| Summary: | Dissertation (Ph.D.) University of Alaska Fairbanks, 2022 Fish species found in high latitude waters are especially vulnerable to climatic changes due to their inability to regulate body temperature and long evolution in cold, oxygen-rich aquatic environments. Antarctic notothenioid fishes have evolved to thrive in an extremely stable, cold, oxygen-rich environment. Likewise, lake trout live in a cold, oxygen-rich environment, but commonly experience a wider range of temperatures than notothenioids. Millions of years of evolution in the cold have shaped the genetics of these fishes, but the effects on their biology remain largely unexplored. This dissertation seeks to learn from the past evolution of these two evolutionarily distant types of high latitude fishes to enhance predictions for how these animals can cope with future environmental changes. Specifically, this dissertation examines the genetics of fishes with limited thermal tolerance from the population level down to a single gene. These studies relied on DNA sequence evidence produced with two different technologies and analyzed under functional, phylogenetic, and population genetic frameworks. In the first study, mitochondrial DNA (mtDNA) variation is examined to determine ancestral affinities and geographic distribution of mtDNA variants in lake trout across Alaska. Lake trout in Alaska descend from two distinct mtDNA lineages. One mtDNA lineage is restricted to Arctic Alaska, north of the Brooks Range, while the other lineage is found across Alaska. Lake trout likely dispersed from glacial refugia in western Canada to recolonize Alaska and the movement patterns from recolonization assist in determining how lake trout are likely to move across the landscape in the future. In the second study, genome wide genetic diversity of lake trout in seven Alaskan lakes is explored to determine ancestral affinities and colonization pathways. Despite past movement, the lake trout population currently found in each of the sampled lakes is genetically distinct ...
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