黑龙江流域哲罗鲑的遗传结构分析

Analysis on population genetic structure of taimen(Hucho taimen) in the Heilongjiang River

哲罗鲑(Hucho taimen)是中国土著濒危鱼类,仅黑龙江和新疆存在极小的繁殖群体,本研究利用17对微卫星分子标记对黑龙江流域哲罗鲑4个野生群体的遗传结构现状进行了分析。结果表明,黑龙江流域哲罗鲑野生群体具有中等水平的遗传多样性,其遗传多样性水平与种群数量具有相关性,呈逐年下降的趋势。遗传结构分析表明,群体间遗传分化显著,黑龙江流域哲罗鲑分化为2个遗传类型,HM遗传类型和WSL遗传类型,且WSL类型群体出现了进一步亚分化。黑龙江流域哲罗鲑各群体具有较小的有效群体,造成了各群体较大的近交压力。较小的有效群体主要是由于群体数量的变化及遗传瓶颈造成的。对黑龙江流域哲罗鲑野生群体近期和长期基因流检测发现,各群体间基因流不一致,迁入和迁出率不对称,表现为大群体向小群体流动。以上分析结果表明,环境的变迁、群体数量的下降等已造成黑龙江流域哲罗鲑遗传多样性的降低、遗传结构的分化,并导致了较小的有效群体数量,且对群体间基因流造成了障碍。本研究旨在为制定哲罗鲑的遗传保护措施提供基础科学依据。

As an endangered fish species,Taimen（Hucho taimen） has been recorded in the Red Lists of Threatened species in 1998 in China.To protect and exploit this endangered species effectively,investigations on population structures,resources and artificial reproduction have been conducted.However,seldom study was reported in analysis of population genetic structure using molecular markers.In this study,17 microsatellite markers were used to analyze genetic diversity and structure of 4 populations of Taimen from Heilongjiang River,named Huma population（HM）,Hutou population（HT）,Haiqing population（HQ） and Zhuaji population（ZJ）,separately.Statistical results showed that each population was on a mediate level in genetic diversity,and the genetic diversity level of Taimen had a positive correlation with population size,which presented a declining trend annually.The analysis of population genetic structure showed that there existed remarkable genetic differentiation among the 4 populations.Taimen in Heilongjiang River was divided into two genetic types,HM type and WSL type,and WSL type was further subdivided.The small size of effective population was caused mainly by the changes of population number and the genetic bottleneck,which led to greater inbreeding pressure within populations.Through the examination of recent and long-term gene flows for Taimen in Heilongjiang River,we found that immigratory rate and migratory rate in each population were asymmetrical,and the large population migrated to the small population.The values of recent gene flow were smaller than those of long-term gene flow,indicating that gene exchanges were blocked due to the harsh environments and shrunk population censuses.According to the above mentioned,we thought that the harsh environments and the decreased population number caused the degradation of genetic diversity,the divergence of genetic structure,the occurrence of genetic bottleneck,the small size of effective population and the obstacle of gene flow amongst populations.Overall,Taimen in Heilongjiang River should be preserved comprehensively as an endangered fish species.