I am using the definition I am reading right here out of a 15 year old college Biology book.
There ARE alternative definitions that are less precise, I agree. But those are not the definition used in classification of species.
Thanks and understood. You are, of course, correct in that it is not practical to breed tiny dogs and giant dogs, and that they cannot manage it on their own for obvious physiological reasons.
Nevertheless, my point was that the many breeds of Canis lupus familiaris, the domestic dog, are actually subspecies. Further, I believe that the basic point of the article's author is correct -- that the wide range of different dog subspecies can lead to a better understanding of how species evolve.