Genetic population structures among mussels ( Mytilus spp.) across the North Atlantic

An incomplete mussel ( Mytilus complex) distribution map makes it difficult to distinguish between morphologically and genetically similar species. Correspondingly, mussel DNA samples from 15 sites across eastern Canada and Europe were genotyped using a specialized panel of 69 single nucleotide polymorphisms (SNPs). These findings helped delineate Mytilus edulis (Linnaeus, 1758), Mytilus trossulus (Gould, 1850), Mytilus galloprovincialis (Lamarck, 1819), and hybrid zones across the North Atlantic. Notably, all mussels sampled within the Northumberland Strait and the southern half of the Gulf of St. Lawrence were Mytilus edulis, with no signs of M. trossulus introgression. In contrast, there were varying levels of M. edulis, M. trossulus, and hybrids identified along the northern coast of the Gaspé Peninsula, Nova Scotia, and eastern Newfoundland. In Europe, pure populations of M. galloprovincialis and M. edulis were found in Spain and the Netherlands, respectively. Mussels in southern Norway were a mixture of M. edulis and hybrids with M. galloprovincialis and M. trossulus. Altogether, these results are valuable in understanding the population dynamics within current and potential future farming sites. Ecologically, this information also serves as a reliable baseline for future assessments of mussel species distributions that may be altered by climate change or other human activities.