Mitochondrial Restriction Enzyme Screening and Phylogenetic Relatedness in the Hard Shell Clam Genus 'Mercenaria'. Part 2. Population Variation

摘要

The report focuses on the population genetics and systematics of the hard shell clam Mercenaria, an important aquaculture species, as determined by restriction enzyme digestion of mitochondrial DNA (mtDNA). Fifteen clam populations were sampled along the east and Gulf coasts of the United States and assayed for mitochondrial genotype to determine the extent of geographic differentiation and thus evaluate the suitability of current hard shell clam breeding practices. Evidence based on mtDNA variation indicated that significant genetic differences do not exist between the more northerly populations of M. mercenaria sampled from New Jersey to North Carolina. The results of the clam study are of some note in that clam mtDNA is unique as compared to the majority of higher animals studied to date. It was found that clam populations demonstrate polymorphism in mtDNA size; the mtDNA molecule ranged from 16.5 to 19.0 kilobases in length. In addition, individual clams were often found to be heteroplasmic; i.e., more than one type of mtDNA molecule was found in many individuals.