Partitioning the influence of host specificity in amphibian populations threatened by multiple emerging infectious diseases

Amphibians face many challenges in their conservation, including threats from emerging infectious pathogens/parasites and habitat degradation. In diverse amphibian communities, where multiple emerging pathogens tend to co-occur, we know little about how the structural partitioning of host specificity impacts population maintenance despite disease. Here, we used field data from amphibian communities in north Florida to investigate host-specific traits influencing the prevalence, intensity, and transmission of three emerging pathogens of amphibians: Batrachochytrium dendrobatidis (Bd), Perkinsea (Pr), and Ranavirus (Rv). We found that Bd exhibited specificity for later developmental stages, and that overall infection patterns differed between ephemeral and semi-permanent sites and across seasons. For each pathogen, we identified key hosts overwhelmingly contributing to community transmission dynamics and found evidence of pathogen interactions that may facilitate Bd-Rv co-infections, and dilution effects of increased host diversity on Pr infection. Our findings confirmed that declining species within the region are routinely infected with emerging pathogens. However, the probability of infection depended on different habitat characteristics and associated host community composition. Thus, our study emphasizes the importance of identifying key and sensitive hosts that drive or succumb to infections in natural communities before reintroducing amphibians into the wild. This approach can help improve conservation efforts in diverse host communities as successful repatriation of sensitive species can benefit from detailed characterization of the established disease dynamics at the release site.