Effects of the coastal brown ant Pheidole megacephala (Fabricius), on the ant fauna of the Perth metropolitan region, Western Australia

Abstract

This paper reports on the apparent displacement of native and exotic ants from gardens in the Perth Metropolitan region by the coastal brown ant (Pheidole megacephala (Fabricius)). Twelve gardens were sampled, four with P. megacephala present, and eight (the controls) where the ant was judged to be absent. Eight out of the 26 ant species recorded (including the coastal brown ant) were introduced. Ninety-two per cent of pitfall trap contents comprised the four most abundant species: P. megacephala, lridomyrmex chasei (Forel), Tetramorium simillimum (F. Smith) and Paratrechina ?obscura (Mayr). Three of the four P. megacephala-dominated gardens were depauperate of almost all other ant species. The fourth P. megacephala-infested garden had a relatively small number of coastal brown ants (104), and the highest number of ant species was found in that garden. The removal of this outlier garden left an average range of one to three species for the other three P. megacephala-infested gardens. Control gardens had between five and 12 ant species. Total ant abundance ranged from an average of 1 027 per P. megacephala-infested garden (increasing to 1 171 if the outlier garden is removed) to 146 at control gardens. There was a significant difference both in ant richness and ant abundance between the controls and P. megacephala-infested gardens (P < 0.05). This remained the case when figures for coastal brown ants were excluded from calculations.