The Evolutionary Ecology of Tolerance to Consumer Damage

Abstract

▪ Abstract Recent theoretical studies suggest that the ability to tolerate consumer damage can be an important adaptive response by plants to selection imposed by consumers. Empirical studies have also found that tolerance is a common response to consumers among plants. Currently recognized mechanisms underlying tolerance include several general sets of traits: allocation patterns; plant architecture; and various other traits that may respond to consumer damage, e.g., photosynthetic rate. Theoretical studies suggest that tolerance to consumer damage may be favored under a range of conditions, even when the risk and intensity of damage varies. However, most of these models assume that the evolution of tolerance is constrained by internal resource allocation trade-offs. While there is some empirical evidence for such trade-offs, it is also clear that external constraints such as pollinator abundance or nutrient availability may also limit the evolution of tolerance. Current research also suggests that a full understanding of plant adaptation to consumers can only be achieved by investigating the joint evolution of tolerance and resistance. While tolerance to consumer damage has just recently received significant attention in the ecological literature, our understanding of it is rapidly increasing as its profound ecological and evolutionary implications become better appreciated.

Genetic variation and constraints on the evolution of defense against spittlebug (Philaenus spumarius) herbivory in Mimulus guttatus

“…This would be consistent with Roy and Kirchner's (2000) model of the evolution of tolerance to pathogens; in this model, traits conferring tolerance are expected to sweep to fixation and maintain their advantage through time, because such traits would not affect the prevalence or fitness of the pathogen. This model, however, does not include costs of tolerance, whereas such costs have been reported in other studies of tolerance to herbivory (Stowe et al, 2000). We also found no evidence for dominance variation for tolerance, even though previous experiments, involving this population as well as others, reported considerable variation among families in the response of tolerance to experimental self-fertilization (Carr and Eubanks, 2002;Ivey et al, 2004).…”

Demographic response to shading and defoliation in two woodland orchids

“…Just as life history costs to sexual reproduction may be paid against two aspects of reproduction, quantity or quality of offspring (AMUNDSEN & SLAGSVOLD 1998, STOWE et al 2000, costs to future growth, and hence to vegetative reproduction, appear to fall into this dichotomy as well. These plants appear to favour a larger number of lower quality ramets over a smaller number of higher quality ramets.…”

“…By diminishing the current photosynthetic capacity of a plant, herbivory and harvesting decrease the amount of photosynthate that may be stored for future use in sprout and flower development. Such resource losses may manifest themselves as reductions in quantity and/or quality not only of seeds and reproductive structures (STOWE et al 2000), but also of leaves and other vegetative structures. Furthermore, herbivory may induce greater allocation to defense, leaving fewer resources for growth and reproduction (RUIZ et al 2002).…”

No interaction between competition and herbivory in limiting introduced Cirsium vulgare rosette growth and reproduction

“…Four hypotheses could explain the lack of an interaction between competition and herbivory in C. vulgare performance. First, there may be no tradeoff in resource allocation for growth versus defense or tolerance of herbivory for C. vulgare in its final, flowering year, in contrast to other studies (e.g., Simms 1992; Strauss and Agrawal 1999;Hochwender et al 2000;Stowe et al 2000). If rosettes in their flowering year have large amounts of stored nutrients in their taproots, then allocation of resources to both growth and defense or tolerance may be possible.…”