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Westergaard, Kristine Bakke  [1], Fior, Simone  [2], Bruederle, Leo P.  [3], Stenøien, Hans K. [4], Zemp, Niklaus [5], Widmer, Alex [6].

Population genomic evidence reveals multiple North American Pleistocene refugia for Carex scirpoidea (Cyperaceae).

Carex scirpoidea (Cyperaceae) is widely distributed across northern North America, largely within the limits of the Cordilleran and Laurentide ice sheets. As such, Quaternary glaciations have played a major role in shaping distribution and genetic diversity in this species. Dunlop (1990) postulated three Pleistocene refugia for C. scirpoidea; these are: 1) Beringia, 2) unglaciated areas of the Middle and Southern Rockies, and 3) south of the LGM as a periglacial element in eastern North America. Here, we use genomic analyses to examine the phylogeography of Carex scirpoidea in North America, with a goal of shedding light on the Pleistocene refugia for this taxon. Range-wide population sampling and variation at ca. 6000 SNPs provide evidence revealed two divergent evolutionary lineages. In the eastern lineage, populations from East Greenland form one well-defined group, while populations from the Northern Lakes and Forest Ecoregion of Minnesota and Michigan form another. High levels of genetic diversity coupled with few private alleles suggest survival in separate refugia, with postglacial gene flow into eastern North America and western Greenland. A second lineage comprises populations associated with the Boreal and Western Cordillera, extending from Alaska to the Southern Rockies. Within this lineage, populations from Alaska and Yukon form a well-defined group, with moderately high genetic diversity, low population differentiation, and many private alleles, consistent with glacial survival in a large Beringian refugium. These data suggest limited expansion following glaciation into British Columbia, where populations are admixed with a large element of another group consistent with persistence in a cryptic LGM refugium in British Columbia. A highly divergent population from the Southern Rockies of Colorado has low genetic diversity, but over twice as many private alleles as any other population included in this study, consistent with high-elevation refugia in the Southern Rocky Mountains. Collectively, these data reveal a complex recent evolutionary history for C. scirpoidea, involving varying levels of expansion from at least four Pleistocene refugia.

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1 - Norwegian Institute for Nature Research, P.O. Box 5585 Torgarden, Trondheim, NO-7485 , NO
2 - ETH Zurich, Environmental Systems Science, Universitätstrasse 16, Zürich, 8092, CH
3 - University Of Colorado Denver, Integrative Biology, CB 171, Pob 173364, Denver, CO, 80217, United States
4 - NTNU University Museum, Department of Natural History, Erling Skakkes gate 47A, Trondheim, N-7491, NO
5 - ETH Zürich, Genetic Diversity Centre, Universitätstrasse 16, Zürich, 8092, CH
6 - ETH Zurich, Environmental Systems Science, Universitaetstr. 16, CHN G 21.1, Zurich, ZH, 8092, Switzerland

glacial refugia.

Presentation Type: Oral Paper
Session: 4, Biogeography
Location: 105/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 11:15 AM
Number: 4013
Abstract ID:839
Candidate for Awards:None

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