Reintroduction of Resistant Frogs Facilitates Landscape-Scale Recovery in the Presence of a Lethal Fungal Disease

Introduction

The emergence of the lethal fungal disease chytridiomycosis has caused widespread declines and extinctions of amphibians worldwide. The disease, caused by the fungus Batrachochytrium dendrobatidis (Bd), infects the skin of amphibians, leading to electrolyte imbalance and death. One species that has been particularly hard hit by chytridiomycosis is the mountain yellow-legged frog (Rana muscosa), which has experienced population declines of over 90% in the Sierra Nevada mountains of California.

In an effort to combat the effects of chytridiomycosis, scientists have been working to reintroduce Bd-resistant mountain yellow-legged frogs into affected areas. One such reintroduction effort was conducted in Yosemite National Park in 2014. The results of this reintroduction have been promising, with the reintroduced frogs showing high survival rates and establishing new populations.

Methods

The reintroduction effort in Yosemite National Park involved the release of over 1,000 Bd-resistant mountain yellow-legged frogs into two high-elevation lakes. The frogs were collected from a population in the Sierra Nevada mountains that had shown resistance to chytridiomycosis. The frogs were released into the lakes in the spring and summer of 2014.

To monitor the success of the reintroduction, scientists conducted surveys of the frog populations in the lakes. The surveys were conducted annually from 2014 to 2018. The scientists counted the number of frogs in the lakes and assessed their health. They also collected water samples to test for the presence of Bd.

Results

The results of the surveys showed that the reintroduced frogs were surviving and establishing new populations in the lakes. The frogs were found to be healthy and free of Bd infection. The water samples collected from the lakes also tested negative for Bd.

In addition to the surveys, the scientists also conducted genetic analysis of the reintroduced frogs. The analysis showed that the frogs were successfully reproducing and that the new populations were genetically diverse.

Discussion

The results of the reintroduction effort in Yosemite National Park are promising and suggest that the reintroduction of Bd-resistant frogs can be an effective way to combat the effects of chytridiomycosis. The reintroduced frogs were surviving and establishing new populations in the lakes, and they were free of Bd infection.

The genetic analysis of the reintroduced frogs showed that the frogs were successfully reproducing and that the new populations were genetically diverse. This is important because it means that the new populations are likely to be resilient to future challenges, such as the emergence of new strains of Bd.

Conclusion

The reintroduction of Bd-resistant mountain yellow-legged frogs into Yosemite National Park has been a success. The reintroduced frogs are surviving and establishing new populations in the lakes, and they are free of Bd infection. The genetic analysis of the reintroduced frogs showed that the frogs are successfully reproducing and that the new populations are genetically diverse. This is an important step towards the recovery of the mountain yellow-legged frog in the Sierra Nevada mountains.