Using ants as bioindicators in land management: simplifying assessment of ant community responses

The indicator qualities of terrestrial invertebrates are widely recognized in thecontext of detecting ecological change associated with human land-use. However, the useof terrestrial invertebrates as bioindicators remains...
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Using ants as bioindicators in land management: simplifying assessment of ant community responses Using ants as bioindicators in land management:Journal of AppliedEcology 2002 simplifying assessment of ant community responses39, 8 – 17 ALA N N. A NDERSEN *, B EN JAMI N D. H OFFMANN *, WA RRE N J. M Ü LLER † AND A N THO N Y D. G RIFFITHS *‡ *Tropical Savannas Cooperative Research Centre, Division of Sustainable Ecosystems, CSIRO Tropical Ecosystems Research Centre, PMB 44 Winnellie, NT 0822, Australia; and †CSIRO Mathematical and Information Sciences, GPO Box 664, Canberra, ACT 2601, Australia Summary 1. The indicator qualities of terrestrial invertebrates are widely recognized in the context of detecting ecological change associated with human land-use. However, the use of terrestrial invertebrates as bioindicators remains more a topic of scientific discourse than a part of land-management practice, largely because their inordinate numbers, taxonomic challenges and general unfamiliarity make invertebrates too intimidating for most land-management agencies. Terrestrial invertebrates will not be widely adopted as bioindicators in land management until simple and efficient protocols have been developed that meet the needs of land managers. 2. In Australia, ants are one group of terrestrial insects that has been commonly adopted as bioindicators in land management, and this study examined the reliability of a simplified ant assessment protocol designed to be within the capacity of a wide range of land managers. 3. Ants had previously been surveyed intensively as part of a comprehensive assessment of biodiversity responses to SO2 emissions from a large copper and lead smelter at Mt Isa in the Australian semi-arid tropics. This intensive ant survey yielded 174 species from 24 genera, and revealed seven key patterns of ant community structure and composition in relation to habitat and SO2 levels. 4. We tested the extent to which a greatly simplifie d ant assessment was able to reproduce these results. Our simplified assessment was based on ant ‘bycatch’ from bucket-sized (20-litre) pitfall traps used to sample vertebrates as part of the broader biodiversity survey. We also greatly simplified the sorting of ant morphospecies by considering only large (using a threshold of 4 mm) species, and we reduced sorting time by considering only the presence or absence of species at each site. In this manner, the inclusion of ants in the assessment process required less than 10% of the effort demanded by the intensive ant survey. 5. Our simplified protocol reproduced virtually all the key findings of the intensive survey. This puts effective ant monitoring within the capacity of a wide range of land managers. Key-words: environmenta l assessment , land-use impacts, monitoring , sampling protocols, SO2 Journal of Applied Ecology (2002) 39, 8 – 17 Introduction Correspondence: Alan Andersen, Tropical Savannas Cooper- ative Research Centre, Division of Sustainable Ecosystems, The indicator qualities of terrestrial invertebrates are CSIRO Tropical Ecosystems Research Centre, PMB 44 Win- widely recognized in the context of detecting ecological nellie, NT 0822, Australia (e-mail Alan.Andersen@csiro.au). change associ ated with human land use (Rosenberg, ‡Present address: Key Centre for Tropical Wildlife Manage- Danks & Lehmkuhl 1986). This contrasts with the use© 2002 British ment, Northern Territory University, Darwin, NT 0909, of particular invertebrate groups as indicators ofEcological Society Australia. general9 diversity patterns (Pearson & Cassola 1992; Kremen 1994), which has been widely disputed (Lawton et al.Simplified ant 1998; Kotze & Samways 1999). Invertebrates makeassessment good indic- ators of ecological condition because they are highly diverse and functional ly important , can integrate a variety of ecol ogical processes, are sensitive to environ- mental change, and are easily sampled (Greenslad e & Greenslad e 1984 ; Brown 1997 ; McGeoch 1998). ...