Reintroduction of resistant frogs facilitates landscape-scale recovery in the presence of a lethal fungal disease

Abstract

Vast alteration of the biosphere by humans is causing a sixth mass extinction, driven in part by an increase in infectious diseases. The emergence of the lethal fungal pathogen Batrachochytrium dendrobatidis (Bd) has devastated global amphibian biodiversity. Given the lack of any broadly applicable methods to reverse these impacts, the future of many amphibians appears grim. The Sierra Nevada yellow-legged frog (Rana sierrae) is highly susceptible to Bd infection and most R. sierrae populations are extirpated following disease outbreaks. However, some populations persist and eventually recover, and frogs in these recovering populations have increased resistance against infection. Here, we conduct a 15-year reintroduction study and show that frogs collected from recovering populations and reintroduced to vacant habitats can reestablish populations despite the presence of Bd. In addition, the likelihood of establishment is influenced by site, cohort, and frog attributes. Results from viability modeling suggest that many reintroduced populations have a low probability of extinction over 50 years. These results provide a rare example of how reintroduction of resistant individuals can allow the landscape-scale recovery of disease-impacted species, and have broad implications for amphibians and other taxa that are threatened with extinction by novel pathogens.

The pathogen Batrachochytrium dendrobatidis (Bd) has devastated amphibian biodiversity, and methods to reverse these impacts are lacking. This study shows that frogs collected from recovering populations and reintroduced to vacant habitats can reestablish populations despite the presence of Bd.