Isolation alone isn't a satisfactory explanation for all physical variety. Similar environments should produce results. Of course there are parts of the world that have been isolated for very long periods. Which result in an environment appearing the same, in terms of climate etc., but being entirely different in the important respect that there are and have always been different competitors.
Bill Bartlett
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I am not in a position to argue this very well. I don't have this stuff down that pat and have to look up details to put together a real response. So, instead, better that you work out these by looking them up. By doing some reading in the traditional views, you will see what is new about some of what Gould proposed. Here is one source:
http://www.sprl.umich.edu/GCL/paper_to_html/speciation.html
There are plenty of others.
The larger point of physical isolation is simply reproductive isolation. There are other factors as well that don't require either sorts of isolation. Some inheritable traits will partition themselves into separate and different frequencies in a population and that sets up the potential to diverge under minor variations of selective pressure and adaptive advantage.
In general, I am dissatisfied with the standard line of argument and even to some extent Gould although that has to wait until I've managed to get through it. There are two problems. The first has to do with the basic physical engine of evolution and the other has to do with the apparently systematic or well organized appearance of biological forms in general.
Neither of these seem to be adequately accounted for. For example, reproduction of inheritable traits, mutation, adaptation, natural selection and the rest of it work fine as long as there are living organisms to work with. But these processes hardly seem adequate as a descriptive theory of how life evolved in the first place. Thus we are thrown back on physical and chemical processes where few or none of these biological concepts work. What gives?
Chuck Grimes