Non‐random association patterns in a plant–mycorrhizal fungal network reveal host–symbiont specificity

Abstract

Arbuscular mycorrhizal (AM) fungi are obligate plant symbionts that have important functions in most terrestrial ecosystems, but there remains an incomplete understanding of host–fungus specificity and the relationships between species and functional groups of plants and AM fungi. Here, we aimed to provide a comprehensive description of plant–AM fungal interactions in a biodiverse semi‐natural grassland. We sampled all plant species in a 1,000‐m2 homogeneous plot of dry calcareous grassland in two seasons (summer and autumn) and identified root‐colonizing AM fungi by SSU rDNA sequencing. In the network of 33 plant and 100 AM fungal species, we found a significant effect of both host plant species and host plant functional group on AM fungal richness and community composition. Comparison with network null models revealed a larger‐than‐random degree of partner selectivity among plants. Grasses harboured a larger number of AM fungal partners and were more generalist in partner selection, compared with forbs. More generalist partner association and lower specialization were apparent among obligately, compared with facultatively, mycorrhizal plant species and among locally more abundant plant species. This study provides the most complete data set of co‐occurring plant and AM fungal taxa to date, showing that at this particular site, the interaction network is assembled non‐randomly, with moderate selectivity in associations between plant species and functional groups and their fungal symbionts.

Introduction: Special issue on species interactions, ecological networks and community dynamics – Untangling the entangled bank using molecular techniques

“…The findings regarding particular interactions range from insight into emergent features such as levels of specialization in ecological interaction networks (Clare et al, ; Doña, Proctor, et al, ; Doña, Serrano, et al, ; Koskinen et al, ; Sepp et al, ) to the role of individual seed dispersers in seed dispersal networks. As a case in point, González‐Varo, Arroyo, and Jordano () are able to show how much of an ecological function (seed dispersal) is concentrated to particular species at particular points in time.…”

“…Sepp et al () examine how root‐colonizing fungi forming arbuscular mycorrhiza (AM) are structured within a homogeneous plot of dry calcareous grassland. They find a significant imprint of host plant species, abundance and functional group on the richness and community composition of AM fungi with which they partner.…”

“…The findings regarding particular interactions range from insight into emergent features such as levels of specialization in ecological interaction networks Doña, Proctor, et al, 2019;Koskinen et al, 2019;Sepp et al, 2019) to the role of individual seed dispersers in seed dispersal networks.…”

“…At local scales, forest management and tree selection have a clearer impact, but at larger scales, environmental cues and host resource traits are the most prevalent forces. From a net perspective, communities still end up very similar in terms of their trophic composition, with highly similar proportions of symbiotrophic, ectomycorrhizal, saprotrophic, endotrophic and pathotrophic fungi.Community assembly processes thus seem to secure functional resilience under the current range of climatic and edaphic conditions Sepp et al (2019). examine how root-colonizing fungi forming arbuscular mycorrhiza (AM) are structured within a homogeneous plot of dry calcareous grassland.…”

Contrasting effects of commercial and native arbuscular mycorrhizal fungal inoculants on plant biomass allocation, nutrients and phenolics

“…However, the outcome of engaging in the AM symbiosis can be highly context dependent, subject to AMF and plant species identities, and on local soil conditions. For example, nutrient exchange between fungus and plant can vary between crop cultivar (Elliott et al , 2020), and studies show a certain level of partner selectivity exists in these plant-fungal associations (Sepp et al , 2019). Additionally, evidence suggests that certain AMF taxa may be more associated with particular functions such as plant nutrient uptake, or plant resistance against pests and pathogens (Bennett & Bever, 2007; Wehner et al , 2010).…”