New insights into the evolution and biogeography of freshwater planarians on islands in the Tyrrhenian Sea, Western Mediterranean Basin, with the integrative description of a new endemic species from Corsica (Platyhelminthes: Tricladida: Dugesia)

A recent study on the freshwater planarian fauna of Corsica and Sardinia established that the formerly presumed single species Dugesia benazzii subsumed a complex of species. In that study, a thorough integrative taxonomic approach, combining molecular, morphological, and karyological data, uncovered the presence of two new endemic species. For the present study, additional samplings were conducted on Corsica, covering several new localities. The data obtained were added to our previous datasets, which included information on specimens collected from both islands. By taking a similar integrative approach to the prior study, we here describe another new endemic species from Corsica, Dugesia xeropotamica. Although our results support the separate status of this new species, it also turned out that the evolutionary relationships among species of the Corso-Sardinian clade remain unclear, because the relationships are not well resolved. Additionally, we corroborate the presence of Dugesia mariae on the Tyrrhenian islets of Montecristo and Molara, representing new records for this group of Dugesia species in the region of the Tyrrhenian Sea. In all, our findings indicate that the evolutionary and biogeographical history of Dugesia species in this region of the Western Mediterranean is more intricate than previously thought.