Tracking down the rationale for POWO synonymization

I’m putting this one in the Curators category as it seems most likely that other curators might know the answer…

In working through IDs for some New World monocot genera, I’m finding that some species that are accepted by active researchers in the field are not available in iNat because Plants of the World Online (POWO) treats them as synonyms. I can find these “not accepted” entries in POWO and the related World Catalog of Seed Plants (WCSP). In some cases, I can look up the “not accepted by” reference, which several times has turned out to be a paper by a researcher not very familiar with the species they decide to combine (e.g. working in a different country and without prior field experience in the environment where the species at issue is found). Those cases are frustrating but manageable. If I feel the evidence for separate taxa is strong enough, I can flag the taxon and make my case. And if relevant iNat users express consensus I can then create a deviation from POWO.

My current trouble, however, is that I can’t even figure out what rationale POWO is using to synonymize certain species. Today’s example is Echeandia graminea, an uncommon white-flowered species with scaled filaments described in 1842 that POWO treats as a synonym of the very widespread E. flavescens, which has yellow flowers and variable filaments. Fine, let me read the rationale for this… POWO says E. graminea is “not accepted by … Govaerts, R. (2001). World Checklist of Seed Plants Database in ACCESS E-F: 1-50919. [Cited as Echeandia flavescens.]” If I check WCSP the reference is the same. But Rafaël Govaerts is the compiler of WCSP and this reference appears to be equivalent of “because I said so”.

What am I missing here? Is there a non-publicly accessible database that includes a reference to the actual source that makes the case why E. graminea is really E. flavescens? Has anyone else run into this?


if you email they usually provide an actual reason within a few days (or change the database)


One thing I often have luck with is typing the names of two species e.g. “species a” “species b” into google scholar (with the quotes, the quotes forces exact matches, so it will only match papers which have both names).

It doesn’t work all the time because sometimes it will be a book which synonymizes them which probably isn’t indexed by google scholar. Sometimes I use “genus” “epiphet1” “epiphet2” in case the genus is abbreviated.

But the problem you’re describing is a frustrating one I have spent much time banging my head against recently


I haven’t emailed POWO much yet, but they were fairly quick to respond when I did. Seems good to do some good research first and come at them well informed. They may not have gotten to a lot of taxa yet and a lot of taxa are pretty messy or controversial, so not a lot they can do until resolved. I love that POWO has “accepted by” and “not accepted by” fields, however, they are mostly not filled out, often lack the most relevant references, and often reference “because I said so” sort of references that lack their own references as noted by rupertclayton. The lack of references is very frustrating but imagine trying to keep all the plant taxa in the world up to date. I asked them about that and they responded with “We started in 1892 so give it another century…”

When they lack good references, I think the best way to approach it is to give them the references and hopefully they will add them. If you make it easy for them to update something, it seems like they are more likely to do it quicker, assuming there aren’t a bunch of taxonomic issues in the way.


POWO is what it is. If your goal is to change POWO, you will almost certainly become frustrated. It’s just not worth it.

That said, if you find a bug in POWO, you should report it. In fact, your first couple of emails to POWO should be obvious bugs. They will appreciate that and remember that when you eventually ask less black-and-white questions.

Yes, that is the best approach, but that too can be frustrating. You have to decide if the desired change is worth the effort. The old adage “pick your battles” applies here.


I have, quite recently! They appear to have combined Pseudogynoxys cordifolia with Pseudogynoxys chenopodioides, which are as different as 2 species of a genus can be.
For comparison:

Pseudogynoxys chenopodioides
Pseudogynoxys cordifolia

This is very frustrating as I’m working on a paper that lists P. cordifolia… but I am not sure what to do. The best I could muster was placing it as P. chenopodioides, and then adding a footnote citing Rafaël Govaerts’ work. But I failed to find a rationale, a DNA study or something along the lines of that to justify Govaerts’ decision of merging the two. And it is posible that the whole paper is compromised now.
Also they have subsumed Capparicordis, Colicodendron and Cynophalla in Morisonia for some reason. Same issue as above.


@junior84 I would not use POWO as a reference in a paper for what to call something. Call them by their distinct names and use papers that actually cite evidence. If there are not papers citing evidence for lumping, I would cite POWO as an example of a conservation concern as it lumps the taxa without evidence and that could lead to misidentifications, which are a threat to the species. And, as mentioned before, if you don’t find rationale for lumping, ask POWO. They may have something you overlooked or they may fix it.


I don’t think you’re missing anything here. POWO has indeed chosen to cite a secret, private database in lieu of giving a rationale. This is not scientific. Maybe they’re working on a new WCSP entry for this group? And these are the notes leading up to its publication? Very strange!


Premise: I like POWO. It’s a very ambitious project and it provides a number of very useful data (above all the distribution of the taxa). Definitively I use POWO with a certain frequency.

Anyway, it happened to remain perplexed when among the references that support a certain taxonomic treatment I could find only checklists when, at the same time, there are available some dedicated studies by taxonomists. This way of doing is totally incomprehensible to me.

PS: I find really frustrating the suggestions to email POWO. Let’s try to face these issues here since inside iNaturalist there are skilled botanists.

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Almost OT but not really: in Northern Europe and Russia lots of vascular plant taxa are treated as valid (e.g. in dissertations, threatened species evaluations, guidebooks, lists, inventories etc.). These are mainly below the species level taxa but sometimes also species. Making observations of those does not make sense here in iNat…

And that’s the way to deal with them inside iNat, if root of problem is fixed, it’s fixed on iNat too, why incorrect taxonomy should stay there?


Thanks for all those thoughts. I’m glad that I’m apparently not missing some way to uncover the rationale for these synonymization decisions. Probably in this case I should follow @bouteloua’s recommendation to email for the reasons. I’ve read most of the papers on this genus, so if there was a publicly accessible article that supported combining these species, I would expect to have come across it. My best guess is the decision was made in a book I don’t have access to, or that there was some error in POWO’s assessment.

If I had a good recent reference that justified keeping these species separate, I would be happy to share that with POWO (or just go ahead and make a deviation to iNat’s taxonomy). The challenge here is that E. graminea was described in 1842 (with characters clearly distinct from E. flavescens) and has been used since then by botanists in Mexico without any apparent need to restate the separate nature of this species. Despite that, POWO says they’re the same without further details. This seems quite similar to @junior84’s experience.

Anyhow, I’ll try the email route and see what I get!

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Thanks for the advice. I changed the name back to P. cordifolia. I think I will do the same for the Capparaceae as Govaerts is the only source, and it’s not leading me further than his own work

(also I need to clarify that I made a mistake on the P. cordifolia, it was Roskov Y. the author, not Govaerts, althrough both are currently giving me the same issue…)

that’s a great idea. Probably what’s going on the footnote now :)

Update: the Catalogue of Life (Roskov et al.'s work) hasn’t lead me anywhere else. It would be nice if they cited at least a study, a paper or something else…

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Honestly, I find rather impolite to write to someone to tell him that he is mistaking something in his site. Probably this is one of my many limitations.
Moreover, I think it is much more productive to solve problems here. Then, once solved, someone could decide to suggest to them a different view on that given taxon.

Just your point of view.

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It is not rude.And they always answer within a day.


All what matters is that it’s easy and working well.

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This has not been my experience at all. They usually respond quickly, and either alert me that they will change POWO, or on occasions let me know why my nomenclature is wrong.

They are actual people putting POWO together, and they work hard to provide the best data that they can. It suffers from all the same shortcomings of large-scale aggregators, but IMO does better than most or all the others.


I agree with mftasp. There is nothing else quite like POWO. Although it is not properly referenced, the response to any queries is fast, efficient and comprehensive. And any mistakes or omissions are dealt with immediately.
Just dont use it as gospel below the species level, although they are addressing the issue.


I haven’t had much luck raising this issue with POWO. I emailed a polite enquiry on Jan 13 and followed up on Jan 19, but received no response to either email. Would anyone happen to have a contact there that might be responsible for Asparagales or monocots more generally?

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@rupertclayton They may not have responded by email but take a look at the POWO entry now.