Evaluation of genetic diversity by using mitochondrial DNA control region and cytochrome b gene for Squaliobarbus curriculus in Yangtze River and Pearl River | 利用CR和Cyt b基因序列组合评价珠江和长江水系赤眼鳟的遗传多样性

Chinese. 利用PCR技术扩增得到珠江和长江水系共24个赤眼鳟（Squaliobarbus curriculus）个体mtDNA CR和Cyt b基因片段，并测定其序列。对1 345bp的组合序列进行分析，共检测到23个单倍型，22个单突变位点，102个简约信息位点。在139个突变位点中：转换位点100个，颠换位点30个，插入/缺失位点14个；A＋T的含量（61.5%）明显高于C＋G的含量（38.5%）。4个水域个体间的遗传变异率在0～7.43%之间，组合序列的单倍型多样性（H）、平均核苷酸差异数（K±SD）和核苷酸多样性（π）分别为0.977 8、17.271 0和0.029 7，均表现出较高的遗传多样性水平。对4个群体的组合序列进行FST分析，并构建分子系统树和单倍型进化网络关系图。结果表明：不同水系群体间存在显著遗传差异，而同一水系内的不同群体间差异不显著。AMOVA分析表明：梧州、新丰、武汉和宜昌4个群体间显著性的遗传分化主要由不同水系群体间的遗传差异所致，珠江或长江流域内群体间不存在遗传分化，进一步印证了FST的分析结果。珠江和长江水系间的遗传分化主要是因地理隔离导致的生殖隔离，分属“长江群体”或“珠江群体”。但在同一水系内，主要因为赤眼鳟的半洄游习性使得它们之间存在广泛的基因交流，没有出现遗传分化。

English. The mitochondrial CR and Cyt b gene segments of 24 Squaliobarbus curriculus from Yangtze River and Pearl River were amplified by PCR technique and sequenced. Analysis of the 1 345 bp combined mtDNA CR and Cyt b gene sequence showed that there were 23 haplotypes, 22 single-base mutation and 102 parsimony-informative sites. In the 139 variable sites, there were 100 transition sites, 30 transversion sites and 14 insertion/deletion sites. The content of A＋T (61.5%) was much higher than that of C＋G (38.5%). The genetic variation among the 4 populations ranged from 0 to 7.43%. The haplotype diversity (H), mean number of pair-wise differences (K±SD) and nucleotide diversity (π) were 0.977 8, 17.271 0 and 0.002 7, respectively, suggesting high genetic diversity. There were significant genetic differences of FST values between Yangtze River and Pearl River, but there were no genetic differences within the same river. The result of molecular phylogenetic tree constructed by NJ and ML methods and median joining network of 23 haplotypes also supported that point. Analysis of molecular variance (AMOVA) showed that the genetic differentiation among four populations was caused by genetic variation between Yangtze River and Pearl River and no genetic differentiation existed between populations within the same river, which further supported the FST result. The obvious genetic differentiation was mainly attributed to the reproductive isolation caused by the geographical isolation between Yangtze River and Pearl River. But, in the same river system, there was no genetic differentiation between different populations because of wide genetic communication caused by the “semi-immigrations” behavior of S. curriculus.