It's not just the one mutation that causes the size range of dogs. That's probably a factor, but I feel comfortable saying that we would have a much wider variety of cat sizes if they had had as much selective breeding for size and type as dogs.
There's evidence that the structure of the dog genome makes it easier to breed for various characteristics – the "slippery genome" theory [1]. It looks like the science isn't fully settled, however [2].
Thanks for the links. I'll read through them when I've got the time.
Having not read any of your references, I'd like to point out that the variation in domestic horses is right up there with dogs. You go from Shires to Miniature Horses, Arabians to Clydesdales. It's a huge spectrum because they were bred for specific tasks. I feel like even domestic rabbits and chickens see more variation than cats.
Maybe cats are just that stubborn or maybe we don't have many jobs for them besides pest control and snuggling.
