Phenolic Content of Vegetation in Two African Rain Forests: Ecological Implications

Mature leaves of abundant trees in rain-forest vegetation on acid white-sand soils of the Douala-Edea Reserve, Cameroon, contain approximately twice the concentration of phenolic compounds found in similar rain-forest vegetation on lateritic soils of the Kibale Forest, Uganda. Phenolics are the most widespread class of ecologically important plant secondary compounds. This study provides support for the hypothesis that vegetation on low-nutrient soils contains relatively high concentrations of chemicals deterrent to herbivores and pathogens. Unlike the two species of Colobus monkeys found in Kibale Forest, black colobus monkeys ( Colobus satanas ) in the Douala-Edea Reserve avoid the leaves of almost all abundant tree species in the area, selectively feeding on leaves of relatively rare components of the vegetation (deciduous trees and second-growth vines). Unlike any other colobine studied to date, black colobus in the Douala-Edea Reserve feed heavily on seeds, which contain lower concentrations of phenolic compounds than do leaves in this site.