Flux in the size of population from environmental factors or increases or decreases in populations of parasites, predators, prey, or competitors for food sources can also affect natural selection by allowing marginally successful variations that occurred in previous generations to suddenly enjoy a new competitive advantage in survival, feeding or reproduction. 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. 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.