Abstract Ralfsia is the largest genus within the family Ralfsiaceae and currently comprises fourteen recognized species. It is characterized by pseudoparenchymatous crusts with firmly adhering straight or curved erect filaments, a single chloroplast per cell, sessile or pedicellate unangia with a paraphysis, and intercalary plurangial reproductive organs typically capped with one or more sterile apical cells. In this study, Ralfsia claviformis sp. nov. from Korea is described based on integrative molecular and morpho-anatomical analyses. Phylogenetic analyses inferred from the concatenated rbc L and COI-5P dataset place R. claviformis sp. nov. within Ralfsia as a distinct lineage with strong bootstrap support although the Ralfsia clade was recovered as a group without statistical support (BS < 50; <0.75). This new species is characterized by olive to greenish brown crustose thalli up to 8 cm in breadth, straight erect filaments, obovate unangia with a paraphysis, and pluangia forming one to two rows of reproductive filaments arising from subterminal cells and each capped with two to six sterile cells forming a clavate-shaped sterile filament. Both molecular divergence and morpho-anatomical characters clearly distinguish R. claviformis sp. nov. from all other congeners. Ralfsia claviformis sp. nov. is distributed along the western and southern coasts of Korea, including Jeju Island, and in Japan.
Oteng’o et al. (Sat,) studied this question.