In Plant Taxonomy, is Order the highest Formal Rank?

Nature Talk
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Is every rank above Order simply known as a Clade? Or are there formal taxonomic ranks above Order in Plant Taxonomy? I’ve heard Suborder, Superorder, Class, Subclass, Division, Subdivison being used but I can’t figure out which rank they refer to.

Is the Clade Superrosids a Class or Superorder? What about Rosids, is it a Superorder too? Is Eduicots a Class or Subclass? What rank is Angiosperms? What rank is Spermaphyte (Does it even have a rank).

For example, does the way I layed these out make sense?

Pawpaw

Kingdom : Plantae
Clade : Tracheophytes
Clade : Spermatophyte
Clade : Angiosperms
Clade : Magnoliids
Order : Magnoliales
Family : Annonaceae
Subfamily : Annonoideae
Tribe : Annoneae
Genus : Asimina
Species : Asimina triloba

Corn

Kingdom : Plantae
Clade : Tracheophytes
Clade : Spermatophyte
Clade : Angiosperms
Clade : Monocots
Clade : Commelinids
Order : Poales
Family : Poaceae
Subfamily : Panicoideae
Supertribe : Andropogonodae
Tribe : Andropogoneae
Subtribe : Tripsacinae
Genus : Zea
Species : Zea mays

Lambsquaters

Kingdom : Plantae
Clade : Tracheophytes
Clade : Spermatophyte
Clade : Angiosperms
Clade : Eudicots
Order : Caryophyllales
Suborder : Caryophyllineae
Family : Amaranthaceae
Subfamily : Chenopodioideae
Tribe : Atripliceae
Genus : Chenopodium
Species : Chenopodium album

Oregano

Kingdom : Plantae
Clade : Tracheophytes
Clade : Spermatophyte
Clade : Angiosperms
Clade : Eudicots
Clade : Superasterids
Clade : Lamiids
Order : Lamiales
Family : Lamiaceae
Subfamily : Nepetoideae
Tribe : Mentheae
Subtribe : Menthinae
Clade/Group : Micromeria
Genus : Origanum
Species : Origanum vulgare

Tomato

Kingdom : Plantae
Clade : Tracheophytes
Clade : Spermatophyte
Clade : Angiosperms
Clade : Eudicots
Clade : Superasterids
Clade : Lamiids
Order : Solanales
Family : Solanaceae
Subfamily : Solanoideae
Tribe : Solaneae
Genus : Solanum
Subgenus : Solanum
Supersection/Clade : Petota
Section : Lycopersicon
Subsection : ?
Species : Solanum lycopersicum

Rose

Kingdom : Plantae
Clade : Tracheophytes
Clade : Spermatophyte
Clade : Angiosperms
Clade : Eudicots
Clade : Superrosids
Clade : Fabids
Order : Rosales
Family : Rosaceae
Subfamily : Rosoideae
Tribe : Roseae
Genus : Rosa
Species : Rosa rugosa

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Phylum and Class.

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Is that for Animals or for Plants?

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In which system? There are several major ones. APG, Cronquist, Takhtajan…

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All binomial nomenclature (and the taxonomy) generally follows the same rules.

Example with Cephalotus:

  • Kingdom Plantae
    • Phylum Tracheophyta
      • Subphylum Angiospermae
        • Class Magnoliopsida
          • Order Oxalidales
            • Family Cephalotaceae
              • Genus Cephalotus
                • Cephalotus follicularis
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See also the taxonomy tab of https://inaturalist.ala.org.au/taxa/83653-Rosa-rugosa in relation to your rose example.

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It seems to me that a lot of the questions you are asking might be answered more effectively by consulting a botany textbook. Curiosity is good, but it is not really the responsibility of forum users to provide detailed lessons in biology, or to do your research for you.

I mention this because I feel like you have a tendency to grab onto a fact or an idea and assign great significance to it without really understanding the conceptual framework that underlies it. In this case – taxonomy is simply a method for trying to represent biological relationships. There is no inherent meaning in formal ranks; there is often debate about how what we know about these relationships should be mapped onto the system kingdom-phylum-class-order-family-genus-species. So I don’t see how it is particularly useful to ask “what is the highest formal rank for plants?” because in a sense this is arbitrary.

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Basically, there are multiple ways how the system can be organized. The traditional systems do use the higher categories with special names, the new APG does not. See their wikipedia pages

https://en.wikipedia.org/wiki/Takhtajan_system
https://en.wikipedia.org/wiki/Cronquist_system
https://en.wikipedia.org/wiki/Angiosperm_Phylogeny_Group#APG_IV_(2016)

There are other systems also listed at the bottom of those pages.

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In plant taxonomy, the highest formal rank is Kingdom (Plantae), though it’s worth mentioning that opinions differ as to what are plants in the first place.

The taxonomic classifications most of you are mentioning are angiosperm classifications, and do not include all plants.

It’s also probably worth mentioning that clades are not taxonomic ranks. They are groupings of related organisms that have, as yet, not been formally described as a taxon.

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Based on our earlier conversation on this forum, I think you are probably looking for a clarification on why the Linnaean ranks are sometimes all used, and sometimes not, based on the actual biology. The explanation is partly biological, but has a lot more to do with human language and history.

Linnaeus himself was a botanist, and botany historically embraced all his ranks, and gradually added many more as the many branchings of the tree became clear. Over time, however, as evolutionary and phylogenetic thinking became predominant, it became clear to most botanists that the ranks have no inherent meaning. For example, it means nothing to compare a family of mosses to a family of grasses in species number. The two families aren’t the same age, they aren’t the same genetic diversity, they aren’t the same anything except taxonomic rank.
After decades of arguments about whether a particular group was a super-family or a sub-order, with no substantive definition of either term, most botanists eventually agreed to just call a clade a clade, and that is reflected in the Angiosperm Phylogeny Group’s practice of simply not using many of Linnaeus’s ranks.
Current taxonomists are mostly calculating big phylogenetic trees with very many branchings. The same data that are used to calculate who is most closely related to whom are also used (sometimes supplemented with fossil data) to calculate how long in the past each branching took place. So rather than saying, “these two Angiosperms are related at the Order level,” they can say, “these two Angiosperms have a most-recent common ancestor 89.3 (±7.2) million years ago. We are going to call the clade that includes both of them the Porcupiales, but assign no rank.” (Note that this example is made up.)
However, after generations of teaching KPCOFGS, publishing textbooks used on that system, etc. and the general diversity of opinion and practice that global science has (and should have), not everyone is onboard with ditching KPCOFGS, and many sources are likely to keep using it indefinitely.

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Well, all the examples mentioned in the OP are Angiosperms.

Also, I never claimed that clades were any kind of rank.

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I didn’t mean to imply that you did, I apologise if this is how it came across. I have heard students and other non-taxonomists get confused and ask what sort of rank a clade is, so I wanted to bring this up.

Some clades eventually get described as a formal taxon and some never do. In my opinion the main part of the problem is that plants and animals don’t read taxonomy textbooks, and unfortunately don’t realise that we would like them to fit themselves into the system we’ve created for them.

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:sweat_smile: oops… hahhaa I thought there was just 1 system.
I’m still confused which rank the clades Superrosids, Malvids are?

So Taxonomy is just the way we organize life? Taxons are simply the boxes we grouped organism into? But not every taxon in the same rank is equally weighted, as not every taxon box we circumcisied is neat equally proportioned taxon boxes. For example the Taxon Cucurbita pepo boxes in more diversity than what’s captured by the taxon Rubus allegheniensis (As Cucurbita pepo contains 2 subspecies & is highly polymorphic vs Rubus allegheniensis is part of a species complex).
Is this why there is no inherent meaning in formal ranks?

I see! That’s why all higher ranks above order are simply known as clades, that’s what the APG system uses. Does this make all the other types outdated? or is APG system itself outdated due to recent phylogeny?

Ahh… that makes so much sense, the Phylogeny is faster than the Taxonomy.
Now that begs the question, what is taking taxonomy so long to catch up with the Phylogeny?

Ah… now that makes a lot of sense. It’s because the Ranks above Order are not equally weighting amongst complety other plant families. For Example Monocots only have 1 major clade grouping above Order called Commelinids & Magnoliids have no “Superorder” grouping, all orders are simply placed under Magnoliids.

Are these at least known as Major Clades? Like Superastrids, Malvids, Eudicots, Rosids, Commelinids, ect?

I see. But those who use & ditch the system at least still use Species, Genus, Family, & Order? It’s after Order where the disagreement happend right?

I see. Are Subgenus, Section, Subfamily, Series, Lineage, Variety, Cultivar, Subspecies all formal taxons too? or is cultivar not a formal taxon & will never be?

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Even that much is not agreed upon. I’ve known taxonomists who prefer not to use any Linnaean rank except species, and even species only because of linguistic rather than biological reasons.The most specific definition of genus I’ve ever heard is, “A monophyletic group of species less diverse than a subfamily and more diverse than a subgenus.” All ranks except species are defined only with reference to ranks, not biology. As we’ve discussed previously, there is no, and will be no, widely agreed definition of species.
Put another way, if we didn’t already have ranks, we would certainly not invent them at this point, and if someone invented them from scratch, there is no reason to think they would bear any resemblance to the ones we have. But because they are a longstanding part of our language, most people will use at least some of them some of the time.

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Again, a basic biology textbook or even a bit of internet research would clarify some of these questions, e.g. https://en.wikipedia.org/wiki/Taxonomic_rank

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What system do they use instead? Just simply clades for everything else?

Ah that makes sense. But species is also fuzzy :sweat_smile: :joy:

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That’s right. Clades for everything, and fuzzy species.

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