Coleman AW

Phylogenetic analysis of "Volvocacae" for comparative genetic studies
P NATL ACAD SCI USA 96 (24): 13892-13897 NOV 23 1999

Abstract:
Sequence analysis based on multiple isolates representing essentially all genera and species of the classic family Volvocaeae has clarified their phylogenetic relationships. Cloned internal transcribed spacer sequences (ITS-1. and ITS-2, flanking the 5.8S gene of the nuclear ribosomal gene cistrons) were aligned, guided by ITS transcript secondary structural features, and subjected to parsimony and neighbor joining distance analysis. Results confirm the notion of a single common ancestor, and Chlamydomonas reinharditii alone among all sequenced green unicells is most similar. interbreeding isolates were nearest neighbors on the evolutionary tree in all cases. Some taxa, at whatever level, prove to be clades by sequence comparisons, but others provide striking exceptions. The morphological species Pandorina morum, known to be widespread and diverse in mating pairs, was found to encompass all of the isolates of the four species of Volvulina. Platydorina appears to have originated early and not to fall within the genus Eudorina, with which it can sometimes be confused by morphology. The four species of Pleodorina appear variously associated with Eudorina examples. Although the species of Volvox are each clades, the genus Volvox is not The conclusions confirm and extend prior, more limited, studies on nuclear SSU and LSU rDNA genes and plastid-encoded rbcL and atpB. The phylogenetic tree suggests which classical taxonomic characters are most misleading and provides a framework for molecular studies of the cell cycle-related and other alterations that have engendered diversity in both vegetative and sexual colony patterns in this classical family.

Angeler DG, Schagerl M, Coleman AW

Phylogenetic relationships among isolates of Eudorina species (Volvocales, Chlorophyta) inferred from molecular and biochemical data
J PHYCOL 35 (4): 815-823 AUG 1999

Abstract:
Phylogenetic analyses of 19 strains representing five species of Eudorina, one strain of Pleodorina indica, and seven strains of Yamagishiella unicocca were carried out by sequencing the internal transcribed spacer region (ITS 1 and ITS 2) of the nuclear ribosomal DNA (rDNA) repeats. The sequence data resolved five phylogenetic groups, one consisting of Y. unicocca and the other four encompassing all the Eudorina species. Two isolates, Eudorina sp, (ASW 05157) and Pleodorina indica (ASW 05153), were of uncertain affiliation, Whereas one monophyletic group included strains of E. elegans only, the other strains of E. elegans appeared alongside E. cylindrica, E. illinoisensis, and E. unicocca var. unicocca in the other Eudorina clades. The distribution pattern of the carotenoid loroxanthin ([3R,3'R,6'R]beta,epsilon-carotene-3,19,3'-triol), a systematically useful biochemical marker within chlorophycean flagellates, was shown to match the evaluated molecular data. Whereas it was either totally absent or universally present in six of the deduced phylogenetic lines, it occurred randomly in the E. elegans clade containing only E, elegans isolates. The results substantiated the current hypothesis that the unique vegetative morphology of E. elegans has independently arisen at various times during evolution and that it is not a marker of a monophyletic group.

Nozaki H, Ohta N, Takano H, et al.

Reexamination of phylogenetic relationships within the colonial Volvocales (Chlorophyta): An analysis of atpB and rbcL gene sequences
J PHYCOL 35 (1): 104-112 FEB 1999

Abstract:
The chloroplast-encoded atpB gene was sequenced from 33 strains representing 28 species of the colonial Volvocales (the Volvocaceae and its relatives) to reexamine phylogenetic relationships as previously deduced by morphological data and rbcL gene sequence data.1128 base pairs in the coding regions of the atpB gene were analyzed by MP, NJ, and ML analyses, Although supported with relatively low bootstrap values (75% and 65% in the NJ and ML analyses, respectively), three anisogamous/oogamous volvocacean genera-Eudorina, Pleodorina, and Volvox, excluding the section Volvox(= Euvolvox, illegitimate name), constituted a large monophyletic group (Eudorina group), Outside the Eudorina group, a robust Lineage composed of three species of Volvox sect, Volvox was resolved as in the rbcL gene trees, rejecting the hypothesis of the previous cladistic analysis based on morphological data that the genus Volvox is monophyletic, In addition, the NJ and ML trees suggested that Eudorina is a non-monophyletic genus as inferred from the morphological data and rbcL gene sequences. Although phylogenetic status of the genus Gonium is ambiguous in the rbcL gene trees and the paraphyly of this genus is resolved in the cladistic analysis based on morphological data, the atpB gene sequence data suggest monophyly of Gonium with relatively low bootstrap values (56-61%) in the NJ and ML trees. On the basis of the combined sequence data (2256 base pairs) from atpB and rbcL genes, Gonium was resolved as a robust monophyletic genus in the NJ and ML trees (with 68-86% bootstrap values), and Eudorina elegans Ehrenberg represented a paraphyletic species positioned most basally within the Eudorina group, However, phylogenetic status and relationships of the families of the colonial Volvocales were still almost ambiguous even in the combined analysis.