Habitat connectivity supports the local abundance of fire salamanders (Salamandra salamandra) but also the spread of Batrachochytrium salamandrivorans

Abstract

Context Habitat connectivity can stabilise animal populations by facilitating immigration and genetic exchange, but it increases the risk of infectious diseases being spread by hosts. Chytridiomycosis caused by Batrachochytrium salamandrivorans (Bsal) threatens European salamander diversity. The extent to which the connectivity of populations of fire salamanders (Salamandra salamandra) contributes to the spread of Bsal remains unclear. Objectives We analysed the impact of habitat connectivity of fire salamanders on the spread of Bsal. Moreover, we show how local salamander abundance is associated with habitat connectivity over a five-year period. Methods We developed fire salamander habitat suitability models (HSMs) for the Eifel area (Germany), currently considered the core of the range of Bsal in Europe. Habitat models were used to calculate pairwise resistance between salamander occurrences to test whether Bsal presence and salamander abundance were associated with habitat connectivity. Results Fire salamanders are widely distributed in the Eifel. Solid bedrock and topographic positioning were important predictors of stream suitability as breeding habitats, while deciduous forests and grassland cover determined overall fire salamander habitat suitability along with breeding habitat suitability. Bsal-positive salamander occurrences were better-connected than Bsal-negative or untested occurrences. Nevertheless, fire salamander larvae were more abundant in well-connected sites. Conclusion The connection of salamander populations by suitable habitat seems to support local salamander abundance while facilitating the spread of Bsal. In situ conservation measures counteracting host species connectivity to interrupt Bsal transmission pathways must be implemented with caution, as they may weaken the demographic advantages of connectivity.

Effects of microclimate on disease prevalence across an urbanization gradient

“…Therefore, forested rural areas may support fewer or less‐well‐connected populations of these host species compared to urban areas that are crisscrossed with roads and dotted with mowed lawns. In general, greater host population connectivity can promote spread of disease (Bolte et al, 2023; Margosian et al, 2009). A role of forests in disrupting host connectivity or blocking wind‐dispersed spores may explain why populations of P. lanceolata with more shade cover (e.g., by forested borders) had lower probability of mildew presence in a metapopulation in Finland (Jousimo et al, 2014).…”

Ecological Barriers for an Amphibian Pathogen: A Narrow Ecological Niche for Batrachochytrium salamandrivorans in an Asian Chytrid Hotspot

“…The absence of Bsal in habitats suitable for its presence, as suggested by the niche models, opens up further possibilities as well. While it is possible that Bsal has not yet been introduced to these regions, it could also be the case that the pathogen has been introduced but is not able to establish itself due to unknown ecological or biological barriers like suboptimal habitat connectivity [ 78 , 81 , 82 ]. For instance, previous studies highlight the significant role of seasonality, driven by variations in temperature and precipitation, in determining Bsal distribution and host susceptibility [ 67 , 83 ].…”