Figure 1.

Biogeographic calibrations can be used in a number of ways. If a geological or climatic event has had an evolutionary or demographic impact, it can be used to calibrate molecular clocks. The age of the biogeographic event must be estimated by independent means, with the associated uncertainty being taken into account. Based on this information, an age constraint or prior distribution can be applied to (a) a divergence event in a phylogenetic tree or genealogy; (b) an estimated shift in diversification rate, as shown here in a lineages-through-time plot; or (c) an inferred change in the population size of a species. (Online version in colour.)