Appreciating the Importance of Parasites: Analyzing and Understanding the Ecology of Parasite-Host Interactions

Abstract

There is a growing interest in the nature of parasite-host interactions, the role these relationships play in ecological communities, and how human activities alter these associations. Furthermore, because inference about these interactions is usually gained by methods of statistical hypothesis testing, additional importance should be placed on the analysis and interpretation of parasite-host interactions. In this dissertation I address these ideas in three separate but interrelated studies with the three following questions: 1) How do two parasites with complex life-cycles alter the behavior of a novel amphipod host, and how do host and non-host predators respond to infected amphipod prey? In contrast to other studies, I found that two parasites of an endemic amphipod at Montezuma Well had little affect on their amphipod host, and that these associations had little affect on predation rates by both host and non-host predators. Results from this study underscore the importance of further investigating novel parasite-host interactions and placing them in their phylogenetic and evolutionary context. 2) Does human recreation affect spatial patterns of infection in an otherwise natural ecosystem? This study demonstrates that human visitors to Montezuma Castle National Monument alter patterns of waterfowl space use that in turn affect spatial patterns of disease in invertebrate hosts. This is the first study to document such an effect, and I discuss the important implications of this finding. 3) How is hypothesis testing applied in studies of wildlife disease, what conclusions can we make about the relative usefulness of these methodologies, and how can the analysis and interpretation of wildlife disease studies be improved? In this final study I conducted a literature review, computed statistical power for methodologies used in the literature, and re-analyzed published data to provide an example of the advantages of my suggested approach. I conclude that many studies report findings using methods that could be more informative and some studies may lack statistical power, demonstrating the importance of using prospective power analysis in the design of future studies. Furthermore, using statistical techniques that estimate the observed effect size can aid in increasing information transfer in studies of wildlife disease.