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Genetic diversity from pre-bottleneck to recovery in two sympatric pinniped species in the Northwest Atlantic

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Abstract

Conservation successes of the past several decades provide natural settings to study post-bottleneck evolutionary processes in species undergoing recovery. Here, we study the impact of demographic change on genetic diversity in parallel natural experiments of historical decline and subsequent recovery in two sympatric pinniped species in the Northwest Atlantic, the gray seal (Halichoerus grypus atlantica) and harbor seal (Phoca vitulina concolor). We compare genetic diversity at the mitochondrial control region today to diversity in archaeological specimens, which represent the populations prior to the regional bounties of the late 1800s to mid-1900s that drastically reduced population sizes and led to local extirpations. We further assess genetic diversity throughout recovery, using biological collections from ongoing long-term studies of both species. Overall, the genetic data are consistent with the historical presence of large, genetically diverse populations of pinnipeds prior to human exploitation, and suggest that gray seals were more dramatically impacted by historical bottlenecks than harbor seals in the Northwest Atlantic. Current mitochondrial diversity in both species is relatively high, and we observe little change over the past several decades during a period of roughly parallel rapid population increases. However, there remain large differences in haplotype composition between pinniped populations of pre-exploitation and today, a lasting genetic signature of historical exploitation that is likely to persist into the future.

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Acknowledgements

We thank the following individuals who helped with access to sample archives or ongoing collections: Christine Bubac, Johanne Guerin, Matthew Harnden, Nell den Heyer, Elizabeth Josephson, and Gordon Waring. We also thank Mike Simpkins, Per Palsbøll, Morten Tange Olsen, and an anonymous reviewer for their thoughtful feedback on the manuscript. The import/export of seal samples between Canada and the United States was conducted under NOAA Permit No. 17670-03 (issued to the NMFS Northeast Fisheries Science Center) and authorization from the NOAA National Marine Fisheries Service and Greater Atlantic Regional Fisheries Office (issued to Brian Robinson). Funding for the fieldwork was provided by the Department of Fisheries and Oceans Canada, Natural Sciences and Engineering Research Council of Canada, NOAA Northeast Fisheries Science Center, Northeast Fisheries Observer Program, and the NIH/NIAID Centers of Excellence for Influenza Research and Surveillance (HHSN272201400008C). K.M.C. was supported by a National Science Foundation Postdoctoral Research Fellowship in Biology under Grant No. 1523568. We are grateful to Brian Robinson’s early contributions to the work, through animated discussion, liaising with the Passamaquoddy Tribe, and providing access to his archaeological collections. Brian passed away prior to the completion of this work; we mourn his loss but continue to appreciate his lasting contributions to archaeology in Maine.

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Correspondence to Kristina M. Cammen.

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Cammen, K.M., Vincze, S., Heller, A.S. et al. Genetic diversity from pre-bottleneck to recovery in two sympatric pinniped species in the Northwest Atlantic. Conserv Genet 19, 555–569 (2018). https://doi.org/10.1007/s10592-017-1032-9

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