Document Type

Dissertation

Degree

Doctor of Philosophy

Major

Biology

Date of Defense

5-15-2007

Graduate Advisor

Robert E. Ricklefs, Ph.D.

Committee

Patricia G Parker, PhD

Roberta K Lee, DrPH

Kirk C Klasing, PhD

Abstract

Over the last several decades, interest in quantifying immune function in comparative studies of wild animals has grown appreciably. Now, the field of ecological immunology is undergoing a transition, and ¿second generation¿ studies are being designed and carried out. With a greater appreciation of the complexity of immune systems, these second generation studies are commonly distinguished from their antecedents by making comparisons using multiple assays and including multiple species. I worked to advance this transition by developing novel approaches to comparative immunology, exploring the interrelationships among indices of immune function, and applying multiple indices to a question of comparative avian evolution. First, I worked to develop individual methodologies that would be broadly applicable given the numerous limitations of field-based immunology. I present methodological details on two assays¿a hemolysis-hemagglutination assay and a bacteria killing assay, and I report on intra- and inter-specific comparisons using both. Relatedly, using ten species of waterfowl, I examine how these and other indices correlate at both the individual and species levels. Next, with an interest in developing a better understanding of the evolutionary forces molding immune function, I set out to broadly compare immune function in 15 phylogenetically matched pairs of bird populations from North America and from the islands of Hawaii, Bermuda, and the Gal¿pagos. If immune defenses were costly, populations from relatively disease-free, oceanic islands are expected to exhibit attenuated immune function in response to reduced pathogen and parasite pressure. In fact, many island animals exhibit this postulated ¿island syndrome,¿ one facet of which is increased susceptibility to disease. After employing three protocols to measure eight indices of immune function, I found no support for my hypothesis. Rather than evidence of depauperate parasite communities and inherent costs of immune defenses selecting for reduced immune function, I found that several indices were elevated in island birds. I suggest that life on islands is accompanied by an apparent reorganization of the relative importance of various immune components. Finally, in collaborative efforts with investigators here and at other institutions, I apply the hemolysis-hemagglutination assay to address a variety of questions across three diverse avian study systems.

OCLC Number

527853238

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