Carabid beetles as biodiversity and ecological indicators

The explicit assumption in the proposed use of ecological and biodiversity indicators is that patterns of diversity and distribution observed in the indicator taxon are reflected in other taxa, yet this assumption has rarely been tested. The use of biodiversity and ecological indicators requires that their representativeness of other taxa be demonstrated. This thesis examines the potential for using carabid beetles as biodiversity and ecological indicators for other Coleoptera in Tasmania. Species-occurrence data for carabids and a range of Coleoptera collected by continuous year-long pitfall trapping at fifty-one sites in three biomes, dry sclerophyll forest, remnant native grasslands and coastal sand dunes were used to investigate the utility of carabid beetles as biodiversity indicators for overall coleopteran diversity and for other selected beetle taxa. Correlated species counts, correlations in rank ordering based on species richness, and coincidence of hotspots revealed that while the patterns of diversity exhibited by carabids did not necessarily predict the patterns of diversity of other individual beetle taxa considered separately, they did, with a reasonable degree of accuracy, indicate overall patterns of diversity for Coleoptera in all the biomes studied. Carabid species richness was a good predictor of overall beetle species richness within biomes and within vegetation community types. Application of three reserve selection approaches: (1) Hotspots, (2) Representative Species Richness and (3) Complementarity, demonstrated that a set of representative areas, based on carabids species richness, gave proportional representation for all Coleoptera. Representation for, all carabids using the complementarity approach also gave protection to over 90% of all coleopteran species. It is therefore likely that a set of representative areas in which carabids are completely represented will substantially represent the diversity of other Coleoptera. To assess the utility of carabids as ecological indicators for other Coleoptera, the response of carabids and other Coleoptera to silvicultural practices (clearfelling and slash burning) were examined and compared. Morisita-Horn community similarity indices demonstrate that carabid and overall Coleoptera species composition showed less variation within grouped age classes than between different age classes in both forests. Results for other beetle taxa considered separately were more complex and varied with forest. In both forests, UPGMA cluster analysis generally grouped the total beetle fauna according to regrowth age, but indicated that the species composition of regrowth sites were often similar to some old-growth sites. This pattern was observed for carabids in the dry sclerophyll forest, but not in the wet. Other beetle taxa demonstrated more complex patterns of clustering, with no clear evidence of site separation on age class. The family Carabidae did not reflect the exact response of other beetle families considered separately. However, they did reflect the overall patterns of diversity and distribution exhibited by beetles as a group in response to forest management practices. Results demonstrated that monitoring particular carabid species would provide evidence of the success or otherwise of management practices for other oldgrowth dependent beetles. The results reported in this thesis support the hypotheses that: (i) the family of ground beetles (Carabidae) is an appropriate biodiversity indicator for identifying and predicting the biodiversity patterns of ground dwelling Coleoptera in most instances in Tasmania, and (ii) that carabids are useful ecological indicators to predict and monitor the effects of forest management on a wider range of ground-dwelling beetles in Tasmania.