Trying to sort out a situation here with the agaves... would appreciate input from @mcvansoest and anyone else who might be able to help. It has to do with the inclusion of Agave leopoldii as a synonym for Agave parryi on this page.

Parry's Agave (Agave parryi)

I'm wondering if this Agave leopoldii is related to the plant I know as Agave x leopoldii (a hybrid between two kinds of filifera, as the species is currently defined), which is in a different subgenus from parryi (which makes branched inflorescences instead of spicate ones), and thus rather distinct. Agave xleopoldii would actually best be described as A. filifera, in the broad sense, if you had to choose.

The CoL appears to be the basis for the inclusion of leopoldii as a synonym for parryi in the database.

http://www.catalogueoflife.org...

There was a thread back in 2015 where the x leopoldii plant was created, but that entry seems to have been since deleted (in favor of the CoL-approved one?).

The thread "Plant database" in Ask a Question forum

And here are a couple of reputable sources on the identity of the hybrid A. x leopoldii.

https://www.smgrowers.com/prod...
http://plantdelights.com/Catal...

Is there a different Agave leopoldii which was once a species? Otherwise I would like to propose the creation of an entry for Agave xleopoldii. Howard Gentry says the two parents of A. xleopoldii (which he calls A. filifera and A. schidigera) intergrade in nature so this definitely could be a naturally occurring hybrid. It sounds that way in the PDN description which refers to the parent of the version they sell as "a plant Gary [Hammer] had discovered in Mexico".

For the record, I am also not happy with the way Agave parryi truncata continues to be included as a synonym for Agave parryi subsp. parryi.

Artichoke Agave (Agave parryi var. truncata)

The type for A. parryi (1874) comes from northern AZ, and truncata comes from the other end of the species' range (its southeastern tip in Mexico, near the Zacatecas-Durango border). There may be some taxonomical reason why Agave parryi truncata is not its own subspecies instead of a variety (this I would defer to experts) but it is geographically and morphologically distinct from the type, as well as the other 2 varieties described in Gentry's landmark book whose type is from AZ (that is to say, all but truncata). In my non-expert opinion it seems like Agave parryi truncata should be a variety of parryi distinct from subsp. parryi.

To see the subspecies and varieties as they currently exist in the database, look here.

https://garden.org/search/inde...

I offer my non-expert opinion not having seen the original publications where the varieties and subspecies were separated. It just seems like the most distinctly different and geographically separate plant in the species would not be the one to use for this name. Experts please correct if I have misunderstood.

The most recent semi-inclusive book on agaves (Greg Starr) describes Agave parryi var. parryi (would this be equivalent to the subspecies as it has been defined above?) as a resident of AZ, NM, and northwestern Mexico and separates Agave parryi var. truncata (which is different in various ways including its form and origin). I would propose the creation of a new, separate entry for Agave parryi var. truncata, where most of the pictures from the current location would be moved, and the removal of truncata as a synonym for the other plant.

Insight on either matter?

Hi, Baja. As you know, I am not an expert on agaves, but I can take some guesses at the reasons for the discrepancies between our database and your findings.

Agave x leopoldii is not listed in any of the four taxonomic databases I consulted (ITIS, GRIN, The Plant List, and the Catalogue of Life). This usually means that the plant is not a natural hybrid and does not occur spontaneously in the wild. Our solution to these cases in the past has been the creation of an entry treating Leopoldii as a cultivar name and listing Agave x leopoldii as an also-sold-as name in that entry.

As for Agave parryi var. truncata, which also is not listed by ITIS and GRIN, but is listed as a synonym in the CoL and The Plant List, I would have to assume that it was reclassified as a synonym on the basis of DNA testing. In these cases, DNA similarities trump geographic and morphological differences. (The Plant List, in its usual misleading fashion, says that A. parryi var. truncata is a synonym for A. parryi, citing WCSP as its source, but WCSP calls it a synonym for A. parryi subsp. parryi.)

Hi Baja and zuzu,

I had noted the entry of leopoldii as a synonym for A. parryi and wondered about that. I also found it listed in the CoL, so stopped worrying about it given the strict adherence here to the CoL. However, I interact with a large number of Agave enthusiasts and no one ever calls Agave parryi, Agave leopoldii, so I am strongly convinced that this must be a mistake in the CoL, or just a listing of a very old historical name that does not have precedence. Given that there is now an Agave xleopoldii in the trade, that is most definitely not Agave parryi maintaining this synonym is highly confusing.
What it leads to is that there is at least one image in the A. parryi image catalog that is actually Agave xleopoldii (the last time I checked), everyone who looks at that can see it is different, but because Agave xleopoldii does not have separate entry in the database it is hard to fault the person posting the picture for adding it to the Agave parryi entry, though it is wrong, but it comes up as a synomym.

Given that Howard S. Gentry describes it in his seminal work on Agaves, I believe like Baja that Agave xleopoldii is a natural hybrid, and I am frankly baffled that the CoL has not listed this plant given that if there was one expert on Agaves in the last 100 years it was H.S. Gentry. It again points to the fact that while these plant lists do their best to be as complete and correct as possible they all have mistakes in them or have omitted plants that are treated as valid species by the community that studies and or propagates them.

However, I also realize that my opinion counts for very little and that you have to choose to follow something to try and create some order in the database, and therefore I will not go on another rant as to the inconsistency of these plant lists, so am going to accept that weirdness and confusion will be part of some of the database entries here.
My suggestion for the solution of the Agave xleopoldii is to create an entry as Agave hybrid xleopoldii and list its parentage as given by Gentry. Then I would either remove the synonym under Agave parryi so that people who are looking to post a picture of their Agave xleopoldii do not end up in the parryi database entry or post a clear note pointing people to the right Agave xleopoldii entry. This is as close to a perfect solution as can be reached here given the constraints put on us by the CoL. Given that the Database contains countless Echinopsis hybrid 'xxxx xxxx' listings, that really do not merit separate species status anymore or less than Agave xleopoldii (well if it is indeed a natural hybrid one could argue Agave xleopoldii merits a separate listing more than those Echinopsis hybrids) that would seem a decent solution.

I have tried very hard to find who at the CoL team is responsible for maintaining the records of Agaves, Yuccas, etc. and I have not managed to find a specific name as to who the expert is, so I am not sure there is such a person on the CoL team. Very little actual genetic research has been done on the Agaves of the SW US (a lot of it is currently in progress at the Desert Botanical Garden as they study the use of Agaves by the native people), where they are not an important crop like many of the Agave species of Mexico. Interestingly, the one study that I have been able to find in my very quick and probably incomplete search did only pertain to Agave parryi ssp. parryi and Agave parryi var. huachucensis and mostly with focus on wild versus pre-historically cultivated remnant populations. The conclusion was that while that are definitely both morphological and genetic differences between ssp. parryi and var. huachucensis it was unclear whether or not it merited species/ssp./var. distinction. This appears to jive with the experience of several acquaintances of mine who have done a lot of fieldwork to document the occurrence and distribution of the Agaves of Arizona. In their opinion A. parryi ssp. parryi, ssp. couesii, and var. huachucensis represent the end members of what would appear to be one widely distributed highly variable species where local/regional conditions have strongly influenced the general appearance of the plants and one can see gradual morphological changes when moving in the areas between the main habitat of one end member to that of another end member.

For parryi ssp. neomexicana I think there is work ongoing that is going to show that that does merit species status - Agave neomexicana. For var. truncata it is less clear. Yes it is geographically quite removed and it is morphologically distinct, but again there are nearby Agave parryi populations that would allow one to argue that again we are looking at end members of the same species. I do not know if genetic work has been done. I will note though that the Huntington Botanical Garden has introduced a specific clone of that plant in its plant introduction program under the name Agave parryi var. truncata 'Huntington' so at least one renowned botanical institution considers it as a valid variety of Agave parryi and not a synonym.

When we have these discussions, I always want to ask what is more important that everything follows the CoL precisely or that we make sure that where necessary the database also reflects what is going on the plant trade and what are people most likely to find on their plant labels or on other websites dealing with these plants. This brings to mind the recent discussion on the inflorescence size of complex composite flowers where I feel that the database team decided to go with what was practical rather than scientifically correct and in the process made it extremely difficult to (correctly) describe the large inflorescences of among other plants Agaves. In my opinion both the synonym of A parryi/ Agave xleopoldii and Agave parryi var. truncata are instances where common sense might trump perceived scientific correctness, definitely in the case of Agave xleopoldii, and given how widely distributed Agave parryi var. truncata is in horticulture and the plant trades in my opinion also for Agave parryi var. truncata.

Anyway, my several cents worth.

Thank you Zuzu and Thijs.

This is the same database that has Agave ferdinandi-regis listed as a synonym of Agave victoriae-reginae subsp. victoriae-reginae instead of Agave nickelsiae (its current name; I suspect the other was never even a synonym, it certainly makes no logical sense).

http://www.catalogueoflife.org...

The story in detail here.

https://www.smgrowers.com/prod...

In my mind (not an expert but having studied the experts) that alone suggests the agaves are perhaps not well supervised, and advocates for informed disagreement with the designation of Agave parryi truncata as a synonym for something it is not (to my knowledge), and according to books on the subject has not been (instead it has been its own variety, Agave parryi var truncata Gentry, since at least 1982). Both of the two serious agave books published since Gentry's landmark work have confirmed this variety.

The error above also argues for disagreement with the exclusion of a naturally occurring agave hybrid from the database based on its designation as a synonym for a completely different plant. (Different to what agave growers understand when they hear Agave leopoldii, anyway.)

I am not a big fan of taxonomic authority when it proves itself mistaken.

First, I'll address this part of your response, Thijs: "When we have these discussions, I always want to ask what is more important that everything follows the CoL precisely or that we make sure that where necessary the database also reflects what is going on the plant trade and what are people most likely to find on their plant labels or on other websites dealing with these plants."

It is much more important to follow a comprehensive and constantly updated taxonomic database precisely than to bother with what's happening in the plant trade. Many plant sellers do not keep up with taxonomic changes in the names and, what's worse, may invent names of their own for merchandising purposes.

Plant labels are notoriously deceptive. I could go out today and buy Sutera cordata plants from four or five different nurseries, for example, and all of them would carry plant labels defining the plants as Bacopa cordata. It would be absolutely wrong to list these plants as Bacopa in our database because there is a genus Bacopa, but it consists only of water plants (Water Hyssop).

We do want to provide an entry for a plant that's grown and sold extensively, however, so I will create an entry for Agave 'Leopoldii,' including Agave x leopoldii as an also-sold-as name in that entry, and I will delete the name from the entry where it's named as a synonym because only one database (the CoL) contains that information. I don't doubt that a spontaneous cross may have occurred, but until a botanist describes the plant officially, it will not be included in any taxonomic database as an accepted name. If the name ever is described officially and the spontaneous cross is accepted as fact, Agave x leopoldii will be listed in taxonomic databases, and our entry can be edited to show a hybrid taxon rather than a cultivar name.

After I have created the entry, I would appreciate your assistance in moving any misplaced photos to the new entry.

I don't want to make any changes in the A. parryi var. truncata's present status as a synonym because it is either ignored or listed as a synonym in all of the taxonomic databases. No taxonomic database lists it as an accepted name. I respect the Huntington Botanical Garden as an institution, but it is not a taxonomic authority.

All the recent published literature on agaves lists Agave parryi truncata as a variety. I am referring to the Gentry, Irish, and Starr books on the subject. I would consider them the authorities on the subject of agaves. Without some specific recent reason for the strange synonym (like the DNA test you have imagined), I would say the databases are wrong and the agave experts (Howard Gentry and Greg Starr in particular) are right. In my mind those are the real authorities on agaves. Gentry in particular, for the reasons he gave in his book, laid out a clear case for truncata as an outlier.

Following the selected taxonomic authorities in lockstep means that their errors will be propagated here, even when there is clear and present evidence to the contrary in the published record, and in real life.

When this clear and present evidence is presented to taxonomic authorities, they will amend their databases accordingly. What has kept Gentry from communicating his findings to the taxonomists? How recent is the recently published literature? The latest taxonomic scrutiny of the Agave genus is dated September 2014. There are experts in every field who disagree with established systems of classification. How can we judge their relevance? I appreciate these discussions, and they really should be added to the appropriate species entries as comments, but I think it's important for our database to be governed by a uniform set of taxonomic rules, not a different set for each genus.

Relying on those databases guarantees errors. Your assumption about the taxonomic authorities is based on an unreasonable amount of trust. I don't really know where to begin with this one. I don't want to get into why Howard Gentry became the authority on agaves, or what these other books did to confirm his observations. It's clearly a waste of time. It doesn't matter what I say, or what exists in the published literature, or what the experts on agaves have said for decades. The echo chamber that is the online database will continue to propagate built-in errors until human beings with actual knowledge interrupt it.

I'm sorry to be so blunt but this is a well documented subject and the literature goes back decades. The most recent book I mentioned was published in 2012. Barring a revision since then based on some big discovery from DNA research (and I'm not seeing that on Google scholar), the databases are wrong, and our database here is propagating their errors.

I could of course be wrong myself, and I fully admit I've been wrong before. But this isn't about me. It's about the published history of the species, at least since Gentry's landmark work on the subject. And the probable error that will be propagated if you do not make use of the human experience here, and our familiarity with that published record. You could judge its relevance by considering the facts as they are presented.

If you are really asking why Howard Gentry did not communicate his findings, you have not seen this published record. Gentry died in 1993, but he left a glorious written and illustrated record of his findings, in incredible botanical detail and with a pretty overwhelming grasp of the distinctions involved in taxonomy (not that I'm an expert, but history has upheld most of his distinctions, to the extent he thought they mattered). But really I don't see the point of discussing it any further because the online databases will always trump it, and all the other publications on paper. So much for actual book knowledge.

Why don't we take a short break from this, as I suspect everyone's getting a bit frustrated with it.

Baja, please consider the possibility that Zuzu doesn't know much about agaves or the published experts you mention and that her questions were simply to improve her understanding.

Zuzu, whilst I'd like to think you're right that the taxonomic authorities would amend their databases when presented with evidence, I don't think that's always the case. I think we need to allow for the possibility that they can be wrong.

I don't think there's much to be gained from further discussion, frankly. The decision has been made and I will abide by it. Thank you for allowing me to voice my disagreement. I am most grateful for the rapid response and all you do to keep the plant database working so smoothly.

I have added the following text to my comment on the problematic Agave parryi page and will not bring up the subject again on the forums.

Artichoke Agave (Agave parryi var. truncata)

==

ALMOST ALL THE PICTURES ON THIS PAGE ARE OF AGAVE PARRYI VAR. TRUNCATA which is not and has never been (to my knowledge) a synonym for A. parryi parryi. The administrators of this database would rather follow online taxonomy databases than the published literature on this plant.