Delimitation of the family Oscillatoriaceae (Cyanobacteria) according to the modern polyphasic approach (introductory review)

The criteria for cyanobacterial taxonomy have changed substantially in the last several years. The most important of the newly introduced methods are molecular sequencing and the genetic approach, which is considered as a major criterion for the classification of organisms. However, molecular results have not always been in agreement with those of the traditional classification system based on morphological or ecological criteria. Thus, application of the polyphasic approach provides the best means of conducting taxonomic practice, and the coincidences and correlations of various criteria must be discovered. Here are discussed the main problems associated with the taxonomy of simple, relatively wide filamentous cyanobacteria with short vegetative cells, but without prominent cells (heterocytes, akinetes). Examples were selected from the family Oscillatoriaceae, which was traditionally based only on morphological criteria. The main markers for delimitation of this family after revisions and the relations and consequences of various genera are discussed, as well as a proposal to base the final revision of this family according to modern criteria. The members of this cyanobacterial group are distributed in numerous ecosystems around the world and form also distinct communities in tropical America.