New contribution to the knowledge of the genus Cystoseira C. Agardh in the Mediterranean Sea, with the reinstatement of species rank for C-schiffneri Hamel

A survey of the species of Cystoseira (Fucales, Phaeophyceae, Ochrophyta) ofTunisia highlighted six Mediterranean endemic taxa rare or new for this country: C. barbataf. aurantia, C. brachycarpa var. claudiae, C. compressa subsp. pustulata, C. foeniculaceaf. dubia, C. hyblaea and C. spinosa var. tenuior. The discovery and the study of these species,some of which were little known, have allowed some taxonomic and biogeographicaluncertainties to be identified and discussed. On the basis of the results, the transfer ofC. discors f. dubia to C. foeniculacea as C. foeniculacea f. dubia and the reinstatementof species rank for the Mediterranean endemic species C. schiffneri are proposed