Intraspecific Variation in Herbivory on Two Tropical Tree Species

Abstract

Levels of herbivory on young and mature leaves were determined for two tree species, Trichilia cipo (Meliaceae) and Cecropia insignis (Moraceae), in a lowland rain forest of Panama. Saplings of both species were studies in light gaps, and in addition, Trichilia was studies in the understory. Rates of leaf damage by insects were measured on marked plants during four 3—wk sample periods conducted at 5—mo intervals. Mature leaves of Cecropia suffered average damage rates that were five times greater than those suffered by Trichilia; the reverse was true for young leaves. Patterns of intraspecific variation in herbivory on mature leaves were similar for the two species, despite differences in life history, habitat, defensive characteristics, and levels of damage. Variation among individuals at any one sample period was high. Damage levels during sequential samples were not significantly correlated within an individual but were highly variable. For each sample period, a different group of individuals (with one exception) comprised the 20% most heavily grazed. These patterns of herbivory are discussed with respect to seasonal effects, possible causal mechanisms, and implications for escape of herbivores and selection of defenses.