Publication Date

2017-05-25

Availability

Embargoed

Embargo Period

2019-05-26

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Biology (Arts and Sciences)

Date of Defense

2017-04-24

First Committee Member

Kevin McCracken

Second Committee Member

William Browne

Third Committee Member

Barbara Whitlock

Fourth Committee Member

Marjorie Oleksiak

Fifth Committee Member

Zachary Cheviron

Abstract

Organisms which reside in high-altitude environments represent ideal species for the study of physiological adaptation, as well as for elucidating the underlying genetic mechanisms associated with such a strong selective constraint (ie. hypoxia). Therefore, the variety of waterfowl species who have independently invaded the altiplano plateaus of the Andean mountains provide crucial representative study organisms in answering such questions. The research encompassed by this dissertation sought to answer questions about [1] the specificity of genetic mechanisms involved in high-altitude adaptation, [2] the potential for evidence of how these molecular adaptations were acquired, either through de novo mutations (convergence, parallel evolution) or collateral evolution through hybridization, and finally [3] to what extent, and at what level, is convergent and/or parallel evolution occurring, all in the context of comparing three different Andean waterfowl species, and their respective high- and low- altitude populations: Speckled teal (Anas flavirostris), Yellow-billed pintail (Anas georgica) and Cinnamon teal (Anas cyanoptera). Given the abundance of research on adaptation to low-oxygen environments, my dissertation takes two different approaches: one that focuses on a priori candidates, and one that takes a genome-wide scan approach. I explored the role of the mitochondrial genome, alpha- and beta- hemoglobin complexes, and the Hypoxia-Inducible Factor (HIF) pathway in the three Andean waterfowl species using target-enrichment datasets, and then looked at overall genomic response to high-altitude adaptation in the Speckled teal, using RAD-seq data. Overall, my dissertation showed a high degree of molecular convergence and parallelism on a number of previously identified genetic mechanisms – more specifically, in hemoglobin and specific HIF-pathway candidates (EPAS1, and EGLN1). Ultimately, I was able to show considerable levels of parallelism not only at the pathway level, but at the gene, exon and even nucleotide/amino-acid level. My dissertation suggests that adaptive molecular evolution is highly predictable, especially for adaptations to high-altitude, low-oxygen environments.

Keywords

hypoxia, adaptation, waterfowl, hemoglobin, HIF pathway, mitochondria

Available for download on Sunday, May 26, 2019

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