The Rainforest Ant Fauna of Australia's Northern Territory

Abstract

An ant survey of Northern Territory (NT) rainforests, which occur as numerous small and isolated patches within a predominantly savanna landscape, yielded 173 species from 46 genera. The richest genera were Polyrhachis (22 species), Pheidole (21 species), Rhytidoponera (12 species) and Monomorium (12 species). Seven genera represented new records for the NT: Discothyrea, Prionopelta, Machomyrma, Strumigenys, Bothriomyrmex, Turneria and Pseudolasius. The most common ants were Generalised myrmicines, particularly species of Pheidole and Monomorium, and Opportunists such as species of Paratrechina, Tetramorium, Odontomachus and Rhytidoponera. This is also the case in rainforests of the Kimberley region of Western Australia. Of NT rainforest species, 59% have Torresian (tropical) affinities, which is only slightly higher than in Kimberley rainforests (48%). However, the NT harbours a far higher proportion of specialist rainforest species (27 v. 9%), including many more with arboreal nests (13 v. 5% of total species). Many of the rainforest specialists are of considerable biogeographic interest, with a substantial number having disjunct distributions in the NT and Queensland (and often also New Guinea) A small number represent the only known Australian records of south-east Asian species. Interestingly, very few species appear to be endemic to NT rainforests, with a previously unrecorded species of Aphaenogaster being a probable exception. The NT rainforest fauna also includes several introduced species, with at least one (Pheidole megacephala) posing a serious conservation threat.