Delineation of species of the Tetramorium caespitum complex (Hymenoptera, Formicidae) in Anatolia with a diagnosis of related species-complexes

The high level of morphological crypsis of the hyper-diverse Palearctic Tetramorium caespitum group have challenged taxonomists for decades. Within this group, Wagner et al. (2017) offered a multidisciplinary solution for the delimitation of ten European species of the Tetramorium caespitum complex. Anatolia, harboring a high level of endemism in ants, has never been subject of focus research within this genus.

In this study, the Tetramorium caespitum complex diversity in Anatolia and the Caucasus region was investigated by examining 191 nest-samples using an in-depth integrative-taxonomic approach. Quantitative morphometric and microsatellite data of 505 and 133 workers, respectively, and genital-morphology data of 33 nests were collected. Unsupervised analyses provided independent species-hypotheses based on the morphological and molecular disciplines.

Based on the final species-hypotheses, we confirm T. caespitum (Linnaeus, 1758), T. hungaricum Röszler, 1935, T. indocile Santschi, 1927, T. caucasicum Wagner et al., 2017, T. impurum (Foerster, 1850), T. immigrans Santschi, 1927, and T. flavidulum Santschi, 1910 as valid species of the T. caespitum complex occurring in Anatolia. A lectotype of T. flavidulum was designated. The host of the temporary social-parasitic species Tetramorium aspina Wagner et al., 2018 is T. caucasicum instead of T. immigrans – as it was suggested before.

An identification key to species complexes of the T. caespitum group and to workers of the species of the T. caespitum complex in Anatolia is provided. Every cluster we identified could be linked to described species and the region’s species-composition is similar to those of the Balkans and Central Europe.