EVOLUTIONARY AND ECOLOGICAL IMPLICATIONS OF PRIMATE SEED DISPERSAL

In this paper, we evaluate patterns of fruit eating and seed dispersal in monkeys and apes and draw an important distinction between 1) the ecological consequences of primates as seed dispersers and 2) the evol utionary implications of primates on the seed and fruit traits of the plant species they exploit. In many forest communities, primates act a s both seed predators and seed dispersers and are likely to have an im portant ecological impact on patterns of forest regeneration and tree species diversity. Evidence from Kibale National Park, Uganda, and Man u National Park, Peru, as well as several other South American sites i ndicates that monkeys and apes display a wide range of fruit-processin g behaviors, including spitting seeds, dropping seeds, masticating see ds, and swallowing seeds. Differences in consumer body size, diet, ran ging patterns, and oral and digestive morphology result in different p atterns in the distance and distribution of seeds from the parent plan t. In the case of South American monkeys, for example, despite their r elatively small body size, platyrrhines were found to exploit larger f ruits and swallow larger seeds on average than did Old World monkeys a nd apes of the Kibale forest. We found little evidence to support the existence of a coevolutionary relationship between a single or set of primate dispersers and the particular plant species they disperse. Thi s is due to variability in the manner in which monkeys and apes select fruits and treat seeds, the fact that many species of primates and no nprimates exploit and disperse the same fruit species, and the fact th at extremely high levels of postdispersal seed, seedling, and sapling mortality serve to dilute the influence that any primate species may h ave on the recruitment of the next generation of adult trees. It is ap parent that many primate lineages exhibit dental, digestive, and/or se nsory adaptations that aid in the exploitation of particular food type s and that many lineages of flowering plants have evolved characterist ics of fruits and seeds that facilitate seed dispersal. However, in Li ght of currently available data, we argue that these represent evoluti onary rather than more strictly defined coevolutionary relationships. (C) 1998 Wiley-Liss, Inc.