Geoscience Reference
In-Depth Information
tropical rainforest ecosystems. Tropical Africa has the richest diversity of termites
in the world, particularly soil-feeding termites. Their ability to feed on dead plant
material makes them vital players in the rainforest. Termites are the dominant
decomposer in the lowland rainforest, where they are estimated to consume up to
one-third of the annual litter by decomposing it completely or making it more avail-
able for other decomposers. Termites themselves are an important food source for
some specialized forest species, such as pangolins. Most live underground or in
dead wood, but a few species build large mounds or elaborate arboreal nests. Like
ants, termites maintain large colonies of a few hundred to several million
individuals.
Three main families of termites inhabit the African rainforest: the dry wood ter-
mites, damp wood termites, and the so-called higher termites. Dry wood termites,
although distributed around the world, seem to be rare in the tropical rainforest.
They are thought to have been outcompeted by the higher termite groups. Damp
wood termites feed on moist and partially decomposed wood in standing and fallen
trees. These lower termites have mutualistic protozoa living in their gut; without
them, they could not digest cellulose, a major portion of their diets. The third group
of termites, the higher termites, includes 73 percent of all termites in Africa. These
termites do not have the protozoa that damp wood termites have, but instead use
anaerobic bacteria cultures in their hindgut to assist in food digestion and assimila-
tion. One subfamily in this group is the soil-eating termites. They make up a large
portion of the African rainforest termite fauna and are assumed to have an African
origin. Many in this subfamily are found nowhere else. Also among the higher ter-
mites is the subfamily of fungus-growing termites. These termites consume dead
wood and leaves. They have developed a mutualistic relationship with a fungus
that grows on termite feces. The fungus breaks down the feces, turning it into a use-
able food source for the termites. A majority of this subfamily is endemic to Africa.
The third subfamily (Nasutitermitinae) is the largest and most specialized group
and includes both wood-eating and soil-eating termites. Various species feed on
rotten wood, dry or rotten leaves, lichens, mosses, and decomposed organic matter
in the soil. Although a large group, they are less abundant and less diverse in Africa
than in Neotropical and Asian rainforests.
Ants, bees, and wasps (order Hymenoptera) are also abundant in the tropical
rainforests of Africa. They can be found at all layers of the forest and use many dif-
ferent food resources. Army ants present in the Neotropical and African rainforests
evolved prior to the breakup of Gondwana. The army ants of both regions share a
number of important characteristics. Army ants forage collectively; this increases
the types of potential prey available to them, including large invertebrates and
small vertebrates. Colonies tend to be nomadic, moving to a new nest when they
have exhausted the food supply of the area.
Driver ants are found throughout the forests of West Africa and the Congo.
Their role is similar to the army ants of the Neotropics. They have the largest colo-
nies of any social insect. Colonies can consist of tens of millions of worker ants that
