InsectNet forum

Does anyone know the rules for recognizing a hybrid taxon as a species?

It seems that for a long time doing so was avoided- and still is. The first known (or confirmed) example I can think of is some bird that was shown to be a recombinant hybrid with a self-sustaining population.

The best known example to most of us is probably Papilio appalachiensis, which is a recombinant hybrid. Still though, I hear grumbling that it should not have been recognized.

Now I read of all sorts of things- plants, snakes, other butterflies, etc. that are recombinant hybrids with self-sustaining populations. It apparently isn't as unusual as was thought. So what shall be done?

Recombination hybridization is a well recognized pathway for speciation over long time scales. Whether or not a particular population of hybrid origin gets to be a species though, according to humans, is probably subjective and contingent upon what’s “fashionable” at the time. I wonder if Adam can shed some light on this in terms of whether the ICZN has an official stance on the matter.

eurytides wrote: Mon Nov 06, 2023 5:56 am I wonder if Adam can shed some light on this in terms of whether the ICZN has an official stance on the matter.

Here are the relevant ICZN Code articles:

1.3. Exclusions. 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);

Article 17. Names found to denote more than one taxon, or taxa of hybrid origin, or
based on parts or stages of animals or on unusual specimens. The availability of a name is not
affected even if
17.2. it is applied to a taxon known, or later found, to be of hybrid origin (see also Article 23.8);

23.8. Application to species-group names established on hybrids. A species-group name
established for an animal later found to be a hybrid [Art. 17] must not be used as the valid name for
either of the parental species, even if it is older than all other available names for them. Such a
name may enter into homonymy. For names based on taxa which are of hybrid origin see Article
17.2.

So basically, names for hybrids are not recognised by the ICZN Code, but names for species of hybrid origin are.

Adam.

And that makes sense. We have plenty of examples where a species arose from hybridization in the past. It makes sense that a single individual that’s a hybrid has no name, but hybrid population stable over time and space can be named.

Thanks guys.

Some cases are cut and dry- the hybrid bird which is now very geographically isolated, for example.

But what of those recombinant hybrids that are arguably still in evolution? Those that have some overlap and interbreeding with the parent population(s)?

eurytides wrote: Mon Nov 06, 2023 6:02 am https://meridian.allenpress.com/pbsw/ar ... m=fulltext

I don't have access, so can only read the abstract. Can you email it to me? Thanks.

Unfortunately, I don’t have access either! But I thought the abstract was telling enough. There is no issue naming hybrid populations. There doesn’t seem to be clear criteria for when a hybrid population “should” get named. I think people just do it, present the evidence, and the rest of the community reaches a consensus about whether they accept that evidence as sufficient or not.

adamcotton wrote: Mon Nov 06, 2023 9:17 am 1.3. Exclusions. 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);

If I understand correctly this article basically refers to man-made hybrids, excluding them from being recognised names under the ICZN Code.

Article 17.2 applies to natural hybrids collected in the wild and named as species but subsequently understood to be hybrids between two species. Article 28.3 then applies in the case that the natural hybrid was actually named before one or both of the parent true species.

Adam.

A good read about homoploid recombinant hybrids.

https://pmc.ncbi.nlm.nih.gov/articles/PMC6308868/

I read the posts. I don't know if I understand it. I didn't read the links.
Can anyone cite an example? That may or may not help me understand.
Is this issue like the various Hyalophora columbia(s)? Like columbia columbia, columbia gloveri, or more like the
Hyalophora kasloensis?

kevinkk wrote: Wed Nov 20, 2024 7:01 pm I read the posts. I don't know if I understand it. I didn't read the links.
Can anyone cite an example? That may or may not help me understand.
Is this issue like the various Hyalophora columbia(s)? Like columbia columbia, columbia gloveri, or more like the
Hyalophora kasloensis?

When I started the thread I didn’t know the answer. A hybrid by itself is not nameable. A clade (group, if you will) that is the long-ago result of the recombination of two parental species and is self sustaining is nameable.

The main focus of science has been on homoploid recombinant birds. One of the best known, if not the first, is a seabird that was described long ago, and was more recently discovered genetically that it’s a self-sustaining islanded population resulting from hybridization between two geographically separated parental species.


It appears, as science learns more, this is not uncommon.

Ok, I get some it, being self sustaining and presumably, appearance. So- how do you know it's a hybrid in the first place, and not just a similar animal?
Seems like you need some forensics for that to be determined. Or is that part of determining species to begin with? Then discovering through DNA or
some other factor that an animal is a hybrid of two different species and now can self replicate.
Have I missed something in the posts that would have answered my own questions?

We don’t, and never had, known what is and not is a hybrid. There have been suspicions, and even Linnaeus made predictions that many butterflies are hybrids.

Troides (ornithoptera) allotei was shown to be a hybrid by breeding efforts. Today though most are revealed by genetics.


There are of course naturally occurring hybrids, some common. It’s when these hybrids reproduce in the absence of parental species that they become a species on their own.

Not to be confused with a subspecies which is a genetic mutation from one species. Genetics reveals which is which.

The Canadian tiger swallowtail split from an ancestor, which also was an ancestor of the eastern tiger, and is now extinct. Two species. Somewhere about 400,000 years ago the two species collided and interbred, starting the Appalachian tiger swallowtail. The two parental species still exist, but generally don’t interbreed with appalachiensis, yet it maintains its own population/ species.

If one is a “lumper” not a “splitter” then appalachiensis would go in the glaucus box. And MST is unequivocally NOT the eastern tiger, we know that would be best stuffed into the canadensis box. But any moron can look at an MST and tell you it’s not canadensis. So the whole species box fit is falling apart.

Thanks Chuck, I was thinking about the issue, and was reminded of the polar bear and grizzly hybrids I've seen on documentaries. I then thought
about trying to study wild hybrids, I wonder if that's easier than studying wild gynandromorphs.
All seems like evolution in progress, something we'll never be sure of.

There’s a difference between an occasional hybrid and two species hybridizing to perhaps eventually create a third.


If you want to study hybrids, North American Speyeria is where it’s at. Be ready though, this is a scientific battleground.