Aliens in changing seascapes: a newly reported non-native sacoglossan (Mollusca, Heterobranchia) in the western Mediterranean Sea

We report the discovery of the Indo-Pacific sacoglossan Elysia nealae Ostergaard, 1955 from northeastern Sardinia (Central Tyrrhenian Sea). This is the first record of this species in the western Mediterranean Sea and only the second for the whole of the Mediterranean Sea following a report from Cape Epanomi, Greece. We discuss the identification of this species as well as the expansion of its geographical range. Data on the ecology and behavior of E. nealae leads us to hypothesize that the increase in the Mediterranean’s water temperature due to climate change has favored this non-native species and contributed to its expanded distribution.