Biological Journal of the Linnean Society (2001), 72: 161–178. With 3 figures doi: 10.1006/bijl.2000.0497, available online at http://www.idealibrary.com on The relationship between fruit production and primate abundance in Neotropical communities PABLO R. STEVENSON* Doctoral Program in Anthropological Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794 4364, USA Received 11 December 1999; accepted for publication 5 October 2000 Ecological models predict a positive correlation between fruit production and primate abundance in the Neotropics. To test this relationship, I compiled information on primate abundance and calculated different indexes of fruit production for 30 Neotropical sites. These indexes can be grouped in three categories: (1) Fruit production estimates based on fruit traps, (2) basal area of endozoochorous trees and (3) density of these trees. The first estimate was the best predictor of both primate biomass (r 2 =0.80) and species richness (r 2 =0.64). The advantage of using fruit trap estimates is that they take into account production rates (which is not the case for basal area or density estimates), while the advantage of using basal area over density estimates is that it includes some of the expected variation due to tree size. However, using both basal area and density indexes I found a positive correlation between the basal area index and primate biomass for frugivorous monkeys and small platyrhines, but there was no correlation for folivorous and seed predator primates. I also found a positive correlation between pitheciine biomass and the abundance of Eschweilera trees. The analyses gave little support to the importance of suggested keystone resources such as figs and palms. Finally, when including climatic, geographic and plant diversity variables, fruit production continued to be a good predictor of primate biomass in the Neotropics, but primate species richness was best predicted by latitudinal gradients and plant species richness.  2001 The Linnean Society of London ADDITIONAL KEYWORDS: fruit production – Neotropical communities – New World monkeys – primate biomass – primate diversity – tropical rain forest. and so on. This base line idea indicates that plant INTRODUCTION abundance is determined mainly by the available solar There are many factors known to affect species richness irradiance (when water and essential nutrients are and the size of animal populations in a particular not in short supply) and the abundance of primary habitat, including physical conditions and interspecific consumers will depend on plant productivity and plant interactions. Among these factors, many authors have resource allocation (Brown, 1981). Thus if more energy argued that available energy in the habitat and prim- is available for production this may result in either ary productivity are the most important ones in de- larger populations or more species in the environment termining the structure of communities (Hutchinson, (Connell & Orians, 1964). 1959; Connell & Orians, 1964; Brown, 1981; Wright, The limited amount of energy available for con- 1983; Currie, 1991). The basic idea is that a fixed sumers has to be partitioned in some way among fraction of the solar energy is captured by plants and all species present, such that a minimum number of this energy decreases as it is transformed and used by individuals is present to sustain their populations consumers at higher trophic levels (Hutchinson, 1959). (Currie, 1991). Therefore, in simple bottom-up struc- This unavoidable physical process generates the com- tured community models, an increase in primary re- mon pyramidal patterns in numbers (Elton, 1927), sources may produce three results: (1) an increment plants being more abundant than primary consumers, in both diversity and biomass of primary consumers herbivores more abundant than secondary consumers, (Connell & Orians, 1964); (2) an increment in biomass but a decrease in diversity, when competition favours only few species (Huston, 1979; Rosenzweig, 1992); or (3) a similar biomass per species but an increment of * Corresponding author: E-mail: psteven@life.bio.sunysb.edu 161 0024–4066/01/010161+18 $35.00/0  2001 The Linnean Society of London