The terete and sub-terete members of the red algal tribe Amansieae (Ceramiales, Rhodomelaceae)

The tribe Amansieae is composed mostly of genera with dorsiventrally flattened thalli with only a few species that are terete or sub-terete in cross-section. Two of these comprise the monotypic genera Rytiphlaea and Halopithys, both natives of the Mediterranean Sea and the northeastern Atlantic Ocean. An investigation of the relationships of these two species to each other and to the remaining terete or sub-terete species, Enantiocladia schottii and Protokuetzingia australasica, was carried out. The monotypic genus Digeneopsis from Mozambique and South Africa, which has been previously placed in the tribe Polysiphonieae, was also studied. No generic distinction was supported between Digeneopsis subopaca, Enantiocladia schottii and Halopithys incurva, and consequently all species have been included in Halopithys. Rytiphlaea tinctoria was shown to be generically distinct. Using molecular phylogenetic analysis, Rytiphlaea and Halopithys were shown to be closely related to each other but to have no particularly close affinity to Protokuetzingia.