Recognizing cyanobacterial diversity through adoption of a new species paradigm

Abstract

In order to recognize the extent of biodiversity in the cyanobacteria, we need to adopt species concepts that will provide theoretical rigor and pragmatic criteria for de- scribing increased numbers of taxa as polyphasic data on cyanobacteria become avail- able. We reject phenetic (similarity) based species concepts, as these are incorrect by modern systematic standards. The Biological Species Concept is also rejected as it does not apply to asexual organisms. Four phylogenetic species concepts seem to be good can- didate constructs for the cyanobacteria: 1) the Evolutionary Species Concept, 2) the Eco- typic Species Concept, 3) the Phylogenetic Species Concept, and 4) the Monophyletic Species Concept. Of these, we consider the Monophyletic Species Concept to be the most theoretically sound and pragmatic when molecular sequence data for phylogenetic analy- sis are available. The Ecotypic Species Concept is appropriate when molecular data are not available, and only morphology and ecology are known.