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The structure of genetic diversity in eelgrass (Zostera marina L.) along the North Pacific and Bering Sea coasts of Alaska

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Full Publication: https://doi.org/10.1371/journal.pone.0152701

Product Type: Journal Article
Year: 2016

Authors: Talbot, S. L., G. K. Sage, J. R. Rearick, M. C. Fowler, R. Muñiz-Salazar, B. Baibak, S. Wyllie-Echeverria, A. Cabello-Pasini, and D. H. Ward

Suggested Citation:
Talbot, S. L., G. K. Sage, J. R. Rearick, M. C. Fowler, R. Muñiz-Salazar, B. Baibak, S. Wyllie-Echeverria, A. Cabello-Pasini, and D. H. Ward. 2016. The structure of genetic diversity in eelgrass (Zostera marina L.) along the North Pacific and Bering Sea coasts of Alaska. PLoS One. doi:10.1371/journal.pone.0152701

Abstract


Eelgrass (Zostera marina) populations occupying coastal waters of Alaska are separated by a peninsula and island archipelago into two Large Marine Ecosystems (LMEs). From populations in both LMEs, we characterize genetic diversity, population structure, and polarity in gene flow using nuclear microsatellite fragment and chloroplast and nuclear sequence data. An inverse relationship between genetic diversity and latitude was observed (heterozygosity: R2 = 0.738, P < 0.001; allelic richness: R2 = 0.327, P = 0.047), as was significant genetic partitioning across most sampling sites (Θ = 0.302, P < 0.0001). Variance in allele frequency was significantly partitioned by region only in cases when a population geographically in the Gulf of Alaska LME (Kinzarof Lagoon) was instead included with populations in the Eastern Bering Sea LME (Θp = 0.128–0.172; P < 0.003), suggesting gene flow between the two LMEs in this region. Gene flow among locales was rarely symmetrical, with notable exceptions generally following net coastal ocean current direction. Genetic data failed to support recent proposals that multiple Zostera species (i.e. Z. japonica and Z. angustifolia) are codistributed with Z. marina in Alaska. Comparative analyses also failed to support the hypothesis that eelgrass populations in the North Atlantic derived from eelgrass retained in northeastern Pacific Last Glacial Maximum refugia. These data suggest northeastern Pacific populations are derived from populations expanding northward from temperate populations following climate amelioration at the terminus of the last Pleistocene glaciation.

Keywords: Eelgrass, marine ecosystems, population expansion

Annotation


Eelgrass (Zostera marina) provides valuable habitat for diverse animal assemblages, functioning as an important primary producer and erosion stabilizer in coastal ecosystems. Major declines of eelgrass populations in North America have been attributed to a variety of both human-induced events, such as the release of oil, farming induced eutrophication, and residential expansion, and natural events, such as disease and anoxia. Due in part to the lack of heavy anthropogenic activity along remote areas of the Alaskan coastline (particularly in the western portion), eelgrass populations here have not suffered declines as found elsewhere along the Pacific coast of North America and in more densely populated regions including the Atlantic coast of North America and Europe. However, natural processes will continue to impact high latitude eelgrass populations, and direct or indirect impacts due to localized human activity (e.g., development of boat harbors and oil spills) as well as large scale climate change are expected to increase in high latitude communities in the future.