Posted: Jun 18, 2010 11:35 pm
Well, the difference between the two curves is not merely one of time. You need some process that turns the blue curve into the red one. Gould and Eldredge in their original paper suggested the founder effect, my view is that non-selective species sorting is responsible (i.e. after speciation you have two species that are very similar in resource use. There´s a good chance that they will be sympatric within a geologically short time and if they use the same resources, one of them will go extinct. This increased likelihood of extinction is less pronounced the higher the rate of change around speciation is and thus we get the second peak in the red graph).