Ecology and applications of cutaneous mechanisms of resistance to amphibian chytridiomycosis

Graduation date: 2014Amphibian biodiversity is in rapid global decline, due in part to the fungal disease chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd). Susceptibility to Bd and chytridiomycosis varies between species and populations. Skin peptides and symbiotic skin bacteria appear to be important mechanisms of Bd resistance. However, not much is known about the ways in which these mechanisms vary between species and locations or about the relative importance of these mechanisms to different amphibian species. This thesis sought to explore the ecology and applications of mechanisms of resistance to Bd. In the second chapter, I use an information theoretic approach to investigate the source of intraspecies and interspecies variation in three measures of predicted resistance against chytridiomycosis: skin peptide inhibition of Bd, skin peptide quantity, and prevalence of Bd-inhibitory bacteria. I collected peptide and bacterial samples from three amphibian species in Mt. Rainier National Park, which is characterized by landscape heterogeneity and low connectivity and hence is likely to produce high variability between amphibian populations in different park regions. I found that skin peptide defenses may vary primarily by species, whereas anti-Bd skin bacteria may vary primarily by location. In the third chapter, I investigate the feasibility of using anti-\ud Bd bacteria to bioaugment an endangered amphibian species, Rana chiricahuensis, against\ud infection with Bd. I screened skin bacterial communities from wild R. chiricahuensis for anti-\ud Bd bacteria and selected Pseudomonas fluorescens as an experimental bioaugmentation agent.\ud I tested P. fluorescens alongside Janthinobacterium lividum in Bd challenges studies with\ud wild adult R. chiricahuensis. Results of these studies do not indicate bioaugmentation with\ud either of these two bacteria as a feasible Bd management strategy for R. chiricahuensis