Recent phylogenetic analyses of members of the Tolypothrichaceae (Nostocales, Cyanobacteria) based on 16S rRNA gene sequence data have demonstrated that the soil-inhabiting members of the family belong to a clade separate from the aquatic and subaerial members of the family. The soil-inhabiting species clade includes Spirirestis, a monophyletic taxon originally defined by its tight spiral coiling. Most of the soil-inhabiting species have been identified in the past as belonging either to Hassallia or Tolypothrix, which are subaerial and aquatic taxa, respectively. A comprehensive study of the terrestrial Tolypothrichaceae led us to conclude that all terrestrial Tolypothrichaceae should be included in the genus Spirirestis, even though most of those isolates lack the spiral coiling diagnostic of the genus. Using a polyphasic approach, we recognize seven distinct clades in Spirirestis, which we split into seven species: S. rafaelensis (the generitype), S. californica comb. nov., S. pseudoramosissima comb. nov., S. lignicolor sp. nov., S. williamsae sp. nov., S. hydroterrestris sp. nov., and S. atacamensis sp. nov. Spirirestis rafaelensis and S. californica are represented by multiple isolates, and we postulate that with time and further taxon sampling, some of the strains we included in these two species may be recognized as additional species. As the study of soil cyanobacteria continues, additional species of Spirirestis will likely be discovered and described.

• Klíčová slova
• Hassallia, Tolypothrix, 16S–23S ITS, Nostocales, Tolypothrichaceae, biological soil crusts, phylogeny,
• Publikační typ
• časopisecké články MeSH

The filamentous cyanobacterium Microcoleus is among the most important global primary producers, especially in hot and cold desert ecosystems. This taxon represents a continuum consisting of a minimum of 12 distinct species with varying levels of gene flow and divergence. The notion of a species continuum is poorly understood in most lineages but is especially challenging in cyanobacteria. Here we show that genomic diversification of the Microcoleus continuum is reflected by morphological adaptation. We compiled a dataset of morphological data from 180 cultured strains and 300 whole genome sequences, including eight herbarium specimens and the type specimen of Microcoleus. We employed a combination of phylogenomic, population genomic, and population-level morphological data analyses to delimit species boundaries. Finally, we suggest that the shape of the filament apices may have an adaptive function to environmental conditions in the soil.

• Klíčová slova
• Biological classification, Evolutionary biology, Microbiology,
• Publikační typ
• časopisecké články MeSH