The invasive brown seaweed Rugulopteryx okamurae (Dictyotales, Ochrophyta) continues to expand: first record in Italy

The brown seaweed Rugulopteryx okamurae (Dictyotales, Ochrophyta), native to Pacific Ocean and widely distributed in Asia, has been recently recognized as emblematic case of biological invasion by marine macroalgae in European waters. 2015 and from the Strait of Gibraltar, R. okamurae has rapidly spread towards and Mediterranean coastal areas exhibiting an invasive behaviour with ecological and socio-economic impacts. Here, we report the first and genetically confirmed observation of this species in Italy, the north-western coast of Sicily (Gulf of Palermo). Specimens were found as material and as an established population on Posidonia oceanica, representing new eastern distribution limit in the Mediterranean Sea, as the species was established in Marseilles (France). Furthermore, we performed a favorability model with the current introduced distribution of the species for the , which shows most of the western Mediterranean, including the archipelago, Corsica and Sardinia, central Mediterranean, including Sicily, the northern coast of Africa together with eastern Mediterranean basin, as favorable for R. okamurae. The most probable vectors for this introduction sea currents and maritime traffic, including fishing activities. This hypothesis was by some of the ranked variables in the favorability model, i.e., current , and the proximity of the introduced population to fishing ports. These are a warning that the species can cover large sea distances via sea currents, also threatening the ecosystems and marine resources of the central and eastern Sea, as these areas are forecasted to be highly favorable regions for species. We suggest coordinated actions at the European level with stakeholders the fishing sector regarding prevention, both because it is a highly affected sector because it potentially has a very important role in the dispersion of the species.