Biology ETDs

Publication Date

Fall 12-15-2016


Landscape features, interspecific introgression, and adaptation work in concert to shape the evolutionary history of a clade. Understanding the independent and cumulative consequences of these evolutionary processes on diversification is critical to revealing the origins of extant biodiversity. Studying these processes within rapid radiations, a significant contributor to global biodiversity, can provide powerful insight into the process of diversification. To assess how diversification is shaped by these evolutionary forces, I examined the biogeographic history, patterns of interspecific introgression and adaptation to high elevation in a recent, rapid radiation of finches, the South American siskins (Fringillidae: Spinus). I found that this continental radiation colonized South America from North America and subsequently diversified at an exceptional rate in the high Andes. Further, my results show that sympatric siskin species within the high Andes form a monophyletic clade. I hypothesized that the close proximity of near relatives at high elevation could challenge species limits in Spinus. I investigated this hypothesis using a genome-wide SNP dataset to construct phylogenetic trees and performed formal tests of introgression among high elevation species. I developed an approach for assessing introgression despite persistent phylogenetic uncertainty, and discovered evidence for multiple introgressive events among different high elevation Spinus species. Cold temperatures and decreased partial pressure of oxygen are chronic stressors on organisms living at high elevation. Finally, to understand the consequences of high elevation on adaptive divergence in Spinus , I sequenced all genes which encode the oxygen-transport protein hemoglobin across the Spinus clade and among several populations of a species with a wide elevational range. I identified multiple instances of non-synonymous mutations at the inter- and intra-specific level in both adult and embryonic hemoglobin proteins. These patterns of genetic variation within functionally significant loci across elevation suggest that hemoglobin genes have had a significant impact on adaptation and potentially diversification within the South American siskins.




Fringillidae, Biogeography, hemoglobin, adaptation, Spinus, introgression

Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

Christopher C. Witt

Second Committee Member

Jeffrey C. Long

Third Committee Member

Zachary A. Cheviron

Fourth Committee Member

Michael J. Andersen

Included in

Biology Commons