Mitochondrial-DNA variation in the bay scallop, Argopecten-irradians (Lamarck, 1819), and the Atlantic calico scallop, Argopecten-Gibbus (Linnaeus, 1758)

Restriction site variation of the mitochondrial DNA of Argopecten irradians ssp, was surveyed within four populations from the U.S. Atlantic coast and the Gulf of Mexico. A population from North Carolina was resampled one year after the first collection to provide a measure of temporal variation within a population. Haplotype diversity was high, with 49 haplotypes revealed among a total of 135 bay scallops screened with 8 restriction endonucleases. Nucleotide sequence divergences corrected for within-sample variation among populations ranged from 0.00%, between the temporal samples, to 0.33% between geographically distant populations. Tests for heterogeneity indicated that no two of the geographically separated populations shared a common gene pool. UPGMA cluster analysis based on nucleotide sequence divergences suggested that bay scallops in North Carolina waters are more closely related to those from New England than to those from the Florida Gulf, though only slightly. Two populations of the calico scallop, Argopecten gibbus Dall, from the Atlantic and Gulf coasts of Florida, were sampled and analyzed similarly. In these, haplotype diversity was high, with 6 restriction endonucleases revealing 19 different haplotypes among 51 individuals. Nucleotide sequence divergence between the geographically distant populations was low, however, and a test for heterogeneity was consistent with the null hypothesis of a shared, common gene pool for the two populations. No restriction fragment patterns were common to the bay and calico scallop, reinforcing their classification as separate species