MOLECULAR PHYLOGENY OF DINOPHYSOID DINOFLAGELLATES: THE SYSTEMATIC POSITION OF OXYPHYSIS OXYTOXOIDES AND THE DINOPHYSIS HASTATA GROUP (DINOPHYSALES, DINOPHYCEAE)

The dinophysoid dinoflagellates are currently divided into three families: Amphisoleniaceae, Dinophysaceae (mainly Dinophysis Ehrenb. and Phalacroma F. Stein), and Oxyphysaceae, the latter including only one member, Oxyphysis oxytoxoides Kof. Phalacroma has been recently reinstated separately from Dinophysis, and its amended description is currently restricted to cells whose epithecae were large but < 1/4 of the cell length. With the aim of improving the phylogeny of Dinophysales, we obtained 54 new SSU rRNA gene sequences of 28 species. Taxon-rich SSU rDNA phylogenetic analysis showed that Dinophysales split into two major clades, one containing the Amphisoleniaceae (Amphisolenia F. Stein-Triposolenia Kof.) and the other containing the Dinophysaceae. The latter are divided into two well-supported sister groups, the Dinophysaceae sensu stricto (s.s.) (Dinophysis, Ornithocercus F. Stein, Histioneis F. Stein) and, tentatively, a separate family for the clade of the type and most of the Phalacroma species. Based on combined phylogenies of new SSU rDNA and available LSU rDNA data, O. oxytoxoides (elongated epitheca, > 1/4 of the cell length) branched with a strong support with the type of Phalacroma. We therefore propose Phalacroma oxytoxoides comb. nov. for O. oxytoxoides. Our SSU rDNA phylogeny also suggests that the assumed high intraspecific variability of Dinophysis hastata F. Stein hides a number of cryptic species. According to their distinct phylogenetic placement, the forms D. hastata f. phalacromides J circle divide rg. and D. hastata f. uracanthides J circle divide rg. should be erected at the species level. We propose for them the names Dinophysis phalacromoides comb. nov. and Dinophysis uracanthoides comb. nov.