Metagenetics of fairy rings reveals complex and variable soil fungal communities

Although fairy rings are widely observed,little is known about the community processes associated with them.Here,we studied fairy rings in a natural grassland in northern Mongolia by sampling soils outside(future stage),directly under(present stage),and within(past stage)the rings,to represent different time stages during the expansion of fairy rings.Soil DNA was extracted for amplicon sequencing of the fungal ITS1 region.The present stage had reduced fungal diversity and different fungal communities toward the other stages.Most strikingly,there was an increase in the pathogenic fungus Gibberella baccata in the present stage of most rings and the saprotrophic fairy ring fungus Lepista luscina in several.However,no mushrooms of Lepista had been recorded from any of these rings during several years of observation.Known fairy ring fungi were not found in the present stage of every ring,even in some known rings to have previously displayed mushrooms of such species.It is possible that these fungi occurred or were more abundant at the unsampled leading edge of the ring.The increase in G.baccata is intriguing,but its importance,if any,is unclear.It is also unclear whether consortia of fungi or other microbes might be present in these rings.The absence or low abundance of the previously reported fairy ring fungal species suggests that their presence is transient,with rapid replacement by other fungi.No differences in soil parameters were found between the fairy ring stages,except for aluminum.There is a need for broader sampling,including analysis of non-fungal biota,to understand the functional diversity of fairy ring fungi and the consequences for plant communities.