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

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 (N_e) varied from 1.519 to 1.754, average observed heterozygosity (H_o) varied from 0.265 to 0.317, average expected heterozygosity (H_e) 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 F_st, 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.