基于CO I和Cyt b序列的丹江口水库鲢群体遗传结构分析

Genetic Structure Analysis of Hypophthalmichthys molitrix Populations in Danjiangkou Reservoir Based on Mitochondrial CO I and Cyt b Sequences

有效的人工增殖放流应监控放流群体和野生群体的遗传结构特征,以避免放流群体对天然群体遗传多样性的负面影响。基于线粒体CO I和Cyt b基因,分析了丹江口库区鲢(Hypophthalmichthys molitrix)、丹江口鱼类增殖站鲢亲本和鲢子代3个群体的遗传结构特征。结果显示,104条646 bp线粒体CO I序列中共检测到多态位点15个,简约信息位点5个,单一变异位点10个,定义了7个单倍型,单倍型多样性为0.544~0.676,核苷酸多样性为0.00221~0.00254;103条1 058 bp线粒体Cyt b序列中共检测到多态位点19个,简约信息位点13个,单一变异位点6个,定义了14个单倍型,单倍型多样性为0.609~0.714,核苷酸多样性为0.00262~0.00424,总体上处于较高单倍型多样性和较低核苷酸多样性。CO I和Cyt b序列遗传距离、遗传分化指数以及基因流分析显示,群体间遗传距离为0.002(CO I)、0.003~0.004(Cyt b),总遗传分化指数为-0.00468(P>0.05)(CO I)、0.03180(P>0.05)(Cyt b),差异均不显著;群体间基因流为14.69~41.47(CO I)、5.49~40.47(Cyt b),AMOVA分子方差分析表明,遗传变异主要来自群体内。单倍型聚类关系表明,3个鲢群体间均存在共享单倍型,不同地理群体间单倍型散乱分布于各支,未形成地理群体聚集。研究表明,3个鲢群体间不存在明显的遗传分化,增殖放流鲢群体与丹江口库区野生群体的遗传多样性和遗传结构相近,可开展增殖放流。研究结果可为丹江口鱼类增殖站鲢群体的增殖放流提供科学依据。

Danjiangkou reservoir is an important source area for the middle route of the South-to-North Water Diversion Project and an important germplasm bank for wild Hypophthalmichthys molitrix.In recent years,captive breeding and release of H.molitrix in Danjiangkou reservoir has been carried out many times to supplement wild populations.Effective artificial breeding and release should monitor the genetic characteristics of both released and wild populations so that the released fish do not reduce the genetic diversity of natural populations.In this study,we analyzed the genetic structure of three H.molitrix populations(Lian QB,Lian-ZD,Lian-KQ)in Danjiangkou reservoir,based on mitochondrial CO I and Cyt b gene amplification of the three populations.We aimed to understand the genetic status of wild H.molitrix populations and evaluate the effect of released fish on wild populations in the reservoir area.The results also provide scientific evidence for the rational exploitation of fishery resources and conservation of the aquatic ecological environment in the Danjiangkou reservoir area.A total of 104 specimens from the three H.molitrix populations were selected for the study.A total of 104 CO I sequences and 103 Cyt b sequences were obtained through gene amplification,with lengths of 646 bp and 1058 bp,respectively.All CO I sequences contained 15 polymorphic sites,5 parsimony information sites and 10 single variant sites that defined 7 haplotypes.The haplotype diversity was 0.544-0.676 and the nucleotide diversity was 0.00221-0.00254.A total of 19 polymorphic sites,13 parsimony information sites and 6 single variant sites were identified in the 103 Cyt b sequences,defining 14 haplotypes.The haplotype diversity was 0.609-0.714 and the nucleotide diversity was 0.00262-0.00424.The CO I and Cyt b genes both presented a high haplotype diversity level and a low nucleotide diversity level.Genetic distance between the three populations was 0.002 for CO I gene and 0.003-0.004 for Cyt b gene,and the total genetic differentiation index(Fst)was-0.00468 for CO I gene(P>0.05)(CO I)and 0.03180 for Cyt b gene(P>0.05),indicating that there was no significant genetic differentiation among the three H.molitrix populations.Genetic flow between the populations was 14.69-41.47(CO I)and 5.49-40.47(Cyt b),respectively.AMOVA analysis shows that the genetic variation of the populations primarily occurred within the population.Cluster analysis of the three populations was carried out based on the haplotype and results show that there were shared haplotypes among the three H.molitrix populations,and the haplotypes were scattered among the branches of different geographic populations,and no geographic clusters were formed.In a word,there was no obvious genetic differentiation among the three H.molitrix populations,indicating that the released silver carps had no adverse impact on the genetic diversity and genetic structure of the wild population in the Danjiangkou reservoir area.