Flag for Taxon: cockleburs (Genus Xanthium)
| Flagger | Content Author | Content | Reason | Flag Created | Resolved by | Resolution |
|---|---|---|---|---|---|---|
| rynxs | cockleburs (Genus Xanthium) |
sweeping changes proposed by POWO |
Dec. 14, 2022 08:11:18 +0000 | Not Resolved |
Comments
Do not run any of these changes without first allowing for discussion.
The taxonomy of the genus Xanthium is extremely complicated and messy.
To be frank, I think that in the absence of modern dedicated studies, the treatment provided by POWO should be taken with a grain of salt. The risk is to put in synonymy taxa that are distinct. The case of X. orientale that was included into strumarium is a good example.
To summarize, if not strictly mandatory, if iNat current taxonomy keeps separated certain taxa, at least at the subspecific level, it could be good to take a little time to get an idea if these taxa deserve to be kept as independent or not.
Quote: "POWO synonymizes all the current infraspecifics under X. orientale with the species."
What we know as X. orientale subsp. italicum is pretty different from what is addressed as X. orientale subsp. orientale.
At the very least we should come up with a deviation so that none of these changes are run individually. We need to determine what taxa should be added, and what should be conserved regardless of POWO.
Are there strong indications that one or some are to be synonymized?
If I were you I would keep all.
PS: I do not know why italicum has been recently linked to strumarium while before it was subsp. of orientale (which is in theory more correct)
Not that it is really helpful in figuring out what to do with this group on iNat, but for what it's worth, Alan Weakley in the Flora of the Southeastern United States treats 5 taxa of X. strumarium sensu lato as distinct species, so that is different from POWO too. That flora (at least the 2023 version) treats the genus as containing the following species in the southeastern US:
Xanthium ambrosioides
Xanthium spinosum
and within the strumarium group:
Xanthium chinense
Xanthium echinatum
Xanthium orientale
Xanthium speciosum
Xanthium strumarium
Are you familiar at all with this group?
Nope! I just was working on IDing a Xanthium specimen from SC and noticed that there were more species than I expected there to be, so I checked iNat to see how it was handled here and saw this flag. In glancing at the top IDers for this genus, it looks like most of them do a lot of general IDing, rather than a focus on this group, so I am guessing that there isn't a Xanthium expert per se on iNat right now.
@arthur_haines please @ other experts in the taxon to discuss this matter. Thanks.
@abounabat I saw that you were previously interested in this taxonomic issue, and wanted to let you know of this thread
No time to investigate on this genus, sorry...
POWO has a mishmash of taxonomy that is amalgamated from several different sources that makes little sense when the genus is viewed from a place of some understanding (I do not profess to have a deep understanding of the group world-wide). For exaxmple, Xanthium echinatum, which is native to North America, is placed with Xanthium orientale (a species of Eurasia that is not considered part of the North American flora by those who have monographed the genus). If one was familiar with the two taxa morphologically then it would be understood how inappropriate this synonymy is. I could go on, but to summarize all the problems with the POWO taxonomy for Xanthium is simply too onerous. Currently, there are native North American endemics, recognized by all those who have monographed the genus on a wide geographic scale, that can't be recognized on iNaturalist. Dinelli and coworkers (multiple papers) have shown that Xanthium italicum must be pulled out of Xanthium orientale using several lines of evidence. But that information isn't being incorporated into iNaturalist and what names we are allowed to put on the images. (I haven't even started with Crataegus because I'm scared of what I will find there.)
I don't know what the solution is, but I don't know of anyone in North Ameriuca giving these species an honest examination that isn't just using some variation of Cronquist's 1945 treatment, which is deplorable. If I can answer questions, I will. But, suffice to say, if you can't name the variation, then you also can't protect the rare elements on a landscape. iNaturalist is currently using information that doesn't come from an experienced examination of Xanthium, rather from someone who threw up their hands and set back our understanding for the last 75 years.
I would also like to add that because iNaturalist uses a democratic approach to taxonomy (which is inappropriate, but I won't get into that here), you have people weighing in on Xanthium taxonomy who have not read the monographs, examined type specimens (very important), surveyed museum collections from wide regions, communicated with other researchers in the group, etc. I have been informed, more than once, that the carpellate involucres (i.e., burs) in Xanthium are too variable and that pubescence and prickle morphology (for examples) don't discriminate species. But, when I press a bit, I learn that these are just words from naturalists who have not examined the group in any detail, but rather enjoyed following simplified treatments so that they could easily put names on pictures. These opinions shouldn't be part of the decision making for identification or taxonomy because they are uninformed. That isn't meant to be a condescending comment, only that those uninformed in a particular group shouldn't be broadcasting opinions that could ultimately impact local plant conservation. I hope that makes sense and comes across without sounding rude or anything negative (it isn't meant to be, but I always fear that writing can be interpreted in a more negative manner that it is intended).
@arthur_haines I think that Xanthium would need and in-depth analysis of the types and the observation of plants from loci classici, if available.
For the moment, I would consider as a reference the work by Tomasello:
How many names for a beloved genus – Coalescent-based species delimitation in Xanthium L. (Ambrosiinae, Asteraceae)
https://www.sciencedirect.com/science/article/pii/S1055790317309363
According to him, X. italicum should be considered a synonym of X. orientale. As regards, the typoe of the last species is very poorly informative but the protologue could suggest that it is closely allied to italicum.
I agree that much is still to be done and that lumping in this case could be really deleterious.
@blue_celery, Good morning. Tomasello's work is a step, but it does not incorporate information from other research that has been done. Dinelli and coworkers have demonstrated in multiple papers that Xanthium orientale and X. italicum are distinct in their taxonomy and biology. I have observed collections of these plants throughout parts of Europe--they are not similar morphologically (if I could post images to show you it would be obvious). Keep in mind that Tomasello's paper was not based on a broad sampling of individuals around the world. While I do believe his work was a contribution, it has shortcomings. The North American taxa have been examined by multiple taxonomists who monographed the genus. They all upheld certain taxa, and these species are not being recognized (some of which are globally rare). It would be wonderful to use iNaturalist to help locate these taxa, but at the moment it is impossible. I hope you have an enjoyable holiday season.
@arthur_haines I agree that the paper by Tomasello is a first step.
Regarding those by Dinelli & al., do they examined type specimens or plants from the loci classici? Regarding X. orientale sensu stricto, I know what it is not (it is different from strumarium) but I still do not know what it exactly is mainly due to its type.
Moreover, has anyone made cultivation tests in order to verify if characters are retained in subsequent generations?
Thank you for the greetings.
Wishing you a happy holiday season
@blue_celery, good morning. I have examined collections of Xanthium orientale in Europe. It is a very different plant than what is here in North America. However, if one wants to subsume a number of taxa into a few species (as Tomasello did), then X. orientale has priority over a number of other names. Several studies have shown that it is a different taxon than Xanthium strumarium. You could check Dinelli et al. (2003), where they show three taxa in Italy--X. strumarium s.s., X. orientale, and X. italicum (the last is also apparently native to North America and the most common taxon in New England). They found these three taxa maintained their distinctions at different localities. I hope this helps.
@arthur_haines could you forward me some observations of what you consider the true X. orientale from North America? In the case, if you prefer, also via pm. Thank you
@blue_celery, that is easy. There aren't any. To be clear, I haven't seen any yet. Millspaugh and Sherff (1919) also did not find any. Fernald (1950) considered Xanthium orientale to be naturalized in northwestern Vermont--but those were collections of the Lake Champlain endemic Xanthium leptocarpum. Outside of his likely misapplication of the name, Xanthium orientale (s.s.) is currently unknown from the United States.
Ok. Do you have any available from somewhere else?
@blue_celery, Let me look around in Europe and try to locate some. Thus far, I have been studying herbarium specimens from France and nearby countries. I should be able to find some on iNaturalist if I look long enough.
The question I have is: how do we get more taxa to be identified on iNaturalist? Thus far, we are still stuck with untenable taxonomy of POWO, which isn't following the results of modern research and floras. How difficult is it to just let us add more names? Right now, iNaturalist is preventing the correct identification of several observations I have come across. For example, I recently found X. chinense (upheld at some rank by everyone who has treated the genus, and supported in modern molecular work), but iNaturalist won't let me identify the plants as this taxon. I would be interested in providing a list of names we need to be able to use (very important for the conservation work I'm embarking in and would love for iNaturalist to be an asset in this work).
The issue of Xanthium chinense is important. It has been found also in Italy and it seems a species deserving to be recognized.
Again as a starting point, it could be proposed to POWO to adopt the taxonomy as deduced from the work by Tomasello. At least this would allow to have available X. chinense.
POWO (bi@kew.org) is typically fairly receptive to proposed changes, especially if they come with evidence. Alternatively, should POWO reject the Xanthium species for some reason, a deviation can be put in place as a last resort.
@rynxs , Yes, if POWO started with Tomasello (2018) it would allow one more taxon to be identified. But, Dinelli et al. (2003) demonstrated that Xanthium italicum must be pulled out of X. orientale. And, if you are going to pull out X. italicum, one must pull out X. echinatum (they are morphologically very similar but distinguished on reproductive, vegetative, and ecological grounds). The problem, if I can just be blunt, is that too few people can understand the comment I just made about X. echinatum. So, it just lands as if it doesn't have any evidence (even though Millspaugh and Sherff (1919, Widder 1923, and Fernald 1950 all recognized this taxon). I will write this again in another way (with no intent to be rude or condescending): the current taxonomy that POWO is using is based on ignorance of the genus. I am hoping that I won't be forced to publish something before I publish something. In other words, I almost need to publish something preliminary so that it can be cited, and then I can do the real work on iNaturalist annotating the observations. Right now, I can't annotate them to the names that need to be used.
If annotating observations is beneficial, observation fields may be useful to you. They're a tad more difficult to learn, and they don't add an actual "ID," but they allow a greater degree of freedom. Using the compare tool, you can map out the notated observations.
Here's a useful guide: https://www.inaturalist.org/pages/extra_fields_nz
Create an observation field here: https://www.inaturalist.org/observation_fields
@rynxs , thank you, I will take a look at this.
I am grateful to both of you for documenting this discussion here. It is in a spot where others can find it in the future, and as more information arises. Thanks so much for taking the time, @arthur_haines @rynxs @blue_celery @cwarneke
If any consensus arises about interim or final ID decisions, I'd be happy to help with reviewing the observations, given direction.
@arthur_haines Since there is as yet no modern treatment of North American Xanthium that distinguishes X. echinatum from X. italicum, what would you suggest as a source of information? In central New York I see plenty of plants corresponding to Tomasello's "orientale" and would like to record them more precisely. A source telling me what details to note and to photograph would be good.
@lmtaylor , good morning. There are references that distinguish these taxa, but you have to go back into the literature. As I mentioned, Cronquist in the late 1940s subsumed everything in Xanthium strumarium. Generally speaking, had these been plants that occurred in beautiful, pristine locations people would have continued to study them. But, because many populations occur on roadsides, along agricultural fields, etc., people were happy not to have to deal with them. Here is a key that distinguishes them (from the upcoming second edition of Flora Novae Angliae):
6a. Carpellate involucre with stout beaks 2–3 mm wide at the base that are strongly incurved; upper portion of stem whitened by dense, hispid hairs; teeth of leaf blade margins usually low, broad, and/or rounded (i.e., the blades usually lacking large, sharp teeth); plants of Atlantic coast beaches, dunes hollows, and margins of saline marshes ..... X. echinatum
6b. Carpellate involucres with beaks mostly 1–2(–2.5) mm wide at the base that are straight or slightly incurved; upper stem sparsely to moderately strigose; teeth of leaf blades (at least some) usually tall and sharp (i.e., the blades coarsely dentate); plants of human-disturbed soils, areas of cultivation, and shorelines ..... X. italicum
@lmtaylor , I forgot to mention--keep in mind that Tomasello's broadly defined Xanthium orientale has been shown in other research to be too inclusive. Research of Dinelli et al. (2003) showed that Xanthium italicum must be recognized apart from X. orientale. While I do think Tomasello is a valuable resource, he is essentially continuing the lumping approach taken by Cronquist (he is just using species rank instead of varietal rank).
@arthur_haines Thanks, that's helpful! Does what you wrote in the first edition about distinguishing X. strumarium var. strumarium (>X. chinense) from X. strumarium var. glabratum (X. orientale/echinatum/italicum) still correspond to your understanding?
Way back in the day, I first learned my cockleburs from the venerable Newcomb's, which predates Cronquist, being based on Fernald's 1950 Gray's Manual, though severely simplified; if I recall rightly, Newcomb selected just 2 of Fernald's 15 species. Those were both sunk into strumarium.
@lmtaylor , regarding Xanthium chinense, the key in Cronquist is oversimplified and I have found much better ways to diagnose this taxon. The following couplet distinguihsed X. chinense from most of the other cockleburs in our flora (save for X. strumarium s.s.):
3a. Fruiting carpellate involucres subglabrous or sparsely sessile-glandular or glandular-puberulent with hairs up to 0.1(–0.2) mm long on the body, the prickles also sessile or shortly glandular-puberulent (rarely with a few longer hairs near the very base), usually light brown at maturity, 10–20(–25) × 9–18 mm; prickle apex with a narrow terminal hook, the radius 0.3–0.6 mm wide ..... X. chinense
3b. Fruiting carpellate involucres sparsely to moderately hirsute with hairs longer than 0.2 mm on the body or on the prickles or usually both (rarely with short glandular-pubescence only on some carpellate involucres in X. curvescens and X. leptocarpum, but those species with shorter and/or narrower involucres), usually brown to red-brown at maturity, (11–)17–30 × (6–)12–22 mm; prickle apex with a narrow to very broad terminal hook, the radius 0.4–2 mm wide
If you send me an email at arthur.d.haines@gmail.com I'll send you the entire key to our northeastern taxa. Best wishes.
POWO divides X. strumarium s.l. into:
Xanthium strumarium s.s.
Xanthium canadense (syn. X. s. ssp. canadense)
Xanthium orientale (syn. X. s. ssp. glabratum)
The other subspecies are synonymized.
POWO synonymizes X. echinatum and X. cavanillesii with X. orientale.
POWO brings X. catharticum down to subspecies level, under X. strumarium.
POWO synonymizes all the current infraspecifics under X. orientale with the species.
Additional species are listed, including Xanthium ambrosioides Hook. & Arn., Xanthium argenteum Widder, and Xanthium chinense Mill.