Phylogenetic analysis of chloroplast small-subunit rRNA genes of the genusEuglena Ehrenberg

Almost complete sequences of plastid SSU rDNA (165 rDNA) from 17 species be longing to the order Euglenales (sensu Nemeth, 1997; Shi et ab, 1999) were determined and used to infer phylogenetic relationships between 10 species of Euglena, three of Phacus, and one of each of Colacium, Lepocinclis, Stro mbomonas, Trachelomonas and Eutreptia. The maximum-parsimony (MP), maximum- likelihood (ML) and distance analyses of the unambiguously aligned sequence fragments imply that the genus Euglena is not monophyletic. Parsimony and distance methods divide Euglenaceae into two sister groups. One comprises o f representatives from the subgenera Phacus, Lepocinclis and Discoglena (se nsu Zakrys, 1986), whereas the other includes members of Euglena and Callig lena subgenera (sensu Zakrys, 1986), intermixed with representatives of Col acium, Strombomonas and Trachelomonas. In all analyses subgenera Euglena - together with Euglena polymorpha (representative of the subgenus Calliglena ) - and Discoglena - together with Phacus and Lepocinclis- form two well-de fined clades. The data clearly indicate that a substantial revision of eugl enoid systematics is very much required, nevertheless it must await while m ore information can be gathered, allowing resolution of outstanding relatio nships.