VARIATION IN HERBIVORY WITHIN AND AMONG PLANTS OF DAPHNE LAUREOLA (THYMELAEACEAE) - CORRELATION WITH PLANT SIZE AND ARCHITECTURE

1 Herbivory by noctuid moth larvae (Lepidoptera, Noctuidae) on plants of Daphne laureola L. (Thymelaeaceae) was studied under natural condit ions in a south-eastern Spanish montane habitat. The main objective of the study was to determine how size and architectural features correl ated with herbivory level (mean percentage leaf area removed by the en d of the larval growth season) and herbivore load (mean number of cate rpillars recorded per day) both among and within plants. 2 A significa nt correlation was found between herbivore load and herbivory level of individual plants. Herbivory levels differed widely (range = 0.1-12.8 % leaf area) and were considerably smaller than those often used in ar tificial defoliation experiments. 3 Variation among plants in the inci dence of noctuid larvae was directly related to the number of leaf who rls, and inversely to the mean basal diameter of stems. These response s to size and architectural traits may be explained by discrimination by ovipositing females. 4 Within plants, larvae preferentially selecte d leaf whorls having shorter supporting stems and lower branching orde rs. Movement costs may be reduced by larvae using plant architectural traits as cues for within-plant food selection. 5 The reasons for and potential implications of the different features used by adult noctuid s discriminating between plants and by their larvae selecting leaf who rls are discussed.