Modelling Batrachochytrium dendrobatidis Presence and Intensity Using High Spatial and Temporal Resolution Weather Data

Abstract

Aim: Species distribution models (SDMs) are an important tool for conservation efforts, and when constructed using high-quality predictor and response data could be useful for identifying portions of a species' range that could serve as refugia from risks that are influenced by environmental conditions, such as pathogens. Batrachochytrium dendrobatidis (Bd) is a fungal pathogen that causes lethal disease in amphibians but is also sensitive to environmental factors including temperature and humidity. SDMs built using high spatial and temporal resolution environmental data may be able to help identify environmental refugia from Bd for amphibians. In this study, we create our own high-resolution remotely sensed environmental dataset and use high-quality presence/absence survey data to build new Bd SDMs of Panama. Location: Panama. Taxa: The amphibian chytrid fungus Bd and amphibian communities. Methods: We used environmental values from various time periods prior to Bd testing (lag of 2, 7, 15, 30 days) and levels of Bd infection intensity from survey swabs (present, medium intensity, high intensity) to run multiple Boosted Regression Trees to model environmental suitability for Bd and evaluated their performance. Results: Our results indicated that the 15-day period prior to testing was the most predictive time-period for Bd environmental suitability in Panama. Additionally, we found that we could not only model the distribution of the pathogen itself but discern unique spatial and temporal patterns of high infection intensities often associated with disease outbreaks. We created daily predictive maps of the probability of Bd occurrence and of medium and high infection intensities in Panama from 2005 to 2018 and averaged them by season. Main Conclusions: Higher environmental suitability for Bd tended to be found at higher elevations, a pattern observed in previous Bd field studies and consistent with Bd's physiological requirements. The high temporal and spatial resolution of these maps gives a unique insight into exploring temporal patterns of Bd intensity in specific locations and to identify environmental refugia from Bd for amphibian reintroduction efforts and surveys for relict populations.