The presence of exotic Hypnea flexicaulis (Rhodophyta) in the Mediterranean Sea as indicated by morphology, rbcL and cox1 analyses.

Here we report the first finding of Hypnea flexicaulis Yamagishi and Masuda in the Mediterranean Sea (Lagoon of Venice, Italy), identified through molecular analyses using the plastid ribulose-1,5- bisphosphate carboxylase/oxygenase (rbcL) and the mitochondrial protein-coding cytochrome c oxidase subunit I (cox1) genes. The phylogenetic reconstruction, based on rbcL+cox1 multiple alignment, showed that all specimens of H. flexicaulis from Venice, Korea, Philippines and Taiwan were included in a monophyletic group supported by a bootstrap value of 100%. It is highly probable that H. flexicaulis has been introduced from Indo-Pacific populations, in particular the Korean one, probably via ship traffic or shellfish transfers. The use of DNA barcoding combined with morphological observations was, in this case, a rapid way to identify this allochthonous species.