Similar, but Not in Functioning: Investigating Diatom Traits in High-Elevation Ponds

On a planet constantly under siege from climate change, temporary ponds represent sentinels for the analysis of landscape and climatic changes at both local and regional scales. In this research, we investigated which local and regional factors shape diatom functional diversity in alpine temporary ponds. We investigated 12 alpine temporary ponds located within the Gran Sasso e Monti della Laga National Park (Italy), sampled in July 2024 together with physicochemical, geographical (elevation), and spatial (kernel isolation) variables. We quantified functional α-diversity using five indices and assessed functional β-diversity from a presence–absence matrix using the Sørensen dissimilarity index. Elevation emerged as a key predictor for functional richness and functional dispersion; temperature was associated with patterns in functional evenness, while, conversely, spatial isolation showed a negative effect on functional evenness. A Mantel test revealed that community dissimilarity and elevational distance were correlated. Physicochemical factors and isolation were not. Community similarity decreased as elevation difference between sites increased. Unexpectedly, community similarity did not vary with increasing isolation among sites.