Temporal effects on the abundance of lethal fungal pathogens of amphibians

Fungal pathogens greatly threaten amphibian diversity, bringing many species near extinction. Consequently, informing on the abundance and ecological characteristics of fungal pathogens, such as Batrachochytrium dendrobatidis (Bd), through tools such as mathematical models is of the utmost importance with respect to current conservation efforts. While traditional mathematical models, such as the logistic growth model, can infer basic details on Bd abundance, the model’s simplistic nature renders it unable to account for myriad external factors. So, to inform on some of these factors, namely temporal fluctuations in the Bd growth rate, and carrying capacity, we extended the logistic growth model to consider combinations of time-varying coefficients. For our new models, we estimated model parameters from publicly available data on Bd zoospore density across multiple temperature ranges and geographies, assessing the quality of model fit relative to complexity by Akaike Information Criterion, and Akaike weights, in addition to characterizing potential long-term behaviors through stability analysis. Our work shows that our time-varying growth rate and carrying capacity model was at least 1.4 times more likely to reflect Bd abundance at optimal temperature ranges. This suggests a multi-pronged approach for hindering Bd, namely at non-optimal temperatures, conservation efforts such as tadpole removal and water disinfection should be utilized consistently, and at optimal temperatures, they should be timed to when they generate the greatest benefit with respect to the elimination of Bd zoospores.