eDNA metabarcoding reveals high soil fungal diversity and variation in community composition among Spanish cliffs.

Environments characterized by physical extremes harbor unique species diversity with particular adaptations. Cliffs are harsh environments for organisms but host a great diversity of specialized plants with many endemics, rare and even endangered species. It is, however, less known which fungal diversity the cliff habitats contain and whether it differs among different cliff locations. We thus sampled soil from three separate cliff locations in the North, Centre, and South of Spain and used eDNA metabarcoding to determine fungal diversity. To better understand whether cliff specialist plants may promote particular fungal communities, we have sampled soil from crevices with cliff specialist plants and no apparent plants as controls. Major lifestyles found in cliff soils were saprotrophs, and major fungal orders were Dothideomycetes, Sordariomycetes, and Eurotiomycetes, while the amount of symbiotrophic fungi was relatively low. We found no significant differences in fungal amplicon sequence variant (ASV) richness among the three sampled locations, but the sites were significantly different in their community composition and their main indicator species. Overall, there were no significant differences in fungal ASV richness or composition between soils from cliff specialist plants and soils without plants, suggesting a unique fungal diversity in cliff soils independent from specialized plants. However, preliminary findings on soils of the specialist cliff plant