Investigation into the effects of herbivory on Pentaclethra macroloba seedling success

Abstract

Pentaclethra macroloba is a dominant tropical canopy tree found throughout Central America and Amazonia. The annual mortality rate of P. macroloba seedlings is 60% in the tropical wet forest at the La Selva OTS biological station in Costa Rica. A possible cause of this dramatic mortality rate is insect herbivory, which can reduce seed production, plant growth, and survivorship, as well as cause leaf abscission. During the summer of 2009, new leaves of P. macroloba seedlings were selectively herbivorized by geometridae caterpillars to remove 25% of leaf material. Rachis growth rates were calculated over a 15-day period to compare differences between controlled and herbivorized leaves. In addition, 115 P. macroloba seedlings were tagged and photographed for leaf area analysis. This data is a part of an ongoing census of P. macroloba that aims to determine factors that contribute to the high mortality in seedlings that are 50 cm to 2 m in height. At the same time, I also collected and reared Lepidoptera larvae from P. macroloba in order to study larval development of the herbivores of P. macroloba. Finally, I conducted trials on P. macroloba leaflets to determine rates of water loss with varying levels of damage that mimicked Lepidoptera herbivory. The goal of each of these experiments was to identify if herbivory is a factor that contributes to the high seedling mortality rate in P. macroloba.