DNA Barcode Reference Library for European Ants: A Roadmap for Phylogeography and Species Discovery.

DNA barcode reference libraries provide useful tools for specimen identification, highlighting potential new species and detecting introduced ones. Here, we present a comprehensive DNA barcode library for European ants and, in order to tackle the Linnean, Wallacean and Darwinian shortfalls of this group, we provide an updated checklist, distribution data, mitochondrial genetic diversity maps and mitochondrial gene trees. The European ant fauna is here established to include 55 genera and 650 species (587 of which are native), including one species newly recorded for Europe and novel citations for 26 species from 11 countries. Our genetic dataset includes 6530 georeferenced COI sequences (62.1% de novo) for 506 species (77.8%) across all genera. On average, 12.9 sequences were obtained per species, and 209 species were sequenced for the first time. We generated intra- and interspecific genetic distance estimates, 52 genus-level trees, mitochondrial genetic diversity and specimen maps for 384 species, as well as haplotype networks for 289 species, available in the Atlas V1.0 'The Mitochondrial Genetic Diversity Maps of European Ants'. We estimate that 56.3% of European ants are monophyletic with respect to the COI gene and can be unambiguously identified by DNA barcoding, though performance varies widely among genera. We observed moderate levels of barcode sharing (19.3%) and of barcode gap presence (47.6%), as well as high levels of intraspecific divergences (up to 17.9%). These findings likely reflect both biological and operational factors and highlight the existence of potential cryptic taxa and the need for taxonomic revisions. The framework presented here aims to facilitate future research, species discovery and conservation of European ants.