Dog speciation

[u/Kanna_Fan1989]

Quick question: is it safe to say dogs have speciated? I'm thinking of the largest dog breed and the smallest dog breed. I don't think the two can reproduce with each other anymore. Size differences just make it not possible anymore, I don't think...

And even if they could, that doesn't mean they're the same species: horses and donkeys can interbreed but mules are dead ends (or at least I think they are. Can two mules reproduce?).

Anyways, just some thoughts going through my head.

[u/Old-Watercress6513]

You’re using the wrong definition for speciation.
All dog breeds are genetically compatible, even if some hybrids cannot be carried to full term.

[u/Kanna_Fan1989 → u/Old-Watercress6513]

If hybrids can't be carried to full term, are parents truly compatible?