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So what you do see here is: (1) mutation; and (2) speciation.

Yes. My question was to the randomness of the mutation.
The basic evolutionary model is speciation by random mutation over time, as filtered by natural selection, correct? However, while that may yet prove to be true, it seems insufficient to me: not evolution, but the mechanism for it. It strikes me that since evolution is such a fundamental principle of life, that somewhere down in our genetic hardwiring there may be some yet unknown evolutionary impulse at work.
I've got nothing to offer in support of that, and I realize that it tiptoes close to Lamarck, but it's a door I leave open for the time being.
Also, it seems at least plausible that hybridizations like the one between the common groundsel and the Oxford ragwort can spontaneously induce mutuations.
Here's a question: suppose in the next few years someone is able to cross a York groundsel back to either a common groundsel or an Oxford ragwort, or both, and produce fertile progeny?
We know, because of exceptions, that the rules of hybridization are in a bit of flux, so it's not idle speculation. Would we then rescind the York groundel's species status, and rule that the groundsels unable to reproduce with their parent species suffered from "birth defects," so to speak?
I do a lot of work with tropical fish, and am aware of a number of instances of fertile hybrids from different species. Swordtails and platies of the genus Xiphophorus are an example. There are over 30 species described, on both sides of the continental divide of Central America, yet most can cross back and forth with each other. There's not a fancy swordtail or platy in a pet shop in the world that isn't the result of a lot of hybridization. I don't think that means that we only had one species to begin with, but that hybridization works differently in other organisms than the ways in which we're used to thinking of it working in mammals.
But if that's the case, then isn't one of our definitions of species, a population only able to reproduce fertile offspring among themselves, not always a good yardstick in all circumstances?

Your questions are good ones, and no doubt professional biologists are doing research in these areas even as we speak. (A quick scan of the tables of contents of the professional journals would almost certainly indicate that this is the situation.) It's always been the case that the specific mechanisms of genetic variation are proper subjects for research. Darwin himself was largely clueless on that score, but he could observe that variation was happening, even though he didn't know the details. I think we're still learning. That's what science does.

However, none of this casts any doubt on the fact that evolution happens. So the creationists can take no comfort from this thread.