This is my favorite topic, what defines a species? I guess Canis is part of the reason why the Biological Species Concept (BSC) doesn’t work. To recap, it’s when a species is a population that can and will only breed with that of it’s open species. Big problem with that idea is, hybrids don’t exist? What about a mule? So we say that BSC accepts hybrids as long as those offspring are infertile? Now what about a Fiesta Macaw? It’s family tree looks like this:
Offspring: Fiesta Macaw
Parents: Camelot Macaw (hybrid) and Harlequin Macaw (hybrid)
Grandparents: Scarlet Macaw, Catalina Macaw (hybrid), Blue-and-gold Macaw and Green-winged Macaw
Great Grandparents: Scarlet Macaw, Scarlet Macaw, Blue-and-gold Macaw, Scarlet Macaw, Blue-and-gold Macaw, Blue-and-gold Macaw, Green-winged Macaw and Green-winged Macaw – or in other words 3/8 Scarlet, 3/8 Blue-and-gold and 1/4 Green-winged.
Now for those unfamiliar with these species, just google them. Clearly they are very different but they can breed freely with each other, right? So under the BSC, does that make these splashes of red, green, blue and yellow feathers under the same species? Not necessarily because the Fiesta, Camelot and Harlequin Macaws are captivity hybrids. They do not occur in the wild and in fact, the Catalina Macaw is the only known wild occurring macaw hybrid. And the lack of hybrids are the not the result of range as Blue-and-gold and Green-winged share practically the same range. It’s because they breed only with their species.
This situation also applies to the Canis situation. As of this comment, I have not heard a convincing report of a Coyote interbreeding with a wolf. I know here in Oregon, they are ecologically separated as coyotes tend to stay in the lowland valleys closer to people while wolves live in the deepest, most remote forests. I would think this would mean they are reproductively isolated and therefore different species. In captivity, they can probably interbred but not in the wild. Same thing goes to the Gray Wolf and the Domestic Dog, except they do interbred quite often in captivity, my own dog being approximately 3/8 wolf. However, if a stray dog encounters a wild wolf pack, it’s more than likely it’s the last thing that dog is going to do.
In summary, my opinion is the distinction between the Gray Wolf and the Domestic Dog is more arbitrary than Gray Wolf and Coyote.