Biodiversity hotspots.

Hotspots of biodiversity-areas particularly rich in species, rare species, threatened species, or some combination of these attributes-are increasingly being delineated to help set priorities for conservation. Only recently have we begun to test key assumptions that determine how useful a hotspot approach can be for conservation planning. The evidence suggests that although at large geographic scales hotspots do provide useful information for conservation planning, at smaller scales their value may be more limited.