Taxonomic and functional patterns of arthropod succession after glacier retreat in the Dolomite Alps

Glacier retreat is heavily affecting the distribution of cold-adapted ground-dwelling arthropods. The Dolomites are a mountain range in the Italian Alps possessing a unique lithology and residual small glaciers, which makes the study of biotic succession after glacier retreat especially interesting. However, no study has so far investigated and compared arthropod diversity across multiple glacier forelands in this area. Here, we investigated key and understudied aspects of carabid beetles and spider succession after glacier retreat across four forelands in the Dolomites. We showed that successional patterns varied across species. Variation in species abundances was mostly related to glacier identity, time since deglaciation and temperature. Environmental variation between forelands also explained differences in the composition of communities and the successional patterns of species. Indeed, species occurring across multiple forelands were detected at different stages of ecological succession according to the foreland. Carabids and spiders showed distinct clusters in the functional space that were related to environmental variation. Species with large body size were associated with later successional stages. Taxonomic and functional changes of community structure along the succession were dominated by addition, although for carabids, taxonomic and functional replacement increased with time since deglaciation. Our study revealed that the ecological context in which post-glacial colonization occurs has a strong impact on its patterns and will serve as a baseline for future investigations of biodiversity responses to glacier retreat in the unique environment of the Dolomites.