Issues in cyanobacterial taxonomy: comprehensive case study of unbranched, false branched and true branched heterocytous cyanobacteria.

The order Nostocales is represented by morphologically diverse forms with respect to the branching patterns and polarity of the filaments. With growing understanding of taxonomy and systematics, members of the order Nostocales have also undergone multiple taxonomic revisions. The last decade has seen a surge in the description of new genera and families within the order Nostocales. In this study, we discuss the taxonomic status of all the newly described and reclassified taxa of some of the prominent morphological forms within the order Nostocales by constructing comprehensive phylogenetic trees. Further, we propose certain strategies that would contribute to resolving the taxonomic complexities arising due to inadequate taxon sampling.