Amphibian-plague strikes frogs harder in pristine ecosystems

[Frog News]

Mongabay News (California, USA) May 31st, 2011 10:35 AM: Amphibian-plague strikes frogs harder in pristine ecosystems

Frog populations worldwide are facing two apocalypses: habitat destruction and a lethal plague, known as chytridiomycosis. Over 30 percent of the world's amphibians are currently threatened with extinction and it is thought at least 120 species have gone extinct in just the last 30 years. Unfortunately, a new study in Proceedings of the National Academy of Sciences (PNAS) finds that the two threats—habitat loss and chytridiomycosis—are likely to leave no frog population undisturbed. According to the study, frogs that live in still-pristine habitats are more susceptible to chytridiomycosis than those that are already suffering from habitat loss.

Examining tropical frog populations in Costa Rica, Australia, and Brazil's Atlantic Forest, the researchers found "that paradoxically, habitat loss is negatively associated with occurrence, prevalence, and infection intensity of [chytridiomycosis] in amphibian populations in the tropics." The finding goes against research of other animal diseases, which usually find that risk of disease increases in disturbed habitats.

In this case the researchers suspect that either the lethal disease depends on the ecosystem having an undisturbed microclimate, or that a decline in amphibian diversity and abundance—due to habitat loss—slows the spread of the disease.

The finding also explains why the presence of chytridiomycosis is often seen in higher altitudes where forest is less disturbed.

The researchers conclude that "disturbed habitats may act as shelters from disease, but only for the very few species that can tolerate deforestation" and recommend that in order to save the world's remaining frogs, conservationists must "look to interactions between habitat loss and disease".

CITATION: C. Guilherme Becker and Kelly Zamudio. Tropical amphibian populations experience higher disease risk in natural habitats. Proceedings of the National Academy of Sciences. 2011. www.pnas.org/cgi/doi/10.1073/pnas.1014497108.

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