Predator Control of Seed Production by a Rain Forest Understory Palm

Abstract

I studied the development of fruit from initiation to maturation in Calyptrogyne ghiesbreghtiana and recorded losses to pre-dispersal seed predators. Some infructescences were enclosed in mesh bags to examine the development of fruit when seed predation was reduced. To assess the effect of resource availability on fruit development I recorded the light environment and size of each plant. Initiated fruit expanded over a period of at least 11 weeks before they began to ripen. Mature fruit contain one seed. On average, infructescences lost more than 60% of initiated fruit to predators, including weevils, katydids, and moth larvae. No fruit abortion occurred, even when the burden of fruit development was greatly increased by insect exclusions. There were no effects of resource availability on the fraction of initiated fruit that ripened, but mean fruit mass was positively correlated with leaf area, and negatively correlated with fruit number. Fruit matured to ripeness more rapidly on plants that received more light. Pre-dispersal seed predation is responsible for most of the variation in seed production per infructescence by C. ghiesbreghtiana. The only means of resource-mediated control of seed production in this species is through the effect of respurce availability on flower production.