Arbuscular mycorrhizal fungi mediate below-ground plant–herbivore interactions: a phylogenetic study
Article first published online: 13 AUG 2012
© 2012 The Authors. Functional Ecology © 2012 British Ecological Society
Volume 26, Issue 5, pages 1033–1042, October 2012
How to Cite
Vannette, R. L., Rasmann, S. (2012), Arbuscular mycorrhizal fungi mediate below-ground plant–herbivore interactions: a phylogenetic study. Functional Ecology, 26: 1033–1042. doi: 10.1111/j.1365-2435.2012.02046.x
- Issue published online: 28 SEP 2012
- Article first published online: 13 AUG 2012
- Manuscript Accepted: 12 JUL 2012
- Manuscript Received: 6 MAR 2012
- Swiss National Science Foundation. Grant Number: PA0033-121483
- University of Michigan, Department of Ecology and Evolutionary Biology and a National Science Foundation DDIG
- Asclepias ;
- Bradysia ;
- chemical ecology;
- Glomus ;
- phylogenetic ecology;
- plant defence;
- plant–herbivore interaction
- Ecological interactions are complex networks, but have typically been studied in a pairwise fashion. Examining how third-party species can modify the outcome of pairwise interactions may allow us to better predict their outcomes in realistic systems. For instance, arbuscular mycorrhizal fungi (AMF) can affect plant interactions with other organisms, including below-ground herbivores, but the mechanisms underlying these effects remain unclear.
- Here, we use a comparative, phylogenetically controlled approach to test the relative importance of mycorrhizal colonization and plant chemical defences (cardenolides) in predicting plant survival and the abundance of a generalist below-ground herbivore across 14 species of milkweeds (Asclepias spp.). Plants were inoculated with a mixture of four generalist AMF species or left uninoculated. After 1 month, larvae of Bradysia sp. (Diptera: Sciaridae), a generalist below-ground herbivore, colonized plant roots.
- We performed phylogenetically controlled analyses to assess the influence of AMF colonization and toxic cardenolides on plant growth, mortality and infestation by fungus gnats. Overall, plants inoculated with AMF exhibited greater survival than did uninoculated plants. Additionally, surviving inoculated plants had lower numbers of larvae in their roots and fewer non-AM fungi than surviving uninoculated plants. In phylogenetic controlled regressions, gnat density in roots was better predicted by the extent of root colonized by AMF than by root cardenolide concentration. Taken as a whole, AMF modify the effect of below-ground herbivores on plants in a species-specific manner, independent of changes in chemical defence.
- This study adds to the growing body of literature demonstrating that mycorrhizal fungi may improve plant fitness by conferring protection against antagonists, rather than growth benefits. In addition, we advocate using comparative analyses to disentangle the roles of shared history and ecology in shaping trait expression and to better predict the outcomes of complex multitrophic interactions.