Museum insights for conservation: Unraveling the Extinction Factors in the Jambato Harlequin Frog, Atelopus ignescens

Natural history museums harbor invaluable resources for conserving endangered species by providing insights into the mechanism of historical population declines. Here we conducted data synthesis to better understand the extinction factors of the iconic Jambato Harlequin frog, Atelopus ignescens , which was widespread in the Ecuadorian Andes before 1985 but vanished in 1988. The mechanism of extinction remains elusive, as it was uncertain whether Batrachochytrium dendrobatidis (Bd) fungus infection, climate change, or the interaction of the two factors primarily contributed to the rapid population decline. Here we synthesize historical data from natural history museums, the Global Biodiversity Information Facility (GBIF), and mitochondrial DNA sequences to uncover the factors that have potentially contributed to the extinction of the Jambato Harlequin frog. We found excessive rare alleles reflected in the negative Tajima’s D estimated from the mitochondrial DNA samples collected in 1984, which indicates a selective sweep or bottleneck in the population shortly before the historical extinction. There was a marginal effect of the time before versus during Bd epizootics on the body sizes of the adult males, which was relatively weaker than the sex effect and geographic effect. The body size of adult males, but not the females form a geographic cline where the individuals in the northeast were larger than the males in the southwest. Species distribution modeling based on temperature and precipitation accurately predicted the occupancy of A. ignescens in 1960-69 (R ² = 0.72, accuracy = 0.9). This model further predicted the rapid decline in species distribution over decades of climate change between 1970-2020, which could have contributed to the rapid population decline in the 1980s. Collectively, our data synthesis revealed a strong climate effect and a weak epizootics effect on A. ignescens extinction, which unravels the mysterious rapid population decline and informs ongoing conservation efforts. This investigation inspires future museum genomic studies to dissect the potential climatic maladaptation behind one of the most dramatic extinction events in modern history.