Phylogenetic analysis of phagotrophic, phototrophic and osmotrophic euglenoids by using the nuclear 18S rDNA sequence

Phylogenetic analyses of 35 strains including 25 previously published seque nces and 10 which have been newly sequenced, representing two species of Eu glena, five species of Phacus and three species of Astasia, were carried ou t using the SSU rDNA. Parsimony, distance and maximum-likelihood inferred p hylogenies support (1) monophyly of the euglenoids, (2) kinetoplastids as t he sister group, (3) the phagotrophic Petalomonas cantuscygni Cann et Penni ck anchoring the base of the euglenoid lineage, (4) evolution of phototroph y within the euglenoids from a single event, (5) multiple origins of osmotr ophic euglenoids and (6) polyphyly of the genera Euglena Ehrenberg and Phac us Dujardin. Analyses also indicate that Lepocinclis Perty, Trachelomonas E hrenberg and Astasia Dujardin are polyphyletic. In addition, the results su ggest that neither the Euglenales nor the Eutreptiales form a monophyletic lineage, thus questioning currently available classifications. Concerning t he phagotrophic mode of nutrition, the data suggest that the feeding appara tus arose multiple times.