海南岛及邻近陆地拟细鲫的种群遗传分化和亲缘地理过程

为了解海南岛及邻近陆地拟细鲫(Aphyocypris normalis)的遗传分化和亲缘地理过程,采用线粒体细胞色素b(Cyt b)对9个种群共124个个体的遗传多样性和遗传分化进行评估,并探讨这一物种的亲缘地理结构及演化历史.结果显示,在1 140 bp的序列中,共检测到87个核苷酸变异位点,定义了34个单倍型.基于Cyt b序列构建的系统发育树结果将所有个体分成3个主要谱系(A、B、C),谱系A包括海南岛大部分种群和邻近陆地全部种群,昌化江全部个体形成独立的谱系B,谱系C则为海南岛万泉河上安乡全部个体,各谱系间的遗传分化指数较高(0.707 5-0.971 9).分化时间估算的结果表明,谱系C的分化时间为2.038百万年前,谱系B的分化时间为0.865百万年前.种群历史动态分析表明,绝大部分种群均没有发生种群扩张,且所有谱系在近期都发生过有效种群数量减小的事件.根据研究结果推测,海南岛内万泉河上安乡种群的分化主要是由于五指山鹦哥岭山脉的隆起而导致的,而海南岛内和邻近陆地大部分群体没有发生分化可能是由于更新世冰期期间,岛屿和邻近陆地之间的水系因海平面下降而发生连接,琼州海峡两岸的拟细鲫种群有机会发生基因交流.因此认为琼州海峡并未对拟细鲫的扩散起到物理阻隔作用,海南岛为拟细鲫这一物种的起源扩散中心.(图4表6参48)

Population genetic structure and phylogeography of Aphyocypris normalis on Hainan island and its neighboring regions

To understand the genetic differentiation and phylogeography of Aphyocypris normalis on Hainan Island and its neighboring regions, 124 individuals from nine populations in nine drainage basins(Changhua, Lingshui, Wangquan, Nandu, Moyang, Jianjiang, Fangcheng, Beilun, and Pearl Rivers) were analyzed using mitochondrial DNA cytochrome b(Cyt b). The results showed that 87 polymorphic sites were detected, and 34 haplotypes were defined in all Cyt b sequences. Phylogenetic trees based on the Cyt b sequences comprised three major lineages(A, B, and C). Lineage A consisted of most populations from Hainan Island and all populations from its neighboring regions. All individuals from the Changhua River formed an independent lineage B. Lineage C was formed by all individuals from Shang’an Village(Wanquan River). The Fst among the lineages was higher(0.707 5-0.971 9). The divergence time of lineage C was 2.038 million years ago, and lineage B originated 0.865 million years ago. The demographic history showed that there was no expansion in most populations, and all lineages had recently experienced an effective population reduction. According to the results, it is speculated that the differentiation between the three lineages A, B, and C resulted from the uplift of the Yinggeling and Wuzhishan Mountains. However, most of the populations from Hainan Island and its neighboring regions were not differentiated. This could be because of the connection between Hainan Island and its neighboring regions caused by the fluctuation of sea level during the Pleistocene glacial period, resulting in gene flow between A. normalis populations on both sides of the Qiongzhou Strait. Based on these findings, we conclude that the Qiongzhou Strait did not act as a geographical barrier during the dispersion of A. normalis, and Hainan Island is the center of origin of the species.