Reconstructed phylogeny and morphometry reveal a substantial geographical variation of Temnothorax sordidulus (Mueller, 1923) in the Mediterranean region (Hymenoptera, Formicidae)

The Central and South European ant lineage Temnothorax sordidulus species complex is one of the most challenging cases in European ant taxonomy. The description of a new subspecies, T. sordidulus saxonicus, the raising of this taxon to a species rank, and the revision of this species group by Csosz et al. implied multiple reclassifications within this lineage in the last decades.The partially different conclusions in taxonomy threw the spotlight on the lineage and suggested that a putatively extraordinarily complex population structure might be responsible for the fact that slightly different morphometric data collection may cause different inferences about species boundaries.To solve the situation, we paid particular attention to collecting richer examination material, with special regard to hot zones, e.g., isolated populations, and hybrid contact zones. We analyzed an extensive set of continuous morphometric data via the ordinating Principal Component Analysis (PCA). In parallel, we sampled 18 specimens from across the geographic range of the unifasciatus complex for targeted enrichment of UCEs, to identify the constituent lineages and their correspondence to morphological clusters.