Taxonomic advancements in the Calotrichaceae: Resolving phylogenetic ambiguities and describing five novel species of Dulcicalothrix from the Konkan region of India

The taxonomy of heteropolar, tapering, and unbranched heterocytous cyanobacteria has undergone significant changes over time. Several novel species, genera, and families have been established using a polyphasic approach, which has provided a greater resolution in the systematics of these organisms. The Calotrichaceae, as of today, stands as a well-resolved and monophyletic clade with at least five genera. The family has had some major revisions as well as additions. In addition, parameters such as the comparison of the 16S-23S ITS rRNA regions for the separation of one species from another have also grown and evolved and been amended recently within the genus Dulcicalothrix of the family Calotrichaceae. This approach has created the need to compare orthologous 16S-23S ITS rRNA region operons for better resolution at the species level. This study reviews the taxonomic advancements within the family Calotrichaceae with a discussion on the taxonomic status of the ambiguous positioning of the genus Neocalothrix and Phayaothrix. Considering the illegitimate status of Neocalothrix based on morphological, ecological, molecular, and phylogenetic evidence and the rules and recommendations of the International Code of Nomenclature for Algae, Fungi, and Plants, we have hereby transferred Neocalothrix to the existing genus Fulbrightiella and describe five novel species of Dulcicalothrix, viz. D. epiphytica, D. tripathii, D. acuminata, D. bombayensis, and D. goaensis from the Konkan region of India identified using a polyphasic approach.