Species Distribution Models Predict The Geographic Expansion Of An Enzootic Amphibian Pathogen

Globally, numerous amphibian species have declined due to the introduction of the chytrid fungusBatrachochytrium dendrobatidis(Bd). However, the understanding of the spatiotemporal dynamics remains incomplete. Therefore, estimating the current geographic distribution ofBdis urgently needed, especially in countries like Costa Rica, where susceptible species are still recovering fromBd-driven declines. We conducted model tuning and spatial analysis to compare the habitat suitability for epizootic and enzooticBdin Costa Rica and to identify data-deficient regions, opportunistic sampling, andBdhotspots. Our dataset combined two methods of detection (histology and PCR methods) for a total of 451Bd-positive records from 34 localities. We found that the distribution of enzooticBdin Costa Rica increased 60% since previous estimates in the early 2000s and extended to highlands and dry lowlands that were considered unsuitable forBd. We also found thatBdis common across protected lands (80%) and within the herpetological provinces containing the highest amphibian richness and endemism in Costa Rica. Opportunistic sampling ofBdhas focused on sites where epizootics occurred with the strongest intensity, leading to deficient or absent sampling across the Talamanca Range, the Nicoya Peninsula, and the northern lowlands. Our results showed that PCR increased the power ofBddetection in lowlands and favored the identification ofBdhotspots across the Caribbean side of Costa Rica. Our results add to the understanding of disease spread during enzootics and can be used to identify new hotspots for disease to mitigate future outbreaks of this pathogen. in Spanish is available with online material