Invasion dynamics of exotic ants: interactions with native ants on Fraser Island, in south-east Queensland

This thesis investigates the mechanisms of invasion by the introduced ant Pheidole megacephala and interactions with native ant biodiversity in the World Heritage listed Fraser Island, an area with high biological diversity values. The research showed that Fraser Island is rich in ant fauna with 172 species from 57 genera collected, and predicted species richness approaching 300 species. The lack of behaviourally dominant taxa and high relative abundance of opportunistic species makes the Fraser Island ant fauna potentially susceptible to invasion by exotic taxa.The introduced ants Pheidole megacephala and Paratrechina longicornis were associated with low native ant species richness and abundance in disturbed native vegetation at Kingfisher Bay and P. megacephala was identified as a particular threat. Annual variation in P. megacephala infestation boundaries were documented at Dilli Village, where vegetation management by Queensland Parks and Wildlife Service interacted with that infestation. The clearing of vegetation by mechanical means had varying effects with a general expansion of the P. megacephala infestation followed by retreat in a regeneration area, with expansion being followed by stability in continually managed areas. Management fires in native vegetation promoted the expansion of the P. megacephala infestation from edge populations. At Dilli Village P. megacephala stopped foraging above 40oC or below 20% relative humidity in open areas, but they foraged 24 hours a day in native vegetation areas. Iridomyrmex bicknelli and Monomorium sydneyense were able to displace P. megacephala on baits when the invader reached these limits of temperature and humidity tolerance.