I always hate losing varieties, so I looked more into this.

The phylogenetic work was done in: Jordon-Thaden, I., Hase, I., Al-Shehbaz, I., & Koch, M. A. (2010). Molecular phylogeny and systematics of the genus Draba (Brassicaceae) and identification of its most closely related genera. Molecular Phylogenetics and Evolution, 55(2), 524–540. doi:10.1016/j.ympev.2010.02.012

That paper shows that Draba cuneifolia var. integrifolia is more closely related to Draba cuneifolia var. sonoare than Draba cuneifolia var. cuneifolia. It goes on to say "The three varieties of D. cuneifolia did not occur exactly on the same branch and did not form a true clade. It is therefore concluded that D. cuneifolia var. sonorae and D. cuneifolia var. integrifolia should both be recognized as separate species of Tomostima."

AL-Shehbaz officially published the new combinations for Tomostima here: Al-Shehbaz, I. A. (2012). A generic and tribal synopsis of the Brassicaceae (Cruciferae). TAXON, 61(5), 931–954. doi:10.1002/tax.615002

The North American species given in Al-Shehbaz 2012 have D.c. var. sonorae elevated to species level as Tomostima sonarae. The 4 options for North American species are now which is also what POWO is recognizing:

Tomostima cuneifolia (Nutt. ex Torr. & A. Gray) Al-Shehbaz, M. Koch & Jordon-Thaden, comb. nov. ≡ Draba cuneifolia Nutt. ex Torr. & A. Gray, Fl. N. Amer. 1: 108. 1838 – Type: U.S.A., Kentucky, C.W. Short s.n. (lectotype: GH!, designated by Hartman & al. in Brittonia 27: 323. 1975; isolectotype: NY!).

Tomostima platycarpa (Torr. & A. Gray) Al-Shehbaz, M. Koch & Jordon-Thaden, comb. nov. ≡ Draba platycarpa Torr. & A. Gray, Fl. N. Amer. 1: 108. 1838 – Type: U.S.A., Texas, 1835, T. Drummond s.n. (lectotype: GH!, designated by Hartman & al. in Brittonia 27: 323. 1975; isolectotype: NY!).

Tomostima reptans (Lam.) Al-Shehbaz, M. Koch & Jordon-Thaden, comb. nov. ≡ Arabis reptans Lam., Encycl. 1: 222. 1783 – Type: [U.S.A.], “Paronychia Myosotis Virginiana foliis subrotundus” (in Plukenet, Phytographia: t. 51, fig. 5. 1691).

Tomostima sonorae (Greene) Al-Shehbaz, M. Koch & Jordon-Thaden, comb. nov. ≡ Draba sonorae Greene in Bull. Calif. Acad. Sci. 2: 59. 1886 – Type: Mexico, Sonora, North-west mountains, 4 Mar 1884, C.G. Pringle s.n. (holotype: US!; isotypes: F!, GH!, K!, NY!, RM!, UC!, US!).

That paper does not specifically mention D. c. var integrifolia or where it ended up, but it seems to me it might be better to have it lumped into Tomostima sonorae than Tomostima cuneifolia. Their physical identification characteristics are more similar also. That's how they are group in the FNA key:

Fruit valves: trichomes usually simple, sometimes with 2-rayed ones; stems hirsute with at least some simple trichomes = Draba cuneifolia var. cuneifolia
Fruit valves: trichomes stalked and 4-rayed, sometimes with 2- or 3-rayed ones; stems pubescent with 3- or 4-rayed trichomes = (next break to D. c. var. integrifolia and D. c. var. sonorae).

I'm not clear on what Al-Shehbaz' intention was from the 2nd paper because var. integrifolia is not specifically mentioned. I'd personally prefer to have it elevated as a third species, but in lieu of that I think lumping with T. sonorae is more appropriate. The only other source I can find that is using the name is the checklist of Mexico, but they don't explicitly specify where D. c. integrifolia goes either. POWO does specify this explicitly, but I don't always trust them to get new stuff right the first time. I've seen them both accidentally throw out valid varieties and mis-lump old varieties before. On their page right now they say they are following Plant life of Kentucky as accepting the name when it still uses Draba.

Another interesting note -> Al-Shehbaz redid the Jepson treatment in the same year 2012. There, he kept them in Draba, but lumped all 3 varieties as just "Draba cunefolia" not recognizing D/T. sonorae at all. But then says in a note "3 +- distinct varieties..." https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=23332

Just checked the phylogeny--yeah, it's hard to argue that Draba cuneifolia var. integrifolia should go in Tomostima cuneifolia rather than Tomostima sonorae, although it's not clear why they recommend recognizing both Draba cuneifolia var. integrifolia and Draba cuneifolia var. sonorae as species. I'll try doing a taxon swap and see what happens.

Apparently there were six:

https://www.inaturalist.org/observations/104148997

That all sounds good to me. Thanks, Patrick.

"Eh, it's only a few observations, I doubt anyone cares either way.

An obscure variety of a tiny plant that most people wouldn't notice even if they unfortunately got stuck walking through a godforsaken desert...that's my specialty! ;)