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. 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. We synthesized historical data from natural history museums, the global biodiversity information facility, and mtDNA sequences to examine whether Batrachochytrium dendrobatidis (Bd) fungus infection, climate change, and/or their interaction contributed to the rapid population decline. We found excessive rare alleles reflected in the negative Tajima's D estimated from the mtDNA samples from 1984, indicating a selective sweep or population bottleneck. Sex and geography showed stronger effects on adult body sizes than Bd epizootic timing. The body sizes of adult males formed a geographic cline. Species distribution modeling based on temperature and precipitation accurately predicted the occupancy of A. ignescens in 1960-69, which further projected a rapid decline in species distribution between 1970 and 2020. This investigation revealed strong climate effect and weak epizootics effect on A. ignescens extinction, and inspires future museum genomic studies to dissect the potential climatic maladaptation behind dramatic historical extinctions.