Τhe ongoing biodiversity crisis reinforces the urgency to unravel diversity patterns and the underlying processes shaping them. Although taxonomic diversity has been extensively studied and is considered the common currency, conserving simultaneously other facets of diversity such as functional diversity is critical to ensure ecosystem functioning and provision of ecosystem services. Here, we explored the effect of key climatic factors (temperature, precipitation temperature seasonality, precipitation seasonality) and factors reflecting human pressures (agricultural land, urban land, land-cover diversity, population density) on functional diversity (functional richness and Rao quadratic entropy) and species richness of amphibians (68 species), reptiles (105 species) and mammals (160 species) in Europe. We explored the relationship between different predictors and diversity metrics using Generalized Additive Mixed Model analysis, to capture non-linear relationships and to account for spatial autocorrelation. We found that at this broad spatial scale, climatic variables exerted a significant effect on functional diversity and species richness of all taxa. On the other hand, variables reflecting human pressures exerted a significant effect only on reptile and mammal diversity, and their explanatory power was lower compared to climatic variables. In most cases, functional richness and Rao quadratic entropy responded similarly to climate and human pressures. Concluding, climate is the most influential factor in shaping both functional diversity and species richness patterns of amphibians, reptiles and mammals in Europe. However, incorporating factors reflecting human pressures complementary to climate could be conducive to our understanding the drivers of functional diversity and richness patterns.

Acknowledgements: The research work was supported by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the “First Call for H.F.R.I. Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant” (Project Number: HFRI-FM17-2024 Mapping Functional Diversity Drivers, Impacts and Threats - MAPFUN).