ABSTRACT
Different environments clearly support varying diversity and densities of both species and individuals. Regardless of how many species remain undiscovered and cryptic, it is still trivial to conclude that there are more species and more biomass in a tropical coral reef than the same size region on a polar ice sheet. Even within one region, you will encounter patches of relatively higher or lower species richness. What are the mechanisms that control the magnitude of regional biodiversity? This is a question that sits at the meeting point of ecology and evolutionary biology.
