This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: In the 1970s, researchers began to observe drastic amphibian declines in Brazil's Atlantic Forest, a global hotspot of frog biodiversity. For decades, these disappearances remained a mystery.
Now, new research from scientists at the Center for Conservation Genomics at the Smithsonian's National Zoo and Conservation Biology Institute (NZCBI) and Pennsylvania State University (PSU), published today in the journal Molecular Ecology, points to amphibian chytridiomycosis, a devastating infectious disease, as the likely culprit. Chytridiomycosis, commonly known as chytrid, is caused by the microscopic fungal pathogen Batrachochytrium dendrobatidis. Believed to have originated in Asia, the chytrid fungus likely swept the globe in the 1970s and 1980s, but scientists did not formally describe the pathogen until 1999.
At that point, amphibian populations around the world had suffered catastrophic declines, with hundreds of species pushed to the brink of extinction or beyond. Because many of these declines occurred before the pathogen's discovery, however, establishing whether the chytrid fungus was responsible has remained a challenge. "After almost 50 years, we still aren't confident what caused many historical amphibian die-offs, making these declines some of the most enduring cold cases in wildlife epidemiology," said Jack Boyette, an NZCBI graduate fellow and doctoral candidate at PSU, who led the study.
In Brazil's Atlantic Forest, amphibian die-offs at the Boracéia Biological Station between 1979 and 1982 have been attributed by some scientists to climate change or extreme weather events. "While environmental factors could have played a role, our findings most directly implicate the chytrid fungus, revealing that regional invasion of the pathogen coincided with these unexplained amphibian disappearances," Boyette said. To crack the case, Boyette and his colleagues turned to the Smithsonian's National Museum of Natural History, which holds the collections of William Ronald Heyer, a former curator of amphibians and reptiles.
Heyer collected specimens at Boracéia across five field campaigns: two in the 1970s, prior to the sudden amphibian declines, and three in the 1980s, during the aftermath of the die-offs. These collections offered a rare opportunity to trace the pathogen's arrival across a critical period of amphibian declines. NZCBI researchers collected samples from more than 370 museum specimens representing 17 species to determine when the chytrid fungus first appeared at Boracéia and how infection prevalence varied through time.
The team also returned to Boracéia six times between 2022 and 2024, alongside researchers from the University of São Paulo, to sample modern amphibian populations. Of the 17 species represented in Heyer's collection, the researchers could find only 12 at the site. The fate of the other five species remains uncertain, although their continued absence raises concerns that they may have been lost locally.
Extract — continue reading at the source.
