Evolutionary modelling from family diversity

Abstract

The Fossil Record 2 database of the times of first and last appearance of plant and animal families can be searched on the Internet. To demonstrate how these data can be used we have compared the output for mammals and angiosperms with plots from other databases. Interestingly, the same trends are also evident in these plots. We have also used this search facility to test the hypothesis that some groups of organisms diversify quickly and decline slowly. We propose a modified logistic curve to model the global trajectory of the diversification pattern that mimics a bell-shaped curve. The diversification pattern fluctuates around the global trajectory until its eventual extinction unless the organisms are exposed to a considerable amount of external perturbation. When the current global trajectory shows a clear downward trend the final extinction date of the group of organisms can be predicted assuming there are no large external perturbations in the future. However, the diversity curve from North American Pleistocene mammal data suggests that a mass extinction caused by human perturbation has already begun. Copyright: Palaeontological Association, 22 October 1999.