Threatened species in a vanishing habitat: plants and invertebrates in calcareous grasslands in the Swiss Jura mountains JARI NIEMELA È * Department of Ecology and Systematics, Division of Population Biology, PO Box 17, FIN-00014 University of Helsinki, Finland BRUNO BAUR Department of Integrative Biology, Section of Conservation Biology (NLU), University of Basel, St. Johanns- Vorstadt 10, CH-4056 Basel, Switzerland Received 27 February 1998; accepted 29 April 1998 We examined the diversity of vascular plants, butter¯ies, grasshoppers, gastropods and carabid beetles in three calcareous grasslands in the northwestern Swiss Jura mountains, a habitat type that has decreased dramatically during the recent decades. As many as 58 species (ca 22%) of the 266 collected are listed as threatened in northern Switzerland. The number of threatened species ranged from 27 to 49 per site, and 26 species occurred in only one of the three grasslands. The species richness of butter¯ies and vascular plants correlated positively among the grasslands, while the species richness of other groups did not covary. An index of complementarity indicated that the species compositions (including non-threatened species, and spiders and oribatid mites) of the groups varied greatly among the grasslands. In addition, herbivorous groups were more widely distributed than predators among the three grasslands. Due to this variation in species composition none of the three sites can substitute for the others, if the biodiversity of these grasslands is to be maintained. Furthermore, the taxonomic groups studied are poor indicators of each others' diversity. Conse- quently, we support the `shopping basket' approach to conservation evaluation, i.e. measuring species richness, species composition and complementarity of several groups instead of just one. Keywords: species diversity; threatened species; indicator species; calcareous grassland; Switzerland. Introduction Measuring the total species richness of a locality is often impossible for reasons such as high species richness and poor taxonomy (Kremen, 1992; Pearson and Cassola, 1992; Wheeler and Cracraft, 1997; Lawton et al., 1998). In order to overcome these problems it has been suggested that a reduced set of taxonomic groups may be used as an indicator for the overall diversity (Noss, 1990; Kremen et al., 1994; Gaston, 1996). This approach has been advocated as especially useful when studying ivertebrate assemblages because their high species richness makes it dicult to sample the entire fauna (Kremen et al., 1993; Samways, 1994; Oliver and Beattie, 1996; Brown, 1997). Furthermore, many inverte- brate sampling methods are destructive for the organisms and may be so for the habitat studied. * To whom correspondence should be addressed. 0960-3115 Ó 1998 Chapman & Hall Biodiversity and Conservation 7, 1407±1416 (1998)