"Rules" for hybrid animal taxon names

I know I’m not a curator but I’m following up on Scott Loarie’s suggestion to bring this up in the forum and it should be best presented among those that actually curate.

We discussed briefly the taxon and curating issues in regards to hybrids. There seems to be no set rules in determining how a taxon hybrid should be named. Here’s to name a few examples:


Ignore the fact that these are all birds, these problems are happening elsewhere. But what’s similar with all of these taxon? They are not… in sync. The first one has the genus followed by species one × species two. While the second one, same genus, has the genus before each species’ name. The third link differs by not being in alphabetical order like the other two but is in taxonomic order. Link four has the “×” followed by a mashed up name of the two genera. Five shows the two species from the two genera. Six shows two species from the same two genera in link five, but genus two is not capitalized. So the point is, everything here is messed up and we should fix these problems. Here’s why I suggest…

Rules or guidelines when creating or curating a hybrid taxon. I would recommend.

  1. For a hybrid within the genus, the genus should only be mentioned once, like unto…

Genus Species 1 × Species 2

  1. For a hybrid with two genera, both genera must be mentioned and capitalized, like this…

Genus 1 *Species 1 × * Genus 2 Species 2

  1. Sequence of the species in the hybrid should go in taxonomic order, not alphabetical order. This is because that is the scientific name and thinking that the two species’ names are interchangeable is to my eyes as bad as misspelling the scientific name.

Larus occidentalis × glaucescens – Western × Glaucous-winged Gull


Mareca americana × Anas acuta – American Wigeon × Northern Pintail

or an unaltered one taxonomically

Buteo jamaicensis × regalis – Red-tailed Hawk × Ferruginous Hawk

So those three rules pretty much cover any taxonomic issues you might encounter while curating a hybrid taxon. I’m open to more suggestions, comments or concerns. I just want to know if this is a yea or nay situation. Thanks for your time.


The “mashed-up” genus name preceded by × was an attempt to follow a predetermined consistency on hybrid naming, following botany. I’m mostly responsible for this on iNat, so I’ll be the one to explain and justify it.

Basically, in botanical terms, the naming rules combine the two genera names in the case of a hybrid involving parents of two different genera. This is quite uncommon, but the rules were established to cover these fringe cases. However, other groups such as birds and insects have never had official hybrid rules. iNat is an unusual case in trying to establish a consistent treatment for a wide range of taxonomic groups, so I thought that by bringing those rules over to birds, it might help promote said consistency.

At this point I’m not really sure where I standard on that matter. I am starting to side with the belief that keeping the format as Genus1 species1 x Genus2 species2 is better off, but I welcome discussion.


Personally, I think botany and zoology exist on two totally separate planes in terms of hybrids and different rules should apply to them, just because of the fact that flora has so many more hybrids than animals and some plant hybrids scientists didn’t even know were hybrids until DNA testing came along and × was just added as predecessor to the scientific name.

And while I’m thinking about it, here’s another “rule” we can use plus some questions.

  1. For intergrades, you only need to add the genus and species once as in…

Genus Species 1 Subspecies 1 × Subspecies 2

But now here’s the question, what do we do about F2 and F3 generation hybrids. I’m not talking about something like an Olympic Gull (Larus occidentalis × glaucescens) that backcrossed with a Glaucous-winged Gull (Larus glauescens). Perhaps the better term to use instead of F2 and F3 generations is what about trihybrids or quad-hybrids.

Example being the Brewster’s Warbler (Vermivora chrysoptera × cyanoptera) × Chestnut-sided Warbler (Setophaga pensylvanica). I’m trying to think of ways to represent the trihybrids scientific name but have not come up with any logically solutions. Obviously we can’t do Vermivora chrysoptera × cyanoptera × Setophaga pensylvanica because you can’t figure out which two species was the parent hybrid and three species is just too confusing. Perhaps using brackets will help and will result in this.

Vermivora [chrysoptera × cyanoptera] × Setophaga pensylvanica

If we want a trihybrid in the same genus, I’ll use the Harligold Macaw, Blue-and-gold Macaw crossbreeding with a Blue-and-gold × Green-winged Macaw hybrid.

Ara [ararauna × chloropterus] × ararauna

Another example using the domestic hybrid Rubalina Macaw, a trihybrid between a Scarlet and Green-winged Macaw (Ruby Macaw) and Blue-and-gold and Scarlet Macaw (Catalina Macaw). Though both parents are hybrids, because two of the grandparents of the hybrid are pure Scarlet, it’s still considered a F2 hybrid.

Ara [macao × chloropterus] × Ara [ararauna × macao]

The only thing I wonder though is, is the second “Ara” genus necessary in a bracketed trihybrid. Would it be more appropriate as this?

Ara [macao × chloropterus] × [ararauna × macao]

And perhaps the same method can be used for F3 hybrids. Let’s use a Fiesta Macaw, a Camelot Macaw cross with Harlequin Macaw. I used indented brackets to show a F2 trihybrid is breeding with a F1 hybrid.

Ara {macao × [ararauna × macao]} × [ararauna × chloropterus]

But probably all I accomplished through this is confusing whoever reads this.


Newbie here, what is taxonomic order? It turns out to be hard to google, because you just end up with definitions for a (Linnaean) order…

What makes A. caerulescens precede A. albifrons?

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So taxonomy is the classification of close-related organisms and taxonomic order is just the list. Species within the list are in a sequence or that and taxonomic order can be used interchangeably. Anyway, sequences are changed all the time. The current sequence for North American Anser species is:

A. canagicus – Emperor Goose
A. caerulescens – Snow Goose
A. rossii – Ross’s Goose
A. anser – Graylag Goose
A. cygnoides – Swan Goose
A. albifrons – Greater White-fronted Goose
A. erythropus – Lesser White-fronted Goose
A. fabalis – Taiga Bean-Goose
A. serrirostris – Tundra Bean-Goose
A. brachyrhynchus – Pink-footed Goose

Anyway, I believe nowadays the sequence or taxonomic order is decided by mtDNA (mitochondria deoxyribonucleic acid) testing to see how closely related one is.


I would say “taxonomic order” is the level between “taxonomic Class” and “taxonomic Family”. I would call your example a taxonomic list, in this case the list represents the members of the genus Anser. It is evidently not in alphabetical order, and other possible orderings might include random, publication date, date of last review, date of last observation, and so on… With potential for “descending order” on each. It could also be alphabetical order on a common name, perhaps the first common name entered and not necessarily the displayed or current common name! I would say that any taxa list that is not in alpha order, the most likely possibility is random or publication date, and it would be possible but strange to have it in “DNA order”

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I think that particular order has nothing to do with alphabetic or “taxonomic”, it’s to do with which of the hybrids parents is male and which female. I can recall very vaguely from highschool horticulture (1980s) the term “pollen parent”…

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eBird uses:
Dendrocygna viduata × bicolor (if in the same genus)
Cairina moschata × Anas platyrhynchos
which seems as good a way as any for birds (and other animals?)

eBird seems to use taxonomic sequence to determine the order. For birds at least, there is a defined taxonomic sequence based on phylogeny, with branches that split off earlier listed first. However, this does tend to change with new data, and iNat lists species alphabetically, not in taxonomic sequence.

The capitalisation problem is a glitch in iNat, the second genus name is meant to be capitalised.


Personally, and I realize you likely will not like my answer, I don’t think the site should even try to incorporate trihybrids or subspecies hybrid crosses etc into the taxonomy.

Any ID of these outside a captive environment is likely a guess. The frequency of encountering these does not match the work involved in implementing such complexity.


There’re a lot of hybrids easily identified in field. And what the complexity of process is about?

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Luckily for us, the only F2 (trihybrid or backcross) or F3 (quadhybrid) hybrid that exacts outside of macaws is the trihybrid Brewster’s Warbler (Blue-winged and Golden-winged Warbler) × Chestnut-sided Warbler. Unfortunately though that was a wild bird and the only reason why we know it was a trihybrid was because it confused Cornell so which with its coloration, they caught it, banded it and DNA tested it. It was sighted by many people, what if one of those people happened to be an iNaturalist? And while I’m thinking about it, I may address the Brewster’s/Lawrence’s Warbler issue in another thread I posted.

My concern though is, even though all the F2 or F3 macaw hybrids probably won’t occur in the wild, I see that it’s only a matter of time before someone posts their pet and no one can identify it properly. That’s also the reason why I’m trying to figure out what’s the scientific name of these trihybrids and beyond. Perhaps for a trihybrid, we should follow @silversea_starsong suggestion and go with botany rules.

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My sense is that these parrot mixes should be treated the same way as are artificially created cultivars in plants, just left out of the iNat taxonomic backbone.

If one of the Cornell researchers who physically handled that bird submits it to the site, so be it, deal with it then.


I’m sure they exist among Larus though.

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How are they going to be identify though? :smile:

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What I do for plants (specifically trees) is enter the part of the name that iNat CAN handle, and then have a field named cultivar that takes the remaining part of the name. In exports etc I just combine the two fields. I’ll try and find an example when back on the computer…

Another possibility is to enter the taxa common to both parents, and create or use a field called hybrid that stores the full hybridised name. So if inter-genus hybrid for example, the ID would go as family, etc.


Hardly. :D But definitely areas with multi-species colony have great works on banding them, so we now can track the life of many generations.

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A post was split to a new topic: Hybrid genus name capitalization is automatically removed

The AOS checklist (and most other bird taxonomies) actively arrange the order of taxa within each genus by relatedness, as Birdwhisperer has suggested, which is commonly called “taxonomic order”. That’s not entirely based on molecular work, but most of
these days is. They similarly order the genera within each family, family within each order, etc. by relatedness.

The expectation for published scholarly work on birds is that tables or any other list of included species will be presented in this order, and many field guides have actively adopted it as well.


Thanks, I am not clued up on birds… clearly!

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My opinion is that anything including more than 2 parents is not suitable for name treatment. I have several reasons for why. The main one being that there is no proper way for databases to accept that format as a taxon entry. iNaturalist included. It would require a change in how the entries are processed and created, I feel, because it quickly results in a large number of pages that are only used once, and may represent fringe cases that are very hard to distinguish (e.g. F3+ hybrids). At that point the data is still useful, but I am not sure iNaturalist is the platform to keep track of those, because of the mentioned reasons and a few more. I might be wrong!

Definitely in terms of databases like GBIF, hybrids are treated at genus anyway for the most part, so the further specialization might not matter there.