High richness of ectomycorrhizal fungi and low host specificity in a coastal sand dune ecosystem revealed by network analysis

Abstract

Ectomycorrhizal (EM) fungi are ubiquitous in temperate and boreal forests, comprising over 20,000 species forming root symbiotic associations with Pinaceae and woody angiosperms. As much as 100 different EM fungal species can coexist and interact with the same tree species, forming complex multispecies networks in soils. The degree of host specificity and structural properties of these interaction networks (e.g., nestedness and modularity) may influence plant and fungal community assembly and species coexistence, yet their structure has been little studied in northern coniferous forests, where trees depend on EM fungi for nutrient acquisition. We used high‐throughput sequencing to characterize the composition and diversity of bulk soil and root‐associated fungal communities in four co‐occurring Pinaceae in a relic foredune plain located at Îles de la Madeleine, Québec, Canada. We found high EM fungal richness across the four hosts, with a total of 200 EM operational taxonomic units (OTUs), mainly belonging to the Agaricomycetes. Network analysis revealed an antinested pattern in both bulk soil and roots EM fungal communities. However, there was no detectable modularity (i.e., subgroups of interacting species) in the interaction networks, indicating a low level of specificity in these EM associations. In addition, there were no differences in EM fungal OTU richness or community structure among the four tree species. Limited shared resources and competitive exclusion typically restrict the number of taxa coexisting within the same niche. As such, our finding of high EM fungal richness and low host specificity highlights the need for further studies to determine the mechanisms enabling such a large number of EM fungal species to coexist locally on the same hosts.

Host Phylogenetic Relatedness and Soil Nutrients Shape Ectomycorrhizal Community Composition in Native and Exotic Pine Plantations

“…Plant-ECM interactions are also believed to be conserved at the family level [55]. Analogous results have been noted in previous studies of ECM in native and exotic pines [8,10,24,26]. However, other studies have found that ECM host specialization contributes significantly to the composition of ECM communities [25,56].…”

“…Studies show that longer distances (>10 km) may limit the stochastic dispersal of fungal propagules from one location (native forest) to another (plantation) whereas deterministic traits such as dispersal via spores [14,18] versus mycorrhizal root tips and hyphal networks may operate at finer scales [19][20][21][22]. In addition, biotic (e.g., host nutrient demands, seed dispersal) and abiotic factors (e.g., soil chemistry) may facilitate ECM fungal species with physiological and ecological adaptations depending on the environmental context [23].Recent evidence has demonstrated that phylogenetic distance between exotic and native hosts might explain their (dis)similarities in ECM community composition and richness [24,25]. For example, studies have shown that co-occurring exotic pine and native trees host similar ECM fungal communities and share the same dominant ECM fungal species [8,10,[26][27][28].…”

“…Recent evidence has demonstrated that phylogenetic distance between exotic and native hosts might explain their (dis)similarities in ECM community composition and richness [24,25]. For example, studies have shown that co-occurring exotic pine and native trees host similar ECM fungal communities and share the same dominant ECM fungal species [8,10,[26][27][28].…”

Community structure and functional group of root‐associated Fungi of Pinus sylvestris var. mongolica across stand ages in the Mu Us Desert

“…The color indicates functional groups. Genera > 1.00% are labelled Tomentella, and Geopora), which have also been confirmed previously by ECM ground surveys using molecular identification, at a global scale (Guo et al, 2020;Hayward, Horton, & Nunez, 2015;Long, Liu, Han, Wang, & Huang, 2016;Roy-Bolduc, Laliberte, & Hijri, 2016 (Nara, 2009;Peay, Schubert, Nguyen, & Bruns, 2012). Tomentella is an ECM fungi with saprotrophic ability, and identification using FUNGuild revealed that some symbiotroph fungi also exhibited free-living saprophytic life strategies.…”

Changes in belowground biodiversity during ecosystem development

“…There are two main reasons why we lack a mechanistic understanding of how belowground biodiversity changes during pedogenesis. First, studies of belowground biodiversity patterns with pedogenesis have mostly been conducted on a few individual soil chronosequences (13)(14)(15)(16)(17), with such work focusing mainly on a single group of belowground organisms, such as bacteria (16), fungi (18) or protists (19), or on changes in microbial biomass and community structure (17). Although such studies provide valuable information, pedogenesis often follows different trajectories depending on such factors as soil parent material and climate (7,8,(19)(20)(21).…”