A taxon under siege from multiple threats: results of analysis of chytrid fungi on the Calabrian Alpine newt

The fungi Batrachochytrium dendrobatidis (Bd) and B. salamandrivorans (Bsal) and their associated disease, i.e., chytridiomycosis, pose significant threats to amphibians occurring in the Western Palearctic. This study aims to assess the prevalence and infection load of Bd and Bsal in the Calabrian Alpine newt, Ichthyosaura alpestris inexpectata, a micro-endemic and endangered subspecies from the Catena Costiera, Calabria, Southern Italy. Ninety newts were sampled from May to October 2023 from five breeding sites, representing the core distribution area of the Calabrian Alpine newt. Molecular analyses revealed that over 50% of the samples tested positive for Bd, while none tested positive for Bsal. No gross external signs of disease were detected in tested individuals. Bd prevalence and load were balanced between sexes but varied significantly among sites and were negatively associated with newt size, likely indicating site-specific and age variations in infection. Although Bsal was not detected, the high prevalence of Bd presents a new conservation challenge for the cold-loving Calabrian Alpine newt, which is already threatened by climate change and the introduction of alien fish in its main breeding sites. Therefore, it is crucial that future conservation actions, including monitoring for potential outbreaks of chytridiomycosis, are implemented adopting rigorous biosecurity measures to prevent further spread of the pathogen and safeguard the entire amphibian community.