Cradles, Museums and Graves

Stebbins (73) began a long tradition of referring to locations with unusually high rates of speciation as “cradles” of diversity, and to locations with unusually low rates of extinction as “museums.” ... our simulations allow us to define and map a third biogeographical category, “graves”—locations with unusually high extinction rates ...

As we define them here, “cradles” are about speciation, “museums” about persistence, and “graves” about extinctions. [Perhaps these terms correspond to phases in the adaptive cycle: cradles → reorganization & exploitation, museums → conservation, graves → release] Previously, cradles and museums have generally been viewed as fixed geographical places (4). Because our simulations take place in both space and time, we treat all three patterns as driven dynamically by the processes of speciation, persistence, and extinction. A cradle, museum, or grave has extension and intensity in both space and time, and may move though space and change shape, size, and intensity as time passes.