Discoid Grindelia squarrosa back to Grindelia nuda again

Grindelia nuda is a rayless (eradiate/discoid) species of Grindelia with blunt or rounded leaf teeth terminated with glands, defined initially by Wood(1878) based on a collection in what is now Oklahoma. For much of its history, it has been treated as a variety of Grindelia squarrosa (Gray 1884; Steyermark 1934; Correll and Johnston 1970) and briefly again as G. nuda (Nesom 1990; Diggs et al 1999) until is was synonomized with Grindelia squarrosa in the Flora of North America by Strother and Wetter(2006). Plants of the World Online (POWO), which iNaturalist uses as its main resource for botanical names, followed this synonomy until some unspecified time in the last couple of years (perhaps following a change in the September 2021 release of the World Checklist of Vascular Plants) when it accepted Grindelia nuda as a valid species again, referencing Powell and Worthington's Flowering Plants of Trans-Pecos Texas and Adjacent Areas. There has been a fair amount of resistance to some of the taxonomy of Strother and Wetter in at least one comprehensive treatment (Bartoli and Tortosa 2012) and a number of regional floras (Moore 2012; Ackerfield 2015; Powell and Worthington 2018), but that is a broader discussion.

On iNaturalist, G. nuda was never synonomized with G. squarrosa due to flagging in 2016 to maintain it as an accepted name. Despite that, following the FNA and POWO, I (and maybe others) identified most G. nuda specimens up to this point as G. squarrosa. As a result, there are at least several hundred specimens (based on research grade specimens of G. squarrosa in Texas) that will need to be reidentified as G. nuda at some point. In Texas, this should be fairly straightforward since G. nuda is the only rayless (eradiate/discoid) species in the state except for the rare G. oolepis in South Texas. However, it will be a manual process as there are a few actual G. squarrosa in northeast Texas. POWO, following Powell and Worthington (which follows Nesom 1990), recognizes two varieties of G. nuda, var. nuda and var. aphanactis. These appear to be distinguished mostly by leaf morphology (specifically the length to width ratio), and might be difficult to differentiate in the field. However, Nesom indicated that var. nuda occurs mostly to the east in Texas, Oklahoma, Kansas and southeast Colorado while var. aphanactis occurs to the west mostly in New Mexico, southern Colorado, and Arizona. He also recognized a zone of intermediacy in areas of west Texas. It is also worth noting that genetic evidence in Moore et al(2012) indicates that the two may be separate species, despite their great morphological similarity, so it is plausible that the two varieties may be separated in the future.

Heads from above (Burnet, Williamson, and Kimble counties in Texas)

Head profile

Leaves, typically cauline mid-stem

Observations used in this post

Burnet county : 62455288
Williamson county: 8003651
Kimble county: 97271324


Ackerfield, J. 2015. Flora of Colorado. BRIT Press.
Bartoli, A. and R.D. Tortosa. 2012. Revision of the North American species of Grindelia (Asteraceae). Ann. Missouri Bot. Gard. 98: 447–513.
Correll, D.S. & M.C. Johnston. 1970. Manual of the Vascular Plants of Texas. Texas Research Foundation, Renner, Texas.
Diggs, G. M., Lipscomb, B. L., O'Kennon, B., Mahler, W. F., & Shinners, L. H. 1999. Shinners & Mahler's Illustrated Flora of North Central Texas. Botanical Research Institute of Texas.
Gray, A. 1884. Synoptical Flora of North America 1(2): 118.
Moore, A.J. 2012, Grindelia, in Jepson Flora Project (eds.) Jepson eFlora, https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=451, accessed on August 30, 2022.
Moore, A.J., Bartoli, A., Tortosa, R. D., & B.G. Baldwin. 2012. Phylogeny, biography, and chromosome evolution of the amphitropical genus Grindelia (Asteraceae) inferred from nuclear ribosomal and chloroplast sequence data. Taxon 61(1): 211-230.
Nesom, G. L. 1990. Studies in the systematics of Mexican and Texan Grindelia (Asteraceae: Astereae). Phytologia 68: 303–332.
POWO. 2022. Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; http://www.plantsoftheworldonline.org/ Accessed 30 August 2022. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:210628-1
Powell, A.M. & Worthington, R.D. 2018. Flowering plants of Trans-Pecos Texas and adjacent areas: 1-1444. BRIT Press.
Steyermark, J. A. 1934. Studies in Grindelia. II. A monograph of the North American species of the genus Grindelia. Ann. Missouri Bot. Gard. 21: 433–608.
Strother, J. L. and M. Wetter. Grindelia. In: Flora of North America Editorial Committee, eds. 1993+. Flora of North America North of Mexico. 20+ vols. New York and Oxford. Vol. 20. http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=114086
Wood, A. 1878. Grindelia nuda. Botanical Gazette 3(6): 50. 1878.


All photos used in this post are the property of Ryan McDaniel, all rights reserved.


0.1 - September 1, 2022 - Initial.
Posted on September 01, 2022 05:52 PM by rymcdaniel rymcdaniel


Just tagging a few possibly interested parties.
@franpfer @katermorgan @sambiology @gcwarbler

Posted by rymcdaniel almost 2 years ago

Like many Asteraceae, it is a difficult genus. We are fairly fortunate that the north central Texas species are fairly easy to differentiate. In other areas, it is quite difficult just to define the species, much less to identify them from photos. The taxonomy is still somewhat unsettled.

Posted by rymcdaniel almost 2 years ago

Thank you for this update. It is vital for experts such as yourself to keep us informed. Although Ackerfield does not place a rayless species in my county of Boulder along the Front Range in Colorado, I have seen them. G. inornata has been documented in the adjacent counties of Jefferson and Broomfield so this is not a great surprise. G. nuda is still a few counties to the south as you have indicated in the discussion so I guess it's possible that things could get interesting in the future around here!

Posted by helenawood almost 2 years ago

Was wondering what you were up to. Hadn't seen you on iNat lately. :-) Onward and forward.

Posted by connlindajo almost 2 years ago

@helenawood I had been looking at the rayless species in Colorado, including G. inornata, up until recently, but they can be difficult to differentiate. As you have mentioned G. inornata makes it into Jefferson county, and in fact there are quite a few observations of it marked as G. squarrosa instead. :)

Posted by rymcdaniel almost 2 years ago

@connlindajo I had been concentrating mostly on IDs of Grindelias in Colorado for the past couple of months or so in preparation for a possible trip up there, but I don't think it will happen this year. Maybe just west Texas instead.

Posted by rymcdaniel almost 2 years ago

It doesn't surprise me that many Grindelia species are misidentified in CO. It is not commonly known that all curly cup gumweeds are not Grindelia squarrosa!

Posted by helenawood almost 2 years ago

@rymcdaniel Thank you for the thoughtful discussion.

Posted by katermorgan almost 2 years ago

Thanks @rymcdaniel ; and west Texas might be a great destination now after all the rainfall.

Posted by franpfer almost 2 years ago

I'm glad to see the more specific treatment come back (the splitter in me is satisfied). Though, I have to admit that I'm not completely convinced one way or the other about the situation. It wouldn't surprise me if the presence of rays were controlled by few genes and there absence arose multiple times. The dimorphic vs. monomorphic achenes is easily explained since the achenes of rays of many species of Asteraceae produce differently shaped achenes than the disks. The group would probably benefit from some genetic work. As such, I'm kind of ambivalent to the treatment.

Posted by nathantaylor almost 2 years ago

@nathantaylor The Moore et al 2012 Phylogeny reference above did genetic work including many of the known taxa. I am not knowledgable enough about the subject to judge the results, but they were interesting, separating most U.S. species into two clades, western and eastern. The relevant part here is that G. nuda (two samples from Texas) segregrated to itself roughly between the clades and not apparently closely related to G. squarrosa (nor G. aphanactis which is currently treated as a variety of G. nuda). As for the monomorphic achenes, according to Nesom's work at least some of the radiate species also have monomorphic achenes, so perhaps it is not just the lack of ray flowers that contributes to that character in Grindelia. I have not examined them personally though, and unfortunately Nesom has only ever addressed some of the taxa. It would be interesting to check that character on some of the other discoid species (there are two others in Colorado, and maybe more which I cannot remember). I do think that G. nuda probably deserves to be either a species or a variety, and probably should have not been lumped so thoroughly in with G. squarrosa, but I understand why they did it.

Posted by rymcdaniel almost 2 years ago

Ok, for some reason I thought I had read Moore et al. 2012, but I guess I hadn't. That certainly gives me more confidence in thinking that G. nuda is real. That said, there are a lot of polytomies and few of the branches have high support. It makes me wonder how much the tree will change if/when given more genetic data. Given the placement and probabilities scores of the G. nuda clade, I imagine it's fairly safe to consider that as a separate species unless someone decides to do some serious lumping.

Posted by nathantaylor almost 2 years ago

I wish I could read the clads in Moore you mention well enough to understand them a little. They are very blurry and not enlargeable on the screen. Is there a link I could get ahold of?

Posted by helenawood almost 2 years ago

@helenawood I think you should be able to access a copy through JSTOR. I think they still have individual accounts allowing you to read and maybe download a limited number of pdfs.

Posted by rymcdaniel almost 2 years ago

Here is her dissertation with all clad diagrams. I was able to magnify and turn my laptop around on its side to get a look at the clads!

I didn't realize the significance of G. grandiflora in the big picture. I will have to look at a few of these.


Posted by helenawood almost 2 years ago

... and also the significance of the FNA narrative under the Grindelia squarrosa key that nathantaylor alludes to :
"Nesom reported cypselae to be dimorphic in heads of radiate plants and monomorphic in discoid plants and noted that populations with discoid plants occur mostly south and west of populations with radiate plants".

@rymcdaniel you have really taken my casual hobby of botany to the next level! I went out yesterday and collected a branch of a roadside G.squarrosa for dissection. It's drying out now. I did a dissection of the flowerhead yesterday and had to laugh when the FNA Grindelia key said "pappus falling away". They sure must've had some bone-dry flowerheads! Mine were super sticky. I only have a 10x lope and no discoid achene to compare but I.m looking forward to dissecting more flowers.

I also read as much as I could understand from a first reading of Moore's thesis linked above. Understanding historical and regional context makes all the difference when looking at plant characteristics. for example, my G.squarrosa from yesterday, and many others I saw along the reaod, have proximal leaves much like subalpina but clearly the plants that line my bikepath are all squarrosa. I sure hope I get to see a genome in my lifetime!

Posted by helenawood almost 2 years ago

Informative post, and FYI it shows up on the first page of google results for G nuda

Posted by egordon88 over 1 year ago

@egordon88 Interesting, if I search on variants of G. nuda (as opposed to Grindelia nuda) I mostly get results that are likely NSFW. Lol. I can't seem to replicate your search results.

BTW, I have sort of let this rest for a while after changing most research grade observations in Texas. There are still quite a few in New Mexico and maybe a few other states that probably need to be changed.

Posted by rymcdaniel over 1 year ago

Add a Comment

Sign In or Sign Up to add comments

Gracias al apoyo de:

¿Quiere apoyarnos? Pregúntenos cómo escribiendo a snib.guatemala@gmail.com