Increased per capita herbivory in the shade: Necessity, feedback, or luxury consumption

ABSTRACT Leaf chemistry and physiology vary with light environment and are often thought to directly affect herbivory patterns. Biotic (e.g., parasitoids and predators) and abiotic (e.g., temperature, relative humidity) factors known to influence herbivory also co-vary with light environment. Irrespective of mechanism, light-based differences in herbivore damage must be the result of variable herbivore abundance, per capita effects, or both. We examined the effect of light environment on leaf defence and leaf nutritional quality in Lindera benzoin (Lauraceae) and relate this to the abundance and impact of its lepidopteran herbivore Epimecis hortaria (Lepidoptera: Geometridae). In this system we consistently observe greater natural field herbivory in shade habitats relative to high light habitats, despite similar herbivore abundances; differences in herbivory are therefore most likely attributable to different per capita impacts of herbivores across environments. Potential herbivore behaviours responsible ...