| Summary: | Global climate change has resulted in geographic range shifts of flora and fauna at a global scale. Extreme environments, like the Arctic, are seeing some of the most pronounced changes. This region covers 14% of the Earth’s land area, and while many arctic species are widespread, understanding ecotypic variation at the genomic level will be important for elucidating how range shifts will affect ecological processes. Increase in shrub cover is a major effect of ongoing climate change in arctic tundra ecosystems. The relative increases in abundance and cover of shrub species such as birch, willow, and alder (Betula, Salix, and Alnus spp.) are predicted to modify ecological communities by altering ecosystem processes and outcompeting other arctic plant species, such as the tussock cottongrass (Eriophorum vaginatum L.). Eriophorum vaginatum is a foundation species of the moist acidic tundra, whose potential decline due to competition from shrubs may affect ecosystem stability in the Arctic. Here, I examine the genomic population structure, local adaption, and genotype-environment associations of two widespread arctic plant species, the tussock cottongrass(Eriophorum vaginatum) and the dwarf birch (Betula nana L.) using thousands of genomic markers obtained from double-digest Restriction-site Associated DNA sequencing (ddRAD-seq). I then compare environmental niche models for both species from the Last Glacial Maximum (LGM) to the year 2070 to examine the potential of range expansion and persistence of each species in a warming arctic. In Chapter 1, genetic variation was identified in 273 individuals of E. vaginatum from 17 sites along a latitudinal gradient in north central Alaska. These 17 sites were selected due to their inclusion in 30+ years of ecological research as well as their location within a region that was part of the Beringian refugium. A genome-wide SNP dataset was used to investigate population structure, genomic diversity, genotype by environment association and environmental niche modeling. A ...
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