Species composition of blue mussel populations in the northeastern Gulf of Maine

摘要

We examined the species composition of eleven blue mussel populations in eastern and central Maine, USA using a set of PCR-based genetic markers. Previous reports suggested that mussel populations in the Gulf of Maine were composed of only a singlespecies, Mytilus edulis. In contrast, our results clearly indicate that the range of a congener, M. trossulus, extends well into the Gulf. The two blue mussels are sympatric in eastern Maine populations, including all of those we sampled within CobscookBay, ME. The frequency of M. trossulus, however, declines dramatically in the vicinity of Little Machias Bay, ME, so that populations along the coast of central Maine are composed predominantly of M. edulis mussels. Among populations containing a mixtureof M. edulis and M. trossulus-specific alleles we observed a low but significant frequency of mussels with hybrid genotypes including putative backcross genotypes, indicating the potential for introgression between these two species. We suggest that larval supply and recruitment, thermal tolerance and perhaps the interplay of these factors likely delimit the southern extent of the range of M. trossulus and influence the species composition of blue mussel populations in the northwest Atlantic.