Herbivory on Diplacus aurantiacus shrubs in sun and shade.

This study tested the hypothesis that carbon allocation to the production of leaf antiherbivore chemicals reflects the intensity of herbivory and interacts with resource allocation to photosynthesis. The amount of herbivory by Euphydryas chalcedona butterfly larvae was measured on Diplacus aurantiacus shrubs growing in different daily solar irradiance regimes. The amount of herbivory sustained by plants was directly related to the degree of solar irradiance the shrubs received and to characteristics which vary with light intensity, e.g. leaf specific weight, but not to leaf resin or nitrogen content. Carbon allocation to the defense of leaf area was marginally related to the light regime, but was not directly related to photosynthetic income.