Original paper

Problem of the taxonomic category "species" in cyanobacteria

Komárek, Jiří

Abstract

In Cyanobacteria (cyanophytes, cyanoprokaryotes) "species" has been traditionally defined on the basis of morphological characters ("Geitlerian system") and these same criteria are still commonly used for identification of natural populations. Modern investigations, based on EM-methods and molecular sequencing have proven the differences between the genotypes which correspond more or less with the traditional phenotypic genera (revised after re-evaluation of morphologial characters). However, within genotypes enormous variability of natural morphotypes and ecotypes has been found and the same diversity has been confirmed in strains in cultures. Genotypically distinct species have not been confirmed, and the separation of them according to morphological criteria is problematic with respect to wide morphological variability. - Because the purely traditional (morphological) concept of cyanobacterial species is frequently in disagreement with modern knowledge of cyanobacteria, the criteria for species delimitation should be changed. Taxonomic classification is always conventional; the definition of "species" in cyanobacteria is possible, if it will be based on rules developed in concordance with modern knowledge of morphology (phenotype variability and stability of different features), physiology, ecology and molecular bases of individual morpho- and ecotypes (e.g. morphospecies belonging to proved and distinct genotypes and characterised by ecological characterization).

Keywords

cyanoprokaryotescyanobacteriataxonomynomenclaturegenus delimitationspecies problem