Generation and maintenance of gradients in taxonomic diversity.

Latitudinal gradients in diversity of organisms represent an equilibrium distribution for at least the last 270 x 10(6) years. Faunas endemic to tropical regions evolved significantly faster than extra-tropical faunas. The latitude-dependent difference in rates of evolution also represents an equilibrium condition for at least the last 270 x 10(6) years and has consequences for paleontological correlation of rocks because the attainable resolution depends on rate of evolution and will thus be greater in tropic regions than in extra-tropical ones.