This is not a good swap. This taxon is no more a hybrid than most other Opuntia taxa, and the listing at POWO is simply copying a random [re-]designation that was made by Parfitt & Baker in 1993 in the Jepson Manual with no supporting data. There is no supporting evidence for this one, nor for most of the others similarly listed, and it is premature to list all these Opuntia species as hybrids, or even to presume that they are hybrids. In fact, cytological and morphological evidence both tend to disprove hybrid status, particularly between the two species listed as supposed parents (O. littoralis and O. phaeacantha). POWO is for the most part not a good resource to follow for Opuntia names, and is just a listing that is copying others who are usually themselves copying others. It simply leads to confusion and misinformation.

Anyway, the following all recognize O. vaseyi as a distinct species:

https://www.opuntiads.com/opuntia-vaseyi/

http://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=35279

https://www.calflora.org/cgi-bin/species_query.cgi?where-taxon=Opuntia+vaseyi

Hi,

Basically yes. However - - -

For now, rather than doing things haphazardly, I'm wondering about proposing an exception for the whole genus regarding POWO. There are numerous taxa involved (likely a majority), where real populations don't jive with nomenclature of the POWO listing. But, yes, I think x vasei, among others, should be listed as a species and swapped back. To list it as a "hybrid" is rather misleading, it is not as if the two supposed parents are constantly crossing and making O. vaseyi, and in fact the supposed parents don't even grow with it anywhere at all, that I'm aware. Also, when one compares traits, it's very unlikely that O. littoralis and O. phaeacantha could create a plant that looks like O. vaseyi (there are many discrepancies in which traits of O. vaseyi are not shared with, nor accounted for by either supposed parent). It is far more likely that O. vaseyi is a parent of some of the other local taxa (though I doubt this too, at least not on a short term one on one recent basis).

There is also a list of additional species that are shown on iNaturalist with the "x", which are similar situations. Some additional appear this way on POWO, but not at iNaturalist yet, while others have been published as such but do not appear on POWO. These mostly exist simply because somebody published them as such (there was a bit of a fad and a rush to do this some years back); however, for most of these there is no supporting data, just an opinion, and for others the data given is questionable and circumstantial at best. This involves numerous populations that behave as distinct reproducing species. Some may have determinable hybrid ancestry, but I would contend that for some it is just as likely that they are the "parents" as it is that they are the "hybrids", and that at the very least all of these polyploid species of Opuntia have just as mixed ancestries as all the rest. I suspect that almost every species in this rapidly evolving genus has convoluted and mixed "reticulate" ancestry involving hybridization events, introgression, and remixing of genes, but that doesn't mean every species [? any] should be treated as "hybrid", nor that such populations are not good biological species - I know it sounds a bit confusing, but evolution involving genetic remixing versus recent hybridization and resulting recent hybrids are two different situations - functionally related - but different.

Anyway, on top of that, there is a whole series of names on two continents that are properly described (some very old and long recognized), with many in the process of being studied and revived or re-defined now - names that are often listed as synonyms or even nomen dubia on POWO (and even some treated as distinct that are nothing more than garden cultivars).

The biggest problem with all of this is that there is not a standard nor up to date published listing or authority for the genus. It is a difficult issue. I know how I would treat most of them, but I'm am just one individual who happens to be addicted to studying the genus. Beyond original descriptions and type species, there is little more published to back the distinction at species level of many names than there is evidence to lump them. It's a bit of a mess.

Anyway, it seems to me that in following POWO for this genus, we are causing and furthering more confusion by lumping things together, and pretty much randomly calling others hybrids, most of which are distinct easily recognizable [nearly all of which are properly named and well described and typified], than we are by recognizing and listing them. I would like to see them listed as distinct species, if for no other reason than to keep them separate so people can see the differences and learn and compare them, making it easier for people who don't now them to sort them out. We don't need to add to the already muddied water. Also, in my 50+ years studying the genus, my conclusion is that nearly all really are recognizable species (not all, but nearly all).

The best on-line listing at present is the Opuntia Web site [https://www.opuntiads.com/], etc. I've noticed that the online Jepson Manual seems to be leaning more toward recognizing these (in California) now too.

So getting back to O. vaseyi. I would, in this and several other cases, definitely prefer to swap the "hybrid" version with the full species version, but I'm not sure after thinking about it, if it is best to do them individually on a case by case, or to come up with a larger more "blanket" exception for the genus (I supposed regardless of any exception, things would need to be swapped, and individual justifications are always good). I'm being a bit wishy-washy I suppose. I'm also still learning how things work in iNaturalist. I definitely prefer to try and represent natural and biological reality than to list by legislated rote.

Sorry, I have a tendency to get overly wordy sometimes.