Biodiversity of arbuscular mycorrhizal fungi and ecosystem function

Abstract

Contents Summary1059I.Introduction: pathways of influence and pervasiveness of effects1060II.AM fungal richness effects on ecosystem functions1062III.Other dimensions of biodiversity1062IV.Back to basics – primary axes of niche differentiation by AM fungi1066V.Functional diversity of AM fungi – a role for biological stoichiometry?1067VI.Past, novel and future ecosystems1068VII.Opportunities and the way forward1071Acknowledgements1072References1072 Summary Arbuscular mycorrhizal (AM) fungi play important functional roles in ecosystems, including the uptake and transfer of nutrients, modification of the physical soil environment and alteration of plant interactions with other biota. Several studies have demonstrated the potential for variation in AM fungal diversity to also affect ecosystem functioning, mainly via effects on primary productivity. Diversity in these studies is usually characterized in terms of the number of species, unique evolutionary lineages or complementary mycorrhizal traits, as well as the ability of plants to discriminate among AM fungi in space and time. However, the emergent outcomes of these relationships are usually indirect, and thus context dependent, and difficult to predict with certainty. Here, we advocate a fungal‐centric view of AM fungal biodiversity–ecosystem function relationships that focuses on the direct and specific links between AM fungal fitness and consequences for their roles in ecosystems, especially highlighting functional diversity in hyphal resource economics. We conclude by arguing that an understanding of AM fungal functional diversity is fundamental to determine whether AM fungi have a role in the exploitation of marginal/novel environments (whether past, present or future) and highlight avenues for future research.

Interactions between functionally diverse fungal mutualists inconsistently affect plant performance and competition

“…Although previous studies have shown that the diversity of belowground mutualists can relax plant competition, these studies used fungal mutualists from the same functional group (AM fungi only) and plants of different functional groups (Wagg et al a, b). We reiterate that our experimental design did not allow for disentangling the effects of other soil microorganisms that could have been present in our mycorrhizal inoculum, however, a recent study pointed that no proper control is feasible when using complex mycorrhizal inoculum (Gryndler et al ). Nevertheless, we highlight that the effect of fungal–fungal interactions on plant communities are likely to be moderated by the functional identity of mutualist fungi and how they form partnerships with the co‐occurring closely‐related plants.…”

“…Mixed‐effects models were run with the lme4 package (Bates et al 2015), whereas post hoc tests were performed using the multcomp package (Hothorn et al 2008). The MuMIn package was used to estimate marginal and conditional R 2 (Barton ). Model diagnostics were performed using the DHARMa package (Hartig 2019).…”

“…For instance, competition among multiple herbivores or pollinators could potentially affect interactions among their host plants, and thus local plant diversity (Olff and Ritchie , Biesmeijer et al 2006, Bagchi et al , Temeles et al 2016). Moreover, it has often been shown that negative interactions among herbivores can weaken their net effects on the dominant plant species within a community, which then reduce the evenness within that plant community (Hulme 1996, Allan and Crawley , Young et al , Mortensen et al ). Currently, we lack an understanding of whether competitive interactions among plant mutualists have similar consequences for plant community structure.…”

“…As a result, plants are able to partition symbiotic partners, which in turn could relax plant competition. Most of the evidence for effects of fungal mutualists on plant–plant interactions comes from plant competition experiments using multiple species of AM fungi (Hart et al , Wagg et al a, b, Powell and Rillig ). Currently it is unknown whether the interaction between functionally diverse groups of fungal species can also foster niche differentiation between plants in terms of partitioning fungal mutualist partners and thereby affecting plant–plant competition.…”

Options for Improved Phosphorus Cycling and Use in Agriculture at the Field and Regional Scales

“…We know that agroecosystem management affects AMF community composition (Dai et al, 2014; Schneider et al, 2015), but the functional differences of these communities are still largely unclear. An increased understanding of AMF functional diversity and how this is affected by management is fundamental to knowing how we might be able to manipulate their role in agroecosystems to contribute to greater PUE (Powell et al, 2018). …”