A total of 27 strains of Oculatella were isolated, characterized and sequenced, and analysed phylogenetically with an additional environmental clone from the Atacama Desert and 10 strains isolated and sequenced by others. The strains were clearly separated based upon phylogenetic analyses conducted with a concatenated alignment of the 16S rRNA and 16S-23S ITS region of the ribosomal operons in the genus Oculatella. Differences in secondary structure of the conserved domains of the ITS region, as well as comparative analysis of P-distance among ITS regions, served to separate the strains into distinct taxonomic units. Seven new species of Oculatella were described, including four from arid to semi-arid soils (O. atacamensis, O. mojaviensis, O. coburnii, O. neakameniensis) and three from more mesic habitats, including a temperate lake (O. hafneriensis), a desert waterfall (O. cataractarum) and a Hawaiian sea cave (O. kauaiensis). The soil forms show statistically significant morphological differences, but the ranges overlap to a degree that they are not diagnosable by morphology, and these four cryptic species are characterized here using molecular characters. The more mesic species, including the type species from Mediterranean hypogea, O. subterranea, are all morphologically distinct from each other and from all four soil taxa. This report is the first to use solely molecular criteria to distinguish cryptic species of cyanobacteria.

Soil cyanobacteria are crucial components of biological soil crusts and carry out many functions in dryland ecosystems. Despite this importance, their taxonomy and population genetics remain poorly known. We isolated 42 strains of simple filamentous cyanobacteria previously identified as Pseudophormidium hollerbachianum from 26 desert locations in the North and South America and characterized these strains using a total evidence approach, that is, using both morphological and molecular data to arrive at taxonomic decisions. Based on a phylogenetic analysis of 16S rRNA gene sequences, we propose and characterize Myxacorys gen. nov. with two new species Myxacorys chilensis, the generitype, and M. californica. We also found distinct 16S‐23S ITS sequence variability within species in our dataset. Especially interesting was the presence of two distinct lineages of M. californica obtained from locations in close spatial proximity (within a few meters to kilometers from each other) suggesting niche differentiation. The detection of such unrecognized lineage‐level variability in soil cyanobacteria has important implications for biocrust restoration practices and conservation efforts.

Little is known about the taxonomic diversity of cyanobacteria in deserts, despite their important ecological roles in these ecosystems. In this study, cyanobacterial strains from the Atacama, Colorado, and Mojave Deserts were isolated and characterized using molecular, morphological, and ecological information. Phylogenetic placement of these strains was revealed through Bayesian and parsimony-based phylogenetic analyses utilizing sequences of the 16S rRNA gene and the associated 16S-23S ITS region. Based on the combined evidence of this polyphasic approach, a new species from desert soils morphologically corresponding to the genus Trichocoleus was described. Trichocoleus desertorum sp. nov. Mühlsteinová, Johansen et Pietrasiak was used to obtain a phylogenetic reference point for Trichocoleus, a genus so far characterized by morphological description only. Through characterization of this new taxon in desert soils we hope to contribute to the general understanding of cyanobacterial diversity in extreme arid habitats.

Cyanobacteria are crucial ecosystem components in dryland soils. Advances in describing α–level taxonomy are needed to understand what drives their abundance and distribution. We describe Trichotorquatus gen. nov. (Oculatellaceae, Synechococcales, Cyanobacteria) based on four new species isolated from dryland soils including the coastal sage scrub near San Diego, California (USA), the Mojave and Colorado Deserts with sites at Joshua Tree National Park and Mojave National Preserve, California (USA), and the Atacama Desert (Chile). The genus is morphologically characterized by having thin trichomes (<4.5 μm wide), cells both shorter and longer than wide, rarely occurring single and double false branching, necridia appearing singly or in rows, and sheaths with a distinctive collar‐like fraying and widening mid‐filament, the feature for which the genus is named. The genus is morphologically nearly identical with Leptolyngbya sensu stricto but is phylogenetically quite distant from that genus. It is consequently a cryptic genus that will likely be differentiated in future studies based on 16S rRNA sequence data. The type species, T. maritimus sp. nov. is morphologically distinct from the other three species, T. coquimbo sp. nov., T. andrei sp. nov. and T. ladouxae sp. nov. However, these latter three species are morphologically very close and are considered by the authors to be cryptic species. All species are separated phylogenetically based on sequence of the 16S‐23S ITS region. Three distinct ribosomal operons were recovered from the genus, lending difficulty to recognizing further diversity in this morphologically cryptic genus.

Two isolates of Oculatella from biological soil crusts in the arid and semi-arid tropical upland region of México were characterized using a polyphasic approach which included morphology, ecology, 16S rRNA and 16S-23S ITS phylogenetic analysis, percent identity of 16S rRNA gene sequence, percent dissimilarity of 16S-23S ITS sequence, and secondary structure of conserved ITS domains. The two species shared the generic synapomorphy of a reddish granule at the tip of mature apical cells, and possessed a single ribosomal operon with both tRNA genes (tRNA Ile and tRNA Ala) based upon our analysis and the analysis of the other species in the genus. After characterization, the strains were compared with 10 previously described and similarly characterized species in the genus, and based upon the evidence obtained, the strains were described as two new species, O. dilatativagina and O. leona. O. dilatativagina has an extensively widened sheath, and thus is morphologically separated from all other taxa described thus far. O. leona is morphologically highly similar to soil species found in North and South America, and should be considered a cryptic species among these taxa. The recently developed criterion for species recognition using percent dissimilarity among ITS gene sequences in orthologous ribosomal operons was found to be effective in separating cryptic species of Oculatella, and has consistently been useful and sufficient for separation of closely related species in other cyanobacterial genera.

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This paper is a contribution to the morphological and molecular characterization of the cyanobacterium Brasilonema robertilamii from populations found in Central Mexico. The general growth form and the morphological, morphometric and ecological characteristics of the populations studied clearly correspond to those described for Brasilonema roberti-lamii (basionym: Tolypothrix roberti-lamii) from the French Antilles. Based on molecular data from DNA sequencing of the16S rRNA gene and the IGS of the cpcB-cpcA phycocyanin operon (cpcBA-IGS), we propose that the populations that we studied are closely related to those of other Brasilonema species, including B. octagenarum UFV-OR1, UFV-E1 and HA4187-MV1-p1F, Brasilonema sennae CENA 114, B. tolantongensis, B. terrestre CENA 116, B. angustatum HA4187-MV1-B2+p1F and HA4187-MV1-B2+p1H and B. bromeliae SPC951. Our findings support the transference of Tolypothrix roberti-lamii, which was made based exclusively on morphological criteria, to Brasilonema. The use of molecular analyses in addition to traditional morphological and ecological criteria, known as polyphasic approach, is a good alternative to describe taxa of cyanobacteria, mainly at the genus and species levels.

While nostocacean cyanobacteria are ubiquitous and play critical roles in terrestrial ecosystems, their taxonomy and biogeography still entail mysteries. We isolated two Nostoc‐like cyanobacteria from biological soil crusts of the Atacama (Chile) and Mojave (USA) Deserts. An initial 16S rRNA gene phylogeny placed both in monophyly with Mojavia pulchra. Here, we describe two new species of the previously monotypic Mojavia using a polyphasic approach including morphology, 16S rRNA phylogenies, secondary structure, and percent similarity of the 16S‐23S ITS region. Like M. pulchra, both new species produce compact microcolonies, arthrospore‐like akinetes, and monocytes, traits characteristic of the genus. Mojavia aguilerae sp. nov. is morphologically distinct from both other species in producing bluntly conical end cells, abundant enlarged akinetes in multiseriate filaments, and gold‐colored cells during senescence. Mojavia dolomitestris sp. nov. exhibited distinctly firm, light‐colored, compartmentalized mucilage. M. dolomitestris is somewhat cryptic with M. pulchra, but has more densely packed microcolonies, rarity and later onset of brownish sheath pigmentation, and an origin from soils derived from dolomite. The two new species strengthened the position of Mojavia as a robust genus sister to Nostoc. Although 16S rRNA gene data could not separate the Mojavia species from each other, the three species showed distinct dissimilarities in secondary ITS structure and differed greatly from Nostoc sensu stricto. The high dissimilarities between their 16S‐23S ITS regions suggest a long evolutionary history of the three species as separate lineages. Mojavia is an evolutionary and ecologically unique nostocacean genus, and its rarity and restricted habitat point to an urgent need for recognition and protection.