Skin Microbiome Disturbance Linked to Drought-Associated Amphibian Disease.

The onset of global climate change has led to abnormal rainfall patterns, disrupting associations between wildlife and their symbiotic microorganisms. We monitored a population of pumpkin toadlets and their skin bacteria in the Brazilian Atlantic Forest during a drought. Given the recognized ability of some amphibian skin bacteria to inhibit the widespread fungal pathogen Batrachochytrium dendrobatidis (Bd), we investigated links between skin microbiome health, susceptibility to Bd and host mortality during a die-off event. We found that rainfall deficit was an indirect predictor of Bd loads through microbiome disruption, while its direct effect on Bd was weak. The microbiome was characterized by fewer putative Bd-inhibitory bacteria following the drought, which points to a one-month lagged effect of drought on the microbiome that may have increased toadlet susceptibility to Bd. Our study underscores the capacity of rainfall variability to disturb complex host-microbiome interactions and alter wildlife disease dynamics. Amphibian skin bacteria are known to play an important role in inhibiting the widespread fungal pathogen Batrachochytrium dendrobatidis (Bd). We monitored a population of pumpkin toadlets in the Brazilian Atlantic Forest throughout a short-term drought and investigated links between skin microbiome health, pathogen susceptibility and host mortality during a die-off event. Our structural equation model showed strong indirect effects of drought on Bd loads through microbiome dispersion, surpassing the magnitude of the direct effect of rainfall deficit on Bd loads.image