Can we add "subspecies" hybrids?

I’m not talking about intergrades (subspecies #1 x subspecies #2 breeding), I’m talking about different subspecies, but parents can be identified to subspecies. I am going to create, since there are numerous iNat observations that remain unidentified, the Gibraltar Buzzard which is a “self-sustanting hybrid population between the Western Common Buzzard Buteo buteo ssp. buteo and Atlas Long-legged Buzzard Buteo rufinus cirtensis in southern Spain and northern Morocco”. This is a distinctly different taxa from the very rare combo of Common Buzzard (ssp. buteo or vulpinus depending on where) and Northern Long-legged Buzzard (nominate subspecies).

I don’t think they exist, taxonomically speaking. The definition of a hybrid, at least according to the ICN, is the offspring of two separate species.


I don’t necessarily agree because that statement implies that subspecies don’t exist. Yes, a hybrid is the offspring of two separate species, but those species can have subspecies and that means if a species with subspecies hybridizes, then the hybrid has a subspecies parent. Here’s a good example:

We know that the Yellow-rumped Warbler (Setophaga coronta) hybridizes with a number of other warbler species, and most of us know that 40 years back, the Yellow-rumped Warbler used to be two species (Audubon’s and Myrtle Warbler). These two populations are so distinct, that when you identify a hybrid like Townsend’s x Yellow-rumped Warbler, you can obviously tell the YRWA parent is an Audubon’s Warbler. Or that the parent of Yellow-throated x Yellow-rumped is a Myrtle Warbler. I don’t know think a Townsend’s x Myrtle Warbler has been reported, given they have no overlapping breeding range, but I’m sure if we do have a rare case scenario, it can identifiable.

Another example is Herring x Iceland Gull. The latter species has two-three “species-like” subspecies, all distinctly different from the darker-backed, black primaried Thayer’s in the West, to the almost complete white glaucoides Iceland in Greenland. But guess what, a Herring x Thayer’s hybrid (if field identifiable at all) is going to look drastically different from a Herring x Iceland hybrid, even though Thayer’s and Iceland are the same species.

One last one for the road, look at any White-throated Sparrow x Dark-eyed Junco photos. The junco parent is clearly a Slate-colored Junco because if the hybrid’s parent was an Oregon Junco, the sides would likely be brown or orangey instead of the classic slate gray.

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I’m not saying that infraspecies cannot form crosses, only that taxonomically they are not a hybrid.

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I’ve seen and used myself the hybrid taxon Trachemys gaigeae x T. scripta elegans. The former (Big Bend Slider) is currently considered monotypic and the hybrid events involve one subspecies of the Pond Slider which has been introduced widely outside of its range. To our knowledge only that subspecies (Red-eared Slider) is involved in these hybridizations. So there’s precedent for such hybrid designations involving a particular subspecies.

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Do you mean nomenclaturally defined according to ICN? The code doesn’t directly deal with taxonomic opinion or taxonomic definitions.

I can’t find the entry in ICN that defines a hybrid. What chapter/article? Some of the examples in Chapter H on naming hybrids quote infra-specific hybrid formulae so it doesn’t seem to exclude their use.
Article H.2 (

I’m not familiar with ICZN but it seems to say little about hybrids.

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Some of the ICNafp rules apply only to hybrid taxa of particular ranks, or address what rank should be assigned to hybrid taxa, but the ICNafp is otherwise agnostic on the topic. E.g., from H.3.1: “Hybrids between representatives of two or more taxa may receive a name.” There is no limitation that only hybrids between taxa at the rank of species or above may receive a name, here or elsewhere. As far as the ICNafp is concerned, the relevant question is whether there is a published, legitimate name that applies to a given hybrid (in which case either that name or a hybrid formula can be used) or not (in which case only a hybrid formula can be used).

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For algae, fungi, and plants governed by the ICNafp, assuming that there is no published name for either one, we would refer to the two hybrids you mention by different hybrid formulae:
Buteo buteo subsp. buteo × Buteo rufinus subsp. cirtensis
Buteo buteo × Buteo rufinus subsp. rufinus

Under the ICNafp, hybrid formulae are composed of names governed by the code, but are not themselves names governed by the code. “Buteo buteo subsp. buteo” is a name and “Buteo rufinus subsp. cirtensis” is a name; “Buteo buteo subsp. buteo × Buteo rufinus subsp. cirtensis” is not a name. This means, among other things, that a hybrid formula does not need to be published or officially created in any fashion, so long as the component names are published and legitimate.

I’m not sure how the ICZN deals with this issue—near as I can tell, it doesn’t address it one way or the other.

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I take that back. The ICZN’s search bar just doesn’t work.

“1.3 Excluded from the provisions of the Code are names proposed
1.3.3. for hybrid specimens as such (for taxa which are of hybrid origin see [Article 17.2]”

So, the ICZN is explicitly agnostic. If it really is a taxon of hybrid origin, we could give it an ICZN name. If it isn’t, the ICZN doesn’t care what we call it.

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Like your namesake, genus Aspidoscelis — many hybrid lineages have an actual binomial if they are perpetuating populations. The occasional weird individual of hybrid origin that is apparently not being perpetuated is described by the hybrid formula Aspidoscelis something x A. something_else.

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I was thinking animalologists used hybrid formulae, too. However, my experience with the nomenclature of hybrid animals is pretty much limited to Aspidoscelis, and it’s not a topic I’ve been much engaged with over the past decade or so. Odd that the ICZN doesn’t mention hybrid formulae, though, at least not that I can find.

Back to the issue at hand, can we or can we not add a trinomial hybrid to iNat?

The Desired Result

  • Gibraltar Buzzard (Buteo buteo buteo x rufinus cirtensis) – Common hybrid taxa in Spain
  • Common x Long-legged Buzzard (Buteo buteo x rufinus rufinus) – Very rare hybrid involving a different species-like taxa.

This may be relevant:

I can’t think of any reason not to add those as iNaturalist taxa, assuming your characterization of the situation is accurate (I know absolutely nothing about birds).

Of course, the curator guide does advise against creating iNaturalist taxa for hybrids. If the relevant parts of the bird community find these to be identifiable things that it is useful to distinguish, though, personally I would just do it.

Just use “×” rather than “x”!

I too am very much in favor of introducing new ranks.

As a botany curator I am missing the nothossp. and series ranks that are still missing on iNaturalist.

There are a lot of different nothossp. and it is not possible to create a correct name for them right now. Thats why we have to create incorrect taxonnames like Orchis × loreziana ssp. kisslingii, the correct name is Orchis × loreziana nothossp. kisslingii in this case.

The rank of series is also important, especially to further split big and complicated genera like Senecio, Echinocereus etc. into species groups.

There’s an easier solution. “Orchis × loreziana nothosubsp. kisslingii” and “Orchis loreziana subsp. kisslingii” are nomenclaturally equivalent. We can stick multiplication signs and "notho-"s in as a way of saying “this is a hybrid”, but that doesn’t necessarily mean we should.

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That’s an infrahybrid or intergrade, a crossbreeding between two subspecies of one species.

I’m talking about a subspecific hybrid between two species. The reason why I think it’s a controversial issue is because you can do it (Domestic Swan x Graylag Geese) but what if only one of the species is monotypic (ex. Townsend’s Warbler)?

Though this is a common terminological distinction (at least in animals—this usage of “intergrade” is rare, in my experience, among botanists), I’m not aware of a reason why the two cases should be treated differently either in terms of the nomenclatural codes or on iNaturalist.

It may be wise for iNaturalist to have consistent formatting rules, though. Omitting the genus and specific eptithet (e.g., Setophaga coronata coronata × auduboni) implies that the genus and specific epithet are identical for both parental taxa. This kind of omission can be ambiguous, though, as in Setophaga coronata auduboni × townsendi. This formatting seems to imply that the parental taxa are both subspecies of Setophaga coronata, but there is no Setophaga coronata townsendi. I assume the second parent is Setophaga townsendi. Formatting the name as “Setophaga coronata auduboni × Setophaga townsendi” would remove the ambiguity.

If one of the parental taxa has no subspecies, just give the binomial: Setophaga coronata auduboni × Setophaga townsendi.

Townsend’s x Audubon’s has a flag though because it doesn’t follow the curator guideline. Flag for Taxon: Audubon's × Townsend's Warbler (Infrahybrid Setophaga coronata auduboni × townsendi) · iNaturalist

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Ah. I missed the statement in the curator guide that, “Hybrids should only be made between taxa of the same rank.” However, the example given in the following sentence, Canis lupus × Canis lupus familiaris, muddies the waters. That particular hybrid formula is indeed incoherent, but the problem is that one parental taxon includes the other. If the intent is to avoid hybrid formulae of that type, the guidance is incorrect—it’s not a question of rank per se. There is no reason I know of for iNaturalist to avoid hybrids between taxa of different rank as a whole.

I’m inclined to ignore policies that have no coherent basis. Perhaps I shouldn’t recommend that behavior in others, though. I’ll start a new thread here specifically recommending a change to that sentence in the guide.