The subject does the question quite nicely, I think.
It’s a little ridiculous, yes, but the thought sprang to mind when one of my neighbor’s bitches was in heat. This was a Jack Russel terrier runt, perhaps six pounds of 3yo dog. The males of my neighbor’s five dogs were both Scottish Woflhounds, magnificent horselike things weighing at least 110 pounds. They knew something was up <ahem> but couldn’t figure out for the life of them where the female was. I guess the appropriate smell signals are the same for all dogs, but the boys thought of her as their wonderful little rodent playmate.
Now, ignoring certain problems with the mating (let’s suppose artificial insemination), will there be a problem with the pregnancy and whelping? Do little dogs have short periods of gestation and the pups will appear only part-formed?
I think the problem with breeding dogs of different sizes is that if the female is smaller, she will die. I’m no dog breeding expert, but that’s what I’ve always heard.
My parents had a beagle that bred with a collie. She had a rough time delivering the puppies.
And before someone asks whether this means that Great Danes and chihuahuas are different species, the answer is no. Even though some breeds can’t breed directly, genetic information can flow freely between all breeds, so they’re all still considered one speices. A big dog can breed with a medim-sized dog, and a medium-sized dog can breed with a small dog, etc.
The bitch wouldn’t explode, but she wouldn’t be able to pass a pup that size through a pelvis that size. Without a c-section, she’d die trying to whelp.
Normal gestation for a dog is nine weeks, regardless of breed. Barring complications, they’re all at the same stage of development, they’re just sized differently.
(So, if all dogs exept chihuahuas and great danes were killed, we would then have two different species of dog? And dogs and wolves are the same species?)
Not necessarially - no reason a small dog couldn’t make a large bitch pregnant, is there? (other than maybe needing a stepladder) If, in the OP, a Jack Russell “runt” of a male managed (somehow) to mate with a female wolfhound the bitch would be able to whelp the puppies with no problem, since, presumably, they’d be smaller than pure wolfhound pups.
That is one way in which speciation is thought to occur; the population becomes diverse (in some cases extremely so - look up ‘ring species’) and then the middle bit gets wiped out, leaving the two ends unable (or unwilling) to interbreed - any mutations which then occur in either population would not be passed to the other and the two populations would be free to evolve separately.
As far as dog and wolves being the same species, barring tradition and politics, that would indeed be the logical conclusion.
In other words, based on our “understanding” of what makes a species (which is utterly tautological, because species is an entirely artificial conception), there is no question whatsoever that dogs and wolves belong to a single species.
It will be a long time, however, before inertia permits such a change in the taxonomy.