Caulacanthus ustulatus (Gigartinales, Rhodophyta) from Brittany (France) is an introduction from the Pacific Ocean

Caulacanthus ustulatus (Turner) Kutzing was originally described from Cadiz (SW Spain) and is the only species of the genus found in Europe. For many years, the known northern limit was in the Bay of Biscay (Biarritz, south-w est France), but the alga was recently recorded in Brittany, France. DNA se quences of the plastid encoded Rubisco spacer and sequences of the nuclear ribosomal DNA internal transcribed spacer (rDNA ITS2) were used to determin e the relationships between samples of Caulacanthus from Brittany (Roscoff) , southern Europe (Gibraltar and Albufeira in Portugal) and East Asia (Chin a, Japan). The sequence data obtained revealed two distinct groupings: a Pa cific group containing the samples from China, Japan and Roscoff and a grou p containing the samples from southern Europe. This finding is consistent w ith the hypothesis that Caulacanthus in Brittany has been introduced from t he Pacific Ocean. Minor morphological differences were observed between iso lates From the two groups grown under identical culture conditions. (C) 200 0 Adac/Editions scientifiques ct medicales Elsevier SAS.