The unnoticed northward expansion of Najas marina subsp. armata (Hydrocharitaceae) in the Mediterranean area: an effect of climate change?

Recent reports of Najas marina L. (Hydrocharitaceae) from Sicily have been interpreted as a confirmation of its presence on the island, where it was earlier mentioned in the 1800s. However the recent finds do not represent “N. marina” (currently N. major All.) but N. marina subsp. armata Horn (= N. delilei Rouy), a different taxon, previously not recorded from Sicily. According to those reports and several new finds presented here, it appears to be invading reservoirs and lakes in southern Sicily and seems to be naturally expanding its range. Climate change is suggested as possible cause of this shift. The same trend appears to be taking place across the whole N Mediterranean area, from Portugal to Cyprus. The old Sicilian record of “N. marina” (i.e. N. major) remains unconfirmed: the only site where it was collected was completely destroyed to make space for houses and touristic exploitation.