Abstract
AbstractHow herbivores respond to resource heterogeneity is important for predicting plant resistance to herbivores. Experimental studies thus far have revealed that herbivore responses differ depending on whether herbivores are offered single or multiple plant types, but the reports have rarely been combined. Here, we conducted a meta‐analysis of 47 publications on choice and no‐choice experiments to reveal how the presence/absence of multiple plants (i.e., choice/no‐choice conditions) alters the extent of behavioral avoidance by herbivores. The herbivore diet breadth and response traits (feeding, growth, or oviposition) explained a significantly large amount of heterogeneity in the herbivore response under choice and no‐choice conditions. In contrast, a small amount of heterogeneity was explained by the herbivore types (vertebrates, exophagous, or endophagous invertebrates), plant resistance traits (chemical or nonchemical), plant life form, and relatedness of plant pairs (intraspecific or interspecific) as well as interactions between the herbivore and plant characteristics. Compared with the no‐choice conditions, specialist herbivores further avoided suboptimal plants under choice conditions. Generalist herbivores more evenly utilized optimal and suboptimal plants under choice conditions. The avoidance of suboptimal plants under choice conditions was the most prominent in oviposition response. Thus, our meta‐analysis found that herbivore characteristics rather than plant traits were more responsible for driving behavioral avoidance by herbivores to a particular plant. The contrasting response between specialist and generalist herbivores to plant heterogeneity may be more ubiquitous than previously thought.
Highlights
There was a moderate amount of heterogeneity attributable to interactions between the plant resistance traits and either of the diet breadth or types of herbivores: The significant amount of heterogeneity was explained by an interaction term between the Random-effect meta-analysis: source of
We identified positive and negative deviations of difference of LRs (diff_LR) from the overall mean for generalist and specialist herbivores, respectively (Fig. 2), indicating a weakened and strengthened avoidance by generalist and specialist herbivores to lower-ranked plants under choice conditions, respectively
Based on the certain amount of heterogeneity explained by some interactions between herbivore categories and plant resistance traits v www.esajournals.org (Table 2), we plotted each group of the herbivore diet breadth or types separately against the plant resistance traits (Fig. 3)
Summary
Our meta-analysis focused on the following seven factors as explanatory variables: herbivore diet breadth (specialist or generalist), herbivore type (vertebrates, exophagous invertebrates, or endophagous invertebrates), herbivore response traits (feeding, growth, or oviposition), plant resistance traits (chemical, nonchemical, or both), plant life form (tree or herb), taxonomic relatedness of plant pairs (intraspecific or interspecific), and the design of choice experiments (pairwise or simultaneous choice on multiple plant types). Analysis that examined the fixed effects of herbivore diet breadth (specialist or generalist), herbivore type (vertebrates, exophagous invertebrates, or endophagous invertebrates), response traits (feeding, growth, or oviposition), plant resistance traits (chemical, nonchemical, or both), plant life form (tree or herb), plant relatedness (within or between species), and choice design. Effect meta-analysis to assess the sampling hetIn the same way as described above, we erogeneity and to test factors moderating analyzed multilevel mixed-effect models that herbivore response, respectively. There was a moderate amount of heterogeneity attributable to interactions between the plant resistance traits and either of the diet breadth or types of herbivores: The significant amount of heterogeneity was explained by an interaction term between the
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