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Over the past two decades, molecular phylogenetic data have allowed evaluations of hypotheses on the evolution of green algae based on vegetative morphological and ultrastructural characters. Higher taxa are now generally recognized on the basis of ultrastructural characters. Molecular analyses have mostly employed primarily nuclear small subunit rDNA (18S)(More)
The osmotic potential and effects of plasmolysis on photosynthetic oxygen evolution and chlorophyll fluorescence were studied in two Arctic Zygnema sp. (strain B, strain G) and two Antarctic Zygnema sp. (strain E, strain D). Antarctic strain D was newly characterized by rbcL sequence analysis in the present study. The two Antarctic strains, D and E, are(More)
Two newly isolated strains of green algae from alpine regions were compared physiologically at different culture ages (1, 6, 9 and 15 months). The strains of Zygnema sp. were from different altitudes (‘Saalach’ (S), 440 m above sea level (a.s.l.), SAG 2419 and ‘Elmau-Alm’ (E-A), 1,500 m a.s.l., SAG 2418). Phylogenetic analysis of rbcL sequences grouped the(More)
The osmotic potential and effects of plasmolysis were investigated in two different Klebsormidium strains from alpine habitats by incubation in 300–2,000 (3,000) mM sorbitol. Several members of this genus were previously found to tolerate desiccation in the vegetative state yet information was lacking on the osmotic potentials of these algae. The strains(More)
Ultraviolet (UV) radiation has become an important stress factor in polar regions due to anthropogenically induced ozone depletion. Although extensive research has been conducted on adaptations of polar organisms to this stress factor, few studies have focused on semi-terrestrial algae so far, in spite of their apparent vulnerability. This study(More)
The Orthonectida is a small, poorly known phylum of parasites of marine invertebrates. Their phylogenetic placement is obscure; they have been considered to be multicellular protozoans, primitive animals at a "mesozoan" grade of organization, or secondarily simplified flatworm-like organisms. The best known species in the phylum, Rhopalura ophiocomae, was(More)
Deserts are not usually considered biodiversity hotspots, but desert microbiotic crust communities exhibit a rich diversity of both eukaryotic and prokaryotic life forms. Like many communities dominated by microscopic organisms, they defy characterization by traditional species-counting approaches to assessing biodiversity. Here we use exclusive molecular(More)
The similarity of certain reported angiosperm rDNA internal transcribed spacer (ITS) region sequences to those of green algae prompted our analysis of the deep-level phylogenetic signal in the highly conserved but short 5.8S and hypervariable ITS2 sequences. We found that 5.8S sequences yield phylogenetic trees similar to but less well supported than those(More)
Phylogenetic relationships in the green algal phylum Chlorophyta have long been subject to debate, especially at higher taxonomic ranks (order, class). The relationships among three traditionally defined and well-studied classes, Chlorophyceae, Trebouxiophyceae, and Ulvophyceae are of particular interest, as these groups are species-rich and ecologically(More)
Characeae (Charophyceae, Charophyta) contains two tribes with six genera: tribe Chareae with four genera and tribe Nitelleae, which includes Tolypella and Nitella. This paper uses molecular and morphological data to elucidate the phylogeny of Tolypella species in North America. In the most comprehensive taxonomic treatment of Characeae, 16 Tolypella species(More)