Benefit/Significance of Adding Subspecies

Could someone please explain to me the benefit of adding subspecies, and the significance of subspecies?
I understand why we designate Muscovy Ducks and Rock Pigeons as “Feral”/Domestic which separates them from truly wild versions, but I don’t understand the significance of adding subspecies for things like Western Palm Warbler (Setophaga palmarum ssp. palmarum), North American Osprey (Pandion haliaetus ssp. carolinensis), ABC Islands Brown Bear (Ursus arctos ssp. sitkensis), among others…
Is this purely a database thing or are there actual differences between the subspecies?


Of course if subspecies were described, there’s a difference between them.
How much it matters depends on a taxon.

  • Some subspecies are rare/extremely rare while the species can be rare or common.
  • Some species live throughout wige range, so if you travel and see many subspecies you may want to be able to see it shown by your observations.
  • Some subspecies are seen by many as separate species, so it make sense to id them so.
  • Some subspecies are common to the area, while others are rare migrants/vagrants, so map should show that.
  • And some people just like subspecies, so can add them when they want.

Some subspecies will be given full species status at some point… so by noting the differences it will be easier to organize if there are taxonomic updates. I’ve heard it referred to as an “armchair tick” in birding, if you see a subspecies that is likely to eventually become its own species. You’re just sitting there reading the revised changes and realize you picked up a lifer.


For many vertebrates, I don’t pay much attention to the subspecies unless a particular one has a different conservation status than other subspecies or the species as a whole. Also, some subspecies are a major invasive threat such as Red-eared Slider (Trachemys scripta elegans) while other subspecies in that species are not … and the Red-eared race is easily IDed from photos. For many vertebrate subspecies, it might require more detailed photos to determine it is indeed that particular race. Geographic range and the location of one’s record can of course tell you what subspecies should be there, at least for less mobile organisms, but that’s not the best way to ID it to subspecies level.


Important subspecies determinations would be in cases where:

  • The subspecies are highly distinct, or those with unique features or distributions.
  • One subspecies is native and another is not, which is an important mapping distinction.
  • Taxonomy is subject to change. Subspecies IDs make it easier to automatically update all older observations to the new names and species following a split.
  • The subspecies holds unique information about a specific niche or ecology.

My argument is if there’s a distinct data point associated with a subspecies, it should be labelled at that level whenever possible. Most contention over “Why do subspecies matter?” understandably comes from two types of cases. The first where a huge number of cryptic subspecies occur, and at that point it feels a bit pointless to designate them. The other case is when a species ranges across multiple continents, which often have different “American” and “European” subspecies, despite not looking overly different. I admit sometimes I am a bit lazy when it comes to the latter case.

But I’d say long story short, at minimum, if a subspecies fulfills criteria in the list above, you should definitely use it.


To cover your examples specifically…

Muscovy Duck and Rock Pigeon: as you point out, these subspecies names distinguish captive-bred lineages from true wild birds, and in some regions they clash and so the designation is actually quite important. For instance, Texas is known to have a small number of true wild muscovy ducks occur as vagrants, and those records of natural migration from Mexico would be missed if all birds were mixed into one label (because there’s a lot of domestic muscovies in Texas too!).

Palm Warbler: The two palm warbler subspecies refer to two geographically different populations, and they are often visually distinct as well. The two subspecies sometimes overlap on migration but each one has a tendency to occur in certain areas over others, so the distinction fuels an interesting dataset for comparing these populations. I would lean towards applying these subspecies if you know it, for these reasons.

Osprey: I would say generally applying subspecies to osprey is not very significant, since it is obvious what subspecies it is just on the location. However there is talk that osprey will be split into further species in future, and if so, it can be worth applying the subspecies to automate the taxonomy change in future. It also makes it easier for researchers to filter data to specific regions (though for osprey that’s not an issue, but for some species it can be).

ABC Islands Bear: By default I would say that any island-endemic taxon is worth designating just due to the unusual distribution from other populations. This bear is an even more unusual case because it is apparently a hybrid between polar bear and grizzly bear, and serves as a very bizarre mix of lineages in a small local area. So the designation of this subspecies highlights that a sighting is part of this very interesting regional phenomenon.


For the Dark-eyed Junco, I used to try to assign subspecies to the different forms I see in my area during winter (the various subspecies breed in different parts of North America but co-occur in some places during winter). Given the complexities of the different Junco races, and disagreement about what names should be recognized, plus the presence of intergrades, I gave up on IDing subspecies for wintering birds.


It’s difficult to generalize across subspecies. How useful and meaningful they are will depend both on which subspecies we’re talking about and what use of the data we’re talking about. Personally, I identify observations to subspecies (or variety) when I know how to distinguish them and believe that this level of classification conveys useful information, if only useful to me. If I simply need to put a name on an observation, I’ll often stop at the species level.


To me this is similar to asking, “why should we identify to the species level instead of genus?”. Certainly some subspecies have little to no visible differences (and this can even be true at the species level, e.g., Eastern/Gray Ratsnake Complex in northern parts of their range), and we shouldn’t add lower taxon IDs beyond what we can actually ID. But for the ones that are discernible, of course it is useful to identify them.

Some subspecies are already of conservation concern (e.g., Ammodramus maritimus mirabilis is listed as endangered under the ESA while other subspecies are not). Differentiating between subspecies of Palm Warblers could provide critical data if one subspecies started to decline suddenly.

It is important to remember that taxonomy is an organizational tool and does not represent true hard lines between taxonomic groups. Preserving diversity, whether it’s between species, subspecies, or even populations, is important.


…and others will be synonymized. Eightteen subspecies of Steller’s Jay and four subspecies of Blue Jay have been described, but I doubt that there will ever be 22 full species of Cyanocitta.

I wonder about the Dominican Republic. Most muscovies there are domestic – and often have both wings amputated – but I have seen muscovies flying high over Rio San Juan. They could have been feral descendants of the domesticated ones, but how could one tell at that distance?

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One situation in which identifying to subspecies is not useful (and could even be counterproductive) is in when a user enters a subspecies ID based purely on the observation’s location. In these cases, adding a subspecies ID doesn’t actually add any information to the observation (the location data is already there). IDing in this way can actually just create a loop of inference between location and subspecies. For instance, it’s possible that another subspecies is found in that area infrequently, or it hasn’t been documented, or subspecies ranges are changing due to climate change, etc. IDing as a subspecies based purely on location could obscure rare and important observations of other subspecies or long term trends.

IDing to subspecies based soley on location can also be an issue if the taxonomy changes in the future, if distinguishing characters are found, or geographic areas delineating subspecies change. Some of these scenarios can be addressed with taxon changes in the iNat system, but in other scenarios, fixing a group of observations identified to subspecies based solely on location would entail more work than if they were only identified to species.


The Chihuahuan Meadowlark was just elevated to its own species. It was formerly considered a ssp of the Eastern. That gave me a new lifer right off the bat!

Animals get renamed or reclassified all the time.

I like to keep subspecies on my life lists.


But also sometimes you lose some. I had the Northwestern Crow, but it since been demoted to ssp of the American.


I don’t strongly disagree with this, but I do partially disagree with this. This could also apply to many things at the species level. While it is possible to differentiate some Gallinula galeata and Gallinula chloropus (see here), in many instances location is the determining factor for the ID. Should many of these observations be left at the genus level too?

Often species- and subspecies-level taxa are treated under a different set of rules based on the perceived value rather than true value of the taxon level.


I disagree with this. This can be extremely helpful, especially for people who are not familiar with the localized ranges and the local area. Where I am there are a number of local bird subspecies, some that are visually distinct, others that are not but that are regionally distinct. Marking those helps others who are not familiar with the area or the extent of the species ranges better understand what the situation is. Providing subspecies IDs also helps to flesh out the range and border areas for them, although this is far more difficult if the subspecies is not visually distinct.

In the case of species transition, having identifications to subspecies can actually make that a more smooth species elevation (if that happens… as has happened in my area with several vertebrates).

The “identifying subspecies based on location is not useful” argument is essentially the same one as saying that you shouldn’t identify a species based on location as it’s ‘not helpful’. Often that’s the only way, unless you happen to have a way to analyze genetic samples in the field in your back pocket.


Sometimes, though, a subspecies really is no more than a geographically-defined subset of a species—although personally I don’t think such taxa are worth recognizing, and in their absence I agree with you.

I’m curious under what conditions you would expect more work to be involved if observations were identified to subspecies.

What occurs to me is that identification inertia could be a problem—iNat requires more IDs to move an observation to “Alpha beta var. gamma” from “Alpha beta var. delta” than from “Alpha beta”. This aspect of the situation applies more broadly, as well—it’s always easier to increase the precision of an identification than to change it to another taxon at the same rank.


Thanks to everyone for your replies, understood.
That being said, what makes a ssp a full stand alone species? Does it just need to evolve/change/adapt enough to be behaviorally and/or physically different? (example of Chihuahuan Meadowlark separating from Eastern Meadowlark)
Separately, what causes a stand alone species to be demoted to ssp? (example of Northwestern Crow to ssp of American Crow)

What we call a species versus a subspecies depends as much on the current philosophy of systematists/taxonomists as on evidence provided by genomics, morphology, geographic distribution, behavior, phenology, etc. Today’s subspecies is tomorrow’s full species, but next week it might be a subspecies again or be considered a junior synonym and no longer recognized. I exaggerate a little.


Only a little…


There was an epoch of splitting species, there was an epoch of merging species. New methods (mostly genetic) allow to make clear borders between populations or erase them. Also it is mostly of phylosophy paradigm to describe the level of differences between species (subspecies, macrospecies, semispecies and complexes of species). And we didn’t talk about circular species yet ;-)

And, by the way, often it is impossible to answer the question “what is specie”.