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Cascades Frogs, Chytrid, and Climate

Amphibians are the most imperiled group of vertebrates on earth, with hundreds of species at risk of extinction. As ectotherms, amphibian body temperature, physiology, and immunity are a function of their environment. Climate can impact amphibian populations directly—temperature and moisture affect amphibian survival and reproduction—or indirectly through effects on disease. Batrachochytrium dendrobatidis (Bd) is an emerging fungal pathogen responsible for the decline or extinction of hundreds of amphibian species. Temperature and moisture affect Bd occurrence, survival, prevalence, infection rate, infection intensity, invasion risk, persistence, growth rate, and disease outcome. However, we know little about how climate and Bd interact to impact long-term amphibian population dynamics. Previous studies have found inconsistent effects of climate variables such as temperature and moisture on Bd outbreaks in amphibian populations. Further, some amphibian species and populations decline or become extinct when exposed to Bd, while others remain relatively unaffected. Developing a framework to understand and predict the impacts of climate and disease on amphibian populations is imperative for the conservation of imperiled amphibian species.

The long-term goal of my research is to understand the complex interactions of climate, disease, and amphibian population dynamics. The overall objective of this proposal is to test hypotheses for how climate-drivers such as temperature and moisture impact Bd’s effect on Cascades frog (Rana cascadae) populations. Cascades frogs have declined due to Bd in some parts of their range while remaining stable in others. We hypothesize that temperature and moisture will be good predictors of disease trends and outbreaks in amphibian populations because both directly affect amphibians and Bd. The rationale for this research is to understand how climate and disease influence amphibian populations to predict population trends under current and future climate conditions and use these predictions to inform conservation and management. We are well prepared to answer these questions because we have existing collaborations with federal, state, and private landowners to monitor several Cascades frog populations and collect demographic, disease, and climate data.

We will investigate our primary hypothesis by examining evidence for three different proposed mechanisms of Bd-climate interactions and their effects on amphibian populations. I will model the interactions of climate, Bd, and frog population trends using long-term datasets from a Cascades frog study system. Our results will be useful for the management and conservation of declining amphibian populations by providing a framework to understand climate-disease interactions and predict amphibian population trends.

Institution: Washington State University 

Lead Researcher: Ryan Wagner

PI: Jonah Piovia-Scott

Collaborators: Karen Pope, Justin Garwood, Bennie Johnson, Matt Reno, Tyler Woollard

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