University of Michigan biologists have documented, for the first time, the widespread presence of the notorious chytrid fungus in 80 species of frogs from lowland rain forest sites in the Peruvian Amazon.

The chytrid fungus causes a deadly skin disease and has been linked to dramatic amphibian declines worldwide over the past 40 years, most notably in moderate- and high-elevation frog communities—where the climate is cool—in mountainous regions of western North America, Central America, South America and eastern Australia.

But little attention has been paid to the role of tropical lowlands in the pathogen’s persistence, because such areas were thought to be too warm to harbor significant levels of the Batrachochytrium dendrobatidis fungus, which is known as Bd.

In a paper published Oct. 16, 2019 in the journal PLOS ONE, the U-M-led research team reports widespread Bd infection across 80 frog species from three sites in lowland tropical rain forests of the Peruvian Amazon, a region with no documented Bd-related amphibian declines.

“Our results showing high and widespread prevalence across a lowland tropical ecosystem contradict the expectations based on the global pattern of pathogenicity of Bd that is largely restricted to higher elevations and colder temperatures,” the authors wrote. “These findings imply that the lowland may play a critical role in the spread and persistence of Bd over time and space.”

The first author of the PLOS ONE paper is Imani Russell, who did the work for a master’s thesis in the U-M Department of Ecology and Evolutionary Biology. Even lowland Peruvian Amazon frogs with very high levels of Bd infection showed none of the external signs of disease usually seen in infected frogs at higher elevations, she said.

Those signs can include reddening and sloughing of skin, lethargy and failure to flee. The skin disease is called chytridiomycosis.

“Many conservation biologists thought they didn’t need to worry about this fungus infecting frogs in hot lowlands,” said Russell, who is now a graduate research fellow in the doctoral program at the University of California, Santa Barbara.

“But now we know that these lowland frogs can harbor high levels of fungal infection without dying or even looking sick. That means they could serve as a large disease reservoir for future fungal infections across many frog populations in Peru.

“This knowledge can help conservation biologists better tailor their management strategies to slow frog population declines around the world.”

In addition to Russell, coauthors (all affiliated with the U-M Department of Ecology and Evolutionary Biology) of the PLOS ONE study include senior author Alison Davis Rabosky, Russell’s faculty co-adviser at U-M and an assistant professor; Timothy James, a mycologist and associate professor; Joanna Larson and Iris Holmes, Ph.D. students; and Rudolf von May, former postdoctoral fellow.

Their research is receiving media attention including these articles in New Scientist and Inverse.

Read full Michigan News press release