Australia: The Land Where Time Began

A biography of the Australian continent 

Ants in Tropical Savannas

Ants are very important in savanna ecosystems, many Acacia species in Kakadu have white arils on their seeds to attract ants that take them back to their nests, the fleshy appendage being eaten by the ants, but not the seeds. In Kakadu National Park, the ant fauna of the eucalypt-dominated savanna is very diverse. Because of the importance of ants in relation to nutrient recycling in these ecosystems research has been carried out on the reaction of different species to different fire regimes. Over a 14 year period, 81 species from 24 genera were studied in plots that were burnt annually, biennially or not burnt. Based on competitive interactions and habitat requirements, the ants were separated into 3 functional groups.

In plots burnt annually, the hot climate specialists and opportunists, the dominant Iridomyrmex were common, the generalised myrmicines and cryptic species were found in low numbers. In the unburnt plots it was the generalised myrmicines and cryptic species that predominated. On plots that were burnt biennially, the ratios were intermediate between the 2 extremes. The overall result was that many species were present in large numbers under 1 regime were rare or absent under another regime. Some structural changes to the habitat affected the ants directly, such as amount of litter and insolation on the soil surface, but they were also affected by the presence of large numbers of the dominant Iridomyrmex after fires, when there was increased competition for resources.

Sources & Further reading

1. Mary E. White, Earth Alive, From Microbes to a Living Planet, Rosenberg Publishing Pty. Ltd., 2003