Genetic variability in four wild and two farmed stocks of the Chinese freshwater pearl mussel (Hyriopsis cumingii) estimated by microsatellite DNA markers

The freshwater mussel Hyriopsis cumingii is the most important pearl mussel species in China. However, limited information about its genetic diversity and stock structure is available. We genotyped 119 individuals from two cultured stocks and 240 individuals from four wild stocks from Poyang Lake for eight microsatellite markers to know the genetic status of these stocks. We detected a total of 96 alleles at the eight loci in the six stocks. The four wild stocks showed slightly higher allelic diversity than the two cultured stocks, while the two cultured stocks showed slightly higher degree of inbreeding (f = 0.10–0.11) as compared to the four wild stocks (f = 0.02–0.10). Fst analysis did not detect significant genetic differentiation among the four wild stocks, suggesting the four wild stocks from Poyang Lake could be regarded as one population. Estimation of effective population size (Ne) using the standardized temporal variance in allele frequencies reveled that the Ne of one cultured stock was smaller than that of the wild stock in Poyang Lake. AMOVA revealed that the variation within stocks was 95.82%, whereas the variation among stocks explained only 4.18% of the total variance. Genetic differentiation between cultured and wild stocks was statistically significant. Our data indicate that although the two cultured stocks still contained high allelic and gene diversity, random genetic drift and inbreeding have led to reduction of genetic diversity of farmed stocks and an increase in population differentiation. Measures should be taken to prevent further erosion of genetic diversity. Microsatellites could be used to monitor changes in genetic variation of farmed stocks.