Molecular and morphological criteria for revision of the genus Microcoleus (Oscillatoriales, Cyanobacteria)

Authors

  • Otakar Strunecký,

    Corresponding author
    1. Institute of Botany, Centre for Phycology, The Academy of Sciences of the Czech Republic, Třeboň, Czech Republic
    2. Centre for Polar Ecology, Department of Ecosystem Biology, Faculty of Science, University of South Bohemia, Ceske Budejovice, Czech Republic
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  • Jiří Komárek,

    1. Institute of Botany, Centre for Phycology, The Academy of Sciences of the Czech Republic, Třeboň, Czech Republic
    2. Institute of Botany, Faculty of Science, University of South Bohemia, Ceske Budejovice, Czech Republic
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  • Jeffrey Johansen,

    1. Biology, John Carroll University, University Heights, Ohio, USA
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  • Alena Lukešová,

    1. Institute of Soil Biology, Biology Centre ASCR, České Budějovice, Czech Republic
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  • Josef Elster

    1. Institute of Botany, Centre for Phycology, The Academy of Sciences of the Czech Republic, Třeboň, Czech Republic
    2. Centre for Polar Ecology, Department of Ecosystem Biology, Faculty of Science, University of South Bohemia, Ceske Budejovice, Czech Republic
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Abstract

Ninety-two strains of Microcoleus vaginatus (=nomenclatural-type species of the genus Microcoleus Desmazières ex Gomont) and Phormidium autumnale Trevisan ex Gomont from a wide diversity of regions and biotopes were examined using a combination of morphological and molecular methods. Phylogenies based on the 16S rDNA and 16S-23S ITS (partial) demonstrated that the 92 strains, together with a number of strains in GenBank, were members of a highly supported monophyletic clade of strains (Bayesian posterior probability = 1.0) distant from the species-cluster containing the generitype of Phormidium. Similarity of the 16S rRNA gene exceeded 95.5% among all members of the Microcoleus clade, but was less than 95% between any Microcoleus strains and species outside of the clade (e.g., Phormidium sensu stricto). These findings, which are in agreement with earlier studies on these taxa, necessitate the revision of Microcoleus to include P. autumnale. Furthermore, the cluster of Phormidium species in the P. autumnale group (known as Group VII) must be moved into Microcoleus as well, and these nomenclatural transfers are included in this study. The main diacritical characters defining Microcoleus are related to the cytomorphology of trichomes, including: narrowed trichome ends, calyptra, cells shorter than wide up to more or less isodiametric, and facultative presence of sheaths. The majority of species are 4–10 μm in diameter. The possession of multiple trichomes in a common sheath is present facultatively in many but not all species.

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