额尔齐斯河与黑龙江流域哲罗鲑群体遗传差异比较

Analysis of Genetic Differentiation for Hucho taimen Populations in the Irtysh and Amur River Basins Based on Mitochondrial DNA Sequencing

由于拦河筑坝、水体污染以及过度捕捞等原因,哲罗鲑(Hucho taimen)野生资源急剧衰退,已被列入中国脊椎动物红色名录,急需开展哲罗鲑野生群体的恢复与保护工作,人工增殖放流已成为最重要的保护方式之一。为了开展科学有效的哲罗鲑人工增殖放流工作,分析其不同来源群体的遗传多样性与遗传差异非常必要。通过测定来自我国额尔齐斯河(IR)、黑龙江(AR)以及人工繁殖(AP,亲本来源于黑龙江流域)的3个哲罗鲑群体线粒体DNA部分序列(COI和D-loop),并从GenBank下载来自俄罗斯鄂毕河(额尔齐斯河下游河流)、黑龙江流域的部分D-loop序列,比较额尔齐斯河与黑龙江流域哲罗鲑的遗传差异。结果表明,在测定的43尾个体中,线粒体DNA测序长度为2 626bp,共检测出37个多态位点,定义了18个单倍型,单倍型多样性为0.520~0.952,核苷酸多样性为0.00032~0.00167,其中IR群体的单倍型多样性最高,AR群体核苷酸多样性最高,而AP群体单倍型与核苷酸多样性均最低。分子方差分析(AMOVA)显示,77.19%的遗传变异来源于群体间,总遗传分化指数(Fst)为0.7719(P<0.01),表明两个流域的哲罗鲑群体间存在显著的遗传分化。无论是仅使用本研究测定的样品,还是加入从GenBank下载的俄罗斯哲罗鲑样品,聚类分析结果均表明存在两个明显的单倍型谱系分支,额尔齐斯河流域哲罗鲑为单独一支,黑龙江流域哲罗鲑聚为另一支。建议加强人工繁殖哲罗鲑的遗传管理和不同水域哲罗鲑增殖放流的遗传学论证,有效维持自然水体哲罗鲑的遗传多样性水平。

Hucho taimen(Pallas,1773)is a carnivorous freshwater fish inhabiting in the Irtysh and Amur River basins in China and is of high economic value.In recent years,wild populations of H.taimen have declined dramatically as a result of river damming,water pollution and overfishing,and it is now on the Red List of China′s Vertebrates.The objectives of this study were to provide data supporting conservation of wild H.taimen populations and technical support for the artificial propagation program in the Irtysh River basin.Partial mitochondrial DNA sequences(COI and D-loop)were characterized for H.taimen populations sampled from Irtysh River(IR),Amur River(AR)and artificially propagated juveniles(AP,parents from Amur River Basin).To compare genetic diversity and differences in H.taimen populations from different areas,D-loop sequences were downloaded from GenBank for H.taimen sampled from Ob River(the lower reaches of the Irtysh River)and Amur River in Russia.A total of 43 H.taimen samples were collected in this study,7 from the IR population,26 from the AP population and 10 from the AR population.The mtDNA sequences of all 43 specimens were successfully sequenced and characterized.The length of the mitochondrial DNA sequence(COI and D-loop)was 2 626 base pairs(bp)and a total of 37 polymorphic sites and 18 different mtDNA haplotypes were identified among the 43 specimens.The number of haplotypes for IR,AR and AP populations was 6,6 and 7,giving respective haplotype diversities of0.952,0.867 and 0.520 and nucleotide diversities of 0.00105,0.00167 and 0.00032.The IR population had the highest haplotype diversity,the AR population had the highest nucleotide diversity,and the AP population had the lowest haplotype and nucleotide diversities.Analysis of molecular variance(AMOVA)indicated that genetic variation among the populations was 77.19% and the genetic differentiation among the H.taimen populations was significant(Fst=0.7719,P<0.01).Phylogenetic analysis also showed that the haplotypes from the Irtysh River basin and Amur River basin lineages had diverged.Thus,the genetic diversity of artificially bred H.taimen should be increased to strengthen the population.