What I find interesting is that the evolution of the dog has happened within 13,000 years. This is because of the human domestication of the dog. Different environments cause different evolution and the early ancestor of all the dogs (Canis Canis I believe) were domesticated and used for hundreds of different purposes.
Humans only used the dogs that were best suited for the job they had domesticated them for, the others didn't survive, this is evolution that is extremely rapid. Dogs that were used for protection became increasingly vicious, dogs that were used to plough fields became big and strong and so on. All this change has happened over just a few millenniums.
So to answer your question stof, yes these dogs are the same species and can mate with each other. However, they will continue to drift apart and in a few more thousand years you might find that they will actually become different species all together, and the difference between species becomes ever more vast.







