基于线粒体控制区序列的塔里木裂腹鱼遗传多样性及种群分化分析

Genetic diversity and population differentiation of Schizothorax biddulphi based on mt DNA control region sequences

为了解塔里木裂腹鱼（Schizothorax biddulphi）种群遗传多样性和遗传结构,本研究分析了库玛拉克河（KMLK）、木扎提河（MZT）、塔什库尔干河（TSKEG）、喀拉喀什河（KLKS）、玉龙喀什河（YLKS）、克孜勒苏河（KZLS）、车尔臣河（CEC）7个群体共143个线粒体控制区序列变异个体,获得了39个单倍型。其中,CEC群体与其他群体间遗传分化显著,无共享单倍性。群体间遗传差异的分子变异分析表明,在所有群体中大多数的变异来源于群体间;而排除CEC群体后,大多数变异则来源于群体内（81.01%）,群体间的遗传变异小（16.68%）。塔里木裂腹鱼不同群体间的基因流（Nm）为0.0464~18.2786,CEC与其余群体间的基因流均小于1。贝叶斯法（BI）构建BI树和单倍型网络图结构一致,塔里木裂腹鱼形成了2个分支。2个分支的最近共同祖先约在2.7 Ma前。单倍型间的歧点分布具有明确的双峰,表明2.7 Ma前罗布泊的干枯或盐化事件使2个分支间产生了地理隔离,后因塔里木盆地冷湿气候的影响罗布泊水面恢复,现今的分布是先前分化居群的二次联系。种群结构分析结果均支持塔里木裂腹鱼已分化出2个明显分化的地理种群的观点,即塔里木河（TLM）种群和CEC种群。TLM种群具有较高的单倍型多态性（0.939±0.008）和核苷酸多态性（0.0125±0.0017）,而CEC种群的单倍型多态性高（H）（0.903±0.025）,核苷酸多态性低（Pi）（0.0051±0.0012）。建议对以上2个种群分开管理,TLM种群为优先保护单元。

Schizothorax biddulphi is an endemic fish in Xinjiang but the population is decreasing because of hu-man activities and natural environmental changes. To understand the population genetic diversity and structureof S. biddulphi, 143 specimens from seven populations in the Kumalake, Muzat, Taxkorgan, Karakax, Yurunkax, Kez-ilesu, and Qarqan Rivers were collected, the mitochondrial DNA control region was sequenced, and 39 haplotypes were detected. The Qarqan River population did not share haplotypes with any other population, and the FST tests were highly significant between the Qarqan and other populations. Analysis of molecular variance showed that most of the variation was apportioned among the populations, whereas the variation within populations was 81.01%, except that of the Qarqan population. Gene flow among populations varied from 0.0464 to 18.2786 and was 〈1 between the Qarqan and other populations. A phylogenetic tree constructed using the Bayes method was consistent with the haplotype network, and the tree was divided into two clades. The most recent common ancestor of the two branches was 2.7 Ma. A mismatch analysis showed a bimodal distribution, indicating geographic isola-tion between the two branches generated by aridification and salinization of Lop Nor at 2.7 Ma, and Lop Nor sub-sequently recovered because of the cold and wet climate of the Tarim Basin. Secondary contact resulted in the present-day distribution pattern. The results of a population structural analysis suggested the presence of two dis-tinct geographic populations, such as the Tarim River and Qarqan River populations. The former had high haplo-type diversity （0.939±0.008） and nucleotide diversity （0.0125±0.0017）, whereas the latter had higher haplotype diversity （0.903±0.025） and lower nucleotide diversity （0.0051±0.0012）. These results suggest that different man-agement strategies should be adopted for these two groups, and that the Tarim River population should be pro-tected as a priority.