Geographic and climatic constraints on bioregionalization of European ants

Abstract

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 expertvalidated 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 × 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.

Unrecognized for centuries: distribution and sexual caste descriptions of the West European Aphaenogaster species of the subterranea group (Hymenoptera, Formicidae)

“…We show that A. ichnusa is frequent across a vast region of the western Mediterranean ( Wang et al 2023 , including Italy’s Tyrrhenian and Ionian coasts, and part of the Adriatic one. Moreover, it is the sole species found on all investigated islands with the only exception of Sicily, where A.…”

Global biogeographic regions for ants have complex relationships with those for plants and tetrapods

“…The ant regionalization also shows high congruence to many tetrapod groups, which suggests that forces shaping zoogeographic regions are deeply shared across taxa, such as the long-term isolation of islands, contemporary physical barriers, and tectonic activity 41,65,66 . However, varied levels of congruence between ants and tetrapod groups were observed, which can possibly be explained by their distinct ecological characteristics 12,66 .…”

“…Ants (Hymenoptera, Formicidae) are progressively becoming an exception, being one of the few insect groups with relatively su cient distributional data 36 . Recent progress in distribution modelling 37 and phylogenetic estimates 38,39,40 has helped to tackle knowledge shortfalls for ants and has led to improved regionalizations for broad spatial scales 41 . Although most insect species are not yet explored or described 20,21 , genus-level taxonomies are often more well-documented, as is the case for ants (Supplementary Fig.…”

Non-native ants are breaking down biogeographic boundaries and homogenizing community assemblages

“…However, this is unlikely to affect our main conclusion that homogenization is heterogeneous and most pronounced on islands, as tropical and mainland regions mostly act as donor regions and islands mostly act as recipient regions of non-native ant species. However, future studies on the impact of ant invasions may analyze biogeographic patterns at finer resolution 53 to detect more precisely biogeographic transitions, as for recent studies on bioregionalization in European ants 54 and global native ant biodiversity 42 . Additionally, in our study we considered islands as entities that are smaller than a continent and surrounded by water (comprising both single islands and island archipelagos).…”

“…Moreover, future work could assess changes in phylogenetic 54 and functional β diversity once such data becomes available, giving complementary results about the potential evolutionary and ecosystem consequences of non-native species introductions. Finally, ant assemblages might be homogenized due to local extinction of endemic native species in addition to the establishment of widespread non-native species 15 , 17 , 24 .…”