淮河野生鲇鱼线粒体Cytb基因的序列变异与遗传结构分析

Genetic Structure and Variation of Wild Chinese Catfish from Huaihe River Based on Cytochrome b Gene Sequences

本研究利用线粒体DNA细胞色素b(Cyt b)基因序列分析淮河信阳段、淮滨段、蚌埠段、洪泽湖及其支流颍河、淠河和池河的野生鲇鱼(Silurus asotus)种群遗传结构及种群历史。结果表明,在841 bp的同源序列中,7个种群共检测到变异位点40个,占全部序列的4.76%,121个个体共检测到32种单倍型;7个种群的平均单倍型多样性(h)、核甘酸多样性(Pi)分别为0.884 8、0.003 8,表明淮河野生鲇鱼种群的遗传多样性水平较高。7个种群间的遗传分化指数Fst为0.115 0,仅12.92%的变异来自种群间(AMOVA分析),基因交流值为3.85,种群间K2-P遗传距离为0.002～0.009,显示鲇鱼种群间没有发生明显的地理分化。NJ树揭示7个种群的个体组成2个谱系,但这2个谱系与地理分布并不相关。中性检验、错配分析和Network网络亲缘关系分析皆表明鲇鱼种群有过种群扩张,扩张时间约在0.17～0.29百万年前的中更新世中期和末期。

The Chinese Catfish Silurus asotus is a commercially valuable aquacuhure fish in some regions of China and Japan, and it is widely distributed throughout the freshwater reservoirs, lakes and rivers of China. Due to overfishing, environmental pollution, water conservancy, human production activities and other causes, wild Chinese Catfish has declined rapidly. Its fishery resource has been gradually exhausted in the Huaihe River Basin in the past decades. In order to analyze the genetic structure and demographic history of S. asotus, the mitochondrial cytochrome b （Cyt b） gene sequences were used in the study. The results showed that Cyt b gene sequence contained 841 bp nucleotides and the T, C, A and G contents were 28.59% , 29. 55% , 27.44% and 14.42% , respectively. A total of 40 nucleotide sites and 32 haplotypes were obtained from 121 individuals collected in 7 different regions, including Xinyang, Huaibin, Bengbu, Hongze Lake, Yinghe River, Pihe River and Chihe River. The average haplotype diversity （h） and nucleotide diversity （Pi） were 0. 884 8, 0. 003 8,respectively, showing that there was a high level genetic diversity in the populations of S. asotus from Huaihe River basin. The AMOVA analysis （total Fat, =0. 115 0） and the level of Nm values （3.58）, as well as the average K2-P distances （0. 002 -0. 009 ） all revealed that the S. asotus had no obviously geographical differentiation. However, the phylogenetic tree estimated by neighbor-joining （N J） method indicated that the individuals of S. asotus formed two monophyletic lineages, and the two lineages were not correlated with geographical populations. Neutrality tests, mismatch distribution and network analysis suggested that this species underwent population expansion in the middle and late phase of middle Pleistocene following bottlenecks and/or they originated from a small number of founding individuals. The time that the total population of S. asotus expanded in the Huaihe River was estimated to be 0.17 -0.29 million years ago.