Echoes of the Past: Long‐Term Climate Stability Shapes Functional and Phylogenetic Diversity in Euro‐Mediterranean Forests

ABSTRACT Aim Understanding the relative influence of past and present environmental and anthropogenic drivers on biodiversity is crucial for predicting future biodiversity trends. We assessed how past climate stability, present climate, habitat characteristics, disturbances (fire and herbivory), and past and present land use shape current functional and phylogenetic diversity across multiple taxa. Location Euro‐Mediterranean forests. Time Period From Last Glacial Maximum to Present Day. Major Taxa Studied Trees, birds, butterflies, reptiles, and mammals. Methods We quantified standardised functional and phylogenetic diversity across three dimensions: richness, dispersion, and originality for five taxonomic groups. Focusing on 54 individual drivers, we applied random forests to evaluate the importance of broad categories of drivers and understand how individual drivers impact each diversity dimension. Results Past temperature stability since the Last Glacial Maximum emerged as a dominant driver of functional and phylogenetic diversity across taxa. Stability was associated with higher functional and phylogenetic richness and dispersion, whereas unstable past climates were linked to lower diversity. Herbivory also played a significant role, though it was less influential than the past climate, particularly for trees and reptiles, whereas the present climate influenced birds' functional diversity. Fire intensity and surface, and land use in the present and past had limited importance, likely because of the study grain resolution. Main Conclusions Our findings underscore that long‐term climate conditions continue to influence biodiversity patterns across various taxa. This highlights the importance of considering both past legacies and present conditions when assessing biodiversity responses to future climate change. Lastly, we revealed dimension and taxon‐specific responses to drivers, reinforcing the need for integrative biodiversity frameworks that incorporate multiple facets and dimensions of biodiversity across different taxa to get a more nuanced understanding of how biodiversity is structured and maintained.