Landscape context influences chytrid fungus distribution in an endangered <scp>E</scp>uropean amphibian

Abstract

Abstract Wildlife disease is an emerging threat to biodiversity. The amphibian chytrid fungus B atrachochytrium dendrobatidis ( B d), which causes the disease chytridiomycosis, has been documented in over 500 amphibian species globally. Understanding conditions under which amphibians are vulnerable to B d is important for evaluating species risk and developing surveillance strategies. Here, we investigate the spatial distribution of B d infection in the ephemeral pond‐breeding yellow‐bellied toad B ombina variegata , a species of high conservation concern in the E uropean U nion. We sampled 550 toads from 60 ponds in a traditional agricultural landscape in S outhern T ransylvania, R omania. Overall, B d prevalence was low in B . variegata , but infected toads were widely dispersed through the landscape and were found in a quarter of all sampled ephemeral ponds. At the pond level, increased B d occurrence was associated with short distances to perennial water sources and high forest cover. These findings suggest that perennial water sources may act as source habitat for B d, with amphibian movements resulting in B d spillover into ephemeral ponds. Increased B d occurrence in ponds surrounded by high levels of forest cover is likely related to cooler and wetter conditions that are more favourable for B d. Throughout the study landscape, patchy environmental suitability for B d appears to restrict the pathogen to a subset of B . variegata habitat. Ephemeral ponds in open landscapes, without nearby perennial habitat, likely provide an environmental refuge from B d, where the risk of infection is low. From a conservation perspective, these findings highlight the importance of maintaining ephemeral ponds in open landscapes, but these are currently threatened by land‐use change.