Chytrid Fungus Arrival Coincided with 1979-1982 Frog Declines at Brazil's Boracéia Station

Researchers at the Smithsonian's Center for Conservation Genomics and Pennsylvania State University tested 370 preserved amphibians from five Heyer expeditions spanning 1970s pre-decline and 1980s post-decline periods. They used qPCR on skin swabs to detect Bd DNA, establishing a clear temporal invasion signal that aligned with documented population crashes between 1979 and 1982. This museum-based retrospective approach bypassed the absence of contemporaneous field samples and provided the first direct evidence that the pathogen reached the site during the exact window of loss.

The pattern was counterintuitive: severely declined species tested negative while stable species carried high infection loads. This suggests either rapid die-off before detectable chronic infection or species-specific resistance thresholds, undermining earlier climate-only hypotheses. The finding reframes conservation priorities toward proactive pathogen surveillance rather than solely habitat protection in biodiversity hotspots.

Next steps require whole-genome sequencing of positive specimens to trace the Bd lineage's Asian origin and spread velocity. Expanded sampling across other Atlantic Forest sites and integration with climate data could test whether temperature anomalies amplified transmission, informing targeted antifungal treatments or assisted evolution programs for at-risk amphibians.

The main limitation remains small pre-1979 sample sizes and potential DNA degradation in older ethanol-fixed tissues; larger, multi-institution museum meta-analyses with standardized Bd assays would strengthen causal inference.