Influence of Argentine and coastal brown ant (Hymenoptera: Formicidae) invasions on ant communities in Perth gardens,Western Australia

A survey examined the influence of Argentine (Linepithema humile (Mayr)) and coastal brown ant (Pheidole megacephala (Fabricius)) populations on other ants in the Perth metropolitan area, Western Australia. Twelve gardens (yards) were sampled; four infested by Argentine ants, three infested by coastal brown ants, and five controls where these two tramp ants were absent or collected only as isolated strays. Collection methods used were pitfall trapping and hand collection. A total of 27 species was recorded. Eight of these species, including the above two tramp ants, are non-native to the region. Pheidole megacephala was the most abundant species, comprising 95.4% of ants in P. megacephala–infested gardens. Linepithema humile comprised 92.1% of ants in L. humile–infested gardens. Other common ants were the native Iridomyrmex chasei and the introduced species Tetramorium simillimum and Tetramorium bicarinatum. The cryptic introduced species Cardiocondyla nuda and Tetramorium simillimum appear able to persist in small numbers in L. humile–infested gardens, but virtually no other ant species occurred where the coastal brown ant was well established. Mean richness, diversity, and evenness were significantly different between P. megacephala–infested and control gardens, and significantly different between L. humile–infested and control gardens. Diversity and evenness, but not richness, were significantly different between P. megacephala–infested and L. humile–infested gardens. Ordination analysis revealed that the three types of gardens had very different ant community profiles.