Abstract
Arbuscular mycorrhizal fungi (AMF) play central roles in terrestrial ecosystems by interacting with both above and belowground communities as well as by influencing edaphic properties. The AMF communities associated with the roots of the fern Botrychium lunaria (Ophioglossaceae) were sampled in four transects at 2400 m a.s.l. in the Swiss Alps and analyzed using metabarcoding. Members of five Glomeromycota genera were identified across the 71 samples. Our analyses revealed the existence of a core microbiome composed of four abundant Glomus operational taxonomic units (OTUs), as well as a low OTU turnover between samples. The AMF communities were not spatially structured, which contrasts with most studies on AMF associated with angiosperms. pH, microbial connectivity and humus cover significantly shaped AMF beta diversity but only explained a minor fraction of variation in beta diversity. AMF OTUs associations were found to be significant by both cohesion and co-occurrence analyses, suggesting a role for fungus-fungus interactions in AMF community assembly. In particular, OTU co-occurrences were more frequent between different genera than among the same genus, rising the hypothesis of functional complementarity among the AMF associated to B. lunaria. Altogether, our results provide new insights into the ecology of fern symbionts in alpine grasslands.
Highlights
Arbuscular mycorrhizal fungi (AMF) are important players in terrestrial ecosystems due to their ability to form mutualistic symbiotic associations with approximately 72% of terrestrial plant species (Brundrett and Tedersoo, 2018), including about 54% of pteridophyte species (Lehnert et al, 2017)
After quality filtering and random subsampling, 101940362 Glomeromycota sequences originating from 71 root samples of Botrychium lunaria were clustered into 53 operational taxonomic units (OTUs)
No significant correlation was found between AMF OTU richness and any of the floristic or edaphic variable measured in the present study
Summary
Arbuscular mycorrhizal fungi (AMF) are important players in terrestrial ecosystems due to their ability to form mutualistic symbiotic associations with approximately 72% of terrestrial plant species (Brundrett and Tedersoo, 2018), including about 54% of pteridophyte species (Lehnert et al, 2017). There are exceptions, with several plant species exchanging little, or even no carbon to the fungal partner (Leake, 2005; Merckx et al, 2009; Selosse and Roy, 2009). This is the case, for instance, in Lycopodiaceae (the lycopods, or club mosses) that have a nonphotosynthetic life-stage for several years and are unable to exchange any carbon to their fungal partners (Winther and Friedman, 2008). Beyond the nutritional exchange, AMF play central roles at the ecosystem level through modifications of soil physical (e.g. aggregation) and chemical (e.g. nutrient concentrations, leaching) properties, as well as by influencing the composition of both plant and soil microbial communities (van der Heijden et al, 1998; Rillig, 2004; Powell and Rillig, 2018)
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