Loss of allele diversity in introduced populations of the hermaphroditic bay scallop Argopecten irradians

The bay scallop Argopecten irradians is a hermaphroditic bivalve native to the Atlantic coast of the United States that was introduced to China for aquaculture production in 1982. It now supports a major aquaculture industry in China. Introduced species often start with limited genetic variability, which is problematic for the further selective breeding. Bay scallop aquaculture is exclusively hatchery based and as the initial introduction consisted of only 26 scallops, there have been concerns about inbreeding and inbreeding depression in cultured populations in China. In this study, eleven simple sequence repeat (SSR) markers were used to compare genetic variation in cultured populations from China with that in a natural population from the east coast of America. Although the difference in heterozygosity was small, the Chinese populations lost 9 of the 45 alleles (20%) found in the wild population. The reduced allele diversity suggests that the Chinese bay scallop populations experienced a bottleneck in genetic diversity that remains significant despite several recent introductions of new stocks aimed at expanding the gene pool. The loss of allele diversity may affect future efforts in selective breeding and domestication, and results of this study highlight the need for additional introductions, advanced breeding programs that minimize inbreeding and continued genetic monitoring.