Leaf traits and herbivore selection in the field and in cafeteria experiments

Abstract

Despite the vast diversity and complexity of herbivores, plants and their interactions, most authors agree that a small number of components of leaf quality affect preference by generalist herbivores in a predictable way. However, herbivore preference is determined not only by intrinsic plant attributes and herbivore biology but also by the environmental context. Within this framework, we aimed to analyse general interspecific trends in the association between herbivory and leaf traits over a wide range of angiosperms from central Argentina. We (i) tested for consistent associations between leaf traits, consumption in the field, and preference of generalist invertebrate herbivores in cafeteria experiments; (ii) assessed how well herbivore preferences in cafeterias matched leaf consumption in the field; and (iii) developed a simple conceptual model linking leaf traits, herbivore preference in cafeterias and consumption in the field. In general, we found that tender leaves with higher nutritional quality were preferred by herbivores, both in the field and in cafeteria experiments. According to our model, this relationship between field and cafeteria consumption and leaf quality is observed when generalist herbivores and plants of high accessibility are considered. However, differences between leaf consumption in the field and in cafeteria experiments can also be found. At least two reasons can account for this: (i) specialized plant-herbivore relationships often occur in the field, whereas cafeteria experiments tend to consider only one or a few generalist herbivores; (ii) different plant species growing in the field often differ in their degree of accessibility to herbivores, whereas in cafeteria experiments all species are equally accessible. Our results add new evidence to a growing consensus that, although herbivory in the field is determined by many factors, consistent patterns of differential susceptibility to foliar feeders can be found in leaves differing in nutritional quality and thus in resource-use strategy.

Herbivore preference drives plant community composition

“…Accordingly, in our experiment the preference of the two herbivore species to the 28 plant species was highly correlated. Both showed higher preferences for legumes, supporting the view of a strong influence of a plant's nutritive value on herbivore preference (Dirzo 1980, Pe´rez-Harguindeguy et al 2003, Loranger et al 2012. Similarly, both herbivores disliked Hypericum perforatum, whose chemical arsenal is known to be toxic to phytophagous insects (Maron et al 2004).…”

“…Arion vulgaris is widespread throughout Europe and occupies a broad range of habitat types, including grasslands. Similar to Spodoptera littoralis, Arion vulgaris is known to feed on a variety of plant species and is often used in bioassays (Dirzo 1980, Pe´rez-Harguindeguy et al 2003. Individuals of Arion vulgaris were collected in the wild (Bremgartenwald, Bern, Switzerland) and kept in the lab for several weeks before they entered the experiments.…”

Synergy between pathogen release and resource availability in plant invasion

“…Differences in pathogen richness might overestimate the strength of resource-enemy release relationships if some pathogens have little effect on their hosts (57), if herbivores are less sensitive than pathogens to resource adaptations, or if herbivore release does not correlate with pathogen release (28). Conversely, if the plant traits hypothesized to increase pathogen richness-fast growth, low defense investment and high nutrient content-also increase susceptibility to other enemies, or effects of individual enemies (49,(58)(59)(60), pathogen richness might underestimate the strength of resource-enemy release relationships. For example, given that most viruses are transmitted by arthropod herbivores (54), the relatively high viral richness and release observed among competitors and species adapted to high-nitrogen environments could reflect relatively strong herbivory and herbivore release for competitors and species adapted to high-nitrogen environments.…”

Phenotyping plants: genes, phenes and machines

“…In so-called 'cafeteria experiments' herbivores such as snails, grasshoppers or deer that are offered equal amounts of leaves of different species show clear preferences for some species, whereas they disfavour others ( Fig. 1; Pérez-Harguindeguy et al 2003). This may be only a matter of taste, but we are only just beginning to discover how rich the phenotyping capacities of certain species are.…”