Amphibians are experiencing alarming population declines worldwide. One prominent factor in many of these declines is the pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd). Due to its sensitivity to heat, desiccation, and UV exposure, Bd is not expected to occur in the isolated water systems of hot deserts. However, limited sampling in 2013 detected Bd in constructed wildlife water catchments in the Sonoran Desert. These catchments are designed to supplement natural water sources, and are constructed with underground reservoirs, which are filled by rain or by water hauled in by managers. Bd may be able to survive in this desert due to the novel conditions created by the underground reservoirs of constructed catchments, which may protect the fungus from thermal, hydric, and UV stress. To explicitly test whether constructed catchments promote Bd exposure in Sonoran Desert anurans, we assayed the presence of Bd in the water of constructed catchments and natural water sites in summer and winter using environmental DNA (eDNA) methods and directly swabbed anurans in the summer monsoon season.
Results/Conclusions
We detected Bd in summer in eDNA from water of one constructed catchment and no natural water sites. We detected Bd on the skin of anurans at one constructed catchment and two natural waters. In winter, we detected Bd in the water of two constructed catchments and no natural water sites. This distribution indicates that Bd is present in the Sonoran Desert water system and within its amphibian population, which signals the need for more research on this possible threat to Sonoran Desert anurans. Continuation of this study will include further eDNA testing of water sites, determination of Bd prevalence within the anuran population through increased swabbing effort and marking of individuals, and culturing and analysis of Bd samples to ascertain if the Bd in this system is more heat tolerant than currently know Bd strains. These results will identify management needs for a previously unrecognized threat to desert anuran populations.