基于线粒体控制区的嘉陵裸裂尻鱼种群遗传结构分析

嘉陵裸裂尻鱼为青藏高原特有鱼类,近年来随自然地理气候的变迁和人类活动的影响,种群数量急剧减少。为了解嘉陵裸裂尻鱼的遗传背景以便更好的保护其遗传资源,本研究采用线粒体控制区部分序列变异,分析了嘉陵裸裂尻鱼6个地理种群的遗传结构和分布动态。在147尾个体中共发现17个变异位点,定义了14种单倍型,群体总的单倍型多样性较高为0.810,核苷酸多样性低为0.00698。AMOVA分析显示,44.29%的分子差异源于群体间,55.71%的分子差异源于群体内,群体间遗传分化极显著。Fst值统计检验表明,除宕昌群体和舟曲群体之间差异不显著外,其余两两群体之间Fst值统计检验均显著。基因流估计显示各群体间的基因流水平较高,遗传交流较频繁。Mantel test检验表明,嘉陵裸裂尻鱼种群之间遗传分化程度与地理距离存在显著相关。系统树和单倍型网络进化图显示,6个地理群体的单倍型按照嘉陵江水系和渭河水系形成两个大的类群。错配分布和中性检验表明嘉陵裸裂尻鱼群体在近期历史上群体大小保持稳定,未出现显著的种群扩张。根据本文所揭示的嘉陵裸裂尻鱼种群遗传结构特征,建议将分布在嘉陵江水系的嘉陵裸裂尻鱼作为一个整体进行保护,嘉陵裸裂尻鱼渭河种群属高度分化的单倍型类群,且遗传多样性极低,需对该种群进行优先保护。

Population genetic structure of Schizopygopsis kialingensis inferred from mitochondrial D-loop sequences

Schizopygopsis kialingensis is an endemic fish of the Bailong River, which is a tributary of the Jialing River. The species'' population has been largely reduced in recent years as a result of overfishing, river pollution, and dam construction. To develop effective strategies forpreserving the species''germplasm, it is first necessary to understand the species'' genetic variation and population structure. Therefore, in the present study, a 706-bp segment of the mitochondrial control region was sequenced from 147 S. kialingensis specimens that were collected from six populations in the Bailong and Weihe Rivers. Seventeen variable sites and 14 haplotypes were identified. The six populations exhibited high haplotype diversity (0.810) and low nucleotide diversity (0.00698), and the genetic diversity of the Zhouqu County Chengguan Township population was highest, whereas that of the Weiyuan County Qiaoyu Township population was the lowest. AMOVA indicated that significant difference among populations, with 44.29% molecular variation among the populations and 55.71% molecular variation within populations. Pairwise fixation index (Fst) values indicated that all the populations were significantly different, except the Tanchang County Nanhe Township and Zhouqu County Chengguan Township populations. Meanwhile, gene flow estimates suggested high levels of gene flow, and the Mantel test indicated that the genetic and geographic distances were significantly correlated. In addition, the construction of a neighbor-joining phylogenetic tree and a minimum spanning network indicated that the 14 haplotypes formed two main groups that corresponded to the Bailong River and Weihe River systems, and mismatch distribution and neutrality analyses indicated that the population has not under gone recent expansion. According to these findings, we suggest that the S. kialingensis population in the Bailong River should be protected and that the protection of the Weihe River population should be prioritized, owing to the group''s high genetic differentiation and very low genetic diversity.