12 Mycorrhizae-Herbivore Interactions: Population and Community Consequences Catherine A. Gehring, Thomas G.Whitham Contents 12.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000 12.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 000 12.3 Effects of Aboveground Herbivores on Mycorrhizal Fungi . 000 12.3.1 Population Level Responses . . . . . . . . . . . . . . . . . . 000 12.3.2 Community Level Responses . . . . . . . . . . . . . . . . . . 000 12.3.3 Carbon Limitation as a Mechanism of Herbivore Impacts on Mycorrhizae . . . . . . . . . . . . . 000 12.3.4 Conditionality in Mycorrhizal Responses to Herbivory . . . 000 12.4 Effects of Mycorrhizal Fungi on the Performance of Herbivores . . . . . . . . . . . . . . . 000 12.4.1 Patterns of Interaction . . . . . . . . . . . . . . . . . . . . . 000 12.4.2 Mechanisms of Mycorrhizal Impacts on Herbivores . . . . . 000 12.4.3 Not All Mycorrhizae Are Equal . . . . . . . . . . . . . . . . . 000 12.5 Ecological and Evolutionary Implications . . . . . . . . . . 000 12.5.1 Herbivore Effects on Mycorrhizae . . . . . . . . . . . . . . . 000 12.5.2 Mycorrhizae Effects on Herbivores . . . . . . . . . . . . . . 000 12.5.3 Combined Effects . . . . . . . . . . . . . . . . . . . . . . . . 000 12.6 Suggestions for Future Research . . . . . . . . . . . . . . . . 000 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 000 12.1 Summary Herbivores and mycorrhizal fungi commonly occur together on host plants and thus are likely to interact in ways that could indirectly affect each other’s performance. In this chapter, we review the published studies on these inter- actions and their implications for plant,herbivore and fungal populations and communities. Six major patterns emerge from our review. First, in the major- ity of cases, aboveground herbivores reduce mycorrhizal colonization and Ecological Studies,Vol. 157 M.G.A. van der Heijden, I. Sanders (Eds.) Mycorrhizal Ecology © Springer-Verlag Berlin Heidelberg 2002