MEPS prepress abstract  -  DOI:

Mitochondrial DNA sequence data reveal the origins of postglacial marine macroalgal flora in the Northwest Atlantic

Trevor T. Bringloe*, Gary W. Saunders


ABSTRACT: Following the Last Glacial Maximum, marine macroalgal flora in the Northwest Atlantic reportedly recolonized from Northeastern refugia. Genetic evidence for the few species tested, however, has indicated that some species survived glaciation in the Northwest Atlantic. Owing to the significant amount of data currently available, we sought to determine if COI-5P (5’ end of the cytochrome c oxidase subunit I gene) could distinguish between populations surviving glaciation on both sides of the Atlantic versus postglacial recolonization. COI-5P results were consistent with published findings using other markers in Chondrus crispus, Mastocarpus stellatus, Palmaria palmata, and Saccharina latissima. Having success, we then analysed molecular data for several species of red and brown macroalgae to date isolation times between Northeast and Northwest Atlantic populations and determine what percentage of species survived in Northwest Atlantic refugia. We generated and gathered genetic data from COI-5P in 1560 specimens representing 20 amphi-Atlantic species, and estimated isolation times between Northeast and Northwest populations using calibrated red and brown COI-5P clocks in IMa2. Sixty percent of the species surveyed had isolation time estimates between Northeast and Northwest Atlantic populations predating the Last Glacial Maximum. Recent shared ancestry was inferred in the remaining cases. Our results indicate local refugia and/or trans-Arctic migration from the Pacific are the source populations for the majority of the Northwest Atlantic macroalgal flora. By shedding light on the phylogeographic history of the North Atlantic we can better understand the nature of postglacial recolonization and forecast future changes to the Northwest Atlantic and Canadian Arctic.