Patterns of (female) mitochondrial DNA diversity were investigated in the blue mussel Mytilus edulis. Mytilus edulis is a ubiquitous member of contemporary North Atlantic hard-substrate communities and well represented in studies of this region. Mytilus edulis was surveyed in North America and Europe, as well as mid-Atlantic sites in Greenland, Iceland, and the Faroe Islands. Mitochondrial DNA sequences revealed considerable population structure but no monophyly of haplotypes between any major regions. Coalescent analyses suggest that migration across the Atlantic Ocean has prominently been from North American source populations and that Greenland was colonized recently and exclusively from North America. In North America, there was support for two regional groups along the North American coastline. Surprisingly, we also found evidence of recombination between some Mytilus edulis and Mytilus galloprovincialis female mtDNA sequences, particularly in northern Europe.
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Acknowledgments We thank the anonymous reviewers and associate editor S. Uthicke along with C. W. Cunningham, P. D. Rawson, and T. Ridgway for comments. D. A. Methven and M. J. Dadswell kindly sent mussel samples. D. Wang, B.Y. Kong, and S. K. Huber assisted in the lab. Part of this work was carried out by using the resources of the Computational Biology Service Unit from Cornell University, which is partially funded by Microsoft Corporation. This project was funded by the Duke University program in Molecular Evolution and Comparative Genomics and the National Science Foundation DEB-0316814 to CR. In addition, this project was supported by funds from Duke University under an award from NSF. The Wndings, opinions, and recommendations expressed therein are those of the authors and are not necessarily those of Duke University or NSF.