Temporary ponds (TPs) are ephemeral freshwater habitats which ecological importance was historically neglected. In an era of rapid and unpredictable climate change, understanding how these vulnerable ephemeral ecosystems respond to shifts in local and regional spatial factors can be crucial for anticipating global impacts. The aim of this research is to investigate whether the differences in the floristic composition of diatom communities at small and large scales are mainly driven by geographical, elevational or environmental factors (physicochemical factors).

Taxonomic α diversity revealed no significant seasonal effects based on linear mixed models. Generalized Additive Models (GAMs) identified pH and electrical conductivity (EC) as significant predictors of species richness, while elevation emerged as the main driver of Shannon and Simpson diversity. Relative importance analysis confirmed EC as the most influential variable across indices. β diversity Mantel analyses showed a strong effect of elevation on community dissimilarity, with community similarity decreasing significantly with increasing elevational distance. Initial Compositional Similarities revealed that community similarity decreased steadily with elevational distance at a rate of approximately 0.00019 per meter, starting from an initial similarity of 41%, with a calculated Halving Distance of 1059 meters. Partial Mantel tests confirmed independent contributions of both elevation and environmental factors, while PERMANOVA analyses highlighted temperature, EC, and ORP as significant environmental drivers of community structure. Similarly, functional α and β diversity were mainly driven by the elevation gradient rather than seasonality, with the turnover component explaining most of the observed β diversity. Physical parameters (T, pH, ORP and TDS) exerted a more significant influence on functional α diversity, underscoring the resilience of functional β diversity, which was not influenced by physicochemical parameters. Our results highlighted the need for a greater focus on the analysis of predictive factors that may influence diatom communities, particularly in the global context of climate changes.