MOLECULAR PHYLOGENY OF SELECTED SPECIES OF THE ORDER DINOPHYSIALES (DINOPHYCEAE)-TESTING THE HYPOTHESIS OF A DINOPHYSIOID RADIATION(1).

Almost 80 years ago, a radiation scheme based on structural resemblance was first outlined for the marine order Dinophysiales. This hypothetical radiation illustrated the relationship between the dinophysioid genera and included several independent, extant lineages. Subsequent studies have supplied additional information on morphology and ecology to these evolutionary lineages. We have for the first time combined morphological information with molecular phylogenies to test the dinophysioid radiation hypothesis in a modern context. Nuclear-encoded LSU rDNA sequences including domains D1-D6 from 27 species belonging to Dinophysis Ehrenb., Ornithocercus F. Stein, Phalacroma F. Stein, Amphisolenia F. Stein, Citharistes F. Stein, and Histioneis F. Stein were obtained from the Indian Ocean. Previously, LSU rDNA has only been determined from one of these. In Bayesian analyses, Amphisolenia formed a long basal clade to the other dinophysioids. These diverged into two separate lineages, the first comprised species with a classical Phalacroma outline, also including the type species P. porodictyum F. Stein. Thus, we propose to reinstate the genus Phalacroma. The relationship between the genera in the second lineage was not well resolved. However, the molecular phylogeny supported monophyly of Histioneis and Citharistes and showed the genus Dinophysis to be polyphyletic and in need of a taxonomic revision. Species of Ornithocercus grouped with Citharistes, but this relationship remained unresolved. The phylogenetic trees furthermore revealed convergent evolution of several morphological characters in the dinophysioids. According to the molecular data, the dinophysioids appeared to have evolved quite differently from the radiation schemes previously hypothesized. Four dinophysioid species had identical LSU rDNA sequences to other well-established species.