Phylogeny of the kinetoplastida: Taxonomic problems and insights into the evolution of parasitism

To further investigate phylogeny of kinetoplastid protozoa, the sequences o f small subtmit (IBS) ribosomal RNA of nine bodonid isolates and ten isolat es of insect trypanosomatids have been determined. The root of the kinetopl astid ti ee was attached to the branch of Bodo designis and/or Cruzella mar ina. The suborder Trypanosomatina appeared as a monophyletic group, while t he suborder Bodonina was paraphyletic. Among bodonid lineages, parasitic or ganisms were intermingled with free-living ones, implying multiple transiti ons to parasitism and supporting the 'vertebrate-first hypothesis: The tree indicated that the genera Cryptobia and Bodo are artificial taxa. Separati on of fish cryptobias and Trypanoplasma borreli as different genera was not supported. In trypanosomatids, the genera Leptomonas and Blastocrithidia w ere polyphyletic, similar to the genera Herpetomonas and Crithidia and in c ontrast to the monophyletic genera Trypanosoma and Phytomonas. This analysi s has shown that the morphological classification of kinetoplastids does no t in general reflect their genetic affinities and needs a revision.