A deadly fungal disease may help explain why amphibian populations collapsed at Brazil’s Boracéia Biological Station between 1979 and 1982. A study reported in *Molecular Ecology* found that chytrid fungus appeared in preserved frogs around the time of the declines. Recent surveys suggest that many local species have since recovered, even though the fungus remains present.
The ScienceDaily report, based on materials provided by the Smithsonian, describes research by scientists at the Smithsonian’s National Zoo and Conservation Biology Institute and Pennsylvania State University. Jack Boyette, a graduate fellow at the Smithsonian institute and doctoral candidate at Penn State, led the research. Chytridiomycosis, or chytrid, is caused by the fungus *Batrachochytrium dendrobatidis*. It was not formally identified until 1999, years after amphibian die-offs had begun, making its role in past declines difficult to establish.
To investigate the Boracéia losses, researchers tested more than 370 preserved amphibians representing 17 species. The specimens came from collections made during five expeditions by William Ronald Heyer, a former curator of amphibians and reptiles at the Smithsonian’s National Museum of Natural History. Two expeditions took place in the 1970s, before the major declines, and three in the 1980s, afterward.
None of the tested specimens collected before 1979 showed evidence of chytrid. More than half of those collected during the 1980s tested positive. That sharp change places the fungus’s arrival and spread in the same period as the population collapse, supporting the idea that the disease contributed to it.
The specimen record also presents a puzzle: frogs from species that suffered the steepest declines showed no detectable infection, while species whose populations remained relatively stable often carried the fungus. The researchers suggest that vulnerable frogs may have died quickly after infection and therefore were less likely to be collected, while more tolerant species could carry the fungus and survive. The preserved samples cannot confirm that explanation, so the pattern does not establish why individual species fared differently.
The team returned to Boracéia for six surveys between 2022 and 2024. Researchers found 12 of the 17 species represented in the historical collection; the other five were not located, leaving their current status uncertain. The surveys indicate that most amphibian species at the site have recovered since the early 1980s. Chytrid infections are still present, and the current pattern may indicate greater tolerance among species once heavily affected. It does not show exactly how that tolerance developed.
The case illustrates how museum collections can help reconstruct outbreaks that went unrecognized when they happened. Specimens preserved decades ago allowed researchers to compare evidence from before and after the decline, using tests unavailable to collectors at the time. The distinction between infection and mortality matters here: a species can carry a pathogen without suffering a population collapse, while deaths among the most susceptible animals may leave little evidence in later collections.
The findings concern Boracéia and cannot automatically explain other amphibian disappearances across the Atlantic Forest. Researchers are now examining DNA from museum specimens for genetic clues to differences in response to chytrid. Other work using environmental DNA may help fill gaps in historical records. Those investigations could clarify why some species survived the outbreak while others declined.
<a href="https://www.sciencedaily.com/releases/2026/11/261102202838.htm">Source: ScienceDaily report</a>