# Weathering the Storm: Legacies of Extreme Meteorological Events and Daily Weather Variability Shape the Skin Microbiota of the Endangered Golden Alpine Salamander Salamandra atra aurorae (Trevisan, 1982)

## TL;DR

Extreme weather events and daily weather changes affect the skin microbes of endangered golden Alpine salamanders, potentially influencing their disease resistance.

## Contribution

First characterization of the skin microbiota of Salamandra atra aurorae and its response to a major windstorm and weather variability.

## Key findings

- Salamanders from windstorm-impacted plots had less variable bacterial communities and higher Aeromonas abundance.
- Rainfall reduced bacterial diversity but increased fungal beta diversity, showing contrasting moisture preferences.
- Weather conditions during sampling explained up to 9% of bacterial and 6% of fungal variation in skin microbiota.

## Abstract

Ecosystems worldwide are undergoing unprecedented changes, and as a result amphibians are experiencing devastating population declines driven by subsequent habitat loss and emerging pathogens. The skin microbiota is an important first line of defence for amphibians against pathogens. Here, for the first time, we characterised the bacteria and fungi comprising the skin microbiota of 56 individual golden Alpine salamanders (
Salamandra atra aurorae
, Trevisan, 1982), a highly endemic and endangered amphibian subspecies. In addition, we investigated the impact of the 2018 Vaia windstorm on skin microbiota of salamanders in plots classified as impacted or non‐impacted based on windthrows. Salamander sex, weather during sampling, and dominant tree species in plots were also investigated as influencers of microbiota. Beta diversity estimates revealed greater variation in bacterial microbiota composition among individuals from non‐impacted plots compared to plots impacted by Vaia. Notably, we found differential abundances of five genera of bacteria and eight genera of fungi in the skin microbiota of salamanders from impacted compared with non‐impacted plots. Further analyses revealed that median relative abundances of
Aeromonas hydrophila
, the causative agent of the potentially fatal red‐leg syndrome, were significantly higher in microbiota of salamanders from impacted plots. Weather conditions during sampling significantly influenced both alpha and beta diversity of the skin microbiota, and explained up to 9% of bacterial and 6% of fungal variation. Bacterial richness and phylogenetic diversity were lower during rainfall, whereas fungal beta diversity increased, suggesting contrasting moisture preferences. These findings suggest that extreme weather events, as well as moderate daily weather fluctuations, may be associated with the microbial communities of amphibian skin, potentially affecting their resilience to pathogens. This study underscores the importance of considering both natural and human‐mediated disturbances in conservation strategies for vulnerable species like the golden Alpine salamander.

In 2018 the Vaia windstorm caused severe damage to much of the woodland habitat of the golden Alpine salamander (
Salamandra atra aurorae
), an endangered subspecies endemic to the Venetian Prealps, the consequences of which are still being understood. We profiled the bacterial and fungal skin microbiota of 56 golden Alpine salamanders from forest plots either impacted (tree falls) or non‐impacted (no fallen trees) by Vaia, and found that salamanders from impacted plots harboured less variable bacterial communities, but higher relative abundances of five genera—including Aeromonas, linked to the fatal red‐leg syndrome. Bacterial diversity was lower during rainfall compared to sunny conditions, indicating that both extreme disturbances and short‐term weather influence skin microbiota and may affect disease resilience.