Dogs have been bred for thousands of years. What dog breeding shows is that you cannot change a species by selection, whether natural or selected. In fact, the more selection, the less viable a species becomes:
That shows that you have no understanding of what speciation is. For starters, plenty of species can interbreed; old scientific definitions make this mistake, but they are woefully out of date, and simply repeating them as dogma does not make them true. One can have two different species that are capable of interbreeding (lions and tigers, for instance). Man cannot breed dogs into seperate "species", by which you mean, groups incapable of interbreeding with each other, because it is not the difference in appearance which makes species unable to breed with each other, but rather genetic drift and mutation, which takes place over millions of years. Given enough time, if these man made dog "species" were kept from breeding with each other, they would develop into species incapable of breeding with each other. But in the short term, speciation is accomplished simply by selecting which features get passed on to the next generation - either by natural selection, or by man made selection. Whether we call these species "species", or something else, is a matter of semantics, not science. But then, the anti-evolutionary crowd has always been big on semantics and weak on actual science.
So what?? They'd still be dogs. They wouldn't have wings, or hooves, or gills, or flight feathers, or horns, or poison fangs, or anything like that at all. And the first time you ever released them into the wild, if they survived at all, after five generations they'd all look just like your ordinary universal 50-lb. wild dog.
Absolutely wrong. The only valid determination of species is the ability to interbreed and produce young which can produce viable offspring. Anything else is subjective. The reason why interbreeding is so important is that it takes in encompasses everything which makes and organism. Anything else just takes part of it into consideraton. In addition, anything else is therefore subjective. More important though, if organisms cannot interbreed as per above, then they are clerly separate from each other, and that is what the concept of species is all about.