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.

Stochasticity dominates assembly processes of soil nematode metacommunities on three Asian mountains

Nematodes play an important role in ecosystems;however,very little is known about their assembly processes and the factors influencing them.We studied nematode communities in bulk soils from three Asian mountain ecosystems to determine the assembly processes of free-living nematode metacommunities and their driving factors.On each mountain,elevations span a range of climatic conditions with the potential to reveal assembly processes that predominate across multiple biomes.A phylogenetic null modeling framework was used to analyze 18S rRNA gene amplicons to quantify various assembly processes.We found that phylogenetic turnover between nematode communities on all mountains was dominated by stochastic processes,with“undominated processes”being the most predominant stochastic factor.Elevation has a significant impact on the relative importance of deterministic and stochastic processes.A variety of climatic and edaphic variables significantly influenced the variations in community assembly processes with elevation,even though their impacts were not consistent between the mountains.Overall,our results indicate that free-living nematode metacommunities in a wide range of environments are largely structured by stochastic processes rather than by niche-based deterministic processes,suggesting that metacommunities of soil free-living nematodes may respond to climate change in a largely unpredictable way.

Soil Metagenome of Tropical White Sand Heath Forests in Borneo:What Functional Traits Are Associated with an Extreme Environment Within the Tropical Rainforest?

White sand heath forests(WS) or kerangas, an unusual variant of tropical forests in Borneo, characterized by open scrubby vegetation, low productivity, and distinctive plant species composition and soil microbial community, are regarded as a stressful lowpH and/or nutrient environment. We investigated whether the functional soil metagenome also shows a predicted set of indicators of stressful conditions in WS. Based on stress-tolerant strategies exhibited by larger organisms, we hypothesized that genes for stress tolerance, dormancy, sporulation, and nutrient processing are more abundant in the soil microbiota of WS. We also hypothesized that there is less evidence of biotic interaction in white sand soils, with lower connectivity and fewer genes related to organismic interactions. In Brunei, we sampled soils from a WS and a normal primary dipterocarp forest, together with an inland heath, an intermediate forest type. Soil DNA was extracted, and shotgun sequencing was performed using Illumina HiSeq platform, with classification by the Metagenomics Rapid Annotation using Subsystem Technology(MG-RAST). The results, on one hand, supported our hypothesis(on greater abundance of dormancy, virulence, and sporulation-related genes). However, some aspects of our results showed no significant difference(specifically in stress tolerance, antibiotic resistance, viruses, and clustered regularly interspaced short palindrome repeats(CRISPRs)). It appears that in certain respects, the extreme white sand environment produces the predicted strategy of less biotic interaction, but exhibits high soil microbiota connectivity and functional diversity.