海南岛宽额鳢(Channa gachua)群体遗传变异与生物地理过程

为了解海南岛宽额鳢(Channa gachua)的群体遗传分化和亲缘生物地理过程,采集了云南元江和海南岛5个水系(昌化江、陵水河、藤桥河、万泉河及南渡江)共6个种群168个宽额鳢个体,基于线粒体细胞色素b(Cyt b)基因全序列(1142 bp)对其遗传多样性和遗传分化程度进行了评估,并探讨了地质和气候等因素如何塑造了这一物种的亲缘地理结构及演化历史。基于Cyt b序列构建的系统树结果将所有个体分成两个主要谱系(A和B),谱系A包括海南岛所有种群,其中,部分昌化江个体形成独立的亚支(A2),其余个体聚为另一亚支(A1),谱系B为云南元江的全部个体,各谱系间的遗传分化指数均较高。种群历史动态分析表明,各谱系均没有发生种群扩张,但A1亚支与谱系B曾在约1万年前发生过有效种群数量减小的事件。根据研究结果推测,更新世冰期期间,北部湾因海平面下降而暴露,大陆和海南岛的水系发生接触,越南北部水系(包括元江/红河)通过一条联系雷州半岛和海南岛的古河道流入南海,因而冰期期间宽额鳢有机会从元江(红河)扩散至海南岛西南部,随后在海南岛内部,宽额鳢进一步扩散,并以五指山为种群间基因交流的重要地理障碍,各水系间种群发生基因交流和遗传分化。

Genetic variation and phylogeography of Channa gachua in Hainan Island

The small air-breathing fish, Channa gachua, is distributed in the shallow regions of the streams and rivers of Yunnan Province and Hainan Island in China. At present, there are limited studies on the genetic differentiation and phylogeography of C. gachua. To understand the genetic diversity of C. gachua and determine how the geological events and climatic changes have influenced the phylogeographic structures and evolutionary history of this species, 168 specimens were collected from 6 populations in 6 drainages (Changhua, Lingshui, Tengqiao, Wanquan, Nandu, and Red rivers) in Hainan Island and Yunnan province, using the mitochondrial DNA cytochrome b gene (1142 bp) as a molecular marker. The phylogenetic tree showed two major lineages (A and B). Lineage A included all samples from Hainan Island. Among them, some samples of the Changhua River fell into an independent subclade (A2), and the remaining samples were clustered into another subclade (A1); Lineage B contained all samples from the Red River. The genetic differentiation index of C. gachua among the different lineages was high. The demographic history indicated that the total populations, lineage A1, A2, and B have not undergone recent expansion. Bayesian skyline plots showed that the effective population size of lineage A1 and B declined at 0.01 millions of years ago. According to our research, during Pleistocene glaciations, the Gulf of Tonkin was exposed owing to a drop in sea level. The drainages in the mainland and Hainan Island were in contact. Drainages in northern Vietnam (including the Red River) flowed into the South China Sea by a paleochannel connecting the Leizhou Peninsula and Hainan Island. At this time, the exposure of the Gulf of Tonkin gave C. gachua a chance for population dispersion between the Red River and southwestern Hainan Island drainage, and subsequently enhanced gene flow between populations in the Hainan Island drainages.