Microsatellite genetic variation between and within wild and cultured pearl oyster Pteria penguin populations

Five polymorphic microsatellite markers were developed for  Pteria penguin  by mining microsatellite sequences in GenBank, and used to evaluate the genetic structure and relativeness of 3 wild (ZW, LW and SW) and 2 cultured Pteria penguin populations (ZC, LC) from Zhanjiang, Guangdong and Lingshui & Sanya, Hainan. These five loci were all in Hardy-Weinberg Equilibrium in the 3 wild populations, but one each deviated in the two cultured populations ( Ppen9 at ZC, and Ppen12 at LC). Comparing to 3 wild populations (5.6/4.9 for SW, 3.6/3.4 for LW, and 6.0/4.8 for ZW), the average number of alleles and allele richness were significantly decreased in the two cultured populations (2.4/2.1 for LC and 3.2/3.1 for ZC); and the average observed and expected heterozygosity (0.16-0.35/0.30-0.48) were also lower than those of the wild populations (0.40-0.45/0.53-0.65). Average inbreeding coefficient F IS of cultured populations (0.28 for LC, and 0.17 for ZC) were significantly higher than that of wild populations (0.00 for SW to 0.12 for ZW). Population SW shows the highest genetic diversity, and relatively large genetic distances to all the other four populations, while the genetic distances between two cultured populations, and ZW were the smallest, which verified that the cultured P. penguin cohurts in Lingshui and Zhanjiang were derived from the wild-caught parents in Zhanjiang hatchery. The genetic differentiation between wild populations LW and ZW was significantly lower than that between LW and SW, possibly due to the persistent introduction of artificial seeds form Zhanjiang to Lingshui in recent years, which may cause extra gene flow from Zhanjiang to Lingshui and consequently affect the wild population genetic structure in Lingshui. The results highlighted the urgency of genetically testing and controlling the artificial mating system of P. penguin , and of monitoring the genetic structure of natural population, especially in the sea area to where the translocation seeds were constantly introduced.