By definition, you are already partially incorrect. That is, by being so disctintly mutated, some aspects of their physiological existence (i.e. deformed and miniaturized organ function, muscle patterns given differing caudal growths, and don't even get my started on those eye deformations)are affected in different manners. Just because they are theoretically the same species does not indicate that they are physiologically identical. Fancies are not suited for colder weather. This is pretty well accepted, and any responsible pond owner does not leave a, say, lionhead out for the winter.