Doctor of Philosophy
Date of Defense
Dr. Robert Ricklefs
Dr. Patricia Parker
Dr. Nathan Muchhala
Dr. Carlos Botero
This dissertation is broadly focused on elucidating how the geographic structure and demographic changes in host and parasite populations relate to one another, and how such interactions contribute to the generation and maintenance of biological diversity.
I begin by investigating the population structure of the Coereba flaveola (bananaquit) population within Puerto Rico, which is the apparent source of several expansions of the species into the Lesser Antilles. These findings indicate that both island and taxon effects influence the observed demographic changes. Because susceptibility to antagonists is related to both host species-specific characteristics and to geographical location, coevolutionary outcomes of these interactions are suspected to be related to the observed demographic changes. Accordingly, in the second part of this dissertation I investigate an abundant and widespread avian antagonist: avian malaria parasites.
I used contemporary genetic variation of a gene related to host immune evasion to characterize population structure of three mitochondrial lineages of West Indian avian malaria parasites. I found evidence of genetic differentiation in association with a single host genus and among some locations, and evidence of mitochondrial introgression from one lineage into a second lineage. These findings have significant implications for the practice of defining parasite lineages based on mitochondrial genetic variation. Moreover, pairwise comparisons of genetic differentiation illustrate complex patterns of parasite population structure among hosts and locations which are likely influenced by migratory and vector spatial dynamics.
In the final chapter, I return to genetic characteristics of hosts to investigate hemoglobin variation, a component of the host genetic background that has been linked to malaria resistance and tolerance in humans. I assessed genetic variation in αA -globin in C. flaveola populations and tested whether this variation is associated with differences in parasitism. I found no association between αA -globin haplotype and infection by particular parasite lineages among all locations, nor any protective association between globin haplotype frequency and the proportion of individuals infected within populations. However, phylogeographic structure and genetic variation at the αA -globin locus, including a highly variable intron, support it as a locus with potential application in biogeographic analyses.
Humphries, Meghann, "Phylogeographic Relationships of Coereba flaveola and Their Malaria Parasites" (2019). Dissertations. 880.