Vertebrate Frugivores and Their Interaction with Invertebrate Fruit Predators: Supporting Evidence from a Costa Rican Dry Forest

Fruit-eating vertebrates may have a significant impact on the population sizes of insect fruit predators that remain inside the fruit after ripening, and it may be predicted that the disappearance or marked reduction of a population of frugivorous vertebrates will lead to a dramatic increase in the population of invertebrate fruit predators. Evidence consistent with this prediction was found for Amblycerus cisteli­ ntis, a bruchid beetle feeding on the seeds of Guazuma ulmifolia in the tropical dry deciduous forests of northwestern Costa Rica. A significant increase in the incidence of A. cistelinus from 1972 to 1986 was found at the site where large mammals eating G. ulmifolia had been removed in that period, but no change was observed in the same period at the site where some mammalian seed dispersers were present. G. ulmifolia plants apparently get two distinct reproductive benefits from their animal mutualists: seed dispersal and a reduction in seed predation through a decrease in seed predator populations.