Figure 4. Evolution of the Size of a Morphological Character (Solid Line) in a Hypothetical Population.

The character size of the ancestor population from the mainland increases by a small amount on the mainland. After the isolation of the population, there is a large and rapid increase of the size of this character, and the evolutionary rate (dotted line) for this character also increases. The rate of evolution on the island then decreases to values comparable to the rate values for the mainland population.