Molecular Phylogeny of Noctilucoid Dinoflagellates (Noctilucales, Dinophyceae)
Résumé
The order Noctilucales or class Noctiluciphyceae encompasses three families of aberrant dinoflagellates (Noctilucaceae, Leptodiscaceae and Kofoidiniaceae) that, at least in some life stages, lack typical dinoflagellate characters such as the ribbon-like transversal flagellumor condensed chromosomes. Noctilucascintillans, the first dinoflagellate to be described, has been intensively investigated. However, its phylogenetic position based on the small subunit ribosomal DNA ( SSU rDNA) sequence is unstable and controversial. Noctiluca has been placed either as a nearly diverging lineage that diverged after Oxyrrhis and before the dinokaryotes-coredinoflagellates- or as a recent lineage branching from unarmoured dinoflagellates in the order Gymnodiniales. So far, the lack of other noctilucoid sequences has hampered the elucidation of their phylogenetic relationships to other dinoflagellates. Furthermore, even the monophyly of the noctilucoids remained uncertain. We have determined SSU rRNA gene sequences for Kofoidiniaceae, those of the type Spatulodinium (=Gymnodinium) pseudonoctiluca and another Spatulodinium species, as well as of two species of Kofoidinium, and the first genesequence of Leptodiscaceae, that of Abedinium (=Leptophyllus) dasypus. These taxa were collected from their type localities, the English Channel and the NW Mediterranean Sea, respectively. Phylogenetic analyses place the Noctilucales as a monophyletic group at a basal position close to parasites of the Marine Alveolate Group I (MAGI) and the Syndiniales (MAGII), before the core of dinokaryotic dinoflagellates, although with moderate support. (C) 2010 Elsevier GmbH. All rights reserved.