基于COI序列的长江中上游鲢6个地理群体遗传多样性分析

为了对长江中上游鲢(Hypophthalmichthys molitrix)种质资源现状进行监测和评价,本研究利用线粒体细胞色素C氧化酶I(cytochrome c oxidase subunit I)基因(COI)对长江中上游宜宾、忠县、万州、石首、监利、湘江6个鲢群体进行了遗传多样性分析。结果表明,在648 bp的COI序列中共检测到42个变异位点,其中单变异位点14个,简约信息位点28个。6个群体123个个体共定义了26个单倍型,单倍型多样性为0.0476~0.0945,核苷酸多样性为0.00196~0.00982。6个鲢群体总体遗传多样性丰富,万州群体单倍型多样性和核苷酸多样性均最高,忠县群体单倍型多样性最低,核苷酸多样性最低的为石首群体。遗传变异主要来自群体内个体间,单倍型网络图和系统进化树显示各群体的单倍型没有形成明显的地理格局。此外,上游宜宾群体和万州群体与中游的石首、监利和湘江群体具有明显的遗传分化,中游的监利群体与石首群体和湘江群体也有一定的遗传分化,上游群体和中游群体应该分属于长江水系两个不同的种群。

Genetic diversity of six silver carp (Hypophthalmichthys molitrix) geographical populations based on mitochondrial COI sequences

The silver carp (Hypophthalmichthys molitrix), one of the four major Chinese carps, is widely distributed in the Yangtze, Pearl, and Heilongjiang River Basins of China. The wild silver carp populations in the Yangtze River, with an excellent production performance, is an important germplasm resource for artificial farming and breeding. Because of overfishing, habitat fragmentation, and water pollution, the natural carp populations have been continuously declining in recent years. The basic genetic background analysis of the silver carp would be theoretically and practically important for the conservation of germplasm resources and genetic improvement. In this study, mitochondrial cytochrome C oxidase subunit I gene (COI) was sequenced to determine the genetic diversity and variation of six geographical silver carp populations:Yibin, Zhongxian, Wanzhou, Shishou, Jianli, and Xiangjiang. The amplified fragment was 648 bp in length, and a total of 26 haplotypes were defined among 123 sequences of COI from the six silver carp populations. The haplotype and nucleotide diversity index of the six populations ranged from 0.0476 to 0.0945, and from 0.00196 to 0.00982, respectively. The six groups exhibited a high genetic diversity, of which the Wanzhou population showed the highest haplotype and nucleotide diversities; the lowest haplotype and nucleotide diversities were observed in the Zhongxian and Shishou populations, respectively. The molecular variance (AMOVA) analysis showed that the variation within populations (accounting for 88.72%) was the main source of variation, and only 11.28% of the variation was found among the groups. The haplotype network was radial, centering on the main haplotype. The neighbor-joining phylogenetic tree of haplotypes based on genetic distances were inconsistent with their geographical distances. According to the differentiation index (Fst) between populations of H. molitrix, there were high differences between the Yinbin, Wanzhou, and 3 populations from the middle reach (P < 0.05); meanwhile, the Jianli population showed a significant differentiation from the Shishou and Xiangjiang populations (P < 0.01). The results revealed that the upper-and middle-reach populations should have originated from different populations in the Yangtze River. This study could provide useful basic data for the scientific protection, and reasonable and sustainable utilization of this germplasm resource in the Yangtze River Basin.