Archaeorhizomycetes Spatial Distribution in Soils Along Wide Elevational and Environmental Gradients Reveal Co-abundance Patterns With Other Fungal Saprobes and Potential Weathering Capacities.

Eric Alejandro Pinto-Figueroa,Emily Seddon,Antoine Guisan,Jan Roelof Van Der Meer,Hélène Niculita-Hirzel,Aline Buri,Erika Yashiro

doi:10.3389/fmicb.2019.00656

Abstract

Archaeorhizomycetes, a widespread fungal class with a dominant presence in many soil environments, contains cryptic filamentous species forming plant-root associations whose role in terrestrial ecosystems remains unclear. Here, we apply a correlative approach to identify the abiotic and biotic environmental variables shaping the distribution of this fungal group. We used a DNA sequencing dataset containing Archaeorhizomycetes sequences and environmental variables from 103 sites, obtained through a random-stratified sampling in the Western Swiss Alps along a wide elevation gradient (>2,500 m). We observed that the relative abundance of Archaeorhizomycetes follows a “humped-shaped” curve. Fitted linear and quadratic generalized linear models revealed that both climatic (minimum temperature, precipitation sum, growing degree-days) and edaphic (carbon, hydrogen, organic carbon, aluminum oxide, and phyllosilicates) factors contribute to explaining the variation in Archaeorhizomycetes abundance. Furthermore, a network inference topology described significant co-abundance patterns between Archaeorhizomycetes and other saprotrophic and ectomycorrhizal fungal taxa. Overall, our results provide strong support to the hypothesis that Archaeorhizomycetes in this area have clear ecological requirements along wide, elevation-driven abiotic and biotic gradients. Additionally, correlations to soil redox parameters, particularly with phyllosilicates minerals, suggest Archaeorhizomycetes might be implied in biological rock weathering. Such soil taxa-environment studies along wide gradients are thus a useful complement to latitudinal field observations and culture-based approaches to uncover the ecological roles of cryptic soil organisms.

Highlights

Microorganisms, like soil fungi, were recently shown to follow similar biogeographic patterns to macroorganisms, such as vascular plants, and were shown to be influenced by similar variables, such as climate and soil composition (Pellissier et al, 2014; Tedersoo et al, 2014)
Biogeographical studies have started focusing on the distribution of soil microorganisms along elevational gradients (Bryant et al, 2008; Fierer et al, 2011; Wang et al, 2012; Pellissier et al, 2014; Tedersoo et al, 2014; Yashiro et al, 2016), but so far very few have attempted to determine the environmental requirements of cryptic soil fungi as done here along wide continuous gradients
Archaeorhizomycetes operational taxonomic units (OTUs) mostly belonged to four groups of non-cultured Archaeorhizomycetes, represented by GenBank accession numbers DQ182455, GU174301, GU174341, and GU174343 (Rosling et al, 2011)

Summary

Introduction

Microorganisms, like soil fungi, were recently shown to follow similar biogeographic patterns to macroorganisms, such as vascular plants, and were shown to be influenced by similar variables, such as climate and soil composition (Pellissier et al, 2014; Tedersoo et al, 2014). As for macroorganisms, their distributions can be expected to be, at least partly, driven by their environmental requirements (i.e., if speaking at the level of their constituent species, by their environmental niche). Biogeographical studies have started focusing on the distribution of soil microorganisms along elevational gradients (Bryant et al, 2008; Fierer et al, 2011; Wang et al, 2012; Pellissier et al, 2014; Tedersoo et al, 2014; Yashiro et al, 2016), but so far very few have attempted to determine the environmental requirements of cryptic soil fungi as done here along wide continuous gradients

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