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.