One genus, four different stories: evolutionary history, bionomics and biogeography of the monotypic tribe Stenostomatini (Coleoptera: Oedemeridae)

The false blister beetle tribe Stenostomatini includes only the genus Stenostoma, with four species showing an intriguing distribution: Stenostoma lowei (Madeira), Stenostoma cossyrense (Pantelleria), Stenostoma melitense (Malta and southern Sicily) and Stenostoma rostratum, widely distributed along the Mediterranean and North Atlantic coasts. The evolutionary history leading to this distribution has not been investigated. Here, we explore the phylogeny and evolutionary history of the tribe, adopting an integrative approach that combines morphological and molecular data (mitochondrial COI and nuclear CAD and 28S). Moreover, we propose a new key for species identification and update the knowledge on adult and larval ecology. Finally, we propose the following explanation for the current distribution of the species. The genus originated in the Miocene, with S. lowei belonging to the oldest lineage. The remaining species share a common ancestor, dating to the Messinian Salinity Crisis. Stenostoma melitense and S. cossyrense are well differentiated according to morphology, but not according to molecular analysis. The wide distribution of S. rostratum might be related to its strategy of laying eggs within beached driftwood, where larvae develop, easily transported by the currents. Given that neither morphological nor molecular differentiation was detected between the two subspecies of S. rostratum, we propose the new synonymy Stenostoma rostratum septentrionale Švihla, 2005 = Stenostoma rostratum (Fabricius, 1787) syn. nov.