RickCorey said:
I suppose that if a naming system can't be nailed down tight and any "intermediate" types assigned unambiguously to one sub-group or the other, taxonomists would rather ignore the differences and have a "neat and tidy" system instead of a real-world-useful system. Grumble grumble!
That's not remotely close to the reason taxonomists do what they do. I often see comments from gardeners to the effect that taxonomists are engaged in some sort of conspiracy to make their lives difficult or they 'must not have anything better to do'. Almost no one gets paid to be a plant taxonomist, per se. For the most part, they are university professors, museum curators, etc. who have plenty of other duties, but work on taxonomy on the side because they have great interest in the plants in question.
The current round of "lumping" is primarily being driven by DNA testing, which has finally become inexpensive enough to be paid for with the paltry grants available for this type of work. What they are finding, in short, is that appearances can be deceiving. Plants that look rather different from each other sometimes turn out to be much more closely related than had been assumed. Hypothetically, some of your chinese cabbage cultivars might be more closely related to some bok choy cultivars than they are to other cultivars of chinese cabbage. In which case, you couldn't really argue that chinese cabbage is distinct from bok choy, regardless of appearance.
