Stressed out symbiotes: hypotheses for the influence of abiotic stress on arbuscular mycorrhizal fungi.

Niall S Millar,Alison E Bennett

doi:10.1007/s00442-016-3673-7

Abstract

Abiotic stress is a widespread threat to both plant and soil communities. Arbuscular mycorrhizal (AM) fungi can alleviate effects of abiotic stress by improving host plant stress tolerance, but the direct effects of abiotic stress on AM fungi are less well understood. We propose two hypotheses predicting how AM fungi will respond to abiotic stress. The stress exclusion hypothesis predicts that AM fungal abundance and diversity will decrease with persistent abiotic stress. The mycorrhizal stress adaptation hypothesis predicts that AM fungi will evolve in response to abiotic stress to maintain their fitness. We conclude that abiotic stress can have effects on AM fungi independent of the effects on the host plant. AM fungal communities will change in composition in response to abiotic stress, which may mean the loss of important individual species. This could alter feedbacks to the plant community and beyond. AM fungi will adapt to abiotic stress independent of their host plant. The adaptation of AM fungi to abiotic stress should allow the maintenance of the plant-AM fungal mutualism in the face of changing climates.Electronic supplementary materialThe online version of this article (doi:10.1007/s00442-016-3673-7) contains supplementary material, which is available to authorized users.

Highlights

IntroductionThe benefits provided to plants by Arbuscular mycorrhizal (AM) fungi will become even more important, due to increasing abiotic stresses caused by climate change (Hanson and Weltzin 2000; Compant et al 2010)
We develop two testable hypotheses that detail how the community composition of Arbuscular mycorrhizal (AM) fungi will be effected by abiotic stress in the short term, and how AM fungi will be selected for improved abiotic stress tolerance following repeated exposure to abiotic stress
The benefits provided to plants by AM fungi will become even more important, due to increasing abiotic stresses caused by climate change (Hanson and Weltzin 2000; Compant et al 2010)

Summary

Introduction

The benefits provided to plants by AM fungi will become even more important, due to increasing abiotic stresses caused by climate change (Hanson and Weltzin 2000; Compant et al 2010) This is demonstrated by the knock-on effects on plant communities that can occur when AM fungal diversity or community composition is changed (van der Heijden et al 1998; Antoninka et al 2009; Sun et al 2013). AM fungi are functionally diverse (Munkvold et al 2004; Powell et al 2009), and vary both phenotypically and genetically in response to abiotic stress (Klironomos et al 2001; Treseder and Allen 2002; Antunes et al 2011), suggesting that abiotic stress likely influences each fungal species differently This can be linked to differences in AM fungal communities between climatic zones. Mycorrhizal stress adaptation: abiotic stress will lead to adaption among AMF species within communities from areas that are repeatedly exposed to abiotic stress

Abiotic stresses affect AMF directly

AMF and plants are equally likely to

AMF adaptation to abiotic stress conditions improves AMF fitness

Findings

Conclusions