Asfiya, Wara, Yeeles, Peter, Lach, Lori, Majer, Jonathan D., Heterick, Brian, and Didham, Raphael K. (2016) Abiotic factors affecting the foraging activity and potential displacement of native ants by the invasive African big-headed ant Pheidole megacephala (Fabricius, 1793) (Hymenoptera: Formicidae). Myrmecological News, 22. pp. 43-54.

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Abstract

The African big-headed ant, Pheidole megacephala, is a widespread invasive species that threatens native ecosystems and has been implicated in the decline of native ants. Although the consequences of P. megacephala invasion have been relatively well studied, the mechanisms responsible for success remain unclear. We examined the survival of P. megacephala under differing thermal conditions in the laboratory, as well as daily and seasonal variation in foraging activity in disturbed urban bushland. In two comparable sets of laboratory experiments, high temperatures had a strong negative effect on worker survival of P. megacephala, particularly under low moisture conditions. In contrast, common native species of Iridomyrmex had significantly greater survival at high temperatures. Foraging activity of P. megacephala at baits was directly related to variation in soil surface temperatures. In addition, proportional bait occupancy by P. megacephala was higher during warm seasons (early autumn) than during cool seasons (early spring), and in autumn, bait occupancy was higher in the cool morning than in the warmer afternoon (all these effects were moderated by significant variation among sites). In contrast, native ants dominated baits under warmer afternoon conditions, with almost no cooccurrence of native ants with P. megacephala. This study suggests that daily and seasonal variation in abiotic conditions can modify the dynamics of P. megacephala foraging interactions with native ants, thereby affecting local community dynamics.

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