Modern classification of dinoflagellates and recently described taxa: a review

Unlike other major taxa ascribed to a lgae, dinoflagellates maintain their stable positi on in the tree of life together with Ciliata and Apicomplexa, forming the clade Alveolat a. After publication of the classification of Dinoflagellata by Fensome et al. (1993), many spe cies and genera and some suprageneric taxa were introduced. Most new families and orders (Toro diniales, Amphidiniales andTovelliales) were described based on both molecular and ultrastructural data during the last three years. In the mole cular trees, the Torodiniales is not closely related to other dinoflagellates;it includes the families Torodiniaceae and Kapelodiniaceae tha t differ significantly in the position and shape of the apical structure complex. The order Amph idiniales is in the basal position in the dinoflagellate tree. The order Tovelliales was erected for freshwater woloszynskioiddinoflagellates with a peculiar anatomy of the eyespot (extraplastidial, composed of lipid globules not surrounded by membranes). Separation of the Thoracosphaerales as an order is under question. The descriptions of the new taxa were principally based on rDNA, r RNA and ITS genes; mitochondrial gene sequences are still few. Morphological characters trad itionally used to distinguish genera have been replaced with features supported by both molec ular and ultrastructural data. Based on mitosis and molecular data, the division Dinoflagellata may be divided into three major groups: th e Oxyrrhinales (perhaps a class), Syndiniophy ceae and Dinophyceae. Polyphyletism of som e orders is not argued (Gymnodiniales, Peridiniales, Blastodiniales andPhytodiniales). Het erotrophic species occupy the branches at the base of the dinoflagellate tree. Chloroplast-encode d genes are of limited use for constructing a phylogenetic tree because only 50% of the species in the division are photosynthetic and dino flagellate chloroplasts arose by at least eight ind ependent symbioses. The most recent dinoflagellate trees are based on nuclear-encoded rDNA sequences. The combined molecular (concatenat ed multi-gene analyses) and ultrastructural data approach should be applied, considering nuc lear and mitochondrial genomes.