PHYLOGENETIC-RELATIONSHIPS OF SELECTED EUGLENOID GENERA BASED ON MORPHOLOGICAL AND MOLECULAR-DATA

The small subunit rRNA (SSU rRNA) coding regions sequenced from the eu glenoids Petalomonas cantuscygni, Peranema trichophorum, and Khawkinea quartana were used to assess the phylogenetic relationships of these genera within the Euglenozoa. Phylogenies derived from distance, parsi mony, and maximum likelihood methods infer that the euglenoids and kin etoplastids form sister clades within a monophyletic assemblage Distan ces representative of closely related lineages separate the genera wit hin the Kinetoplastida, whereas larger distance values separate genera within the euglenoid assemblage. The results of the morphological and molecular studies suggest that phagotrophy arose early in the eugleno zoan lineage with the subsequent acquisition of phototrophy, osmotroph y, and parasitism. Phagotrophic euglenoids with a pellicle composed of longitudinal strips appear to have diverged prior to genera with heli cally arranged strips. This study suggests that the hypothetical ances tor to the Euglenozoa was a phagotroph with two flagella, both contain ing paraxonemal rods. Furthermore, its basal bodies contained proximal cartwheels, were connected by a prominent fiber, and were anchored wi th three asymmetrically arranged flagellar roots.