Representative conservation area-networks are needed to ensure persistence of species diversity within regions. Frequently, however, there are neither resources nor time to carry out detailed inventories before areas are selected. Consequently, areas may be chosen using in- formation other than species. One promising approach is to represent as much environmental variation as possible (environmental diversity, ED) as a surrogate for species diversity (e.g. Anon. 1974, DeVellice et al. 1988, Belbin 1993, Faith and Walker 1996a). This would achieve great economies in all sectors, if true. To our knowledge no formal empirical tests have been made to assess the performance of environmental diver- sity as a surrogate for species diversity. Indeed, a positive relationship between these two measures has often been assumed rather than estimated. For example Pressey et al. (1996) and Woinarski et al. (1996) asked whether reserve networks sampled representative por- tions of environmental variation, but did not question whether this would represent biodiversity at a rate higher than expected by chance. We test this idea using species and environmental data for Europe. The p-me- dian location-allocation model was applied to select representative portions of environmental-space (Faith and Walker 1996a, b). The consequences of this selec- tion are compared to those of choosing areas at ran- dom and to solutions using an optimising area-selection algorithm (hotspots of complementarity). We show that ED does not always represent species at a rate consis- tently higher than that expected by chance, let alone approximate to that of the optimising solution. This is because particular distributions among restricted-range size species do not fit the underlying assumptions of the ED model. With these data, ED is a poor predictor of species diversity.
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