Molecular and morphological evidence of a new sibling species of Calobius (Coleoptera: Hydraenidae) of the C. quadricollis complex from peninsular Italy

A molecular and morphological analysis was performed to clarify the taxonomic status of Italian members of the Calobius quadricollis complex (Coleoptera, Hydraenidae, Ochthebiinae), including species strictly associated with hypersaline marine rock pools along the Mediterranean and Macaronesian coasts. The analysis was mainly focused on the specific distinction and formal description of a new species, Calobius urbanelliae n. sp., from peninsular Italy. This species is of difficult morphological distinction, but, on the basis of the mitochondrial DNA marker cytochrome c oxidase subunit I, it is highly differentiated from C. quadricollis Mulsant, 1844 (NW Mediterranean) and C. steinbuehleri Baudi, 1864 (NE Mediterranean), which are partially sympatric with it along part of the western and eastern coasts of peninsular Italy. One possible palaeogeographical scenario underlying the specific differentiation of the three species is briefly discussed.