Quantification of conservation criteria using invertebrates.
Rarity indices and typicalness measurements were generated for sites within habitat groups defined by classifications of water beetle (including Haliplidae and Hydroporidae) and ground beetle (Carabidae) communities in north-eastern England. Differences in the rarity values of sites were most easily interpreted when a geometric scale was used to calculate species rarity scores and when the estimate was standardized by the number of species. Inclusion of an extra weighting for associations of rare species led to sites that were likely to have conservation potential being more easily distinguished. No consistent relationship between measurements of site rarity value and typicalness was found, in contrast to accepted thought.