鳙长江中下游群体的D-loop序列遗传分析

Population genetic analyses in bighead carp(Hypophthalmichthys nobilis)from the middle and lower reaches of the Yangtze River based on D-loop sequences

为了探究长江中下游鳙的种质遗传现状,该研究收集了石首(SS)、长沙(CS)、瑞昌(RC)、扬州(YZ)和张家港(ZJG)的长江种群(YR,219尾),对其D-loop序列进行检测分析,并结合NCBI下载整理的珠江种群(PR,213尾)和北美种群(NA,33尾)开展比较研究。结果显示,在YR、PR和NA的D-loop序列中分别检测到35、96和11个变异位点,并分别界定37、62和3个单倍型。在长江中下游的5个鳙群体中,单倍型多样性(H_(d))为0.798~0.897,核苷酸多样性(π)为0.00338~0.00653。长江中下游5个鳙群体间,RC与ZJG(F_(ST)=0.012)和CS与YZ(F_(ST)=0.018)的遗传分化不显著,其余群体间均存在显著遗传分化(F_(ST)为0.031~0.125);群体间检测到不同程度的基因流(N_(m)为3.509~39.993)。基于单倍型网络分析,长江中下游的鳙D-loop序列单倍型存在多个分支,并在群体间存在明显的共享;YR和PR的中心单倍型存在广泛共享,PR的特有单倍型均为外围单倍型,并推测NA的形成存在不同的遗传来源。基于中性检验结果,推测PR在历史上经历过种群扩张。研究表明,长江和珠江的鳙种群维持了较高的遗传多样性,可为其种质资源保护和利用奠定物质基础。

Bighead carp(Hypophthalmichthys nobilis)is a common freshwater fish species in China.In order to reveal the genetic status of H.nobilis in the middle and lower reaches of the Yangtze River(YR),219 individuals were collected from five locations respectively in Shishou(SS),Changsha(CS),Ruichang(RC),Yangzhou(YZ)and Zhangjiagang(ZJG).The D-loop sequences were tested and analyzed in comparison with those of H.nobilis from the Pearl River(PR,213 individuals)and Northern America(NA,33 individuals)downloaded from the NCBI.As a result,35,96,and 11 variable sites were observed and 37,62,and 3 haplotypes were defined in YR,PR,and NA,respectively.Among the YR H.nobilis,high haplotype diversity(H_(d),0.798-0.897)and moderate nucleotide diversity(π,0.00338-0.00653)were detected,except the pairwise pairs of RC vs.ZJG(F_(ST)=0.012,P>0.05)and CS vs.YZ(F_(ST)=0.018,P>0.05),significant genetic differentiations(F_(ST)ranged from 0.031 to 0.125,P<0.05)were found among all the other pairwise stock pairs,and gene flows(N_(m)ranged from 3.509 to 39.993)were generally detected within the five stocks.According to the haplotype network analysis,the D-loop haplotypes contained multiple clades which were obviously shared among different stocks in YR.Meanwhile,the central haplotypes of YR and PR populations were generally mutual-shared,whereas the haplotypes specific to PR were peripherally distributed.The haplotypes sharing situation further evidenced the possible multiple introductions of NA.Based on the neutrality test,it was predicted that only PR went through population expansion in history.Overall,the study revealed an abundance of genetic variations in H.nobilis of YR and PR,laying a solid foundation for the further protection and utilization of the relevant genetic resources.