The Caulerpa racemosa complex (Caulerpales, Ulvophyceae) in the Mediterranean Sea

The compendium of literature citations for Caulerpa racemosa (Forsskal) J. Agardh in the Mediterranean Sea, together with available fresh and preserved material from both known and new localities, were critically examined. This analysis suggests that three distinct taxa of C. racemosa co-exist in the Mediterranean Sea. (i) C. racemosa var, turbinata - uvifera, known since 1926 and 1931 in Tunisia and in the Levantine basin (ii) var. lamourouxii f. requienii, known since the 1950s in the Levantine basin and (iii) an invasive variety which has been quickly spreading, since the early 1990s, throughout most of the Mediterranean Sea (Balearic Islands, France, Western and Southern Italy, Sardinia, Sicily, Greece, Crete, Turkey, Cyprus, Libya and Lampedusa Island, off Tunisia). The last variety differs mainly from the two first varieties by its upright axes with clavate, more or less inflated branchlets, which are uncrowded and radially to distichously disposed. Within the C. racemosa complex, several taxa are known to bear uncrowded, radially and/or distichously arranged branchlets. Among them, C. racemosa var, occidentalis, a tropical taxon widely distributed throughout the tropical seas, appears to be closest to the invasive Mediterranean variety of C. racemosa. Various criteria (taxonomy, kinetics of spread, tendancy to pullulate) suggest that C. racemosa aff. var, occidentalis could be a taxon recently introduced to the Mediterranean Sea.