Description of Formica tibetana

This study presents the taxonomic description and ecological data of two unique ant species, Formica sentschuensis Ruzsky 1915 and Formica tibetana n.sp., found in the high-altitude grasslands of the Tibetan Plateau. Based on expeditions conducted in 2011 and 2012, F. tibetana n .sp. w as i dentified a s a d istinct s pecies. It develops locally an unusual nest architecture showing a flat, hardened, south-facing upper surface that optimizes solar heat absorption for early brood development. Morphological analyses revealed that F. tibetana n.sp. and F. sentschuensis form a common clade that may have split off near to the root of the genus Formica. Both species are characterized by a rare anteromedian clypeal excavation, a feature otherwise known for the Palaearctic only in Formica sanguinea Latreille, 1798 and several Nearctic species of the Formica sanguinea group. Morphology does not indicate a close relatedness of F. tibetana n.sp. and F. sentschuensis with members of the Formica sanguinea group which is supported by full absence of dulosis and independent single-queen colony foundation confirmed for F. tibetana n.sp. A stereomicroscopic analysis of morphological traits, including shape characters, seta characters and absolute body size proved that both species are clearly separable on worker individual level. This study provides insights into the biology of F. tibetana n.sp. and shows that the species plays a significant role in the Tibetan grassland ecosystems.