Amphibians After Disease-Induced Declines: Genetic Insights Into Population Recoveries

Infectious diseases can cause severe population declines, which often result in genetic bottlenecks, with small, isolated populations that are especially vulnerable to extinction due to genetic drift and inbreeding. Chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd), has led to global amphibian declines. Yet, some populations now show signs of recovery, even though Bd is present and pathogenic. In this study, we use a genomic approach to investigate the genetic patterns underlying recoveries in three amphibian species from Panama that experienced Bd-related declines followed by apparent recoveries. Our results reveal recent genetic bottlenecks and low effective population sizes across all three species, consistent with evidence of past disease-driven declines. However, we found distinct patterns of gene flow and immune genetic diversity among species. These findings suggest that gene flow may serve as a key demographic and adaptive contributor to recovery in some species by introducing novel genetic variation.