基于线粒体Cyt b基因的虾夷扇贝群体遗传结构分析

本研究利用线粒体细胞色素b(Cyt b)基因标记对虾夷扇贝(Patinopecten yessoensis)6个群体(长岛底播增殖群、海洋岛底播增殖群、獐子岛底播增殖群、旅顺自然群、"獐子红"人工选育群以及日本青森陆奥湾群)进行种质状况评估,研究结果表明,6个群体120个个体的Cyt b基因序列共检测到20种单倍型,其中"獐子红"人工选育群单倍型最少,日本群体单倍型最为丰富,两者单倍型多样性指数分别为0.10000和0.88400。分子方差分析(AMOVA)发现,日本群体与中国群体间变异百分比为15.34%,明显高于作为一个基因池时群体间遗传变异水平;就中国组群而言,其83.41%的遗传变异来自于群体内部,组内群体间的变异只占1.52%,说明中国群体个体间的遗传变异远大于群体间的遗传变异。F_(st)分析显示,中国群体与日本群体之间发生了中等水平的遗传分化(0.07455~0.17895,Fst0.05)。以遗传距离矩阵构建群体间分子系统树(UPGMA树),拓扑结构图显示中国5个群体先聚为一支,再与日本群体聚为一支。由此可见,中国养殖区的虾夷扇贝与日本原产地群体间已出现明显的遗传分化,且虾夷扇贝中国群体的遗传多样性处于较低水平。本研究结果可为虾夷扇贝的种质资源保护与可持续开发利用提供理论依据。

Population-genetics analysis of the Japanese scallop Patinopecten yessoensis based on mitochondrial Cyt b gene

The introduced Japanese scallop Patinopecten yessoensis has been farmed in China, primarily along the coasts of the Bohai Sea and the North Yellow Sea, since the 1980s. Following the adaptation and localization ofP. yessoensis in China, specific problems have appeared after several decades of aquafarming: especially low sur-vival and slower grow. This can be associated with an effectively small population that experiences inbreeding, eventually leading to unknown degrees of decline in its genetic diversity after several generations. Consequently, it is important to carry out genetic diversity research onP. yessoensis in its main mariculture area of China. In this study, mitochondrial cytochrome-b (Cytb) gene-sequencing techniques were used to determine genetic diversity and variations among six stocks ofP. yessoensis:the bottom-sowing cultured stocks of Changdao, Haiyangdao and Zhangzidao; the natural stocks of Lüshun and Japan; and the artificial selected stock of Zhangzihong. A total of 20 haplotypes were found among 120 sequences of Cytb gene from the six stocks ofP. yessoensis. The minimum number of haplotypes was found in the Zhangzihong artificial breeding stock, and the maximum number occurred in the Japan Aomori Mutsu Bay stock, with a haplotype diversity (Hd) of 0.10000 and 0.88400, respectively. Analysis of molecular variance (AMOVA) showed the percentage of variation between the Japan and China groups was 15.34%, which was significantly higher than when measured as one genetic pool. For the China group, 83.41% of the genetic variation come from within the stocks, and only 1.52% of the variation was among the stocks in the group, indicating that genetic variation between individuals of the China group was higher than be-tween the stocks.Fst analysis showed a moderate level of genetic variance among the Japan stock and China stocks (0.07455?0.17895,Fst>0.05). The genetic distance between the six stocks ofP. yessoensis was calculated based on the Tamura-Nei model; the maximum genetic distance was found between the Japan Aomori Mutsu Bay stock and the Haiyangdao bottom-sowing cultured stock; the minimum genetic distance was found between the Zhangzidao bottom-sowing cultured stock and the Zhangzihong artificial breeding stock. The UPGMA method was used to construct a phylogenetic tree based on genetic distances among the six stocks ofP. yessoensis; the tree shows that the five China stocks clustered into a genetic branch, and then these clustered together with the Japan group. These results demonstrate obvious genetic differentiation between the China stocks and the Japan stock of this scallop. Moreover, genetic diversity was lower in theP. yessoensis China stocks as compared with the Japanese stock. The findings of this study could be usefully applied to scientific strategies for the protection, sustainable development and commercial utilization of scallop germplasm resources.