基于Cytb基因序列的江淮下游湖泊鲢群体遗传多样性分析

Genetic diversity analysis of Hypophthalmichthys molitrix populations from freshwater lakes in the lower reaches of Yangtze River and Huaihe River based on Cyt b gene sequences

鲢(Hypophthalmichthys molitrix)是长江、淮河下游湖泊中重要的渔业资源。为了解湖泊鲢种质资源遗传状况,采用线粒体Cyt b基因序列作为分子标记,对江淮下游8个湖泊(太湖、滆湖、长荡湖、淀山湖、高邮湖、洪泽湖、骆马湖、金沙湖)群体的239尾鲢进行扩增和测序。结果显示,鲢Cty b基因全长为1 141 bp, 239条Cyt b序列检出74个变异位点,定义24种单倍型,平均单倍型多样性和核苷酸多样性分别为0.697和0.010 12。太湖群体的单倍型多样性和核苷酸多样性最高,分别为0.830和0.015 84,长荡湖群体的单倍型多样性和核苷酸多样性最低,分别为0.379和0.003 98。8个鲢群体间的遗传距离变幅为0.005~0.015;分子方差分析结果显示,遗传变异主要来自群体内部(98.0%),群体的遗传分化指数Fst值为0.019 97;两两群体间Fst值统计表明,长江水系和淮河水系群体间有显著的遗传差异(P<0.05)。单倍型系统进化树和网络结构图显示,单倍型划分为2个谱系,但没有形成明显的地理聚群。歧点分布曲线与中性检验结果表明,鲢群体进化过程中较为稳定,没有经历过种群扩张事件。研究结果表明,应将长江水系和淮河水系鲢群体作为不同的管理单元进行保护。

Hypophthalmichthys molitrix is widely distributed in freshwater lakes in the lower reaches of the Yangtze River and Huaihe River,and it plays an important role in the aquatic ecosystem.In recent years,the natural resources of H.molitrix have sharply decreased due to multiple adverse reasons.In order to understand its genetic status,the genetic diversity and genetic structure of H.molitrix populations from eight freshwater lakes were investigated using the mitochondrial cytochrome b gene sequence as the genetic marker.The results showed that the full length of Cty b gene sequence was 1141 bp,with 58.3%A+T and 41.7%G+C.A total of 74 variable sites were detected in the Cyt b gene from 239 H.molitrix and 24 haplotypes(Hap1-24)were defined,and the mean haplotype diversity and nucleotide diversity were 0.697 and 0.01012,respectively.Among eight H.molitrix populations,Tai Lake population had the highest haplotype diversity(0.830)and nucleotide diversity(0.01584),and Changdang Lake population had the lowest haplotype diversity(0.379)and nucleotide diversity(0.00398).The genetic distance among eight H.molitrix populations ranged from 0.005 to 0.015.Analysis of molecular variance(AMOVA)showed that the genetic variation mainly originated from within the population,and the value of genetic differentiation index was 0.01997(P>0.05).Pairwise Fst indicated that there were significant genetic differences between Yangtze River and Huaihe River populations(P<0.05).The NJ phylogenetic tree and haplotypes minimum network structure demonstrated that the 24 haplotypes were clustered into two clades,but there was no obvious geographic cluster.The mismatch distribution and neutral test indicated that H.molitrix populations were relatively stable and had not experienced population expansion events.According to research results,H.molitrix populations in the Yangtze River system and Huaihe River system should be protected as different management units.