Differential impacts of mycorrhizal fungal communities on plant growth and defences drive the performance of invertebrate herbivores

Arbuscular mycorrhizal (AM) fungi can be key drivers of soil health, plant productivity, diversity and community structure. Yet the influence of the AM symbiosis reaches far beyond their host plants. More than half of the world’s described insects feed on living plant material. The growth and fitness of these insect herbivores is largely determined by the quality of their host plants, most of which will form associations with AM fungi. Indeed, AM fungi do not only affect the nutrient status of their host, but also impact plant physiology and secondary chemistry which are significant components of plant resistance to herbivory.

Using a variety of glasshouse and controlled environment experiments on sugarcane (Saccharum spp. hybrids) and wheat (Triticum aestivum) we investigated how AM fungal communities impact plant productivity and secondary chemistry, and how this affects invertebrate herbivores. Combining results from these experiments suggests that inoculation with AM fungal communities can either promote or reduce herbivore performance. This is driven by different mycorrhizal-induced changes in plant growth, nutrient status and defence chemistry, which depend on the host plant species.

Considering the ubiquity of mycorrhizal-plant-invertebrate interactions, it is vital that mycorrhizal fungal communities are effectively incorporated into natural resource management strategies within agriculture, restoration and conservation. However, predicting the strength and direction of the effects of AM fungal communities on aspects of plant success and diversity is often challenged by the context specific nature of the outcomes.