Question Regarding Subspecies Identification

I have seen a few IDs now by seemingly seasoned identifiers marked as subspecies (i.e.; ‘Pica pica’ to ‘P. pica pica’/‘Anser anser’ as ‘A. anser anser’) with the only difference being Location.

Since many of these species move about, some even migrating across continents, why the subspecies ID? I was under the impression that a subspecies ID would require some kind of genetic difference and could be made by eye if there is a physical variation but these IDs are not visibly different to each other so it cannot be that, and if it is Location then surely their moving about would confuse that?

I know this is a basic question and I did try asking elsewhere before bringing it here but have received no answer to the question - what makes those identifiers mark something as a subspecies with no visible variation between individuals?


You don’t need any DNA to id most of bird subspecies, they’re morphologically different e.g. magpies differ by amount of white on wings and general length of tail (also depends on sex), greylag also includes domestic goose, so iding the spp may allow to filter for wild geese only. Many Eurasian subspecies are not moving around different places of breeding (plus it’s known they come back breeding very close to where they were born, rarely going somewhere else with other migrating flocks), so a subspecies from middle of Siberia in summer is very unlikely to get in Central Europe.
The most of confusion comes from how many subspecies each scientific database sees, e.g. european scientist sees all alba-group ssp. of white wagtail as one subspeies, others see it as three (or more).


Because there are in fact visible differences between subspecies of these taxa.

Anser anser rubrirostris has a pink bill and A. a. anser has an orange bill. Also, rubrirostris has overall paler plumage than anser.

In addition to what Marina has already mentioned for Pica pica, subspecies differ in the amount/presence of white on the rump and color/amount of iridescence in the tail.


Unfortunately, “subspecies” is probably the most controversial taxonomic category. Species (in the general sense, without some edge cases) have unique characters that distinguish them from other taxa, and higher-ranking taxa are groups of species with a common set of characters and a common (likely) origin. But “subspecies” is a something like a “some form within a species”.

The modern concept of subspecies as a taxonomic category was formulated (using birds as an example) in the middle of the last century by Ernst Mayr in a rather general sense:

geographically defined aggregates of local populations which differ taxonomically from other such subdivisions of a species

Although this concept is still more or less followed by taxonomists, it has been the subject of criticism almost since its publication. E.g. A. Landsborough Thomson (1969) The Subspecies Concept, Bird Study, 16:1, 1-13.

The broad definition allows the term to be used rather arbitrarily. Which is hardly a good thing for a scientific category. In addition, the modern view of evolution and the origin of species probably leads to a new view of the concept of species. See some details: Guiding Principles for Identifying Species and Subspecies

Anyway, Mayr’s classical geographic “subspecies” cannot have always clear unique characters. Otherwise, they would be considered as separate species. There is always (except perhaps for “island” “subspecies”) a “transitional zone” between subspecies within a species. And there are always some individuals that cannot be confidently morphologically classified as either subspecies. Or identified as both, depending on one’s point of view. Perhaps it is better to leave the identification of such “morphologically uncertain” or hybrid individuals to the species level.

Therefore, I try not to use this taxonomic category unless it is an established tradition.


All the issues you highlight here for subspecies are applicable at the species level or even higher taxa. As I’ve said in other topics:

I would say many more than just “some edge cases” of species do not necessarily have readily-apparent distinguishing characteristics. If you type “complex” in the species search bar on iNat, you will see many, many examples. And that doesn’t even include things like Gallinula chloropus and Gallinula galeata that are so geographically separate that a complex designation is not needed even though they are remarkably similar.

Again, this applies to many higher taxon levels. There are few guidelines determining amount of morphological/genetic/etc. variation needed to be separate taxa at any level.

Again, there are many exceptions to this as well. Subspecies of Ensatina eschscholtzii are very distinct and yet are not geographically separated into “island” populations. While they do have “transitional zones” between subspecies, so do many cases at the species level (e.g., Poecile carolinensis and P. atricapillus). As already stated, the two specific subspecies mentioned by the OP do have visually-distinct mophological differences.

In my opinion, much of the controversy surrounding subspecies is really based more in perceived notions than in actual distinctions between the subspecies level and higher taxon levels. Taxonomy at all levels is messy. It draws hard lines between things that exist on a gradient. While it is necessarily to have such an organizational tool, it should also be coupled with the knowledge that it is not some hard and fast distinction drawn by nature.


Thank you for the informative response!

On the one hand, I often say that any classification is artificial. And of course, species (most likely) do not appear instantly as something genetically and morphologically isolated. The process of isolation (which may be not only geographical, but also ecological and other) is an extended process in time, and there is no clear “moment” of transitions from population to subspecies and further to species. Moreover, there is no evidence that it is a unidirectional and irreversible process. Modern science has sufficient facts to consider the other point of view obsolete and erroneous.

But on the other hand, it also seems to me that it would be incorrect to think of biodiversity as some kind of structureless continuum. If, however, this continuum consists of some evolutionary structures, it would be good to have tools to recognize them.

In the case of species, although such tools are imperfect, and do not cover the entire diversity of cases of microevolution (even only animals), they do exist. There are “morphological species” - continuous series of character variability separated by “gap” in which there are no intermediate forms - at least at the present “slice” of evolution. There is reproductive isolation of species, and so on. These are all “measurable” or experimentally verifiable categories. They can be proven regardless of beliefs and viewpoints.

But what could be such a tool for distinguishing subspecies? Can any form within a species be considered a subspecies? What should be the degree of its geographical isolation? It seems to me that without clear criteria for distinguishing and methods of evaluating them (at least as imperfect as for species) it is difficult to use this concept as something objective. Without it, I fear that we may find ourselves in the abyss of solipsism.

I am skeptical of superspecific taxa for the same reason. Every time I hear someone tell me that “these species are objectively a separate genus” (for example), I ask by what criteria and by what method the “genus” is recognized as an object of reality. Why not subgenus or tribe? So far, I have never received a clear answer.


Taxonomy is imperfect. It is our attempt to apply simple labels to a complex biological world. It is useful for us to have names to communicate with, but not all groups of organisms are equally easy to define.

I think of subspecies as speciation in action. They have become different enough that we notice them (maybe just through DNA differences or maybe they have some distinct morphological differences, too), but not so different that we’re ready to consider them a different species (though taxonomists do argue all the time over whether to call X a species or a subspecies).

I use subspecies if I feel like they are clearly recognizable and apply to a distinct subgroup within the species. If I have my doubts, or I’m just shaky on my ability to identify that finely, then I don’t feel guilty just identifying something to species.


There’s been a fair amount of conversation about this issue in previous posts. Some useful ones are:
so referring to the ideas there may be useful.


This reminds me of some research one of my grad school labmates (JP Huang) did on the lack of objective standards for taxonomy in Hercules beetles (Dynastes). Basically, he found that South American varieties had been usually described as subspecies because nobody wanted to break up the sacred Linnaean name, whereas North / Central American varieties had just been each split into their own species. But when you compared the DNA and the morphometrics across them all, they almost all represented lineages that should be considered at essentially the same level of evolutionary radiation, whether that was species or subspecies.

I generally agree with this. Yes, there are exceptions to hard species boundaries and ring species and hybrids and microspecies and etc are all fun edge cases that make biology exciting. But I’m of the camp that the species is perhaps the one taxonomic unit that actually means anything, because it’s supposed to capture discrete lineages that have a distinct evolutionary trajectory (or whatever species concept is being used). Higher taxonomy is all subjective, e.g., what makes a certain cluster of species a genus as opposed to a species group / tribe / family is very non-standardized and unobjective. And subspecies can be ridiculous or tautological self-reinforcing loops so I basically never bother with them.


I’m specifically referring here to birds which do not visibly differ being tagged by supposed experts as a subspecies based purely on location. And yeah there also seems to be a lot of confusion in who accepts what subspecies. I know that P. pica pica specifically, for instance, dates back to Linnaeus.

unfortunately taxonomy is moving away from this (broadly, not just on iNat). Over time, expect things that were previously subspecies to be elevated to species. This will result in a lot more issues like this. if you identify only based on range you create self-fulfilling data with potentially a lot of errors. Otherwise you are forced to genus level most of the time.

For subspecies or species, well, it’s a balance. When they are adjacent to each other, it’s bad practice especially for animals which move around a lot. When broad differences in range and habitat exist it kind of makes sense. I don’t look for Fremont Cottonwood in Vermont, it looks nearly identical to Eastern Cottonwood but grows thousands of miles away in different biomes. If you considered literally every global oak species any time you identified an oak, you’d never identify anything without DNA in most cases.

Some subspecies seem to truly only be distinguished by range, and given their lower taxonomic level plus this uncertainty, i don’t identify subspecies based on location at all. I don’t see any upside to doing so, and i see potential downsides.


I understand if there are noticeable differences. Where that is the case, I want to learn what they are and learn to ID them. My confusion comes in where people are tagging these inconsistently, especially where I cannot see any source for learning these differences where they do exist. Do you have any links?

Thank you. This answers the question I asked 100%

I appreciate the detail you went to. It answers my question, in a very roundabout fashion. The question was - when is it actually possible to be certain of these IDs for myself and where would I find that information. The answer is that most of the IDs I’ve been confused about fall into the “One cannot be certain.” category and therefore I will be firmly maintaining them at species level.

This neatly encapsulates the problem with classification generally. In this case, for the sake of as close to accuracy as possible within the iNaturalist system, I will not be classifying any subspecies which isn’t blatantly obvious (such as Pied Wagtails) as it seems an unnecessary gamble which will only muddy the waters further.

Thank you, I feel similarly.

I’ve appreciated all of the thoughtful comments and qualified insights very much. Since the question has been answered, this thread can be closed. Thanks again, all!

Subspecies are super tough! I try to avoid adding subspecies on others’ observations unless:

  1. It’s distinguishing between a wild/captive population
  2. The subspecies are highly visually distinct
  3. The subspecies are geographically isolated and/or well-defined enough to make a reasonable assumption. Mostly island subspecies, but occasionally also something like the eastern american red fox (V. v. fulvus) or the tiger/leopard subspecies (especially Bengal and Amur for the tiger and Sri Lankan and African for the leopard)

On my own observations, however, I like to use subspecies because I keep a personal life list outside of iNat (on a google doc-- how retro!) and in cases where I observe a species in two different locations, I tend to ID them to different subspecies if possible to represent observations of two populations – for example, to show that I’ve observed wild turkeys in New Mexico and in Maine, common raccoons in Maryland and West Virginia, common ravens in Maine and New Mexico, or turkey vultures in Maryland and Costa Rica.


You refer to birds easily ided visibly to subspecies. In birds subspecies are old and were “created” before DNA was even found to exist. You can look up local subspecies for you and see if you can notice differences that literature claims there is. I do that a lot and learn more this way.
People id subspecies only when they want, I can one day id jays to subspecies (they’re easy), and next day id as species, so any inconsistency you see comes from human factor.

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The availability of ‘subspecies’ designations should not be discontinued in iNaturalist. If one adheres to a concept of species in which species are real entities (a tenant of all modern species concepts)… the recognition of ssp is incongruous with that view.
There are many additional practical issues to recognizing subspecies in a system like iNat, the least of which (though significant) being, at what arbitrary threshold does one subspecies become another for the user or subsequent identifier… best to leave it at the species level where the ambiguity is less (because you’re dealing with real entities).
‘Subspecies’ is the outlier among the traditionally recognized taxonomic categories. Species are real, all higher taxonomic categories are natural (share a common ancestor) groups of species. ‘Subspecies’ are not even incipient species, though many like to think of them that way.

See for the latest review of the topic… Burbrink, Frank T., Brian I. Crother, Christopher M. Murray, Brian Tilston Smith, Sara Ruane, Edward A. Myers, and Robert Alexander Pyron. 2022. Empirical and philosophical problems with the subspecies rank. Ecology and Evolution ():17