Arrival of the non-indigenous brown alga Mutimo cylindricus to the Atlantic Ocean

Every introduction of a non-indigenous species (NIS) in coastal environments poses a threat to the native species and communities, as its effects in the ecosystem are not readily predictable. Introduction rates have kept increasing in the last decades, and our finding of the brown alga Mutimo cylindricus in the Canary Islands is another example of this general trend. This work represents the first record of the species outside its native range (Japan, Korea and the Philippines) in half a century, since its report in 1973 in Baja California, and marks the first report of M. cylindricus in the Atlantic Ocean. We analyzed the morphology of a male gametophyte observed in the Canary Islands and its phylogenetic relationship with other known populations using rbcL and cox3 genes. The morphology of M. cylindricus in the Canary Islands is consistent with previous descriptions and the phylogenetic analyses revealed the close relationship with native populations from Japan. The finding of a male gametophyte is noteworthy, as introduced and some native populations of this species are composed exclusively by female gametophytes and thought to be parthenogenic, whereas androgenesis is considered rare in the field. Maritime traffic appears as the most apparent introduction vector of the species and it seems plausible that microscopic crustose sporophytes were present near the collecting site, highlighting the need of further monitoring of the invasive potential of this species in the Atlantic Ocean.