Modelling the future distribution of the amphibian chytrid fungus: the influence of climate and human-associated factors.
Many of the global losses of amphibians are believed to be caused by the chytrid fungus, Batrachochytrium dendrobatidis (Bd). Hence, determining its present and future environmental suitability should help to inform management and surveillance of this pathogen and curtail the amphibian biodiversity crisis. In this issue of Journal of Applied Ecology, Murray etal. (2010) offer an important step in this direction by providing a species distribution model that projects the environmental suitability of Bd across Australia and predicts locations of chytridiomycosis and amphibian declines. Batrachochytrium dendrobatidis presence was predicted by diurnal temperature range (a measure of temperature variability) and mean precipitation. Human population density, a positive predictor of Bd, accounted for the most variation when removed from the statistical model. This work represents an invaluable case study and has great potential for managing chytridiomycosis and associated amphibian declines, but its value in practice will depend on how well managers understand the limitations of species distribution models. Synthesis and applications. To improve the management of chytridiomycosis, amphibian-chytrid research should attempt to understand how humans may affect the distribution of Bd, how climatic means and variances affect Bd transmission, how much variation in the distribution of Bd is unique to and shared among climate, human, and other factors, whether human-related factors and climate statistically interact, and how these potentially correlated factors and any interactions affect the predictability of species distribution models. In response to the swift spread of Bd and our rapidly changing planet, we encourage the application of Bd distribution models to other regions of the globe and predictions of Bd's distribution under future climate change scenarios.