D3039: Using a meta-analysis approach to explore systemic plant responses to above- and belowground insect herbivory

Aboveground (AG) and belowground (BG) plant tissues are susceptible to herbivory by invertebrates. Herbivory induces plant defense responses locally in directly attacked tissues, and also systemically in non-attacked tissues. Cross-compartment plant tissues (like AG tissues of plants attacked by BG herbivores and vice versa) both contribute to local defense and are modified by cross-compartment herbivory. Yet, predictable response patterns in these tissues following cross-compartment herbivory have not been identified across plant and herbivore species. To fill this knowledge gap, we examined a suite of plant traits to explore AG herbivore effects on BG root tissues and, conversely, BG herbivore effects on AG plant tissues. We compiled two separate datasets for our meta-analysis, and we extracted data from studies published prior to September 2020. We analyzed our datasets using multi-level mixed-effect models and incorporated plant phylogeny into the model structure to control for differences across plant families. Overall, we found general patterns in cross-compartment responses to AG or BG herbivory. Both types of herbivory induced cross-compartment responses typically associated with systemic resistance such as changes in defense signaling molecules. Notably, cross-compartment responses also exhibited specific differences including BG herbivory reducing AG growth and increasing AG secondary metabolites, while AG herbivory decreased BG nutrients. These findings demonstrate AG and BG herbivores induce distinct changes in cross-compartment plant tissues, implying plants rely on different defense strategies against AG and BG herbivores, and that these strategies indirectly influence traits of non-attacked plant tissues in contrasting ways.