Three‐Way Interactions among Mutualistic Mycorrhizal Fungi, Plants, and Plant Enemies: Hypotheses and Synthesis

Abstract

A number of studies have shown that an association with mycorrhizal fungi can alter the outcome of interactions between plants and their enemies. While the directions of these effects vary, their strength suggests the need for greater attention to multispecies interactions among plant enemies, plants, and mycorrhizal fungi. We recognize that mycorrhizal fungi could effect plant enemies by improving plant nutrition, modifying plant tolerance, or modifying plant defenses. In addition, mycorrhizal fungi could directly interfere with pathogen infection, herbivory, or parasitism by occupying root space. We formalize these alternative outcomes of multispecies interactions and explore the long-term dynamics of the plant-enemy interactions based on these different scenarios using a general model of interactions between plants and plant enemies. We then review the literature in terms of the assumptions of the alternative mechanisms and the predictions of these models. Through this effort, we identify new directions in the study of tritrophic interactions between enemies, plants, and soil mutualists.

Mycorrhiza-induced trophic cascade enhances fitness and population growth of an acarine predator

“…Like other plant-associated belowground organisms, AM fungi may have variable effects on herbivores feeding on aboveground plant parts (Gehring and Whitham 2002;Bennett et al 2006;Gange 2007), one of which is herbivore proliferation, possibly due to improved nutritional quality of the host plant (e.g., Borowicz 1997;Hoffmann et al 2009). The plants used in the current study were produced by strictly following the protocol established by Hoffmann et al (2009).…”

“…Only three studies have addressed the effect of arbuscular mycorrhizal (AM) symbiosis on third trophic level natural enemies (Gange et al 2003;Guerrieri et al 2004;Hempel et al 2009). Association with AM fungi may induce a broad range of changes in plant quality (Read 1998) and can result in diverse effects, ranging from positive to negative, on aboveground herbivores (Gehring and Whitham 2002;Bennett et al 2006;Gange 2007). AM symbiosis may affect aboveground herbivores by changing the composition and quantity of plant defensive compounds and/or nutrients (Borowicz 1997;Hoffmann et al 2009).…”

Root fungal symbionts interact with mammalian herbivory, soil nutrient availability and specific habitat conditions

“…Herbivory, plant-plant competition and soil nutrient availability play key roles in shaping plant performance and community dynamics (e.g., Grace and Tilman 1990;Crawley 1997) and should, therefore, play important roles in modifying the conditions for host-dependent fungal symbiosis, such as mycorrhiza (Smith and Read 2008). On the other hand, mycorrhiza and other members of the soil are considered important drivers of aboveground ecosystem function and diversity (Reynolds et al 2003;Bennett et al 2006; Van der Heijden et al 2008).…”

Two fungal symbioses collide: endophytic fungi are not welcome in leaf-cutting ant gardens

“…It is increasingly recognized that such symbioses affect host success and can ultimately regulate host populations, and thus community composition and diversity (Hajek & St Leger 1994;Gilbert & Strong 2007). For example, mycorrhizae associate with plant roots and enhance plant growth, which may indirectly modify the plant's success via interactions with competitors, foliar herbivores and pathogens (Bennett et al 2006;Herre et al 2007). While the reciprocal benefits of many host-fungal mutualisms have been studied, less understood are the interactions among the component members of different symbioses.…”