Thesis
Resistance Is Not Futile: Fleay’s barred frogs Mixophyes fleayi show low susceptibility to chytridiomycosis in recovered populations
Southern Cross University
Doctor of Philosophy (PhD), Southern Cross University
2023
DOI:
https://doi.org/10.25918/thesis.283
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Abstract
Amphibians are the most imperilled class of animals on the planet. A major contributor to this has been the amphibian disease chytridiomycosis, caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), which spread around the world during the 20th century because of increasing global trade. Following epizootic waves across multiple continents which contributed to the extinction of around 100 species, several species appear to have recovered after often precipitous declines. However, few of these species have been studied extensively to investigate their current response to chytridiomycosis. The purpose of this project was to understand the effects of Bd infection on mortality and to quantify infection dynamics across multiple life stages of a recovering species in the field. I conducted extensive surveys of all life stages of Fleay’s barred frog (Mixophyes fleayi) across three sites. I applied rigorous, bespoke statistical models to assess the effect of Bd infection on mortality. Upon the recognition of imperfect pathogen detection in the Bd sampling protocols, I developed a novel extension to multistate models to propagate this uncertainty into the ecological inference. Chapter 3 reports on a four-year mark-recapture study on adults across three sites, where I show that Bd infection intensity, and not infection status, is an important predictor of mortality, but that populations remain stable despite infections. Chapter 4 details the development of a novel multievent model to account for imperfect pathogen detection, where I show that infection dynamics parameters are severely biased in traditional models. In Chapter 5, I report the findings of a four-month mark-recapture study on juveniles—the first of its kind—where I found that this life stage of M. fleayi is not more vulnerable to chytridiomycosis than adults, in contrast to results reported in previous literature. In Chapter 6, I assessed the seasonal patterns of Bd infections in tadpoles at two independent streams and investigated the effect of infection on mouthpart abnormalities. Finally, the general discussion provides an integrated assessment of the response of M. fleayi to Bd, where I suggest continued persistence is likely and that other recovered species can potentially follow similar trajectories. This project represents a significant contribution to the literature of post-epizootic species recovery. Additionally, the statistical methods presented herein are considered an important methodological advance for improved inference on infection prevalence and dynamics in a wide range of disease systems.
Details
- Title
- Resistance Is Not Futile: Fleay’s barred frogs Mixophyes fleayi show low susceptibility to chytridiomycosis in recovered populations
- Creators
- Matthijs Hollanders
- Contributors
- David A Newell (Supervisor) - Southern Cross UniversityLaura Grogan (Supervisor) - Southern Cross UniversityHamish Ian McCallum (Supervisor) - Southern Cross University
- Awarding Institution
- Southern Cross University; Doctor of Philosophy (PhD)
- Theses
- Doctor of Philosophy (PhD), Southern Cross University
- Publisher
- Southern Cross University
- Number of pages
- xv, 164
- Identifiers
- 991013127013602368
- Copyright
- © 2023 State of NSW and Office of Environment & Heritage
- Academic Unit
- Faculty of Science and Engineering
- Resource Type
- Thesis