Simultaneous Detection of Missing Amphibians and Their Fungal Pathogen in a Biodiversity Hotspot Using eDNA

Area of Science:

• Tropical Ecology
• Conservation Biology
• Amphibian Disease Ecology

Background:

• Global amphibian populations have declined significantly since the 1970s.
• The chytrid fungus Batrachochytrium dendrobatidis (Bd) is a major driver of these declines.
• Understanding Bd's impact on Brazilian amphibians is crucial for conservation.

Purpose of the Study:

• To investigate the role of Bd in amphibian declines in the Brazilian Atlantic forest.
• To survey for threatened amphibian species and Bd lineages using environmental DNA (eDNA).
• To examine the relationship between amphibian presence/absence and Bd lineages.

Main Methods:

• eDNA metabarcoding was used to detect DNA traces of 10 threatened amphibian species in the Southern Brazilian Atlantic forest (SBAF).
• eDNA data from 32 threatened species in the Northern Brazilian Atlantic forest (NBAF) were analyzed alongside SBAF data.
• The presence of amphibian DNA was correlated with the presence of Bd lineages (Bd-GPL and Bd-Brazil).

Main Results:

• DNA traces of two of 10 targeted species were detected in SBAF, including Cycloramphus cedrensis, missing for over 40 years.
• Two Bd lineages were detected at nine of 12 sites with reported amphibian declines since the 1970s.
• Evidence suggests a post-panzootic scenario where some amphibians coexist with enzootic Bd.

Conclusions:

• The study supports a post-panzootic scenario for amphibian declines in Brazil.
• Some threatened amphibian species may be adapting to persist with enzootic Bd.
• Simultaneous eDNA surveys for hosts and pathogens offer valuable methodological insights for tropical ecology and conservation.