缢蛏5个群体遗传多样性和遗传分化的SNP分析

GENETIC DIVERSITY AND GENETIC DIFFERENTIATION ANALYSIS OF SINONOVACULA CONSTRICTA POPULATIONS REVEALED BY SNP MARKERS

利用多态性SNP标记,采用SNaPShot方法分析了缢蛏(Sinonovacula constricta)5个群体(山东东营群体DY、浙江乐清群体YQ、福建云霄群体YX、广东湛江群体ZJ及广西钦州群体QZ)的遗传多样性和遗传结构。结果表明,DY、YQ、YX、ZJ和QZ的平均有效等位基因数(Ne)分别是1.754、1.555、1.558、1.533和1.519;平均香农指数(I)为0.605、0.501、0.502、0.489和0.471;平均观测杂合度(Ho)为0.317、0.282、0.282、0.265和0.285;平均期望杂合度(He)为0.423、0.336、0.338、0.325和0.313;平均最小等位基因频率(MAF)为0.336、0.241、0.238、0.234和0.229;缢蛏5个群体具有较高遗传多样性。STRUCTURE分析显示所有的缢蛏个体可以划分为5个聚类簇,5个群体在每个聚类簇中占比为0.075—0.397,均未聚集到单个聚类簇中;AMOVA分析结果显示,群体间遗传分化系数(Fst)值为–0.0061—0.0829;群体两两之间遗传距离为0.0023—0.0537,Nei’遗传相似度为0.9477—0.9977;UPGMA聚类分析表明乐清群体和云霄群体聚为一支,湛江群体和钦州群体聚为一支,东营群体与其他4个群体遗传距离最远,单独为一支。群体遗传结构分析表明,群体间遗传变异主要来自群体内部,群体间具有较高的遗传相似度和较低的遗传分化,推测缢蛏在养殖过程中频繁的亲贝引种和苗种移养可能是导致群体遗传分化程度不高的主要原因。

In this study,fifteen single nucleotide polymorphisms(SNPs)were used to estimate the genetic diversity and differentiation among the five populations of Sinonovacula constricta(DY:Shandong Dongying population,YQ:Zhejiang Yueqing population,YX:Fujian Yunxiao population,ZJ:Guangdong Zhanjiang population,QZ:Guangxi Qinzhou population)based on SNaPShot method.The average values of effective alleles(Ne)varied from 1.519 to 1.754,average observed heterozygosity(Ho)varied from 0.265 to 0.317,average expected heterozygosity(He)varied from 0.313 to 0.423,average Shannon index varied from 0.471 to 0.605,and average Minor allele frequency(MAF)varied from 0.229 to 0.336,which showed high genetic diversities of the five populations.The optimum K value observed by STRUCTURE program was five.The proportion of the five populations in each of the five clusters ranged from 0.075 to 0.397,and none of the five populations gathered into a single cluster.The pairwise Fst,the genetic identity and the genetic distance ranged from 0.0061 to 0.0829,0.9477 to 0.9977,and 0.0023 to 0.0537,respectively.The UPGMA tree generated from the genetic distance showed the five populations were divided into 2 groups.One group included DY population only,indicating DY population was the farthest away from the other populations in genetic distance.The other group consisted of two clusters,one of which was YQ and YX populations,whereas the other one included ZJ and QZ populations.Our findings revealed the genetic structure of five populations that most of the variation comes from within populations,which is further confirmed by the high genetic identity and the low genetic differentiation of these populations.As a result,frequent introduction of adult clams and juveniles during the culture of S.constricta may be responsible for low genetic differentiation.