North meets south – Taxonomic and biogeographic implications of a phylogenetic assessment of Sargassumsubgenera Arthrophycusand Bactrophycus(Fucales, Phaeophyceae)

Abstract:The Sargassumsubgenera Bactrophycusand Arthrophycuswere considered to be geographically restricted to the northern and southern hemispheres, respectively. Phylogenetic analyses of 19 Sargassumsubgenus Bactrophycusspecies and eight Sargassumsubgenus Arthrophycusspecies, based on a concatenated dataset of the loci ITS-2, cox3 and the rbcL-S spacer, showed that they formed a single clade, with Arthrophycusspecies nested within Bactrophycussection Halochloa. We merged the two subgenera as subgenus Bactrophycusand transferred “Arthrophycus”species to Sargassumsection Halochloa. The genus now includes only the two subgenera, Sargassumand Bactrophycus, and both were found at temperate and subtropical latitudes; only subgenus Sargassumoccurred at low latitudes near the equator, whereas subgenus Bactrophycushad an antitropical, disjunct distribution.