Geographic and climatic constraints on bioregionalization of European ants

Aim: Biogeographical regionalization is scant for most insect groups due to shortfalls in distribution and phylogenetic information, namely the Wallacean and Darwinian shortfalls respectively. Here, we focused on the European ants and compared new techniques to classical analyses based on regional lists and taxonomic methods. We asked the following: (1) Can grid-based regionalizations using novel distribution data improve biogeographical transitions? and (2) Can phylogenetic approaches reveal new insights regarding ant evolutionary history? Location: Europe and Anatolia. Taxon: Ants (Formicidae). Methods: First, we developed a refined database integrating the occurrences of 747 ant species across 207 regions of Europe and Anatolia, based on newly expert-validated records derived from the existing Global Ant Biodiversity Informatics database. Using range estimates for these species derived from polygons and species distribution modelling, we produced species assemblages in 50 x 50 km grid cells. We calculated taxonomic and phylogenetic turnover of ant assemblages, then performed a hierarchical clustering procedure to delineate biogeographical structure. Results: At both the regional list and grid assemblage levels, the Mediterranean has higher turnover and more biogeographical regions than northern Europe, both taxonomically and phylogenetically. Delineations based on grid assemblages detected more detailed biogeographical transitions, while those based on regional lists showed stronger insularity in biogeographical structure. The phylogenetic regionalization suggested a very similar spatial structure but varied affinities between assemblages in comparison to the taxonomic approach. Main Conclusions: Here, we integrated expert-validated regional lists, species distribution modelling and a recent phylogeny to tackle Wallacean and Darwinian shortfalls for an important insect group by developing a next-generation map of biogeographical regionalization for European ants. The results of this study suggest strong constraints from geographical barriers and potential effects of climatic history on ant distributions and evolutionary history, and also provide baseline spatial information for future investigations of regional insect distributions.