It's probably very unlikely that any of these databases is comprehensive or can be assumed to be a finished product. It seems that ITIS is the favoured database here but, for example, it lists only one species of
Onosma.
Is it possible in ITIS to see which species, subspecies, etc. have been subsumed under its currently accepted species?
P. S. Using italics seems to cause words to show up out of line for some reason... ?