Patterns of Leaf Development and Herbivory in a Tropical Understory Community

Most plant—herbivore studies have demonstrated that young leaves are preferred over mature leaves, and that the majority of lifetime damage occurs during the 1st mo. In spite of this, we know little about how young leaves are defended. Young leaves are an ephemeral resource, and herbivore damage may be reduced by (1) producing leaves at times of low herbivore abundance, (2) synchronous leaf production, or (3) rapid leaf expansion. To address these hypothesis I examined patterns of leaf phenology, leaf expansion, and herbivory in saplings of 32 species in a Panamanian lowland moist forest. Leaf phenology ranged from continuous to highly synchronous, and mean monthly damage rates varied from 6 to 60%. Within species, leaves produced during the dry season, a period of relatively low insect abundance, received less damage than leaves produced during the west season. Leaves produced during synchronous flushes received less damage than leaves produced out of synchrony. Species with continuous or synchronous leaf production had lower damage rates than intermediate species, but growth rates and survivorship were not correlated with leaf production. It appears that higher damage rates in intermediate species may be compensated by reduced investment in chemical defense compared with continuous species, and a less restricted growing season and reduced storage costs compared with synchronous species. Previous studies have identified leaf expansion rate as an important young leaf defense, but in this study there was no correlation between expansion rate and herbivory.