Ants as bioindicators of habitat disturbance: validation of the functionalgroup model for Australia's humid tropics

A functional group model of ant community composition has been widely used in Australia to analyse biogeographical patterns of ant community structure and the responses of ant communities to disturbance. The model has provide d valuable support to the widespread use of ant communities as bioindicator s of ecological change. However, the model was developed from studies of ar id-zone faunas, and its applicability to the World Heritage rainforests of Queensland's humid tropics has not yet been validated. Here we test predict ions based on the functional group model for ant communities in Queensland' s humid rainforests, by documenting ant community composition and its respo nses to disturbance on the Atherton Tablelands. Five sites were studied, co mprising two relatively undisturbed reference sites representing contrastin g rainforest types, and three previously cleared sites, two of which were u ndergoing revegetation. A variety of sampling techniques were employed, inc luding pitfall trapping, litter extractions, baiting, and general searching . A total of 50 ant species from 29 genera were collected. Site species ric hness was highest at the reference sites, and lowest at the unvegetated dis turbed site, and overall was negatively related to mean ground temperature. As predicted by the functional group model, behaviorally dominant dolichod erines were uncommon or absent at the reference sites, and the most common ants were Generalized myrmicines and Opportunists. Also as predicted, habit at disturbance favored Opportunists, and, as the disturbance involved canop y clearance, this led to colonization by Iridomyrmex and other Dominant dol ichoderines. Opportunists represented about 40% of total ants in traps at t he reference sites, compared with 80-95% at the disturbed sites. Except one species, Tropical Climate Specialists and Specialist Predators were absent from disturbed sites. In conclusion, patterns of ant composition in relation to disturbance on th e Atherton Tablelands conform to the functional group model that has been w idely applied to ant faunas elsewhere in Australia. The model may therefore play an important role in the use of ants as bioindicators of ecological c hange in the World Heritage rainforests of this region.