Short-Term Coexistence and Long-Term Competitive Displacement of Two Dominant Species of Iridomyrmex: The Successional Response of Ants to Regenerating Habitats

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Abstract
The existence and role of interspecific competition between two dominant species of Iridomyrmex was investigated on an area of coastal heathland regenerating after sand mining. This study has provided strong evidence of spatial competition between Iridomyrmex sp. A and Iridomyrmex sp. C. In both instances the experimental removal of one species from an area resulted in a substantial expansion into the area by the other species. These species actively defend space by patrolling territorial boundaries which are highly dynamic and readily breached when patrols are eliminated. Interspecific colony boundaries are separated by a narrow zone of vacant space that has the effect of reducing large-scale confrontations to a few individual skirmishes. These species coexist terrestrially by the establishment and maintenance of mutually exclusive spatial distributions mediated by competition. The mechanism of competition is interference, or more exactly, territorial competition. Competitive displacement facilitates the successional replacement of these two ant species in response to the gradual shift in habitat parameters as vegetation regenerates after mining.