ABUNDANCE AND STRATIFICATION OF FOLIAGE ARTHROPODS IN A LOWLAND RAIN-FOREST OF CAMEROON

1. Arthropod densities and apparent leaf damage were compared within the canopy ecotone and the shrub layer of a lowland rain forest in Cameroon, using a branch clipping method. 2. Most of the individuals collected consisted of ants (average 44%) and various herbivores (31%). Overall arthropod densities amounted to 17 individuals per sample, which, on average, consisted of 0.85 m2 of foliage area. Arthropod densities were lower than on temperate foliage. 3. Arthropod densities were about 3 times higher in the canopy than within the shrub layer. In particular, ants and herbivores were significantly more abundant in the canopy than within the shrub layer. Usually, layer effects rather than site effects appeared to cause greater variance in arthropod abundance. 4. Arthropod species-richness, as estimated by the number of operational taxonomic units sorted, was higher in canopy samples than in samples obtained from the shrub layer. However, apparent leaf damage was higher within the shrub layer (10.9%) than on the canopy (5.2%). 5. Possible factors responsible for the high densities of ants and herbivores on the canopy and for the high-leaf damage within the shrub layer are discussed.