Wow, I can't believe I didn't think of that. I've been studying Japanese, and yet it didn't even occur to me to search Japanese pages (and I had forgotten that Google filters out foreign language pages by default).
So many pages on キダチアサガオ, and many of them do reference Ipomoea crassicaulis, or I carnea subsp. fistulosa, as you said. I'm going to have to do some reading.
Thanks so much.
(and as a side rant, while I greatly appreciate the work that's being done to better understand the relationships of genetic groups these days, the accelerated reorganization and renaming of hierarchies threatens to undermine all of the strengths, and even the purposes of having official taxonomies. We need a central registry or something where you're not allowed to publish a paper proposing new names and organization without adding them and your proposals to the registry with proper links to the current and historical taxonomy...)