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.

Department of Biology John Carroll University University Heights Ohio 44118 USA

Department of Botany Faculty of Sciences University of South Bohemia Branišovská 31 České Budějovice 370 05 Czech Republic

Department of Comparative Biology Faculty of Science Universidad Nacional Autonóma de México Coyoacán Distrito Federal 04510 México

Plant and Environmental Sciences Department New Mexico State University 945 College Drive Las Cruces New Mexico 88003 USA

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High genomic differentiation and limited gene flow indicate recent cryptic speciation within the genus Laspinema (cyanobacteria)

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