Fottea

Fottea 2024, 24(2):137-184 | DOI: 10.5507/fot.2024.002

Revision of the pantropical genus Brasilonema (Nostocales, Cyanobacteria), with the description of 24 species new to science

Markéta Bohunická^1*, Jeffrey R. Johansen^{2, 3}, Chelsea D. Villanueva^{2, 4}, Jan Mareš⁵, Lenka Štenclová^{3, 5}, Itzel Becerra-Absalón⁶, Tomáš Hauer³, Jan Kaštovský³

¹ Department of Biology, Faculty of Science, University of Hradec Králové, Rokitanského 62, CZ-50003 Hradec Králové, Czech Republic;

^* Corresponding author e-mail: marketa.bohunicka@uhk.cz

² Department of Biology, John Carroll University, 1 John Carroll Blvd., University Heights, OH 44118, USA

³ Faculty of Science, University of South Bohemia, Branišovská 1760, CZ-37005 České Budějovice, Czech Republic

⁴ Department of Biological, Geological, & Ecological Sciences, Cleveland State University, Cleveland, OH, 44115 U.S.A.

⁵ Biology Centre of the CAS, Institute of Hydrobiology, Na Sádkách 7, CZ-37005, České Budějovice, Czech Republic

⁶ National Autonomous University of Mexico (UNAM), Facultad de Ciencias, Colonia Coyoacán, Código Postal 04510, P.O. Box 70-474, México, Distrito Federal, México

Brasilonema was separated from Scytonema only in 2007 (Fiore et al. 2007). It possesses diagnostic morphological characteristics such as vacuole-like structures in older cells, frequent purple pigmentation of cells, rare false branching and fasciculate growth of filaments. Prior to this study, Brasilonema was always found attached to the substrate in subaerophytic habitats, exclusively in tropical-subtropical biomes (Brazil, Guadeloupe, Hawaii, Mexico). We have gathered 76 new Brasilonema strains from North, Central and South America, central Africa, South and East Asia and Europe, including specialized subaerophytic habitats in temperate climates, and applied a polyphasic approach to their species delineation. All taxa were first examined morphologically and subsequently their relationships were tested using the traditionally applied 16S rRNA gene sequence together with three additional markers (nifD, rpoC1, rbcLX). The results revealed close relationships between specimens obtained from very distant localities (different continents) as well as phylogenetic distance between single Brasilonema strains collected from the same biotope. Our results provide evidence that Brasilonema, although previously overlooked (or misidentified), is a morphologically easy genus to distinguish that is common over the world in tropical and subtropical regions with humid climate. It can be also found in tropical greenhouses, power-plant cooling towers and other microhabitats that mimic subtropical to tropical conditions in other climatic regions. We conclude that Brasilonema is a pantropical genus, there are few geographical constraints in Brasilonema dispersal, and its absence in natural habitats in temperate and polar climatic zones may be due to intolerance to desiccation or winter freezing.

Keywords: 16S rRNA gene sequence, 16S-23S rRNA ITS, biodiversity, morphology, orthologous ribosomal operons, phylogenetic relationships, polyphasic approach, protein-coding genes, Scytonemataceae, cyanobacterial taxonomy

Received: August 11, 2023; Revised: December 27, 2023; Accepted: January 5, 2024; Prepublished online: July 26, 2024; Published: October 22, 2024  Show citation