Coleman AW
Phylogenetic analysis of "Volvocacae"
for comparative genetic studies
P NATL ACAD SCI USA 96 (24): 13892-13897
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.