The formation of a new species b/c of population isolation

Using the scientific method as a framework, how would YOU as a scientist describe how a new species could arise by genetic isolation? Mechanisms of Speciation, What would be your observation, question, hypothesis, prediction, the experiment and finally the results using your own expertise. BELOW is an answer I received before-based upon Darwin's theory but I would like your own opionion, theorioes/ and or hypothesis and finally the results in this problem.

You can take an actual historic case as an example. Actually described by Charles Darwin himself when he was part of the Beagle expedition and was visiting the Galapagos islands in the Pacific Ocean outside South America (Equador). He could there on different islands and in different environments observe finches. These finches had however differences in their anatomy (for example with regards to their beaks). Darwin could observe that these differences were correlated to 1. the environment in which they lived and 2. the way they lived and gathered food. Based on this he made a hypothesis that a wind driven flock of finches at some time in the past had reached these islands from South America and settled there. They had then evolved according to what was the best possible solution for each environmental niche in which each different group of them lived. Darwin thought that each group became rather isolated from the others and adapted to the local needs by "survival of the fittest" for that particular environment and that the survivors then passed these characteristics on to their offspring. You have to realise that Darwin had very little knowledge of genetics and none of mutations. All he knew was practical farming breeding of plants and animals. And he used Malthus' ideas about population growth and competition for food as a model for the competition that led to selective survival of the "fittest" for each environment. If each group was isolated by geography or habits or something else this process would be more prominent. Based on these bird observations he could form this hypothesis and then use it in order to predict other findings as he went along visiting these islands. The predictions turned out to be right and therefore supported his hypothesis. You can see this as a kind of Nature's own experiment which Darwin could observe and draw his conclusions from. Based on these observations and other similar ones from elsewhere he could later form his theory of evolution where isolated groups by adaptations to their different environments become more and more different from each other until they no longer can interbreed and therefore new species have been formed. To some extent Darwin could also confirm parts of this theory by observations from farm breeding of domestic animals and plants and by the breeding of different dog and cat races. Such breeding also formed experiments from which such conclusions could be drawn. I hope I have been able to explain this clearly enough! If anything is unclear please just ask and I'll try to explain. Good luck!