中间黄颡鱼群体遗传变异与亲缘生物地理

通过分析81尾采自华南西部12条水系的中间黄颡鱼(Pelteobagrus intermedius)mtDNA控制区435 bp的序列,研究其群体遗传变异及亲缘生物地理格局。结果显示,中间黄颡鱼群体间的遗传分化较小,核苷酸变异只有0.54%。12条水系的群体共有7个单倍型,其中一些现已相互隔离的水系中的群体共享同一个单倍型,提示这些水系曾经有非常密切的联系。根据嵌套进化支序分析,中间黄颡鱼可能起源于峒中河、北仑河、防城河所在的广西与越南交界地区,并通过两条途径向华南沿海西部诸独立水系和海南岛扩散,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。

Population genetic variations and phylogeography of Pelteobagrus intermedius

The phylogeographical patterns and population genetic variations of 81 Pelteobagrus intermedius from 12 drainage systems in western south China were investigated based on 435 bp nucleotide sequences of mtDNA control region.The results showed a low genetic variation among populations of these 12 drainage systems with only 0.813 of haplotype diversity and 0.00542 of nucleotide diversity.The fish samples from the 12 drainage systems fall into 7 haplotypes,indicating that some of the 12 drainage systems had physical connection before they became geographically separated.These 12 drainage systems were divided into 3 geographic regions.Hierarchical analyses of sequence differences with AMOVA indicated that a substantial proportion(83.02%) of the variations was attributable to differences among populations within the region,and a lesser proportion of variation(20.76%) was due to variation within populations.The relative contribution of differences among geographic regions was small(3.78%).All this suggests that isolation among drainage systems is the key factor that produced genetic diversity among populations of Pelteobagrus intermedius,not the recent geographic barrier between the mainland and Hainan Island.Nested clade phylogeographic analysis revealed that this fish originated from the joining area of Guangxi and Vietnam(in which the Dongzhong River,the Beilun River and the Fangcheng River are located) and spread to other drainages of western south China and Hainan Island in two ways: 1) the Xijiang drainage system spread southward through 3 major rivers,eventually draining east of the Leizhou Penisula;2)through ancient river systems between Hainan Island and Vietnam to Hainan Island,then back to the mainland expanding northward to rivers eventually draining west of the Leizhou Penisula,with some individuals returning again to the Xijiang drainage system. The current phylogeographical distribution of the populations might have occurred due to two events: geographical isolation through territory fragmentation,followed by long-distance colonization,as well as contiguous range expansion.