Genetic structure and diversity of Crassostrea gigas in Korea revealed from microsatellite markers

The Pacific oyster, Crassostrea gigas, is the main oyster species cultivated in Korea. Despite a long history of hatchery practices, little is known about the population genetics of native populations of C. gigas in Korea. This study examined the population structure and genetic diversity of 297 individuals of C. gigas in six populations, representing two major geographically separated habitats along the coast of Korea, using multiplex assays with nine highly polymorphic loci. All populations showed very high genetic diversity, with a deficit of heterozygotes and a recent bottleneck. No significant differences were found in the genetic diversity of the two geographically separated oyster groups, although significant, but minimal, genetic differentiation was observed (FST = 0.003, p = 0.002). This was mainly due to genetic differences between the oyster populations from Taean and Gaduk, suggesting that the oyster is not panmictic. This result was corroborated by an analysis of molecular variance (AMOVA) and multidimensional scaling analysis. It was inconsistent with a previous finding of no population differentiation using mitochondrial sequence analysis, implying rather recent separation of the two geographic populations. This genetic differentiation might have resulted from the combined of various factors, such as historical dispersal, the local environment, and ocean currents. Nonetheless, these results mean that the two geographical groups should be treated as independent units for proper resource management. Our results provide critical information on the ecological and economic potential of the Korean Pacific oyster.