Abstract
Ectomycorrhizal (EM) fungi play vital roles in ensuring host plants’ health, plant diversity, and the functionality of the ecosystem. However, EM fungal diversity, community composition, and underlying assembly processes in Inner Mongolia, China, where forests are typically semiarid and cold-temperate zones, attract less attention. In this study, we investigated EM fungal communities from 63 root samples of five common pine plants in Inner Mongolia across 1,900 km using Illumina Miseq sequencing of the fungal internal transcribed spacer 2 region. We evaluated the impact of host plant phylogeny, soil, climatic, and spatial variables on EM fungal diversity and community turnover. Deterministic vs. stochastic processes for EM fungal community assembly were quantified using β-nearest taxon index scores. In total, we identified 288 EM fungal operational taxonomic units (OTUs) belonging to 31 lineages, of which the most abundant lineages were Tomentella–Thelephora, Wilcoxina, Tricholoma, and Suillus–Rhizopogon. Variations in EM fungal OTU richness and community composition were significantly predicted by host phylogeny, soil (total nitrogen, phosphorus, nitrogen–phosphorus ratio, and magnesium), climate, and spatial distance, with the host plant being the most important factor. β-nearest taxon index demonstrated that both deterministic and stochastic processes jointly determined the community assembly of EM fungi, with the predominance of stochastic processes. At the Saihanwula site selected for preference analysis, all plant species (100%) presented significant preferences for EM fungi, 54% of abundant EM fungal OTUs showed significant preferences for host plants, and 26% of pairs of plant species and abundant fungal OTUs exhibited remarkably strong preferences. Overall, we inferred that the high diversity and distinctive community composition of EM fungi associated with natural pine species in Inner Mongolia and the stochastic processes prevailed in determining the community assembly of EM fungi. Our study shed light on the diversity and community assembly of EM fungi associated with common pine species in semiarid and cold temperate forests in Inner Mongolia, China, for the first time and provided a better understanding of the ecological processes underlying the community assembly of mutualistic fungi.
Highlights
The long-standing principle of community ecology is to examine the mechanisms underlying biodiversity conservation and community assembly (Chase, 2003; Nemergut et al, 2013; Zhou and Ning, 2017; Ladau and Eloe-Fadrosh, 2019)
A total of 969,290 non-chimeric internal transcribed fungal spacer 2 (ITS2) sequences were generated from 1,017,759 raw sequences, and these high-quality sequences were clustered into 1,734 nonsingleton operational taxonomic units (OTUs) (951,673), of which 349 (750,517) were identified as EM fungal
The accumulation curves of each plant species did not show any signs of reaching an asymptote, suggesting that further sample collection may result in more unknown EM fungal OTUs (Supplementary Figure 4)
Summary
The long-standing principle of community ecology is to examine the mechanisms underlying biodiversity conservation and community assembly (Chase, 2003; Nemergut et al, 2013; Zhou and Ning, 2017; Ladau and Eloe-Fadrosh, 2019). As an integral part of soil microorganisms, ectomycorrhizal (EM) fungi often establish mutual symbionts with many woody plants They play vital roles in facilitating host plant fitness, forest biodiversity, and global nutrient cycling (Smith and Read, 2008; Tedersoo et al, 2020). The niche theory emphasizes that the species are under ecological selection pressure imposed by biotic and abiotic factors due to different habitats preference and fitness (Dumbrell et al, 2009; Stegen et al, 2012); neutral theory asserts the role of dispersal limitation, ecological drift, and diversification in predicting community assembly independent of ecological selection (Hubbell, 2001). The effect of the deterministic process in defining the EM fungal community could be attributed to the selection of biotic and abiotic environmental variables on EM fungi through their fitness in response to the surrounding conditions (De Wit and Bouvier, 2006)
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