Advances on the study of dinoflagellates (Dinophyceae) with the molecular phylogeny

Abstract

This study reviews the advances on the knowledge of the dinoflagellates with the application of the molecular phylogeny. Most of the available sequences correspond to the genes that codify the small and large subunits of the ribosomal RNA (SSU and LSU rDNA, respectively). The LSU rDNA marker, with several highly variable domains, has been preferentially used for the species separation, while the SSU rDNA marker is more useful for the separation at the genus level or to establish clades that may correspond to family ranks. These markers are unable to solve the interrelations between the classical orders, and the available sequences of other markers are still insufficient. Peridiniales, Gymnodiniales and Blastodiniales are polyphyletic, and Prorocentrales and Gonyaulacales (Crypthecodinium, Thecadinium) are matter of debate. The clades of Gymnodiniales branched between clades of thecate dinoflagellates, although in no case armoured and unarmoured species branched in the same clade. In comparison with the type of habitat, nutrition or general appearance (i.e. Blepharocysta-Roscoffia), the differences in the tabulation are, in most of cases, supported by the molecular data. Unfortunately, the collection and preservation methods render our knowledge of a great portion of the dinoflagellate diversity, in particular small naked forms and delicate species, as well as parasites or symbionts in marine invertebrates or protists. Sequences are lacking of numerous of the known genera, clades exclusively composed of environmental sequences have not been yet characterized, and extensive ocean regions, especially the deep and bottom ocean, remain nearly unexplored.