The relationship of local to regional species richness If local richness is limited by interspecific factors such as competition and predation, then it will not depend on the number of species in the region. Tectonic events Pleistocene events E.g. the temperate forest floras in North America, Europe, and Asia. Asia's flora is much more diverse than the other two. This provided a source of colonists for evolution of many more species over the past 65 my. The connection also provided a migration corridor for species displaced by climate change in the Pleistocene to a refugium in tropical Asia.
Most evidence is from marine invertebrates with hard shells or skeletons.
Patterns seen in the fossil record often differ statistically from this random model. This background rate is interrupted by five periods of high extinction rates, called mass extinctions. Introduced predators have occasionally wiped out prey species Even fewer cases of interspecific competition. Extinction can be avoided if the change in conditions is sufficiently slow that genetic change can keep up with it. Also was the least severe of the five.