The Maintenance of the Ant Mosaic in Ghana Cocoa Farms

Publisher Website
Google Scholar
Abstract
The factors which maintain the mosaic of dominant ants in cocoa were investigated by a series of observations, surveys and a field experiment in which dominant ants were selectively mechanically removed from plots of cocoa. The heterogeneity of the environment was one factor contributing to the patchy ant distribution. Different species of ants existed in particular densities of cocoa canopy. Although Macromischoides aculeatus (Mayr) was associated with dense cocoa canopy, it spread into thinner cocoa canopy when adjacent dominants were removed. This suggests that its distribution was also limited by competition from other ants. The interspecific ant mosaic is maintained by a combination of competition and habitat requirements. Interspecific competition may be for food, for nesting and foraging sites, or it may take the form of aggressive competition between adjacent colonies or mature colonies and founding queens. Aggressive behavior is particularly intense between inter-specific blocks of the mosaic. M. aculeatus is able to reduce competition with Crematogaster depressa (Latr.) within its territory by spacing out its foraging time while C. castanea F. Smith may co-exist with Oecophylla longinoda (Latr.) by adopting a similar colony odor. O. longinoda may aid species segregation by having queens which select their habitats when dispersing. New colony establishment is rare in mature cocoa since changes in the ant mosaic are usually compensated for by lateral spread of existing colonies. The role of dispersing queens is probably more important in developing cocoa farms. Climate and weather influence the structure of the mosaic by directly influencing the features of the habitat, the availability of certain types of food or by physically weakening colonies of certain species. It would be feasible to alter the structure of the ant mosaic by artificially interfering with the competitive balance between species or by altering the nature of the habitat so as to favor the spread of certain species.
Keywords