Fungal community turnover along steep environmental gradients from geothermal soils in Yellowstone National Park

Abstract

Geothermal soils offer unique insight into the way extreme environmental factors shape communities of organisms. However, little is known about the fungi growing in these environments and in particular how localized steep abiotic gradients affect fungal diversity. We used metabarcoding to characterize soil fungi surrounding a hot spring-fed thermal creek with water up to ~85 C and pH ~10 in Yellowstone National Park. No soil variable we measured determined fungal community composition. However, soils with pH >8 had lower fungal richness and different fungal assemblages when compared to less extreme soils. Saprotrophic fungi community profile followed more closely overall community patterns while ectomycorrhizal fungi did not, highlighting potential differences in the factors that structure these different fungal trophic guilds. In addition, in vitro growth experiments in four target fungal species revealed a wide range of tolerances to pH levels but not to heat. Overall, our results documenting fungal communities within a few hundred meters suggest stronger statistical power and wider sampling are needed to untangle so many co-varying environmental factors affecting such diverse species communities.