| Summary: | Mapping plant communities is core business for many geographers and conservation ecologists. However a troubling assumption underpins these maps and it frequently remains unexamined, despite almost a century of criticism. Are the communities real, discrete assemblages that can be expected to respond to environmental change uniformly and therefore be treated as valis scientific units? Instability and ambiguity in community definitions pose serious problems when such maps are used to measure the ecological impacts of environmental change or management interventions.On Macquarie Island, researchers have historically defined plant communities in conflicting ways. Tall tussock vegetation on the coastal slopes might constitute a single community, ot three, or seven, or nine. We examined the capacity of statistical clustering tools to distinguish floristic communities on the basis of a large, stratified-random dataset, and the stability of the resulting clusters. We were unable to produce stable clusters and suggest that mapping individual species is more likely to be useful gor detecting changes in vegetation patterns.
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