SPECIES conservation in situ requires networks of protected areas sele
cted for high conservation interest1-3. Throughout most of the world,
however, there are neither the resources nor the time to carry out det
ailed inventories for most taxa2,4 before designating protected areas.
Site selection (on grounds other than availability) would be easier a
nd more effective if two things were true: (1) habitats that are speci
es-rich for one taxon are also species-rich for others5; and (2) rare1
species occur in, and therefore benefit from the conservation of, spe
cies-rich habitats. Diversity (usually, species richness) and the pres
ence of rare species are the most frequently cited criteria for site s
election by conservationists6-8. Here, we use data on British plants a
nd animals held by the Biological Records Centre (BRC)9 and the Britis
h Trust for Ornithology (BTO), mapped on a grid of 10 km x 10 km ('10
km squares') to examine the extent to which species-rich areas for dif
ferent taxa coincide, and whether species-rich areas contain substanti
al numbers of rare species. The fine scale and high intensity of recor
ding in Britain produces distributional datasets at least as good as a
nd, in most cases, better than those available elsewhere. For Britain
at least, we do not find strong support for either proposition. Specie
s-rich areas ('hotspots'10) frequently do not coincide for different t
axa, and many rare species do not occur in the most species-rich squar
es.