PS 14-183 - Biotic and abiotic factors influencing Batrachochytrium salamandrivorans (Bsal) prevalence in communities

Abstract: Amphibians are one of the most obvious examples of recent species declines. One of the most prominent drivers of these declines is chytridiomycosis, a fungal disease caused by Batrachochytrium dendrobatidis (Bd) and, more recently, Batrachochytrium salamandrivorans (Bsal). Since its discovery, the known range of Bsal has rapidly expanded, devastating salamander populations across Europe. Research thus far has shown that temperature and moisture play a major role in its persistence in the environment and that susceptibility to Bsal is variable among species, leading to concerns about potential reservoir hosts and how they might impact Bsal persistence. However, little research has investigated the role community structure might play regarding Bsal prevalence. Here, we used publicly available data to investigate how community structure (i.e., site abundance and richness) impacts Bsal prevalence for all species in the community. Furthermore, we subset the data to only include fire salamander (Salamandra salamandra) observations to see 1) how community structure impacted disease prevalence in this species and 2) if average monthly temperature at sites that had tested positive for Bsal at least once influenced mortality.

Binomial glmms were used to perform our analyses. Temperature and soil moisture were accounted for at the time of the initial observation (t₀), one month prior (t_-30days), and two months prior (t_-60days). At t_0, species richness and abundance had a significant negative effect on Bsal prevalence, but there were no significant interactions. At t_-30days, there were significant positive interactions between richness and abundance as well as soil moisture and temperature. Finally, at t_-60days there was a significant positive interaction between richness and abundance, but not between temperature and soil moisture. Overall, these models suggest that 1) the positive Bsal observations in our data are more likely influenced by the weather shortly prior to the observation than weather at the time of the observation, and 2) as richness and abundance increase, Bsal prevalence decreases. In our fire salamander-only models, abundance, temperature, and soil moisture were significant at t₀, but there were no significant interactions. At both t_-30 and t_-60days, temperature and abundance were significant and there was a significant positive interaction between temperature and soil moisture, meaning that as temperature and soil moisture increased, Bsal prevalence in fire salamanders tended to increase. Finally, there was a significant positive interaction between average annual temperature and sites that were previously positive for Bsal, suggesting that higher annual temperature meant greater Bsal-related mortality in fire salamanders.