Abstract
Microcoleus is a cosmopolitan, filamentous cyanobacterium and a key component of biological soil crusts-complex microbial communities essential for primary production in diverse terrestrial environments. Here, we performed a taxonomic revision of several species of Microcoleus based on a large population genomic dataset. The dataset was based on a Microcoleus speciation continuum characterized by variable levels of gene flow between the species. The putative species ranged from cryptic to distinctly morphologically defined lineages. We identify the type herbarium specimen and obtained a genome for the type species M. vaginatus and herein describe 10 novel species of Microcoleus. We provide epitypifications for the previously described species M. vaginatus and M. attenuatus. This research contributes to a more comprehensive understanding of terrestrial cyanobacterial biodiversity and cryptic species in cyanobacteria. It highlights the need for an extensive genomic and phenotypic dataset in the taxonomy of Cyanobacteria.