A new, putatively semisubterranean, Rhithrodytes diving beetle from southwestern Sardinia (Coleoptera: Dytiscidae)

The diving beetle genus Rhithrodytes Bameul, 1989 is endemic to areas surrounding the Western Mediterranean Basin, and currently includes six lotic species; three each in Europe and North Africa. Here we describe a striking new species, Rhithrodytes pantaleonii sp. nov., discovered during recent fieldwork in southwestern Sardinia. The new species differs markedly from the only previously known Rhithrodytes from the Tyrrhenian Islands, R. sexguttatus (Aubé, 1838). The pale, flattened appearance of R. pantaleonii sp. nov., together with its small eyes and scarcity during collecting, all point to it being semisubterranean. A combination of mitochondrial and nuclear DNA sequences, obtained non-destructively from the holotype, allow us to reconstruct the evolutionary history and historical biogeography of this taxon and take the opportunity to publish the mitogenome of the new species. Rhithrodytes pantaleonii sp. nov. is shown to be sister to R. sexguttatus, these taxa apparently having diverged during the Miocene, when the Sulcis-Iglesiente region of southwestern Sardinia was separated from the rest of Corsico-Sardinia by the Sardinian Seaway. Our discovery adds to our understanding of the biogeography of the Tyrrhenian Islands, and further highlights the importance of the Sulcis-Iglesiente region as an area of endemism in its own right.