The grimy side of Grime's CSR theory: How we can use life history strategy to better understand mycorrhizal ecology

Background/Question/Methods

Arbuscular mycorrhizal (AM) fungi are ubiquitous soil fungi that live symbiotically in roots of a majority of terrestrial plant species. Due to a lack of understanding of AM fungal life history strategies, we still have very little power to predict the outcome of mutualistic interactions between plant and AM fungal individuals. This hampers utilizing this mycorrhizal symbiosis for large-scale agricultural or restoration purposes. Here we tackle the challenge of characterizing AMF functional/life history strategies, building upon Grime’s CSR model, developed in plant ecology. Having a common framework to categorize both plant and AM fungal life history strategies would allow to make specific predictions regarding plant-fungal community assembly and dynamics.

Results/Conclusions

By exploring AMF functional differentiation along two major niche axes, namely stress and disturbance, our framework identifies core functional traits (e.g. maximal growth rate, sensitivity to host shading, carbon sink strength) most likely to functionally discriminate AMF taxa. A brief review of comparative studies using pure AM fungal strains points towards a certain degree of phylogenetic conservatism in AM fungal life history strategies. This integrative CSR framework, by explicitly considering both AM fungal and plant life histories, yields insightful predictions about preferential plant-fungal associations that should be expected in natural communities. Future testing of the predictions made in our framework should include (1) observational studies linking plant functional traits to AM fungal assemblages in their roots and (2) verifying trait correlations expected from the CSR model using multiple AM fungal strains. Confirming the relevance of our model as a tool to predict the outcome of one-to-one plant-AM fungal symbiotic interactions and ultimately plant-AM fungal community assembly would have far-reaching implications, both to our fundamental understanding of this mycorrhizal symbiosis but also in applied contexts using AM fungi as a tool for ecosystem management.