三峡库区干支流似鳊群体的遗传结构

为全面了解三峡库区小型鱼类优势物种似鳊（Pseudobrama simoni）群体的遗传结构，利用线粒体细胞色素b（Cyt b）基因序列分析了三峡库首的太平溪（干流）、青干河（支流）和袁水河（支流），库中的万州（干流）和甘井河（支流）以及库尾的木洞河（支流）和嘉陵江（支流）共7个似鳊群体的遗传多样性、群体之间的遗传分化情况和种群的历史动态。结果显示，三峡库区似鳊群体遗传多样性较低，单倍型多样性为0.061~0.326、核苷酸多样性为0.005%~0.036%；分子方差变异分析（AMOVA）表明，似鳊群体的遗传变异绝大部分源自于群体内部（99.82%），只有0.18%的变异来自群体之间；遗传分化指数（Fst）显示，所有群体之间不存在显著的遗传分化；系统进化树和单倍型网络图表明，三峡库区似鳊群体没有形成明显的系统地理格局；Mantel 检验显示，三峡库区各似鳊群体群体之间的遗传分化程度与地理距离的远近无相关性；中性检验Tajima''s D值和Fu''s Fs值表明，三峡库区似鳊群体在6.58万年前可能发生过种群扩张现象。

Genetic Structure of Pseudobrama simoni Populations in the Mainstream and Tributaries of Three Gorges Reservoir

Pseudobrama simoni is a small fish preferring static and slow flowing waters, and it is widely distributed in the Yangtze River, Yellow River and Pearl River basins. Previous research showed that P. simoni has become the dominant species in Three Gorges Reservoir and plays a key role in stabilizing the food web, population structure and fish ecology in the Three Georges Reservoir area. However, little is known about the genetic structure of the P. simoni populations. In this study, we explored the genetic structure of seven P. simoni populations in the mainstream and tributaries of Three Gorges Reservoir using the mitochondrial cytochrome b (Cyt b) gene, and focusing on the genetic diversity, genetic differentiation, and historical dynamics of the seven P. simoni populations. The aim of the study was to provide basic data of the genetic diversity of P. simoni populations in the Three Georges Reservoir area. From August 2019 to October 2020, P. simoni samples were collected in Taipingxi and Wanzhou (the mainstream of Three Gorges Reservoir), Qinggan River, Yuanshui River, Ganjing River, Mudong River and Jialing River (tributaries of Three Gorges Reservoir). A total of 184 mitochondrial cytochrome b (Cyt b) gene sequences were obtained, with a total length of 1 140 bp and 13 mutation sites. The genetic diversity of P. simoni populations was quite low, with a haplotype diversity of 0.061-0.326 and a nucleotide diversity of 0.005%-0.036%. Analysis of Molecular Variance (AMOVA) indicated that 99.82% of the genetic variation occurred within populations, and only 0.18% of the genetic variation occurred among populations. The genetic differentiation index Fst among P. simoni populations in the Three Gorges Reservoir indicated that there was no significant genetic differentiation among the populations. The phylogenetic tree and haplotype network of the seven P. simoni populations showed that no obvious phylogenetic geographic pattern of P. simoni populations formed in the Three Gorges Reservoir area. Mantel test shows that there was no correlation between the degree of genetic differentiation and the geographical distance among the P. simoni populations in Three Gorges Reservoir area. Tajima''s D value and Fu''s Fs value of neutral test indicated that the P. simoni populations in the Three Gorges Reservoir may have occurred a population expansion about 65 800 years ago.