Abstract
Damage to plants by herbivores is ubiquitous and sometimes severe. Tolerance is the capacity of a plant to maintain its fitness through growth and reproduction after sustaining herbivore damage. Recent physiological and ecological work indicates that tolerance mechanisms are numerous and varied. Some of the plant traits involved may reflect selection by herbivores, while others are likely to be by-products of selection for other ecological functions. Similarly, some tolerance mechanisms may participate in tradeoffs with plant defence, while many do not. Regardless of its ultimate origin or physiological relationship to plant defence, tolerance often may influence the evolution of piant defence and the composition of plant communities.