Spatiotemporal infection patterns and interpatch movement in Notopthalmus viridescens populations
Open Access
- Author:
- Lor, Jim
- Graduate Program:
- Ecology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- March 04, 2022
- Committee Members:
- Jason Kaye, Program Head/Chair
David Andrew Miller, Thesis Advisor/Co-Advisor
Julian D Avery, Committee Member
David A Kennedy, Committee Member - Keywords:
- Seasonality
Batrachochytrium dendrobatidis
temperature
host density
infection intensity
infection prevalence
Infectious disease
interpatch movement
Notophthalmus viridescens - Abstract:
- Infectious diseases have been associated with the decline of wildlife populations and the extinction of species worldwide. Amphibians are an especially vulnerable taxa to multiple threats including infectious diseases. Chytridiomycosis is an amphibian disease caused by the fungal pathogen, Batrachochytrium dendrobatidis (Bd), that has a wide host-range with varying impacts on its hosts. Individuals and environmental conditions can vary in time and space. When these dynamics factors interact, they can affect disease risk and result in heterogeneity with disease impact and transmission. This variation occurs at and has consequences for individuals, populations, and species. To improve our understanding of disease dynamics, we examined how host and environmental factors can affect population-level infection patterns and explored how such dynamics can interact with host movement patterns. We investigated how patterns in Bd infections changed spatiotemporally in populations of the adult eastern red-spotted newt, Notophthalmus viridescens, from 2018 to 2021. Using extensive capture-mark-recapture data, we investigated how infection levels (infection prevalence and infection intensity) fluctuated in response to temporal and spatial covariates (i.e., temperature, host density, and hydroperiod) and individual characteristics (i.e., sex and size) in central Pennsylvania, and compared the observed temporal patterns to two other newt populations in Wisconsin and Massachusetts (Chapter 1). Additionally, we examined the connectivity of the Pennsylvanian ponds through adult newt interpatch movements and determined how infection state and movement related to one another (Chapter 2). Our results show that infection levels in adult newt populations vary spatiotemporally and such patterns in infection dynamics can interact with and affect the movements of newts between the ponds. Quadratic relationships between environmental temperature and infection levels were present in all of our study areas and show peak infection levels occurring in early-summer when other species are metamorphosing. This pattern in newt infection dynamics could have larger impacts for more vulnerable species as they expend energy to metamorphose and affect their response to Bd infection. Additionally, larger individuals were more likely to have lower Bd infection intensities compared to smaller individuals, and this result could indicate potential age or size specific immunity or resistance to disease. From our movement and infection analyses, we found that 10% of a pond’s adult newt population made interpatch movements. Even though we observed a trend where infected newts were less likely to move between ponds in a breeding season compared to healthy conspecifics, this connectivity between the ponds suggest that there is potential for disease transmission between different habitats. Still, regardless of starting infection state, newts that moved to a different pond within a breeding season were more likely to have lower infection levels. Our study is one of the first to intensively sample adult N. viridescens populations for spatiotemporal patterns of Bd infections and to investigate the relationship between interpatch movements and Bd infection. We demonstrate that Bd infections are common, persistent, and cyclical in newt populations and that newts have the potential to be a reservoir species that spread Bd through interpatch movements between aquatic habitats.