A new species of yellow acorn ant discovered in Italy via integrative taxonomy (Temnothorax luteus-complex, Formicidae)

The Mediterranean, a global hotspot for rare ant species, hosts a significant representation of the global diversity of the mainly Holarctic ant genus Temnothorax. However, several groups still require significant taxonomic efforts. The taxonomy of the T. luteus complex species was revised in 2014 when morphometrics allowed distinguishing two valid species and two synonyms out of four taxa that had been originally described from France. The two species recognized since then are T. luteus, distributed from Iberia to the Alps, and the largely sympatric but much more xerotermophilic T. racovitzai. In Italy, only a few records of the complex were ever published, and the identity of the Italian population was never thoroughly assessed. We combined morphometrics with phylogenomic data to assess the identity of the T. luteus populations that spanned from Sicily to the Italian Alps and discovered that all Italian samples belong to a new cryptic species, which we describe as T. appenninicus sp. n. and whose glacial refugium was probably in the southern Appennines.