A molecular study of euglenoid phylogeny using small subunit rDNA

The euglenoids are an ancient and extremely diverse lineage of eukaryotic f lagellates with unclear relationships among taxa. Synapomorphies for the eu glenoids include a surface pellicle and a closed mitosis with a series of s eparate sub-spindles. The taxonomy currently in use is inconsistent with th e available data and needs revision. Most euglenoid phylogenies are largely intuitive reconstructions based on a limited number of morphological chara cters. Therefore, we have added molecular characters from the Small Subunit (SSU) rDNA to generate an overall phylogenetic framework for the euglenoid s. SSU rDNA sequences from photosynthetic, osmotrophic, and phagotrophic eu glenoids were aligned based on secondary structure. Phylogenetic analysis u sing the conserved areas of the sequence was performed using parsimony, max imum likelihood, and distance methods. Trees derived using different criter ia are in agreement. The euglenoids form a distinct monophyletic clade with phagotrophic members diverging prior to the phototrophic and osmotrophic m embers. Among photosynthetic members, the biflagellate form diverged prior to the uniflagellate form. Additionally, the genus Euglena appears to be pa raphyletic, with osmotrophic taxa, such as Astasia and Khawkinea, diverging independently within the clade containing the photosynthetic genus Euglena .