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Northern Territory University (2000)

Responses of ant communities to land-use impacts in arid Australia

Hoffmann, Benjamin Daniel

Titre : Responses of ant communities to land-use impacts in arid Australia

Auteur : Hoffmann, Benjamin Daniel

Université de soutenance : Northern Territory University.

Grade : Doctor of Philosophy (PhD) 2000

This thesis examines the responses of ant communities to land-use in arid Australia, in the context of ants as biological indicators. Four independent case studies are presented documenting disturbance induced dynamics of ant communities throughout Australia’s arid zones to : 1. SO2 emissions at Mount Isa (Qld) ; 2. Sheep grazing in the Kingoonya region (SA) ; 3. Cattle grazing in the Victoria River District (NT) ; and 4. Fire in the Victoria River District. Ants were sampled in all studies by pitfall traps and identified to the species level. Species richness, total ant abundance, the abundance of species and the relative abundance of functional groups were compared with and without disturbance. Only the study of the responses of ants to fire was sampled more than once. Ants were responsive to disturbance in all studies. Generally disturbance reduced total abundance and species richness, and induced significant changes in the abundance of many species, but did not greatly change functional group composition. The greatest number of responses were found following the most severe disturbance of SO2 emissions, whereas ants were least responsive to sheep grazing. Where multiple habitats were sampled within a study, results were often conflicting between the habitats. The results of these independent studies are compared with ant community dynamics in relation to disturbance in more mesic regions. The thesis culminates in the first synthesis and review of the dynamics of ants following disturbance throughout Australia, with particular focus on the functional group classification system. The results of 43 studies are summarised, and (where data could be obtained) the results are re-analysed according to latest species classifications into functional groups. These classifications are provided for the first time for the entire known Australian ant fauna. Functional group dynamics are interpreted within the context of biogeography and disturbance type. While the functional group scheme is a useful tool for disturbance analysis, it appears to have limited appliation within the arid zones.


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