Metabarcoding reveals soil fungal diversity shifts in the artificial cloud forest and volcanic desert of Ascension Island

Ascension Island is a remote oceanic island that was a volcanic desert prior to human colonisation. In the 19th century, an artificial cloud forest was established by a military garrison to improve the scarce water supply. Using ITS metabarcoding of topsoil environmental DNA, we compared the fungal communities of the desert and the Green Mountain cloud forest. Forest soils had higher total nitrogen and carbon, and lower pH than desert soils. Fungal richness was higher in forest soils and ordination analysis revealed distinct fungal communities in each habitat. Both habitats contained a high percentage of unclassified fungal OTUs, implying the presence of native/endemic fungal flora, with a shift from Ascomycota in the desert to Asco-Basidiomycota in the forest. Indicator species analysis revealed habitat- and vegetation-specific fungal taxa, and the presence of cosmopolitan fungi in forest and unknown fungi in the desert soils, suggesting reshaping of fungal communities due to the afforestation.