Plant tolerance and resistance in food webs: community-level predictions and evolutionary implications

While evolutionary ecologists emphasize different ways in which plants can evolutionarily respond to herbivory, such as resistance or tolerance, community ecology has lagged in its understanding of how these different plant traits can influence interactions, abundance, composition, and diversity within more complex food webs. In this paper, we present a series of models comparing community level outcomes when plants either resist or tolerate herbivory. We show that resistance and tolerance can lead to very different outcomes. A particularly important result is that resistant species should often coexist locally with other, less resistant competitors, whereas tolerant species should not be able to coexist locally with less tolerant competitors, although priority effects allow them to coexist regionally. We also use these models to suggest some insights into the evolution of these traits within more complex communities. We emphasize how understanding the differential effects of plant tolerance and resistance in food webs provides greater appreciation of a variety of empirical patterns that heretofore have appeared enigmatic.