Nozaki H, Ito M, Uchida H, et al.
Phylogenetic
analysis of Eudorina species
(Valvocaceae, Chlorophyta) based on rbcL gene sequences
J PHYCOL 33 (5): 859-863 OCT 1997
Abstract:
Species and varieties in the genus Eudorina Ehrenberg (Volvocaceae,
Chlorophyta) were evaluated on the basis of phylogenetic analyses of the large
subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) gene sequence
from 14 strains of four Eudorina species, as well as from nine species
of Pleodorina and Volvox. The sequence data suggested that 10 of the 14 Eudorina
strains form three separate and robust monophyletic groups within the
nonmonophyletic genus Eudorina. The first group comprises ail three
strains off. unicocca G. M. Smith; the second group consists of one of the E,
elegans Ehrenberg var elegans strains, the E. cylindrica Korshikov strain, and
both E. illinoisensis (Kofoid) Pascher strains; and the third group consists of
two monoecious varieties off, elegans [two strains of E. elegans var synoica
Goldstein and one strain of E. elegans var. carteri (G. hi. Smith) Goldstein].
In addition, E. illinoisensis represents a poly- or paraphyletic species within
the second group. The remaining four strains, all of which are assigned to E.
elegans var. elegans, are nonmonophyletic. Although their position in the
phylogenetic trees is more or less ambiguous, they are ancestral to other taxa
ill the large anisogamous/oogamous monophyletic group including Eudorina,
Pleodorina, and Volvox (except for sect. Volvox). Thus, the four Eudorina
groups resolved in the present molecular phylogeny do not correspond with the
species concepts of Eudorina based on vegetative morphology, but they do
reflect the results Of the previous intercrossing experiments and modes of
monoecious and dioecious sexual reproduction.
Angeler DG, Schagerl M
Distribution
of the xanthophyll loroxanthin in selected members of the Chlamydomonadales and
Volvocales (Chlorophyta)
PHYTON-ANN REI BOT A 37 (1): 119-132 1997
Abstract:
The distribution of the xanthophyll loroxanthin in selected members of the
chlorophycean flagellate orders Chlamydomonadales and Volvocales
(Chlamydophyceae) was established by rp-HPLC. The newly found facts of our
study are: (1) the absence of loroxanthin in the Tetrabaenaceae and (2) the
presence of loroxanthin in members of the Volvocaceae: Pandorina morum and Eudorina
elegans exhibit an intraspecific disjunct occurence of this pigment. This is in
contrast to previous studies where loroxanthin was found to be absent within
this family. The consequences of our data on the recently proposed usefulness
as phylogenetical marker within chlorophycean flagellates are discussed.
Nozaki H, Ito M, Sano R, et al.
Phylogenetic
analysis of Yamagishiella and Platydorina (Volvocaceae, Chlorophyta) based on
rbcL gene sequences
J PHYCOL 33 (2): 272-278 APR 1997
Abstract:
Yamagishiella, based on Pandorina unicocca Rayburn et Starr is distinguished
from Eudorina by its isogamous sexual reproduction, whereas Platydorina
exhibits anisogamous sexual reproduction. In the present study, rue sequenced
the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL)
genes from five Japanese and North American strains of Y. unicocca (Rayburn et
Stair) Nozaki, true Platydorina caudata Kofoid strains, and two strains of Eudorina
unicocca G. M. Smith, as well as eight related colonial and unicellular
species. Phylogenetic trees were constructed based on these sequence data and
on previously published rbcL gene sequences from 23 volvocalean species in
order to deduce phylogenetic relationships within the colonial Volvocales, with
particular regard to the phylogenetic positions and status of the genera
Yamagishiella and Platydorina. Two robust monophyletic groups of the
anisogamous/oogamous volvocacean species were resolved in the maximum-parsimony
tree as well as in the neighbor-joining distance tree. One of the two groups
comprises three species of Volvox section Volvox, whereas the other is composed
of other sections of Volvox as well as of all the species of Eudorina
and Pleodorina. Platydorina, however, was positioned outside these two
monophyletic groups. Therefore, derivation of the Platydorina lineage may be
earlier than that of such anisogamous/oogamous groups, or origin of ''anisogamy
with sperm, packets'' in Platydorina may De independent of sperm packet
evolution in Eudorina, Pleodorina, and Volvox. It was also resolved with
high bootstrap values that all of the Y. unicocca strains form a monophyletic
group positioned outside the large monophyletic group including Eudorina
and Pleodorina. These reject the possibility of the reverse evolution of
isogamy from anisogamy to give rise to Yamagishiella within the lineage of Eudorina.
Liss M, Kirk DL, Beyser K, et al.
Intron
sequences provide a tool for high-resolution phylogenetic analysis of volvocine
algae
CURR GENET 31 (3): 214-227 MAR 1997
Abstract:
Three nuclear spliceosomal introns in conserved locations were amplified and
sequenced from 28 strains representing 14 species and 4 genera of volvocalean
green algae. Data derived from the three different introns yielded congruent
results in nearly all cases. In pairwise comparisons, a spectrum of
taxon-specific sequence differences ranging from complete identity to no
significant similarity was observed, with the most distantly related organisms
lacking any conserved elements apart from exon-intron boundaries and a
pyrimidine-rich stretch near the 3' splice site. A metric (SI50), providing a
measure of the degree of similarity of any pair of intron sequences, was
defined and used to calculate phylogenetic distances between organisms whose
introns displayed statistically significant similarities. The rate of sequences
divergence in the introns was great enough to provide useful information about
relationships among different geographical isolates of a single species, but in
most cases was too great to provide reliable guides to relationships above the
species level. A substitution rate of approximately 3 x 10(-8) per intron
position per year was estimated, which is about 150-fold higher than in nuclear
genes encoding rRNA and about 10-fold higher than the synonymous substitution
rate in protein-coding regions. Thus, these homologous introns not only provide
useful information about intraspecific phylogenetic relationships, but also
illustrate the concept that different parts of a gene may be subject to
extremely different intensities of selection. The intron data generated here
(1) reliably resolve for the first;time the relationships among the five most
extensively studied strains of Volvox, (2) reveal that two other Volvox species
may be more closely related than had previously been suspected, (3) confirm
prior evidence that particular isolates of Eudorina elegans and
Pleodorina illinoisensis appear to be sibling taxa, and (4) contribute to the
resolution of several hitherto unsettled issues in Chlamydomonas taxonomy.