UC Riverside

Biocrusts are the living skin of drylands, comprising diverse microbial communities that are essential to desert ecosystems. Despite extensive knowledge on biocrust ecosystem functions and lichen and moss biodiversity, little is known about factors structuring diversity among their microbial communities. We used amplicon-based metabarcode sequencing to survey microbial communities from biocrust surface and subsurface soils at 4 sites located within the Mojave Desert. Five biocrust types were examined: Light-algal/Cyanobacteria, Cyano-lichen, Green-algal lichen, Smooth-moss, and Rough-moss crust types. Microbial diversity in biocrusts was structured by several characteristics 1) central versus southern Mojave sites displayed different community signatures, 2) indicator taxa of plant associated fungi (plant pathogens and wood saprotrophs) were identified at each site, 3) surface and subsurface microbial communities were distinct, and 4) crust types had distinct indicator taxa. Network analysis ranked bacteria-bacteria interactions as the most connected of all within-domain and cross-domain interaction networks in biocrust surface samples, with Actinobacteria, Proteobacteria, Cyanobacteria, and Ascomycota as hubs among all phyla. Specifically, the genera with highest node degree was Pseudonocardia sp. (Pseudonocardiales, Actinobacteria) in bacteria and Alternaria sp. (Pleosporales, Ascomycota) among fungal genera. Our findings provide crucial insights for dryland microbial community ecology, conservation, and sustainable management.