Date of Award

Spring 1-1-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ecology & Evolutionary Biology

First Advisor

Rebecca J. Safran

Second Advisor

Samuel M. Flaxman

Third Advisor

Pieter Johnson

Fourth Advisor

Valerie McKenzie

Fifth Advisor

Jeb Owen

Abstract

Parasites generate strong selective pressures that can shape host physiology, behavior, and evolutionary history. My dissertation research examines how complex interactions among hosts and parasites can shape patterns across spatial scales, from individual-level variation within populations to larger-scale patterns across populations, with emphasis on the association between parasites and evolution by mate-selection, or sexual selection. Sexual traits are used by females in mate-choice decisions to assess male quality and have often been linked to parasites within populations. Yet, broad patterns for links between sexual traits and parasites are unclear, and a unifying framework remains elusive. Thus, I first developed an approach for detecting connections between sexual traits, fitness costs, and the parasite community which I then applied in North American barn swallows, Hirundo rustica erythrogaster. I found that two costly parasites with different life histories were both associated with sexual trait expression. I performed further manipulation experiments with one of these parasites, nest mites, using an experimental technique that I developed. The results of these experiments show that fitness costs were due to size specific immune responses and mortality in nestlings and that a behavioral mechanism, territory settlement and defense, connected male sexual trait expression with parasites. Further, nest mites also influenced parental care in sex specific ways that were dynamic across development. To better understand how parasites may shape patterns of trait divergence among closely related populations, I tested whether adaptation to local parasite communities was tied to sexual trait divergence in the barn swallow species complex. I replicated my study of parasite communities and sexual traits in two additional species of barn swallow, Hirundo rustica rustica in the Czech Republic and Hirundo rustica transitiva in Israel. Within each population, sexual traits provide relevant information to females about local parasites, and associations between traits and parasites were flexible across populations, suggesting that divergent sexual traits are tied to variation in local ecology. Together, these results demonstrate that parasites interact to shape the behavior of their hosts in complex ways and that variation in parasites across closely related groups may play an important role in sexual trait divergence and speciation.

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Parasitology Commons

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