The genus Sargassum is taxonomically complex and poorly studied in the Eastern Tropical Pacific. We analyzed specimens collected along the Pacific coast of Central America and compared them with historical records and herbarium material to clarify species identities. Using detailed morphological analyses with molecular phylogenetic reconstruction based on concatenated ITS2 (Internal Transcribed Spacer 2) and COX3 (Cytochrome Oxidase Subunit 3) sequences, we identify two distinct morphotypes corresponding to two well-supported clades. One clade matches the morphology and molecular profile of Sargassum liebmannii. We provide the most comprehensive description of this species to date, including the first published ITS2 and COX3 sequences. Since Taylor’s 1945 work on the tropical Pacific of the Americas, S. liebmannii has been widely reported and considered the predominant species. It forms a genetic clade with other species from the Gulf of California; therefore, we propose a new section, Herporhizum/Sinicola. The second clade represents a previously unrecognized taxon from Central America, which we describe as a new species: Sargassum lacrucense, within the subgenus Sargassum, section Sargassum. Contrary to previous reports, Sargassum brandegeei—now recognized as Sargassum herporhizum—was not found in the region. This study underscores the importance of integrating morphological and molecular data to resolve Sargassum taxonomy in Central America.
Viales-Cubillo et al. (Sat,) studied this question.