Climbing the elevational gradient: Diatom diversity patterns across temporary ponds

Temporary ponds are peculiar and vulnerable habitats widespread in different biogeographical regions, which ecological and social importance was historically neglected. Among all the life forms supported by ponds, diatoms represent a key tool for assessing the conservation status of temporary waters. In this perspective, this study investigates patterns of diatom α and β diversity across an elevation gradient in low-elevation (LP) and high-elevation (HP) temporary ponds, assessing the influence of environmental, local, and seasonal factors. Samplings were performed throughout the entire year in six temporary ponds located along an altitudinal gradient. Species richness did not differ significantly between LP and HP sites, but Shannon diversity was lower in LP, indicating fewer even communities. Species richness, as predicted by our models, was influenced by pH and electrical conductivity (EC), while elevation was the main driver of both Shannon and Simpson diversity. EC consistently had the strongest influence on α diversity indices. Community similarity declined with increasing elevation, halving every ∼1059 m, demonstrating rapid species turnover along elevational gradients. Both elevation and environmental factors independently shaped community structure, whereas seasonal effects contributed little to community variation. Ecologically, these results suggest that diatom communities in temporary ponds are strongly structured by elevational and physicochemical gradients, making them sensitive to environmental changes such as climate shifts or pollution. Conservation efforts should prioritize protecting a range of habitats across elevations to preserve regional biodiversity, as loss of specific habitats could lead to significant declines in diversity.