Integrating qualitative and quantitative morphology with UCEs-based phylogeny to describe four Sicilian endemic Temnothorax species (Hymenoptera, Formicidae)

Temnothorax (Myrmicinae, Crematogastrini) is one of the most diverse Holarctic ant genera, and new taxonomic advancements are still frequent worldwide. The Mediterranean region, a global biodiversity hotspot characterized by a complex geographic history, is home to a substantial portion of the its described diversity. Sicily is the region's largest island, and, as ongoing investigations are revealing, it is inhabited by a long-overlooked but highly diverse ant fauna that combines multiple biogeographic influences. We combined qualitative and quantitative morphology of multiple castes with phylogenetic data based on ultra-conserved elements (UCEs) to describe four Temnothorax species endemic to Sicily and the neighboring Maltese Islands (Sicilian Channel). Three of these species, T. marae sp. nov., T. poldii sp. nov. and T. vivianoi sp. nov., are new to science, while a redescription finally clarifies the identity of T. lagrecai (Baroni Urbani, 1964). These descriptions provide an opportunity to discuss the current difficulties of delimiting monophyletic species-groups of Temnothorax based on morphological characters, and uncover intra-insular endemicity patterns that highlight the importance of Mediterranean paleogeography to present ant diversity and distribution.