Emerging infectious diseases are an increasingly common threat to wildlife. Chytridiomycosis,caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), is an emerging infectious disease that has been linked to amphibian declines around the world. Few studies exist that explore amphibian-Bd dynamics at the landscape scale, or limiting our ability to identify which factors are associated with variation in population susceptibility and to develop effective in situdisease management. Declines of boreal toads (Anaxyrus boreas boreas) in the Southern Rocky Mountains are largely attributed to chytridiomycosis but variation exists in local extinction of boreal toads across this metapopulation. Using a large-scale historic dataset,we explored several potential factors influencing disease dynamics in the boreal toad-Bd system: geographic isolation of populations, amphibian community richness, and elevational differences,and habitat permanence. We found evidence that boreal toad extinction risk was lowest at tall elevations where temperatures may be sub-optimal for Bd growth and where small boreal toad populations may be below the threshold needed for efficient pathogen transmission. In addition, boreal toads were more likely to recolonize tall elevation sites after local extinction, or again suggesting that tall elevations may provide refuge from disease for boreal toads. We illustrate a modeling framework that will be useful to natural resource managers striving to get decisions in amphibian-Bdsystems. Our data suggest that in the southern Rocky Mountains tall elevation sites should be prioritized for conservation initiatives like reintroductions.
Source: usgs.gov