A review of mosaics of dominant ants in rainforests and plantations.
Dejean A., Corbara B.
Author Affiliation: Laboratoire d'Ecologie Terrestre, Université Toulouse III, 31062 Toulouse, France.
: 341-347
Abstract : The rain forest canopy is considered to be a habitat where a high proportion of the Earth's biodiversity resides. Nevertheless, ant species richness is relatively low in the canopy, although with their high abundance ants represent a major part of the animal biomass. The most abundant ant species, called dominants, are characterized by large colonies with territories that are distributed in a mosaic pattern. Dominant species tolerate within their territory non-dominant species, which have less populous colonies. An intermediary status, subdominant, also exists, which corresponds to species generally recorded as non-dominants but which, under certain conditions, are able to develop larger colonies and to defend territories in much the same way that dominants do. By studying African forests of different ages as well as tree crop plantations, we have been able to contribute to the knowledge of ant mosaics and the protective role of these ants vis-ŕ-vis their supporting trees. The distribution of dominant ant species on trees is not merely the result of chance. Choice tests permitted us to demonstrate that Oecophylla longinoda workers are attracted by citrus or mango trees rather than cocoa trees, whereas the contrary is true for Tetramorium aculeatum. Nevertheless, environmental influences can modify the choice of founding queens or workers (the latter play a role during colony budding) through imprinting. Although most dominant ant species are good predators that protect their supporting trees, they mostly feed on sugary substances such as extrafloral nectar and honeydew produced by hemipterans. In the latter situation, the negative effect of sap sucking is offset by the positive effect the ants have on the plant by eliminating defoliators. However, although some ant species tend hemipterans that do not affect their supporting tree, others may be associated with hemipterans that transmit diseases to these trees.