Shifts in mycorrhizal fungal communities due to plant competition, parasitism and herbivory: Consequences for fungi and host plants

Plants and mycorrhizal fungi influence each other’s abundance, diversity and distribution in the environment.  How other biotic interactions affect the mycorrhizal symbiosis is less well understood.  We review our recent field studies on the influence of plant parasites, insect herbivores, and plant competitors on the ectomycorrhizal fungi associated with pinyon pine and describe how these changes feed back to affect host plant performance.  We find consistent and similar changes in ectomycorrhizal fungal community composition associated with all three of these biotic interactions.  In addition, we provide evidence that climate change is linked to increased prevalence of herbivores and parasites, and that the ectomycorrhizal fungal community shifts due to these factors are likely to have occurred across larger landscapes.  Field experiments conducted over more than ten years suggest that interactions with herbivores also influence the ability of the ectomycorrhizal fungal community to rebound during years of normal precipitation.  Our preliminary results suggest that the potentially persistent changes in ectomycorrhizal fungal communities associated with parasitism, herbivory, and plant competition may negatively affect host plant establishment and growth, emphasizing the need to examine other biotic interactions to improve our understanding of the functioning of the plant-mycorrhizal symbiosis.