江苏省4个太湖新银鱼种群遗传多样性和遗传结构分析

Genetic Diversity and Population Structure of Four Neosalanx taihuensis Populations in Jiangsu Province

中文关键词: 太湖新银鱼  细胞色素b  遗传多样性  遗传结构

英文关键词: Neosalanx taihuensis  Cyt b  Genetic diversity  Genetic structure

中文摘要:

      太湖新银鱼(Neosalanx taihuensis)是我国特有的银鱼种类，主要分布在长江和淮河中下游及其附属湖泊，近年来其资源量呈明显下降趋势。为了解太湖新银鱼遗传背景，本研究采用线粒体细胞色素b (Cytochrome b, Cyt b)基因序列，分析了江苏省太湖、高邮湖、洪泽湖和骆马湖4个太湖新银鱼野生群体共144尾样本的遗传多样性及遗传结构。结果显示，太湖新银鱼Cyt b基因序列共发现29个变异位点，定义25个单倍型；平均单倍型多样性(Hd)为0.682±0.037，核苷酸多样性(π)为0.00231±0.00021；4个群体中，高邮湖群体的遗传多样性最高(Hd: 0.609±0.078; π: 0.00094± 0.00027)，太湖群体的遗传多样性最低(Hd: 0.343±0.107; π: 0.00075±0.00033)。分子方差分析(AMOVA)显示，太湖新银鱼群体间遗传差异(71.53%)大于群体内遗传差异(28.47%)，遗传变异主要来自于群体间。遗传分化指数Fst值统计检验表明，骆马湖群体与太湖、高邮湖和洪泽湖群体之间有显著性差异。分子系统树和单倍型网络进化图分析显示，25个单倍型形成2个明显的地理分支，一支由太湖群体、高邮湖群体和洪泽湖群体组成，另一支由骆马湖群体组成。中性检验和错配分布图分析表明，太湖新银鱼历史上发生过群体扩张。整体来看，太湖新银鱼野生种群遗传多样性较低，应加强种质资源保护。建议将太湖、高邮湖群体和洪泽湖群体作为整体进行管理和保护，骆马湖群体单独管理和保护。

英文摘要:

      Neosalanx taihuensis is an icefish endemic to China and mainly distributed in the middle and lower reaches of the Yangtze and Huaihe rivers and affiliated lakes. In recent years, the natural resources of this species have declined markedly. To assess the genetic diversity and genetic structure of wild populations of N. taihuensis, we amplified and sequenced mitochondrial cyt b gene sequences from 144 individuals from four lakes [Tai Lake (TH), Gaoyou Lake (GY), Hongze Lake (HZ) and Luoma Lake (LM)] in Jiangsu Province. The results detected 29 polymorphic nucleotide sites and 25 haplotypes among the cyt b sequences of the 144 individuals. Haplotype diversity was 0.682±0.037, and nucleotide diversity was 0.00231±0.00021. The GY population showed the highest genetic diversity among the four populations and the TH population the lowest. Analysis of molecular variance showed that 71.53% of the molecular variation was among populations and 28.47% was within populations, with the molecular variation originating mainly from interpopulation differences. A pairwise fixation index (Fst) revealed significant differences between the LM population and the TH, GY, and HZ populations, and no significant differences among the TH, GY, and HZ populations. A phylogenetic tree and a minimum spanning network showed that the 25 haplotypes form two distinct geographical clades: one consisting of the TH, GY, and HZ populations, and the other consisting of the LM population. The results of a neutrality test showed that the values of Tajima’s D and Fu’s Fs were negative, and had significant differences. The mismatch distribution was unimodal, which indicated that the four N. taihuensis populations had experienced population expansion. As the genetic diversity of the N. taihuensis populations is low, measures to protect its wild resources are warranted. The TH, GY, and HZ populations should be protected and managed as a whole population and the LM population as a distinct population.