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

ABSTRACTMolecular sequence analyses of specimens previously identified as Cirrulicarpus sp. in the southeastern Brazil (Espírito 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.KEYWORDS: COI-5PGigartinalesMolecular phylogenyrbcLRhodoliths bedsTaxonomy ACKNOWLEDGEMENTSWe thank Feresa Cabrera for providing sequences of Meredithia hawaiiensis, and Gary Saunders by sequences of Commanderella, Hommersandia and Velatocarpus. LPS thanks the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (Bolsista CAPES/BRASIL 88887.515974/2020-00) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for Postdoctoral Fellowship (152282/2022-0). MTF thanks CNPq for the Productivity Fellowship (311195/2021-0).Supplementary materialSupplemental data for this article can be accessed online at https://doi.org/10.1080/00318884.2023.2241123DISCLOSURE STATEMENTNo potential conflict of interest was reported by the authors.Additional informationFundingThis study was partially supported by a research grant from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP 2016/50370-7 and 2017/50341-0).