Molecular and morphological characterization of a novel dihydroanatoxin-a producing Microcoleus species (cyanobacteria) from the Russian River, California, USA.

Reports of anatoxins poisoning of wildlife and domestic animals by toxigenic cyanobacteria in streams and rivers are increasing globally. Little is known about the taxonomy, morphology and genomics of anatoxins producing species, limiting our knowledge about their environmental preferences. We isolated three benthic non-heterocystous filamentous cyanobacterial strains from the Russian River in Northern California (USA), which produce anatoxin-a and dihydroanatoxin-a. Both 16S rRNA and protein sequence phylogenetic analyses showed that the strains represent a distinct new member of the cyanobacterial genus Microcoleus (Oscillatoriales). A novel species, Microcoleus anatoxicus is described and accompanied with light microscope photomicrographs, toxin profiles and the complete anatoxin-a gene cassette with the first description of the anaK gene in Microcoleus.

Conjugation morphology of Zygogonium ericetorum (Zygnematophyceae, Charophyta) from a high alpine habitat.

Reproductive characteristics are important for defining taxonomic groups of filamentous Zygnematophyceae, but they have not been fully observed in the genus Zygogonium. Specimens of Z. ericetorum previously studied and used to clarify the generic concept lacked fertile material, which was obtained recently. This study illustrates for the first time, using color light microscopic and fluorescence images, a consequent conjugation stage in Z. ericetorum, including completely developed zygospores and purple cytoplasmic residue content left outside the zygospores, similar to aplanospore formation. Structures confirmed earlier reports and provided new observation informative regarding phylogenetically relevant reproductive characters of Z. ericetorum.

Phylogenetic position of Zygogonium ericetorum (zygnematophyceae, charophyta) from a high alpine habitat and ultrastructural characterization of unusual aplanospores.

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 worldwide were subsumed into two species, T. intricata and T. nidifica, in two sections, Rothia and Tolypella respectively. It was further suggested that Tolypella might be a derived group within Nitella. In this investigation into species diversity and relationships in North American Tolypella, sequence data from the plastid genes atpB, psbC, and rbcL were assembled for a broad range of charophycean and land plant taxa. Molecular data were used in conjunction with morphology to test monophyly of the genus and species within it. Phylogenetic analyses of the sequence data showed that Characeae is monophyletic but that Nitelleae is paraphyletic with Tolypella sister to a monophyletic Nitella + Chareae. The results also supported the monophyly of Tolypella and the sections Rothia and Tolypella. Morphologically defined species were supported as clades with little or no DNA sequence differences. In addition, molecular data revealed several lineages and a new species (T. ramosissima sp. nov.), which suggests greater species diversity in Tolypella than previously recognized.

Identity and phylogenetic placement of Spirogyra species (Zygnematophyceae, Charophyta) from California streams and elsewhere(1).

Diversity of the filamentous green algae in the genus Spirogyra (Zygnematophyceae) was investigated from more than 1,200 stream samples from California. We identified 12 species of Spirogyra not previously known for California (CA), including two species new to science, Spirogyra californica sp. nov. and Spirogyra juliana sp. nov. Environmental preferences of the Californian species are discussed in the light of their restricted distribution to stream habitats with contrasting nutrient levels. We also investigated the systematic relationships of Spirogyra species from several continents using the chloroplast-encoded genes ribulose-1,5-bisphosphate carboxylase/hydrogenase large subunit (rbcL) and the beta subunit of the ATP synthase (atpB). Californian species were positioned in most major clades of Spirogyra. The phylogeny of Spirogyra and its taxonomic implications are discussed, such as the benefits of combining structural and molecular data for more accurate and consistent species identification. Considerable infraspecific genetic variation of globally distributed Spirogyra species was observed across continental scales. This finding suggests that structurally similar species from distant regions may be genetically dissimilar and that Spirogyra may contain a large number of cryptic species. Correlating the morphological and genetic variation within the genus will be a major challenge for future researchers.

SYSTEMATICS OF THE GENUS ZYGNEMA (ZYGNEMATOPHYCEAE, CHAROPHYTA) FROM CALIFORNIAN WATERSHEDS(1).

Natural populations of Zygnema were collected from 80 stream sites across California, and eight species were identified and characterized morphologically. Generic and infrageneric concepts of Zygnema and Zygogonium were tested with cox3 and rbcL gene sequence analysis. Strains of Zygnema were positioned in a single monophyletic clade sister to Zygogonium tunetanum Gauth.-Lièvre. In both the rbcL and cox3 phylogenies, strains of Zygnema formed two major clades. The first clade contained species that have zygospores with a blue-colored mesospore or akinetes with a colorless mesospore. The second clade contained species that have a yellow or brown mesospore. The existing taxonomic concepts for Zygnema classification are not consistent with our molecular phylogeny and do not correspond to natural groups. We propose that mesospore color may be useful in the infrageneric classification of Zygnema. Newly described Zygnema aplanosporum sp. nov. and Zygnema californicum sp. nov. have zygospores with a blue mesospore formed in the conjugation tube and separated by a cellulosic sporangial wall. Z. aplanosporum also possessed a combination of vegetative and reproductive features characteristic of Zygogonium, such as presence of short branches, rhizoidal outgrowths, thickened vegetative cell walls, purple-colored cell content, small compressed-globular chloroplasts as well as predominant asexual reproduction. Z. aplanosporum and Z. californicum were deeply embedded in a larger clade of Zygnema both in rbcL and cox3 analyses. Based on our observations, there are no features or combination of features that separate Zygnema and Zygogonium. Therefore, we conclude that Zygogonium is probably a synonym of Zygnema.