Toward a spatial perspective of plant-based indirect interaction webs: Scaling up trait-mediated indirect interactions

• Arthropod community is determined by induced plant phenotypes following herbivory.
• Community consequences of the induced phenotypes are considered in a spatial context.
• Neighbor effects are incorporated into a conceptual framework.
• Herbivore feeding mode characterizes community structure via induced phenotypes.
• Herbivore movement connects communities on induced and non-induced plants.

Phenotypic plasticity of plants following herbivory is ubiquitous in a wide range of terrestrial systems. Importantly, it can largely determine community properties of arthropods associated with induced plants. Effects of herbivore-induced plant phenotypes on species diversity, abundance, and community composition of higher trophic levels would depend on spatial variations in the altered phenotypes. To understand how arthropod communities are organized by plant phenotypic plasticity, we should focus on neighbor effects, as well as how these effects scale up to influence community structure and biodiversity within and between plant populations. Here, we encourage ecologists to meet the challenge of this novel issue by addressing the scaling up of trait-mediated indirect effects of the prevalent herbivory via plant phenotypic plasticity in a spatial context. We first examine how herbivore-induced phenotypic plasticity in terrestrial plants affects arthropod communities. Specifically, we review how different types of induced plant traits alter species diversity, overall abundance, and community composition of associated arthropods. Second, we provide a conceptual framework addressing how the combinations of induced and constitutive (i.e., non-induced) traits in a plant population result in resource heterogeneity available to herbivores in a more explicit spatial context. In particular, we pay special attention to the contrasting responses of specialist and generalist herbivores to induced plant phenotypes. Last, we highlight how induced resource heterogeneity affects distribution and diversity of arthropods through movements onto and away from plant individuals in a plant patch.