Climate change expected to increase pathogen invasibility in Asia

Background/Question/Methods

Changing environmental conditions (e.g. temperature, precipitation, etc.) caused by climate change may affect species in subtle ways. For instance, amphibian, threatened worldwide, may become immunocompromised when exposed to temperature ranges beyond their native habitat, or some species may benefit by changes in temperature by expanding the future possible range of suitable habitat. Introduced worldwide, the American Bullfrog (Rana (Lithobates) catesbeiana) is a carrier of the deadly pathogenic fungus, Batrachochytrium dendrobatidis(Bd), which causes amphibian chytridiomycosis, a disease linked to hundreds of amphibian extinctions globally. We propose that future climate change scenarios (i.e. temperature increases) may help both increase the future distribution of the invasive American bullfrog and pose a serious threat to native amphibian hosts, which may already by stressed by climate change. We used DIVA-GIS to build habitat suitability models (HSM) for the American bullfrog and Bd susceptible native amphibians based on present (2000's) and future (2050) climate conditions. We chose to focus on Asia due to its unique Bd dynamics and lack of Bd epizootics compared to other continents. We then used Q GIS to calculate the percent change in overlap between American bullfrogs and native amphibians based on the possible changes in distribution predicted by our HSMs.

Results/Conclusions

We found an increase in predicted habitat suitability for the American bullfrog in Japan, Korea, China, and India. We found the difference between the present and future distributional overlap of the American bullfrog and native Bd susceptible amphibians to increase by 61.4% (per Km²) in South Korea, by 9.4% in Japan, and to decrease by 1% in China by 2050. If American bullfrogs are efficient spreaders of Bd, these results indicate an increasing threat of Bd exposure to native species in South Korea as well as other areas in Asia. We believe that habitat suitability models can help to better predict the future distribution of invasive species like the American bullfrog and may also help predict areas vulnerable to Bd invasions. We may also be able to focus conservation efforts to the most vulnerable species of susceptible amphibian hosts.