Incorporating traits into consumer-resource models for a mechanistic trait ecology

Philip G Hahn , Lucia Navia, Antonia J. Millet, Robert D. Holt , Carolina Baruzzi

Traits provide a powerful way to infer community assembly processes, responses to environmental perturbations, and coexistence mechanisms, although most work has focused on plants and has not incorporated the role of trophic interactions. Here, we briefly review the main goals of trait-based ecology and highlight recent examples that use traits to study insect communities, specifically focusing on multitrophic communities and interactions between plants and insect herbivores. We then introduce a mechanistic multi-species consumer-resource model that incorporates traits involved in trophic interactions (i.e., leaf toughness and mandible strength) to outline mechanistic hypotheses for how interactions structure communities. Models show that different ways in which plants and herbivores interact through their traits, trait-matching vs. strong mandibles, substantially changes community coexistence patterns. Furthermore, we simulate interactions across a productivity gradient to generate predictions for how community composition changes across gradients, given a mechanistic hypothesis. Finally, we evaluate these patterns through the lens of community trait metrics and Modern Coexistence Theory. The modeling output highlights that, even under one mechanistic structure (i.e., trait matching between plants and herbivores), community composition patterns and the relative strength of equalizing and stabilizing mechanisms change strongly across environmental gradients. Our review provides an avenue for future research that combines functional traits and mechanistic models to provide a richer understanding of the processes that structure and maintain diversity in insect communities.