Habitat disturbance alters Bd infection patterns but not skinmicrobiome diversity in Neotropical Poison Frog

Anthropogenic habitat disturbance can increase animals’ susceptibility to infectious diseases byenhancing their exposure to pathogens and weakening their natural immune defences. Inamphibians, the skin microbiome plays a key role in protecting against the chytrid fungus Batrachocytrium dendrobatidis (Bd), but the way habitat disturbance may disrupt these host-microbiome-pathogen interactions remains poorly understood. Here, we swabbed the skin of thepoison frog Dendrobates tinctorius across six populations experiencing different degrees ofanthropogenic disturbance measured as Human Footprint Index (HFI) to investigate how itinfluences Bd infection prevalence, the frogs’ skin bacterial community, and consequently, itsprotective function against Bd infection. We found that the probability of Bd infection increased insites with higher HFI, where frogs also exhibited greater spatial clustering. In contrast, HFI had noor weak effect on the skin bacterial community alpha and beta diversity, respectively. Instead, theskin microbiome was strongly associated with Bd infection, with frogs with similar parasite loadssharing a more alike microbiome composition, indicating a deterministic, dose-dependent effect ofinfection. Combined, our findings suggest that anthropogenic habitat disturbance may influencehost-parasite interactions by increasing pathogen exposure and/or transmission rates, but not bydirectly affecting susceptibility derived from strong microbiome differences. Understanding how habitat characteristics influence amphibians’ skin microbiome is crucial for conservation efforts, asit can help to identify vulnerable populations and guide strategies to mitigate disease impacts inrapidly changing environments.

• Impacts of global change on a Neotropical poison frog