Douglas Erwin

Paper #: 00-12-067

Although mass extinctions probably account for the disappearance of less than 5% of all extinct species, the evolutionary opportunities they have created have had a disproportionate effect on the history of life. Theoretical considerations and simulations have suggested that the empty niches created by a mass extinction should refill rapidly after extinction ameliorates. Under logistic models, this biotic rebound should be exponential, slowing as the environmental carrying capacity is approached. Empirical studies reveal a more complex dynamic, including positive feedback and exponential growth phase during recoveries. Far from a model of refilling ecospace, mass extinctions appear to cause a collapse of ecospace, which must be rebuilt during the recovery. Other generalities include the absence of a clear correlation between the magnitude of extinction and the pace of recovery, or the resulting ecological and evolutionary disruption; the presence of a survival interval, with few originations, immediately following an extinction and preceding the recovery phase; and the presence of many lineages which persist through an extinction event only to disappear during the subsequent recovery. Several recoveries encompass numerous missing lineages, groups which are found before the extinction, then later in the recovery, but are missing during the initial survival-recovery phase. The limited biogeographic studies of recoveries suggest considerable variability between regions.