Colonization of the northwest Atlantic by the blue mussel, Mytilus trossulus postdates the last glacial maximum
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Blue mussels in the genus Mytilus first arrived in the Atlantic Ocean from the Pacific during the Pliocene, following the opening of the Bering Strait. Repeated periods of glaciation throughout the Pleistocene led to re-isolation of the two ocean basins and the allopatric divergence of Mytilus edulis in the Atlantic and M. trossulus in the Pacific. Mytilus trossulus has subsequently colonized the northwest Atlantic (NW Atlantic) so that the two species are presently sympatric and hybridize throughout much of the Canadian Maritimes and the Gulf of Maine. To estimate when M. trossulus arrived in the NW Atlantic, we have examined sequence variation within a portion of the female mtDNA lineage large untranslated region (F-LUR) for 156 mussels sampled from three Pacific and eleven Atlantic populations of M. trossulus. Although we found no evidence of reciprocal monophyly for Pacific and NW Atlantic M. trossulus, limited gene flow between ocean basins has led to the divergence of unique sequence clades within each ocean basin. In contrast, relative genetic homogeneity indicates high levels of gene flow within each basin. Coalescence-based analysis of the F-LUR sequences suggests that M. trossulus recolonized the NW Atlantic from the northeast Pacific subsequent to a demographic expansion in the Pacific that occurred ~96,000 years before present (ybp). Estimates of timing of divergence for Pacific and NW Atlantic populations and the time since expansion among NW Atlantic sequence clades indicate that M. trossulus arrived in the NW Atlantic more recently, between 20,000 and 46,000 ybp. Given that these estimates overlap with the dates of peak ice in the NW Atlantic during the last glacial maximum (LGM, ~18,000–21,000 ybp), we suggest that colonization of the NW Atlantic by M. trossulus occurred during, but more likely just subsequent to, the LGM and was followed by rapid temporal and spatial expansion in the region.
KeywordsMolecular Clock Hybrid Zone Blue Mussel Demographic Expansion Macoma Balthica
We thank R. Tremblay, B. Konar, D. Heath, A. Mallet, D. Innes, M. Miranda, and C. Langdon for providing samples of blue mussels or blue mussel DNA from populations we could not visit ourselves. A. McGowen provided technical support on this project and C. Riginos provided constructive comments on several earlier drafts. This project was funded by the National Science Foundation (DEB0315891) and the Maine Sea Grant College (R/FMD-279).
- Addison JA, Hart MW (2005) Colonization, dispersal, and hybridization influence phylogeography of north Atlantic sea urchins (Strongylocentrotus droebachiensis). Evol Int J Org Evol 59:532–543Google Scholar
- Cao L, Kenchington E, Zouros E, Rodakis GC (2004) Evidence tha the large noncoding sequence is the main control region of maternally and paternally transmitted mitochondrial genomes of the marine mussel (Mytilus spp.). Genetics 167:835–850. doi: https://doi.org/10.1534/genetics.103.026187 CrossRefGoogle Scholar
- Dawson AG (1992) Ice age earth: late quaternary geology and climate. Routledge, New YorkGoogle Scholar
- Hoffman RJ, Boore JL, Brown WM (1992) A novel mitochondrial genome organization for the blue mussel, Mytilus edulis. Genetics 131:397–412Google Scholar
- Kaufman DS, Ager TA, Anderson NJ, Anderson PM, Andrews JT, Bartlein PJ, Brubaker LB, Coats LL, Cwynar LC, Duvall ML, Dyke AS, Edwards ME, Eisner WR, Gajewski K, Geirsdottir A, Hu FS, Jennings AE, Kaplan MR, Kerwin MW, Lozhkin AV, MacDonald GM, Miller GH, Mock CJ, Oswald WW, Otto-Bliesner BL, Porinchu DF, Ruhland K, Smol JP, Steig EJ, Wolfe BB (2004) Holocene thermal maximum in the western Arctic. Quat Sci Rev 23:529–560. doi: https://doi.org/10.1016/j.quascirev.2003.09.007 CrossRefGoogle Scholar
- Rawson PD, Hayhurst S, VanScoyoc B (2001) Species composition of blue mussel populations in the northeastern Gulf of Maine. J Shellfish Res 20:31–38Google Scholar
- Riser JAM (2001) Quaternary geology and the environment. Praxis Publishing, ChichesterGoogle Scholar
- Rogers AR, Harpending H (1992) Population growth makes waves in the distribution of pairwise genetic differences. Mol Biol Evol 9:552–569Google Scholar
- Schneider S, Roessli D, Excoffier L (2000) Arlequin ver. 2.0. software for population genetic data analysis. Genetics and Biometry Laboratory, University of Geneva, SwitzerlandGoogle Scholar
- Swofford DL (2001) PAUP*: Phylogenetic analysis using parsimony (* and Other Methods), Ver. 4. Sinauer Associates. Massachusetts, SunderlandGoogle Scholar
- Väinölä R, Varvio SL (1989) Biosystematics of Macoma balthica in northwestern Europe. In: Ryland JS, Tyler PA (eds) Reproduction, genetics and distribution of marine organisms. 23rd Eur Mar Bio Symp Olsen & Olsen. Fredensborg, Denmark, pp 309–316Google Scholar