The arboreal ant mosaic in a Cameroonian rainforest (Hymenoptera : Formicidae)

The ant mosaic of the canopy of a Cameroonian rainforest was studied by dir ectly sampling 167 large trees and 20 vines reaching the canopy level using a dirigible and the "canopy raft", the "canopy sled", and, when necessary, the single rope technique. Although plant species diversity was high (tree s: 63 species from 29 families; vines: 9 species from 7 families), our resu lts show an ant assemblage characterized by high abundance but low diversit y (28 ant species in total). We recorded only four "dominant" ant species ( i.e., species with populous colonies that build their own nests, exhibit st rong territoriality, and have mutually exclusive territories distributed in a mosaic pattern). The most frequent species, Crematogaster depressa, occu pied 87.4% of the trees and 85% of the vines, and its colonies reached seve ral million workers. Other dominants were recorded at low frequencies (Crem atogaster sp.1: 1.8% of the trees; Oecophylla longinoda: 6.0%; Tetramorium aculeatum: on one vine). Among the nine ant species tolerated on the territ ories of Cr. depressa(i.e., "non-dominant" species with smaller colonies), the workers of three species shared their trails with Cr. depressa, while C amponotus brutus, with colonies sometimes able to occupy the entire crown o f a tree, rather had the status of "subdominant". Extrafloral nectaries (EF N) played a role in ant species distribution. The large ecological success of Cr. depressa is probably due to its ability to nest on trees with or wit hout EFN. O. longinoda, which rarely tolerated non-dominant ant species, wa s significantly more frequently recorded on trees without EFN. While domina nt ants depended principally on attended homopterans (Coccidae and Stictoco ccidae; globally: 300,000 to 700,000 individuals per tree), nondominant spe cies depended primarily on EFN.