Do backcrossed hybrids get marked as the hybrid or the main species in it's DNA?

I have an observation of what appears to be an oracle oak crossed back with an interior live oak. It has leaves that appear to be that of an interior live but they are much too thin and slightly lobed. Now, because it is backcrossed (and only appears to be an F1 backcross, or 75% wislizeni & 25% kelloggii) would it be labeled as Q. x morehus or wislizeni? And if wislizeni would it still be able to be called Q. wislizeni var. wislizeni or is possible that it’s var. frutescens and it’s only a tree due too the kelloggii DNA? But if x morehus at what ratio should it no longer be labeled as a hybrid? Sorry for so many questions, I’m very curious lol


I think you’re out in uncharted territory here, and maybe more importantly, unchartable territory (at least from the perspective of binomials on iNat).

For starters, there’s not an obvious direct correlation between the amount of DNA from a parent and the amount of influence that DNA has on the phenotype, or the chemotype, or the ecology, etc… So it’s probably difficult to the point of being impossibe to precisely define what is meant by “main species in its DNA”.

I’d argue for either using the genus level ID, or an established hybrid if the parents are known, and putting any additional information in the Notes/comments/tags. If you wanted to, you could consider using a purpose-built Field.


Given that hybrids don’t breed true, isn’t it equally possible that it is just an F2 oracle oak that favors one grandparent in appearance? I do not know this taxa at all.


The oaks here tend to stick to generally the same phenotype when hybridized, there’s some variability but from what I’ve seen at least there’s not enough to where this is possible

Actually with the oaks up here the phenotype tends to stay the same for hybrids so it’s relatively easy to tell the parent species and get a general idea of the DNA percentages

Taxonomically, a plant is a hybrid or it isn’t. If this is indeed an F1 backcross, then the ‘correct’ label would be Q. x morehus, or maybe Q. morehus x Q. wislizeni.

I don’t know this group at all, but I’m skeptical you could determine with certainty that a given plant is an F1 backcross, as opposed to a later generation hybrid, based on morphology alone. Maybe you can, but regardless this is beyond the scope of iNaturalist, so I think label it what you think best and add notes (as you have).


The phenology is weirdly generalized for our oak hybrids, you can get a good gauge but can’t be certain without DNA

The International Code of Nomenclature is very clear about this: H.4.1. When all the parent taxa can be postulated or are known, a nothotaxon is circumscribed so as to include all individuals recognizably derived from the crossing of representatives of the stated parent taxa (i.e. not only the F1 but subsequent filial generations and also back-crosses and combinations of these).


The real world isn’t that simple… Should practically all modern Eurasian-descended humans homo sapiens x neanderthalensis because it can be postulated or known that ~2-3% of their DNA is introgression from neanderthals. Purity is not a real thing that nature cares about.


The question was what taxonomic name should be attached to a particular plant with hybrid origin. The answer to that is simple, and described very clearly in the Botanical Code, as @marcoschmidtffm points out.

Of course the real world is more complex. We just don’t have formal taxonomic names to describe it more precisely.

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I agree that the rule you quoted says that. What I was disputing was whether the rule as written is practically workable, ecologically sensible, or philosophically defensible.


Even the concepts of species don’t check those boxes :slightly_frowning_face:


lol! Is a screwdriver “philosophically defensible” :)

The point of botanical nomenclature is to provide a single, consistent, universal naming scheme. It is a tool for communication. To the extent possible, it is meant to reflect biological reality, but it regularly falls short. That’s because clarity of communication is prioritized over biological reality.

Take a look:

You’ll find lots of legalistic phrasing to explain the requirements for a valid species name. You won’t find any reference to what a valid species is. It’s the system we use for defining labels, not the things we attach them to.

I think people get hung up on the idea that a scientific name encapsulates the entire biological reality of a species, that it is a single, complete answer. And that being the case, if it doesn’t jive with something about the biology of a species, it is flawed.

That’s incorrect. A scientific name is a convenient label for discussing the organisms it applies to. In this case, the name Quercus x morehus refers to the hybrid progeny of Q. wislizeni and Q. kelloggii, including first and later generations and backcrosses, collectively. That doesn’t mean there aren’t important distinctions between F1 hybrids and backcrosses, it just means they aren’t distinguished by the botanical code.

It’s certainly practically workable. But only because it doesn’t try to be ecologically sensible, or account for all the different contexts in which we concern ourselves with biological diversity.


Sure! Why wouldn’t using a screwdriver as a tool be philosophically defensible? It does not cause extinctions. But, the ‘any % hybrid is still a hybrid’ philosophy is going to cause the extinction of the Red Wolf.

For an example, lets say 10% of vertebrate speciation events, completely at random, are hybrid speciation. Lets estimate that a vertebrate species lasts on average 1 million years, and vertebrates have been around for about 450 million years, so vertebrates would have on average 450 distinct species as ancestors vertebrate family tree. Each speciation event has a 90% chance of not being hybrid speciation, so the probability of a given species having zero hybrid speciation events in its family tree should be about (0.9)^450~10^-21, or about one in a billion trillion. Now say there are about 100,000 vertebrates, so there should be about a one in ten quadrillion chance that there exists a single living vertebrate species with no hybrid speciation events in its family tree. Of course, the first vertebrate also wasn’t the first life form, so if you go back further the odds would get even worse.

Similar logic should apply elsewhere in the tree of life, so, logically, no living species is worth conserving because all were probably hybrids at some point. Of course, the rule says we have to be able to “postulate or know” the ancestors, so maybe the solution to this dilemma is that we should stop all taxonomy and molecular systematics, so that we don’t accidentally develop any new postulates. Problem solved!

I think the problem is that “Quercus × morehus” stops being a convenient label in systems with widespread introgression if it really has to be applied (as per the code!) to every single plant with so much as a hint of mixed ancestry. This is especially true once those hints are only detectable on the molecular level. You end up being forced to call nearly everything the hybrid, letter-of-the-law.

I think in practice people use system-specific heuristics for where they “draw the line”, ignoring the code because it is not useful. @leytonjfreid - I know this is an annoying non-answer. :)


given the - must keep the first name, even when it is wrong
Words are easier for us to say (and remember) than a barcode or a QR code or the random string POWO uses.

First, we’re talking about the botanical code, which doesn’t apply to animals. They have their own code, and I don’t know what the details of that are.

Second, the botanical code doesn’t say anything about what should or shouldn’t be conserved. The Canadian Species at Risk Act, and the US Endangered Species Act include the concept of “designatable unit” or “evolutionarily significant unit”. This allows us to identify and protect groups of organisms for which there is no taxonomic label. Usually isolated regional populations. This means we can protect a group of organisms based on ecological, evolutionary or biogeographic grounds, regardless of their taxonomic status.

Third, the scientific name of an organism doesn’t prevent you from also using any other descriptive information you want when you talk about it. F1, F2, backcross etc still exist, you’re still able to use them. You can even use them to make a case for recognizing an evolutionary significant unit, if you like.

All of which is a long way from the question what taxonomic name applies to a hybrid.

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It allows for the possibility, is it used? This article is from 2021:

“However, despite different outcomes, most conservation laws do not offer any possibility of hybrids being protected since they are perceived as a threat to the survival of pure species. […] the reasons for not conserving hybrids seem subjective rather than empirically supported. In a genomic era where hybridization is being more frequently detected, the debate involving the conservation of hybrids should be re-opened.”

Welcome to my world, which is even worse- recombinant hybrids. Some of these DO have an iNat “species” that being species1 x species2. Though they are far and few between on iNat. The scientific community has generally recognized some of these recombinant hybrids as species unto themselves, and that’s reflected in iNat as species3. For a simple hybrid though (to be clear) it would never get its own species-level designation, so one can pick one of the parent species and put a note on the observation that it’s a hybrid (that’s what we’ve been doing.)

I think this is the real problem that you are getting at - and rightfully so. And, as has already been said, it’s not something that the Code of Nomenclature for Algae, Fungi, and Plants attempts to address, its sole concern being to adjudicate the one correct name for “each taxonomic group with a particular circumscription, position, and rank.” (Principle IV). Instead it is something that needs to be reconsidered by conservation agencies, organizations, and scientists. That is what the article is advocating, not changing how we label hybrids.

For the labeling question originally raised in this topic, I agree with the other responders:

  • If you believe the plant in hand is a hybrid, use the correct hybrid name or formula for that plant.

  • If you believe the plant in hand is a member of a named species, then use that name instead.

Note that, as with the term “species,” the term “hybrid” is not defined by the Code beyond being a particular rank with particular naming rules. It is up to the user to determine by other evidence whether they have a species or a hybrid.

In botanical circles at least, general practice is to use hybrid names or formulae only for plants produced by active ongoing hybridization processes. Plants descended from hybrid products, but which have since become an independent self-replicating lineage, are generally given species names instead of hybrid names.