Floristics, Primary Productivity and Primate Diversity in Amazonia: Contrasting a Eutrophic Várzea Forest and an Oligotrophic Caatinga Forest in Brazil

Abstract

Several factors such as rainfall, primary productivity, and plant species richness have been hypothesized to affect consumer species richness, possibly explaining differences in species richness among communities and on different continents. Primary productivity in particular has been suggested as important in determining species richness of consumer taxa, such as the primates, in the Neotropics. Here I contrast the floristics and phenological patterns of two Amazonian rainforest sites that differ markedly in primary productivity and yet have the same number of primate species: 1) an oligotrophic site—caatinga forests of Pico da Neblina National Park; and 2) a eutrophic site—várzea forests of Mamirauá. The objective of this comparison is to see how primary productivity interacts with floristics and phenology and ultimately, with primate species richness. With only 4 species each, the compared sites are characterized by low primate species richness. At both sites, low numbers of primate species are associated with an unusually low abundance of important primate food plants such as trees from the Burseraceae, Moraceae, Myristicaceae, Palmae and Sapotaceae. Moreover, in Neblina there is a long period of fruit scarcity and an overall low availability of fleshy fruits, which probably also contributes to the observed low primate species richness. In contrast, productivity in Mamirauá is high and fleshy fruits are abundant. These fruits, however, are mostly small in size and their seeds are most likely dispersed by birds, bats, fish, or water, not by primates. In this case then, primary productivity is not being largely transferred to primates as may be the case in other productive sites where preferred primate plant families are more abundant. Thus, when intertrophic interactions have a mutualistic nature such as the interaction between a fruit and a frugivore, a direct effect of primary productivity on all consumer taxa should not be expected. I suggest that in order to understand the effects of intertrophic interactions on consumer species richness in tropical rainforests it is important to first determine how the primary productivity is funnelled to the second trophic level.