Trends in Ranavirus Prevalence Among Plethodontid Salamanders in the Great Smoky Mountains National Park

Emerging pathogens are a potential contributor to global amphibian declines. Ranaviruses, which infect ectothermic vertebrates and are common in aquatic environments, have been implicated in die-offs of at least 72 amphibian species worldwide. Most studies on the subject have focused on pool-breeding amphibians, and infection trends in other amphibian species assemblages have been understudied. Our primary study objective was to evaluate hypotheses explaining ranavirus prevalence within a lungless salamander assemblage (Family Plethodontidae) in the Great Smoky Mountains National Park, USA. We sampled 566 total plethodontid salamanders representing 14 species at five sites over a 6-year period (2007-2012). We identified ranavirus-positive individuals in 11 of the 14 (78.6%) sampled species, with salamanders in the genus Desmognathus having greatest infection prevalence. Overall, we found the greatest support for site elevation and sampling year determining infection prevalence. We detected the greatest number of infections in 2007 with 82.5% of sampled individuals testing positive for ranavirus, which we attribute to record drought during this year. Infection prevalence remained relatively high in low-elevation sites in 2008 and 2009. Neither body condition nor aquatic dependence was a significant predictor of ranavirus prevalence. Overall, our results indicate that life history differences among species play a minor role determining ranavirus prevalence compared to the larger effects of site elevation and yearly fluctuations (likely due to environmental stressors) during sampling years.