title: Temperature alters reproductive life history patterns in Batrachochytrium dendrobatidis, a lethal pathogen associated with the global loss of amphibians.
abstract: Understanding how pathogens respond to changing environmental conditions is a central challenge in disease ecology. The environmentally sensitive fungal pathogen Batrachochytrium dendrobatidis (Bd), which causes the amphibian disease chytridiomycosis, has spread globally causing amphibian extirpations in a wide variety of climatic regions. To gain an in-depth understanding of Bd's responses to temperature, we used an integrative approach, combining empirical laboratory experiments with mathematical modeling. First, we selected a single Bd isolate and serially propagated two lineages of the isolate for multiple generations in two stable thermal conditions: 4°C (cold-adapted lineage) and 23°C (warm-adapted lineage). We quantified the production of infectious zoospores (fecundity), the timing of zoospore release, and zoospore activity in reciprocal temperature transplant experiments in which both Bd lineages were grown in either high or low temperature conditions. We then developed population growth models for the Bd lineages under each set of temperature conditions. We found that Bd had lower population growth rates, but longer periods of zoospore activity in the low temperature treatment (4°C) compared to the high temperature treatment (23°C). This effect was more pronounced in Bd lineages that were propagated in the low temperature treatment (4°C), suggesting a shift in Bd's response to low temperature conditions. Our results provide novel insights into the mechanisms by which Bd can thrive in a wide variety of temperature conditions, potentially altering the dynamics of chytridiomycosis and thus, the propensity for Bd to cause amphibian population collapse. We also suggest that the adaptive responses of Bd to thermal conditions warrant further investigation, especially in the face of global climate change.
authors.affiliation: Department of Environmental Science, Policy and Management, University of California- Berkeley Berkeley, California, 94720-3144, USA ; School of Public Health, Tropical Medicine and Rehabilitation Sciences, Amphibian Disease Ecology Group, James Cook University Townsville, Queensland, 4811, Australia.
authors.forename: Jamie
authors.initials: J
authors.lastname: Voyles
authors.forename: Leah R
authors.initials: LR
authors.lastname: Johnson
authors.forename: Cheryl J
authors.initials: CJ
authors.lastname: Briggs
authors.forename: Scott D
authors.initials: SD
authors.lastname: Cashins
authors.forename: Ross A
authors.initials: RA
authors.lastname: Alford
authors.forename: Lee
authors.initials: L
authors.lastname: Berger
authors.forename: Lee F
authors.initials: LF
authors.lastname: Skerratt
authors.forename: Rick
authors.initials: R
authors.lastname: Speare
authors.forename: Erica Bree
authors.initials: EB
authors.lastname: Rosenblum
keywords: Amphibian declines; Batrachochytrium dendrobatidis; chytridiomycosis; climate change; emerging infectious disease; temperature