Date of Award

6-2014

Degree Name

Doctor of Philosophy

Department

Biological Sciences

First Advisor

Dr. Maarten J. Vonhof

Second Advisor

Dr. Steven L. Kohler

Third Advisor

Dr. Sharon A. Gill

Fourth Advisor

Dr. Jeffrey M. Lotz

Keywords

Trematoda, nematode, community dissimilarity, cestoda, chiroptera, parasite aggregation

Abstract

Parasite abundance and community structure could vary depending on conditions that are both extrinsic and intrinsic to the host. Variation in parasite burden, resulting from heterogeneous exposure to parasites or heterogeneous establishment of parasites in the host, often drives transmission dynamics. Changes in parasite community structure influence parasite species diversity and thus, diversity of infection within a single host or entire host population. I sought to quantify relative roles of exposure and establishment in producing patterns of infection using bats, Eptesicus fuscus, and their helminths. I utilized subsets of data from bats captured in 16 colonies from three states to answer: 1) Are differences in helminth communities among host populations influenced by variation in environmental characteristics or by geographical distance alone? 2) Do male and female bats use different strategies to resist or tolerate helminths? and 3) Is variation in parasite burden among hosts best explained by ecological factors that determine exposure to infective stages or by intrinsic factors that promote parasite establishment within hosts? To accomplish this we recorded sex, age, date, location, body condition, and helminth burden for each bat. I performed three immune assays to determine immunocompetence and assessed host genetic heterozygosity at 11 neutral microsatellite markers. Using a variance partitioning approach, I found that helminth communities did not differ based on geographical distance; rather community composition was significantly associated with anthropogenic disturbance. Thus, human land use could drive significant patterns of parasite community dissimilarity, most likely by changing the presence or abundance of intermediate hosts. Using generalized linear models, I found that individual bats invest in different facets of immunity based on body condition and relative costs of parasite resistance. Thus, host condition regulates trade-offs between self-maintenance and immunity, not sex. Using structural equation modeling, I found that both exposure and establishment play significant roles in creating heterogeneous helminth burdens. By uncovering associations between extrinsic conditions, intrinsic variation, helminth abundance, and parasite community structure I discovered that hostparasite relationships are highly contextual. Thus, we cannot take one-size-fits-all approaches to transmission dynamics and must carefully consider host and worm when predicting helminth burdens or diversity of infection.

Access Setting

Dissertation-Open Access

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