Molecular assessment of specimens previously assigned to Cirrulicarpus (Kallymeniaceae, Rhodophyta) in Brazil, with the description of Meredithia dichotoma sp. nov.

Molecular sequence analyses of specimens previously identified as Cirrulicarpus sp. in the southeastern Brazil (Espirito Santo coast), indicated that they are more closely related to the genus Meredithia than to the genus Cirrulicarpus. The new species Meredithia dichotoma is herein proposed to accommodate this uncommon and endemic taxon, morphologically characterized by an erect, narrow, strap-shaped thallus, up to 16 cm long, mostly dichotomously branched, with regular constrictions, densely to moderately filamentous medulla, with occasional ganglionic cells, and an expanded medullary region in the basal transverse sections, resembling a midrib in surface view. The species is also supported by the sequence divergence from its congeners: =4.3% and 2.2% in the COI-5P and rbcL markers, respectively. Meredithia dichotoma differs from other 11 species of the genus by its dimensions and general habit, never forming expanded blades. This is a new genus record for Brazil and the first species of Meredithia known to occur in the western South Atlantic, increasing the known diversity in the red algal family Kallymeniaceae.