Ant Communities in the Gulf Region of Australia Semiarid Tropics - Species Composition, Patterns of Organization, and Biogeography

Abstract

The ant communities of nine sites near Lawn Hill (540 mm mean annual rainfall) in semi-arid north-western Queensland are documented, and compared with the known faunas of arid, semi-arid and seasonally arid sites elsewhere in Australia. The sites were surveyed primarily by pitfall trapping, during April (end of wet season) 1991, September (late dry season) 1991, and February (mid-wet season) 1992. A total of 111 ant species was recorded, with the most common being Iridomyrmex spp. and Rhytidoponera rufithorax. The richest genera were Melophorus (26 species), Monomorium (17), Iridomyrmex (16) and Camponotus (10) and Pheidole (10). The maj or functional groups were Dominant Dolichoderinae (Iridomyrmex spp.; 14% of the total number of species, 47% of the total number of ants in traps), Hot-climate specialists (mostly Melophorus spp.; 39%, 22%) and Generalised Myrmicinae (mostly Monomorium and Pheidole spp.; 20%, 11%). Multivariate analysis indicated that site differences in species composition were related primarily to landform, geology and soil type. Comparisons with other ant faunas show the Lawn Hill fauna to have closer affinities with those of the central arid zone than with those of high rainfall areas of the seasonal tropics. The arid-zone characteristics of the Lawn Hill fauna include a high proportion (38%) of Eyrean species, a high mean number of species per genus (6.5), and a very high combined representation of Iridomyrmex, Melophorus and Camponotus (45% of the total number of species, 69% of the total number of ants in traps).