Shared and Divergent Processes Linked to Monocot Diversity Across the Mediterranean Climate Regions

ABSTRACT Aim The five Mediterranean regions of the globe are plant biodiversity hotspots, and there has not been a comparative analytical framework examining correlates of diversity across these regions. Of Mediterranean plant diversity, monocots constitute a considerable proportion that has yet to be explicitly examined comparatively. We combine phylogenetic, spatial biodiversity and environmental data to test if shared or divergent processes predict diversity within each of the regions, focusing on the whole monocot flora and on geophytes in particular. Location Mediterranean regions. Time Period Present day, with a deep‐time phylogenetic framework. Major Taxa Studied Monocotyledons. Methods We generate an unprecedented data set of species distributional models, phylogenetic and trait data for monocots found in core Mediterranean regions and surrounding areas. We employ randomisations and quantify phylogenetic alpha‐ and beta‐diversity patterns and determine whether key climatic and edaphic processes are concordant across regions. Results Mediterranean climate zones contained higher phylogenetic diversity with generally less phylogenetic clustering compared to their surrounding areas (yet with region‐specific patterns, particularly regarding relative ages). Seasonal variability in temperature and the timing and amount of precipitation were key correlates across regions, but significant differences across regions, especially the Mediterranean Basin, were found. Proportional geophyte diversity was not constrained to Mediterranean regions and correlated with overall different climatic indices compared to the rest of the monocots. Phylogenetic beta diversity showed consistent nested patterns, rather than one of wholesale turnover, with the adjacent regions consisting of a subset of lineages found in the core Mediterranean. Main Conclusions Our work represents a foundational step to understanding the interplay of environmental and evolutionary processes generating diversity patterns in Mediterranean regions. While monocot phylogenetic diversity was generally greater within the core climate zones, key differences in each region, both in terms of processes (summer/winter rainfall) and the structure of diversity, were present.