Carollina de Abrantes Casa¹, Maria Teresa de Menezes de Széchy¹, Valéria Cassano², Inara R. Mendonça², Vitória Miranda², José Eduardo Martinelli Filho³, Maria Beatriz Barbosa de Barros Barreto¹, Mariana Cabral Oliveira².
¹ Botany Department, Federal University of Rio de Janeiro
² Botany Department, University of São Paulo
³ Oceanography, Federal University of Pará
Sargassum C. Agardh, 1820 (Fucales, Phaeophyceae) is one of the most diverse genera of marine macroalgae, with 351 benthic and two pelagic species, the latter form the Sargasso Sea. Most species of Sargassum are described only on the basis of morphological characters, some of which have been shown to vary in the same individual and/or population. The plastic morphology in species of the genus causes problems such as doubtful identifications, overestimation of species and, consequently, doubts about their occurrence. Benthic species of Sargassum are common along the Brazilian coast and are a structuring component of marine communities, but the number of species is still uncertain. Currently, 14 species have been cited, by different authors, for the genus on the coast of Brazil. In this work we investigated the diversity of Sargassum species on the Brazilian coast using molecular markers and morphological analysis. Samples (benthic and holopelagic) were collected along the coast, identified based on morphological criteria and four different molecular markers (ITS2, cox2, cox3, cox3-atp6) were sequenced. Phylogenetic analyses and species delimitation methods were used. Nine morphospecies were identified, however, molecular data agreed with only two genetically distinct species occurring on the Brazilian coast. The implications of future taxonomic changes will be discussed.