the full sequence). Analysis of molecular variance (AMOVA) revealed that most of the genetic variation resides within populations (58.53%) and among populations within a geographic region (42.84%). Neighbor-joining analysis with 39 haplotypes of the mtDNA Cyt b gene revealed that the populations from the 12 drainage systems can be divided into two major lineages. Populations from the separate drainages in Guangxi (Fangcheng, Dongzhong, Beilun, and Nanliujiang Rivers) and the Xijiang River drainages across Guangxi and Guangdong Provinces were closely related to those from the Moyangjiang and Tanjiang River drainages in Guangdong Province; populations from the Wanquanhe and Nandujiang River drainages on Hainan Island were closely related to those from the Jianjiang River drainage in Guangdong Province. Nested-clade phylogeographic analysis indicates that the fish may have originated from the border area of Guangxi and Vietnam, where the Dongzhong River, Beilun River and Fangcheng River are located, and dispersed to other drainages in two ways: 1) through the Xijiang River to the coastal drainages in Guangxi and those of the Moyangjiang and Tanjiang Rivers in Guangdong Province; 2) through the ancient river systems between Hainan Island and Vietnam to Hainan Island, then back to the mainland expanding northward to the Jianjiang River of the Leizhou Peninsula in Guangdong Province. The current phylogeographic distribution of Micronemacheilus pulcher might have been formed by events such as allopatric fragmentation, long-distance colonization (possibly coupled with subsequent allopatric fragmentation), and contiguous range expansion [Acta Zoologica Sinica 54(5): 805– 813, 2008].