When Different Taxonomic Authorities Disagree (Especially About Plants)

I’ve been surprised at how often I see disagreement in different authorities and online resources when it comes to plant taxonomy.

The big references I use when it comes to plants are BONAP, USDA material (including the USDA PLANTS database, Silvics manual, FEIS, Plant Fact sheets, and other material), POWO, and TPL. I also sometimes look stuff up in ITIS, which covers more than just plants. I also recently learned of the LCVP, but it is not accessible online (it is available as an R library) and I have not tried using it yet.

I am surprised at how often these different sources use different names to refer to things. Often, there are names marked as accepted by POWO but not by ITIS, and vice versa. BONAP frequently uses different names from either of these authorities and from the USDA.

I’m curious, for people who do work with plants:

  • How do you decide what taxonomic scheme to use for disputed taxa?
  • Do you just pick an authority like POWO and stick with what they “accept”?
  • Do you ever go out and look at why taxa have been split up, merged, moved, and/or renamed?
  • Do you ever form an opinion of your own on which scheme and/or names you prefer?
  • How do you figure out whether the difference in usage is merely a function of the age of resources, vs. actual disputes? I.e. sometimes there is a scientific consensus on a new scheme but older sources continue to refer to the old name, whereas in other cases there is ongoing dispute about how to classify things, and no consensus.
  • Do you list or mention alternate names? Or do you just cite a name an an authority figuring that’s enough for anyone to figure out what you’re talking about and people who want can look it up? If you mention alternate names, how do you decide which names are important enough to mention, especially when the list of synonyms is long?

In my experience these sources tend to lag well behind POWO in reflecting even broadly accepted taxonomic changes. In some cases, this kind of passive “conservatism” in name changes may be seen as a good thing, because in some cases POWO does jump on the latest bandwagon a little too quickly. But in most cases I find BONAP and USDA to be just flat out-of-date for many groups. Probably just a reflection of their funding and support levels relative to POWO.

Being a plant taxonomist myself, I tend to review the literature and form my own opinions, and those are inherently unlikely to all align with any single authority. But if I had to adhere to a single reference, I would probably choose POWO, perhaps updated by more recent volumes of Flora of North America North of Mexico (FNANM) when applicable.

Depending on the context I definitely do try cite synonyms that are accepted names in other contemporary and widely-used references. Beyond that, exhaustive lists of synonyms are really only necessary in certain academic works.


Can’t speak to plant taxonomy other than that it is undoubtedly more complex than for vertebrate animals which I mainly focus on. Seems there are a lot of active synonyms and a number of parallel taxonomies with plants. Plus a whole lot more species.

For iNat purposes I obviously use the taxonomy that the site provides, but sometimes note in the Notes or Comments section if there are other names in use that might eventually replace the iNat name. For vertebrates, there are many sources of taxonomy that sometime disagree but it’s generally not too complicated.


I use the one that makes most sense. Some taxonomers really don’t have a clue (it’s not a real science (yet)).

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Systematics is science. Taxonomy is the cataloging and naming method by which systematists organize organisms into neat boxes (taxa). There can be disagreements in either but taxonomy does have a little more personal preference imbedded in its decision-making. I stopped worrying about taxonomic disagreements a long time ago. Any scientific name is a hypothesis about relationships and so can be revised, and all are wrong to one degree or another but some are more wrong than others. The goal of the process is finding the nomenclatural arrangements that are the least wrong.


In preparing reports on sites and ecologies within the state of New York for work I tend to use the taxonomy of the most recent Checklist of the Vascular Flora of New York (reflected online by the New York Flora Atlas. It doesn’t agree 100% with any one of the authorities listed above, but taxonomy is a moving target and I feel the person who put that together is pretty sharp about keeping up with phylogenetic research, which I tend to feel taxonomy should more or less reflect. I’ll make an exception for certain groups, like Harvey Ballard’s new treatment of Viola came out more recently and I’ll cite that I follow Ballard for genus Viola. In cases where taxa recognized under those schemes are lumped with something else in iNat I usually put the name I’d use in the observation description or a comment. More straightforward one-for-one synonymies just are what they are.

In some cases there are variations and forms given names and status under one or another outdated description that are lumped under most current schemes that I accept are probably not “good” species or subspecies, but are still interesting to differentiate (I tend to want to maximize information rather than streamline and potentially lose information as we’ve seen in the past with things being lumped that shouldn’t have been), and so those I also sometimes make a note of, as referencing an invalid name still carries information specific to the description under that name, even if that name does not carry valid specific rank.


I follow Weakley’s Flora of the Southeastern United States (for the most part) in my professional life (my herbarium specimens, surveys in the field, etc). My iNaturalist identifications are a compromise between POWO and Weakley. With groups like Dichanthelium I recognize that there’s more going on than POWO does. Weakley isn’t perfect, but it’s the closest I’ve seen to documenting the absolutely maddening lineages of Dichanthelium grasses well. I appreciate however that iNaturalist has to follow a general standard, and POWO is a good one for a database of plants across the globe.

When approximately 70% of all plant species are likely of hybrid origin, it’s a fun world to be a botanist in ;)


I didn’t know Ballard published a new treatment of Viola - where is it? His website it great, but definitely reflects a project in progress.

Some of my best friends are plant taxonomists :roll_eyes: :sweat_smile:, but although I love them dearly, following them (and others) is a REAL headache! On a personal side, it makes it difficult to keep my well-stocked archives up-to-date, but I suppose in the general order of things that’s just a problem for needle-picking me. But I also often find myself comparing vegetation studies and checklists from different periods, which means fighting my way through a forest of sometimes almost incomprehensible synonyms, if I’m lucky! As far as Italy where I operate is concerned, I’ve decided to just adopt the latest accepted checklist of the Italian flora, but often that makes it difficult to find the equivalent species in other databases (such as iNat) which uses a different source. Alas… we must suffer for science :smiling_face_with_tear: :sweat_smile:!


The World Checklist of Vascular Plants (https://wcvp.science.kew.org/) is the most actively curated worldwide taxonomic backbone for plants afaik. It acts as POWO’s taxonomic index. Much of it is expert-reviewed and subsets of it are published in Catalogue of Life and serve as the basis for much of GBIF’s backbone. TPL was replaced as the taxonomic standard for World Flora Online by WCVP. Since 2013, TPL has not been updated.

This table compares WCVP/POWO, WorldPlants (also forms a part of the taxonomic index for Catalogue of Life and GBIF), and LCVP: https://www.nature.com/articles/s41597-021-00997-6/tables/2

There are certainly recent lists at the regional or national levels that are more relevant in terms of what names are accepted and used locally, but WCVP/POWO is a good default global resource.

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Is it really surprising that science often hasn’t just one agreed point of view?
I think that many bad choices in recent times have been done just in the name of a presumed “only one science’s point of view”.

Apart this,

I try to find which are the references on whose basis a certain treatment for a given taxon has been done. Often checklists are not-so-good references. Revisions are usually better despite not necessarily free from errors. Common sense is another helpful instrument.

Yes, as far as I can.

Newer treatments are not necessarily better. I remember some new combinations made on the basis of phylogenetic data that were hard to be agreed. Indeed, they were eventually discarded. Anyway, phylogeny does not necessarily aligns with morphology. Sometimes it seems conceivable to include very heterogeneous taxa into one genus.

Mentioning synonyms can be sometimes useful and sometimes also redundant. It depends on many factors, for example which is the aim of the document.

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Yes, definitely still in progress. You can cite the website directly, but the printed document I work from is to my understanding the treatment he’s prepared for the New Manual of Vascular Plants (a G&C update), so it may go through additional changes before that’s published. That said, most things like the separation of the former Viola pubescens varieties are likely to stay. I expect the most continued changes in the stemless blues, but find it to work better with those than other sources for now and just take the time expand on uncertainties when relevant.

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One of the things that absolutely blows my mind about plant taxonomy is how many examples there are of people shuffling things around and renaming them multiple times, only to reach, in the long-run, a new scientific consensus that Linnaeus’s original scheme actually was best. Like I’ve encountered dozens of species like this.

It blows my mind that someone in the 18th century, just by observation and without access to all the modern genetic tools, could come up with that many classifications that could stand the test of time.


Taxonomic authority disagreements, or mismatches due to some being outdated, are common. Especially for plants given the number of species and frequency of revisions. I think iNat taxonomy (and that of other similar databases) tries to use the main or multiple most standard/official sources. Even if primarily using only one, that source often reflects multiple others. Taxon curation changes also allow some individual-case deviations from primary external source(s) if the reasoning and citation is provided and agreed with by other curators. All users can create curation request on corresponding taxon pages if they notice a needed change.

You’re also asking why some sources are regarded more primary than others. That’s also complicated and debated, but iNat uses different primary source(s) for different groups. I think considering all taxa Catalogue of Life is most frequently used. iNat RG records are sent to GBIF, which itself receives taxonomic info. from many sources.

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Some of the same has gone on with vertebrate taxonomy. An explosion in naming during the 1800s was followed by some lumping in the 20th century and then re-splitting in the 21st. Lots of old synonyms that were sunk decades ago have been resurrected to live again. Unless the organism group was poorly described until very recently, there are a lot of available names in the literature for many “new” species that biomolecular research has re-recognized. The old-timers often had it right in the first place.


It’s all part of the scientific process that sometimes multiple hypotheses are floated and tested as new experimental tools and data become available, before it becomes apparent which hypothesis best fits or explains the data. (Until even better tools and data come along…)

They did their best with the data they had at the time - morphology, anatomy, and an as-yet very incomplete picture of the diversity of life on the planet, present and past. Hard to say how much of the surviving 18th-century taxonomy remains by accident or by insight. A lot more of the 18th-century taxonomy has not stood the test of time. But there have been insightful systematists in all periods, Linnaeus included, who could arrive at very solid hypotheses of relatedness based on morphology alone.


Same here. I’m in Brooklyn, and specialize in urban habitat gardening with native plants. I wrote about this on my blog earlier this year:


To support ecological associations, I prioritize NYC-native species; currently, about 75% of my collection are species native to NYC. So the New York Flora Atlas is an essential resource for me, not just for names, but for nativity and locality. For example, here is a checklist of species and infraspecies native to Kings County (aka Brooklyn); some of these may only be historical records now extirpated from the state or region:


I still need to keep track of alternative names and synonyms when sourcing. For example, dwarf prairie willow is one species I’m trying to acquire. It’s one of our smallest lowland (non-alpine) willow species. It would be a valuable addition to my garden both as an early-blooming floral host for emerging bees, and as a plant host for leaf-eaters. NYFA lists it as Salix humilis var. tristis:


Everyone else calls it S. occidentalis; GoBotany, for example:


So, when sourcing new plant species for my garden, I need to look for all names by which it might be listed, and carefully consider my trust in the grower that they have the right species/infraspecies.


I generally do the following:

Follow Kelly Allred’s current edition of Flora Neomexicana III unless I have a reason not to. Outside of New Mexico, use the Flora of North America treatment (if there is one) or whichever recent flora seems to be good (Ackerfield for Colorado, Dorn for Wyoming, Welsh for Utah, good luck with Arizona, etc.).

If different floras give different answers and I care which one is correct, go to the primary literature, type specimens, and herbarium specimen images until I either think I understand what’s going on or reach the conclusion that I’m not going to figure it out.

If the correct name arrived at by the above process isn’t on iNaturalist, either stop putting IDs on that genus, or start IDing to genus and putting the correct name in the comments.

Try to avoid putting mental energy into the question of whether or not aggregators like USDA PLANTS, ITIS, and POWO are using the correct names or what unfathomable process led them into error if not.


Or, just go with the name iNaturalist uses. Let curation sort it out later if necessary.


This is what I do. I am not concerned with whether or not a record is listed with the correct name, I’m concerned with whether or not information has been recorded in a way that it is clear what I and others meant with our ID’s, and information is not lost.

For example I’ve seen some quibbling on iNaturalist and elsewhere about the classification of Cardinal Climber, which is currently classified as Ipomoea × multifida, the same name I use. Some people classify it as Ipomoea ×sloteri, and I’ve even seen Ipomoea sloteri. Furthermore, I’ve seen some authorities that separate these two on the basis of polyploidy. When I look at a plant in the field or in a garden, I can’t do a lab test for polyploidy, so I can’t distinguish these even if they were considered separate taxa, so…the debate is irrelevant to me. If people later want to move or rename my ID, that’s fine.

Where I, in theory, might run into problems is in the cases where a taxon gets split up into multiple taxa that then get assigned to different taxa at the same rank as the original taxon that the ID was for. Examples would be one species split into two or more. People presumably made their original identifications within a certain taxonomic context, and this context no longer exists in the new scheme. They may or may not have enough information to know how to distinguish between the new groups.

I don’t know how iNat handles this, but there is no rigorous way of doing it without information loss. I.e. the only rigorous way would be to move up to a higher taxon because otherwise you might make mis-IDs.

I would assume this would be what iNat would do in this case?

But anyway I am not really worried about any of this. The situations where I have had genuine problems with these disagreements are not on iNaturalist, they’re when I’m researching a plant, such as its range or habitat requirements, and I’m trying to synthesize information from different sources, and I run into the problem that different authorities group things differently. That’s when it’s a royal mess to sort out. Frankly there are a lot of situations where, in the short-term at least, I’ve given up, putting things in a “messy” bin to deal with later.

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