The Influence of Fire, Vegetation Age and Argentine Ants (Iridomyrmex humilis) on Ant Communities in Swartboskloof

Abstract

In terms of numerical abundance and species richness, ants (Hymenoptera: Formicidae) are prominent in many terrestrial ecosystems (Majer 1983; Stork 1988). The total of 8800 known species of the family Formicidae is estimated to make up about 10–15% of the world’s animal biomass (Hölldobler and Wilson 1990). Some of the reasons for their success lie in the fact that they have a competitive advantage over many other invertebrates because they are omnivorous (Beattie 1985), they can store food (Petal 1978) and they have effective defence mechanisms. Furthermore, they are of considerable ecological importance. In mutual ant-plant relationships they derive food and nest sites from plants, they disperse and store seeds, they protect foliage, buds and reproductive structures from folivores and seed predators, they may fertilize plants with essential nutrients, and sometimes they function as pollinators (Beattie 1985). In the fynbos, ants play a major ecological role, particularly in dispersing seeds. About 1300 (20%) of fynbos plant species are dependent on ants for the dispersal of their seeds, a process known as myrmecochory (Milewski and Bond 1982; Bond and Slingsby 1983). In this process ants, attracted to these seeds by fatty, edible coatings or appendages (known as elaiosomes), carry seeds into their nests.