That's why I would not put natural selection in the same set as the other four factors you mentioned. In this plant there are many peripheral populations, where there is an extreme boom-bust cycle of population growth. The biogeography and ecology of these Clarkia plants is consistent with the mode of speciation. Natural selection does not create new genes. It selects genes that are already present.
Mutation is the ONLY source of novel genetic material.
However, huge recombinant changes can lead to dramatic differences. I keep trying to tell him that, and for some reason JP simply ignores me and asks the same question again. Several of these are likely necessary for reproductive isolating mechanisms to evolve. But I have to disagree with you that natural selection should be in the same list with the other four you mention. Maybe it is just the way I look at it, but I don't think so.