A revision of the genus Sargassum (Fucales, Phaeophyceae) in South Africa

• We revised the 27 different Sargassum epithets listed for South Africa.
• Combined morphological and molecular analyses revealed only 7 species.
• We propose 5 new synonyms.
• A key for identification and detailed illustrations are provided.
• We discuss the distribution of the genus in the South West Indian Ocean.

A total of 27 different Sargassum epithets are listed in the literature for South Africa. The main aim of our study was to revise this species list using newly collected specimens in order to provide a reliable and illustrated tool for the identification of South African Sargassum. Based on morphological and molecular analyses of the nuclear ITS2, chloroplastic partial RuBisCO operon and mitochondrial cox3 and 23S, we identified a total of seven taxa including two new records (*) for South Africa: Sargassum elegans, Sargassum cymosum var. scabriusculum, Sargassum ilicifolium, Sargassum ilicifolium var. acaraeocarpum*, Sargassum incisifolium, Sargassum obovatum and, Sargassum polycystum*. As a result of our taxonomic revision, we conclude that a number of the species listed in the literature for South Africa were misapplied or not current and we propose five new taxonomic synonyms. We provide an exhaustive list of the Sargassum species present in South Africa, a key for identification and detailed illustrations.