西江流域卷口鱼线粒体D-loop序列的遗传多样性分析

Genetic Diversity Analysis of Mitochondrial D-loop Sequence of Ptychidio jordani in Xijiang River Basin

中文关键词: 卷口鱼  D-loop  遗传多样性  遗传分化  西江流域

英文关键词: Ptychidio jordani  D-loop  Genetic diversity  Genetic differentiation  Xijiang River Basin

中文摘要:

      为研究西江流域广西境内卷口鱼(Ptychidio jordani)种群的遗传变异情况，自广西境内6个江段采集了139尾样本，采用PCR与DNA测序技术分析其线粒体D-loop序列的遗传多样性及群体历史动态；139条D-loop序列长度均为725 bp，碱基组成A+T (65.7%)远远高于C+G (34.3%)，共检测到变异位点25个，转颠换比R值为11.5。139尾样本共定义23个单倍型。单倍型的NJ系统树以及网络结构图显示，23个单倍型间有2个明显分支，不同地理群体来源的单倍型混杂分布在2个分支中，未能观察到明显的地理聚群。6个群体遗传多样性较好，单倍型多样性Hd=0.71585~0.92063，核苷酸多样性Pi=0.00173~0.00668，遗传分化极其显著(遗传分化系数Fst=0.36737，P<0.001)。AMOVA分析表明，群体内变异占63.26%，群体间为36.74%。中性检验(Tajima’s D= –0.50322，P=0.34600；Fu’s Fs= –5.05210，P=0.08800)与核苷酸错配分布表明，西江流域卷口鱼种群近期内未经历过种群扩张。综上所述，西江流域广西境内的卷口鱼遗传多样性表现为高单倍型、低核苷酸多样性的特征，群体间不同程度的遗传分化表明水坝阻隔及捕捞因素可能促进其发生，而水利梯级开发可能是促进卷口鱼群体遗传分化的首要原因。

英文摘要:

      To study the genetic diversity and genetic differentiation of a Ptychidio jordani population in the Xijiang River Basin, Guangxi Province, China, mitochondrial D-loop sequences from six rivers were subjected to polymer chain reaction and DNA sequencing analysis. The A+T base composition was much higher (65.7%) than the C+G combination (34.3%) in 139 individuals, which have a D-loop sequence length of 725 bp, and a transversion ratio R of 11.5. Twenty-five polymorphic sites were defined. An NJ system tree of haplotypes and network structure diagram revealed two distinct branches among 23 haplotypes but no obvious geographic clusters, because the haplotypes from different geographic groups were mixed in two branches. Individuals from six different geographic populations had superior genetic diversity (Hd=0.71585~0.92063, Pi=0.00173~0.00668) and extremely significant genetic differentiation (Fst=0.36737, P<0.001). Analysis of molecular variance indicated that most of the variation was intragroup (63.26%). The results of a neutrality test (Tajima’s D= –0.50322, P-value=0.34600; Fu’s Fs= –5.05210, P-value=0.08800) and nucleotide mismatch distribution showed that the population of P. jordani in the Xijiang River Basin had not experienced a population expansion in recent years. The genetic diversity of the P. jordani in the Xijiang River Basin exhibited high haplotype and low nucleotide diversity. Various degrees of genetic differentiation intergroups indicate that a dam barrier and fishing factors may be contributing to their occurrence, and a cascade development of water resources may be the primary cause of population genetic differentiation of P. jordani.