Phylogenetic relationships among isolates of Eudorina species (Volvocales,Chlorophyta) inferred from molecular and biochemical data

Phylogenetic analyses of 19 strains representing five species of Eudorina, one strain of Pleodorina indica, and seven strains of Yamagishiella unicocc a were carried out by sequencing the internal transcribed spacer region (IT S 1 and ITS 2) of the nuclear ribosomal DNA (rDNA) repeats. The sequence da ta resolved five phylogenetic groups, one consisting of Y. unicocca and the other four encompassing all the Eudorina species. Two isolates, Eudorina s p, (ASW 05157) and Pleodorina indica (ASW 05153), were of uncertain affilia tion, Whereas one monophyletic group included strains of E. elegans only, t he other strains of E. elegans appeared alongside E. cylindrica, E. illinoi sensis, and E. unicocca var. unicocca in the other Eudorina clades. The dis tribution pattern of the carotenoid loroxanthin ([3R,3'R,6'R]beta,epsilon-c arotene-3,19,3'-triol), a systematically useful biochemical marker within c hlorophycean flagellates, was shown to match the evaluated molecular data. Whereas it was either totally absent or universally present in six of the d educed phylogenetic lines, it occurred randomly in the E. elegans clade con taining only E, elegans isolates. The results substantiated the current hyp othesis that the unique vegetative morphology of E. elegans has independent ly arisen at various times during evolution and that it is not a marker of a monophyletic group.