Masters Theses
Date of Award
8-2025
Degree Type
Thesis
Degree Name
Master of Science
Major
Wildlife and Fisheries Science
Major Professor
Mark Q. Wilber
Committee Members
Michel E. B. Ohmer, Matthew J. Gray
Abstract
Understanding the conditions that enable pathogens to persist is instrumental for predicting disease dynamics and informing disease management strategies. Persistence results from complex interactions of system-specific traits that are often heterogeneous across the landscape and exhibit seasonal fluctuations. These spatiotemporal variations can profoundly affect the processes involved in pathogen persistence, necessitating the use of a modeling approach that can capture the complex and dynamic nature of such systems. In this paper, we develop a multi-host, seasonal model that can be parameterized using readily available field data to quantify the seasonal drivers of host persistence. Our model quantifies time-varying species contributions to pathogen persistence using the basic reproduction number R0. We parameterized our model using two years of empirical data on the amphibian fungal pathogen Batrachochytrium dendrobatidis (Bd) in eastern Tennessee, where the pathogen persists enzootically. Bd is responsible for worldwide declines in amphibian populations, and understanding how Bd persists has important implications for predicting disease trajectories and informing conservation efforts. We collected data on host abundance, Bd prevalence and intensity, and species spatial overlap throughout the year and used this data to parameterize our model. Using our model, we i) quantified the seasonal contribution of amphibian species to Bd persistence and ii) simulated the effect of removing a host species on community R0 to compare species-specific contribution to persistence among sites. We found that both ecological (abundance and species spatial overlap) and epidemiological traits (Bd prevalence and infection intensity) tended to shift seasonally. Due to these variations, host species-specific maintenance potential (R0) was also seasonally dependent. Moreover, host contributions to persistence differed between communities, with some hosts being dominant maintenance hosts at one site while contributing minimally to persistence at others. Notably, however, eastern newts (Notophthalmus viridescens), when present, demonstrated relatively high, although variable, maintenance potential compared to other species. Broadly, our results demonstrate that maintenance potential is not an intrinsic species characteristic and, instead, is seasonally and spatially dependent, emphasizing the importance of context for pathogen persistence.
Recommended Citation
Schrock, Sarah A., "Who, what, when, & where? Seasonally varying host traits influence persistence of a fungal pathogen in amphibian communities. " Master's Thesis, University of Tennessee, 2025.
https://trace.tennessee.edu/utk_gradthes/14555
Included in
Immunology of Infectious Disease Commons, Other Ecology and Evolutionary Biology Commons