Abstract

In this paper I ask two questions: Is fruit ever limiting to vertebrate frugivores and, if so, do frugivores presently compete for food, either with closely- or distantly-related species? A brief review of the fruiting strategies of tropical plants indicates that fruit can occasionally be superabundant, but it is often produced at low rates and in low quantities. Variation in fruit abundance results from several biotic selective pressures, including variation in the density, diversity, and reliability of potential dispersal agents. To judge from the size structure, dietary similarities, habitat preferences and foraging behaviors of taxonomically-restricted guilds of frugivorous birds and mammals, members of these guilds have competed for food in the past and must occasionally do so today. Unusual climatic conditions can occasionally “upset” phenological patterns and can create food shortages that promote competition among closely-related species of frugivores. Avian and mammalian frugivores, however, probably seldom compete with each other for food in present-day tropical ecosystems. A major reason for this is that many tropical plants have evolved fruits that are attractive to only a limited subset of frugivores (e.g., only birds or only bats). Plants apparently “perceive” qualitative differences in the dispersal services of birds and mammals and attempt to attract members of one group but not the other.