华南西部及海南岛美丽小条鳅种群遗传变异与亲缘地理

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

通过分析108尾采自华南西部12条水系的美丽小条鳅(Micronemacheilus pulcher)mtDNA细胞色素b(cytb)基因全序列,研究其种群遗传变异和亲缘生物地理格局。美丽小条鳅的cytb序列包含138个核苷酸变异位点(占全序列12.11%)。分子变异分析(AMOVA)显示,分子遗传变异主要来自种群内(58.53%)和地理区内种群间(42.84%)。采用邻接法构建的39个单倍型的NJ系统树显示,12条水系的美丽小条鳅聚成两支。其中,广西沿海诸独立水系(防城河、峒中河、北仑河、南流江)和横穿广东和广西的西江水系与广东漠阳江和潭江水系关系密切;而海南岛万泉河和南渡江与广东鉴江水系关系密切。根据嵌套进化枝系地理分析(NCPA)推测,与越南毗邻的防城河周边地区可能是美丽小条鳅的扩散中心,该物种可由此区域通过两条途径扩散:1)沿西江水系向广西沿海独立水系至广东漠阳江和潭江水系扩散;2)向海南岛诸水系再至雷州半岛的鉴江水系扩散。在演化过程中,曾发生片断化事件、长距离建群和持续的分布区扩张。

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 Guallgdong 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