Phylogenetic placement of Dapisostemon gen. nov. and Streptostemon, two tropical heterocytous genera (Cyanobacteria)

Abstract

Two species of heterocytous cyanobacteria from the Mata Atlântica of Southeastern Brazil were studied intensively to determine if they were congeneric or belong to different genera. Additionally, their affinity to established genera in the Tolypothricaceae such as Tolypothrix Bornet & Flahault, Hassallia Bornet & Flahault and Spirirestis Flechtner & Johansen was investigated. Dapisostemon apicaliramis gen. et sp. nov. isolated from a wooden bridge in a mangrove swamp was found to be basal to a clade containing Tolypothricaceae, Nostocaceae, and Aphanizomenonaceae (but with weak support) by means of 16S rRNA gene sequence analyses. Moreover, D. apicaliramis had a 16S-23S ITS region similar in length, sequence, and secondary structure to the members of the terrestrial Tolypothricaceae. Streptostemon Sant’Anna et al. was placed in the Microchaetaceae (now the Tolypothricaceae) at the time of its description based on unsequenced natural material, but in this study it was found to be even more phylogenetically distant from that clade than Dapisostemon based on 16S rRNA gene sequence. It is in an unsupported and unresolved basal position in the Nostocales. It also presents a unique 16S-23S ITS region. The higher level evolutionary relationships of both genera are uncertain at this time, but neither genus can remain in the Microchaetaceae or Tolypothricaceae as the Nostocales undergo future revision. We conclude that Dapisostemon is sufficiently unique and separate that it requires a new family, the Dapisostemonaceae. This study further demonstrates that the cyanobacteria of tropical regions often represent novel taxa in unstudied lineages and that the study of tropical cyanobacteria will yield new insights in the biodiversity of this ecologically important group of photosynthetic microorganisms.

Nunduva, a new marine genus of Rivulariaceae (Nostocales, Cyanobacteria) from marine rocky shores

“…Several special morphotypes representing new species and genera of cyanobacteria have recently been described in tropical and extreme habitats (Komárek & Komárková 2007;Gamma et al 2014;Gold-Morgan et al 2015;Alvarenga et al 2016;Hentschke et al 2016;Miscoe et al 2016). The polyphasic approach, which combines morphological and molecular methods, allows greater precision and recognition of taxonomic diversity, as well as a means of revision of the hierarchical classification of some cyanobacterial taxa to better reflect their evolutionary history (Fiore et al 2007;Hauer et al 2014;Genuario et al 2015).…”

Komarekiella atlantica gen. et sp. nov. (Nostocaceae, Cyanobacteria): a new subaerial taxon from the Atlantic Rainforest and Kauai, Hawaii

“…Carrying on the extensive study of cyanobacterial diversity of the Atlantic Rainforest, in which our research group has described many new taxa (sant'anna et al 2013;HentscHke & komárek 2014;genuário et al 2015;HentscHke et al 2016), we describe another new terrestrial Nostoc-like genus using a combination of 16S rRNA phylogeny, 16S-23S ITS primary sequence and secondary structures, and morphological characters visible in the light microscope.…”

Estimating genetic structure and diversity of cyanobacterial communities in Atlantic forest phyllosphere

“…Floristics surveys have shown huge morphological richness of cyanobacteria (Branco et al 2009, Sant´anna et al 2013, Gama et al 2014) and novel species and genera have been described (Fiore te al. 2007, Sant´Anna et al 2010, Hentschke et al 2016 in this biome. Nevertheless, the 4 genetic diversity of the phylum Cyanobacteria inhabiting the Atlantic Forest is still poorly understood.…”

“…Cyanobacteria diversity in the Atlantic Forest have been explored mainly using culturedependent approaches (Fiore et al 2007, Branco et al 2009, Sant´Anna et al 2010, Gama et al 2014, Hentschke et al 2016. Also, none of the available studies about this biome focused on the phyllosphere micro-habitat.…”

“…This can be an indicative that a diversity of novel species or species which no genetic information available are represented by these retrieved sequences. Several novel genera and species have been described inhabiting Atlantic Forest different micro-habitats (Fiore et al 2007, Aguiar et al 2008, Sant´Anna et al 2010, Hentschke et al, 2016.…”