Abstract
Arbuscular mycorrhizal fungi (AMF) have been shown to influence plant community structure and diversity. Studies based on single plant–single AMF isolate experiments show that within AMF species variation leads to large differential growth responses of different plant species. Because of these differential effects, genetic differences among isolates of an AMF species could potentially have strong effects on the structure of plant communities. We tested the hypothesis that within species variation in the AMF Rhizophagus irregularis significantly affects plant community structure and plant co-existence. We took advantage of a recent genetic characterization of several isolates using double-digest restriction-site associated DNA sequencing (ddRADseq). This allowed us to test not only for the impact of within AMF species variation on plant community structure but also for the role of the R. irregularis phylogeny on plant community metrics. Nine isolates of R. irregularis, belonging to three different genetic groups (Gp1, Gp3 and Gp4), were used as either single inoculum or as mixed diversity inoculum. Plants in a mesocosm representing common species that naturally co-exist in European grasslands were inoculated with the different AMF treatments. We found that within-species differences in R. irregularis did not strongly influence the performance of individual plants or the structure of the overall plant community. However, the evenness of the plant community was affected by the phylogeny of the fungal isolates, where more closely-related AMF isolates were more likely to affect plant community evenness in a similar way compared to more genetically distant isolates. This study underlines the effect of within AMF species variability on plant community structure. While differential effects of the AMF isolates were not strong, a single AMF species had enough functional variability to change the equilibrium of a plant community in a way that is associated with the evolutionary history of the fungus.
Highlights
Soil microorganisms that influence plant-plant interactions play a central role in terrestrial ecosystems [1]
This is true for arbuscular mycorrhizal fungi (AMF; subphylum Glomeromycotina), which are considered the commonest of plant root symbionts, due to their unique capacity to form endosymbioses and to exchange nutrients with 74% of land plants [2]
Colonization of the roots by the fungi was significantly affected by the different AMF treatments as well as by plant species identity
Summary
Soil microorganisms that influence plant-plant interactions play a central role in terrestrial ecosystems [1] This is true for arbuscular mycorrhizal fungi (AMF; subphylum Glomeromycotina), which are considered the commonest of plant root symbionts, due to their unique capacity to form endosymbioses and to exchange nutrients with 74% of land plants [2]. In addition to direct effects on plant physiology, AMF have been shown to alter competitive interactions between plants [3]. This impacts common metrics of plant community structure, such as community richness, community evenness (i.e the relative abundance of community members) and it affects the community productivity. Other studies demonstrated that AMF could promote or limit community productivity depending on the AMF taxon involved, regardless of plant community species richness [11]
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