Genetic diversity of six mud crab(Scylla paramamosain) populations in Beibu Gulf of South China based on ISSR analysis

ISSR-PCR technique was adopted to investigate the genetic variation and genetic structure of six Scylla paramamosain geographic populations(QH,DJ,QZW,LSW,ZZW,and ZK) in the Beibu Gulf of South China.A total of 111 individuals were amplified by 8 ISSR primers,and 66 valid loci were analyzed,of which,56 loci were polymorphic.The percentage of polymorphic loci(PPL) was 84.85% at species level.The PPL of the six populations ranged from 51.52% to 63.64%,with an average of 57.58%.The genetic diversity of the six populations decreased in the order of QH DJ QZW LSW ZZW ZK.The PPL and the Shannon's information index at species or population level showed that the genetic diversity of S.paramamosain arrived at a higher level within the crustacean,but was still lower than that of the other several marine animals of economic importance.The total coefficient of genetic differentiation(GST=0.1841) showed that most of the total genetic variation variance(81.59%) indwelled within populations,suggesting a higher level of genetic differentiation among the populations.However,the coefficient of genetic differentiation(GST=0.0689-0.1276) of pairwise populations suggested the medium-degree genetic differentiation among the populations.The analysis of molecular variance(AMOVA) showed that the genetic variation variance within and among the populations accounted for 87.03% and 12.97%,respectively,suggesting that the genetic differentiation among the populations was at a medium level,but the differentiation was significant(P0.001).The Mantel test suggested that there was no significant correlation between the genetic distance and geographic distance of the six S.paramamosain populations.Clustering analysis showed that the four populations from Guangxi coastal areas could be clustered into a clade.