Pollinators, Herbivores, and Plant Neighborhood Effects

Abstract

Pollinator and herbivore interactions with individual plants can be strongly influenced by the densities and frequencies of other plants in local neighborhoods. The importance of these neighborhood effects is not yet clear, due in part to a profound disconnect between studies of pollinator and herbivore neighborhood effects. Considering these effects jointly is critical for understanding the role of plant spatial heterogeneity because plant fitness is often affected by pollinators, herbivores, and their interactions. We bring together these two types of neighborhood effects, describing the pathways through which these insects mediate neighborhood effects, and comparing their implementation in mathematical models. We find that ideas from each field can improve work in the other. For example, pollinator theory should broaden consideration of how pollinator traits influence responses to plant neighborhoods, while herbivore theory should consider adaptive foraging and connect herbivore neighborhood effects to plant fitness. We discuss approaches to theory that integrate pollinator and herbivore effects, particularly considering the nested spatial and temporal scales of these insects’ responses to neighborhoods. Ultimately, models will need to combine neighborhood effects from the diverse species that affect plants with direct plant interactions to determine the importance of spatial structure for plant performance and evolution.