Should we consider lumping more subspecies? (3 Viewers)

[Maffong]

Reading up on subspecies, I sometimes come upon statements that read something like: "Not readily diagnosable" sometimes not even with measurements. For example I tried to learn about Taiga Bean Goose subpopulations, but apparently it's impossible to distinguish Anser fabalis fabalis from A. f. johanseni.
Similarly, Bearded Reedling has three subspecies that differ slightly in plumage colour saturation, but other than that they’re identical. Perhaps some wing or beak measurements may differ slightly, but looking at migrationatlas.org there's so much movement between populations that I have a hard time believing that there’s a significant difference between Panurus biarmicus biarmicus and P. b. russicus.

Therefore, I would like to ask the birdforum crowd:
What's the use of subspecies that are not diagnosable (except perhaps by range) or only by minute characteristics? Do we need fewer subspecies?
And how should we treat subspecies that are morphologically identical to conspecifics but differ drastically in life history, such as vulpinus- and buteo-Common Buzzards or fuscus- and intermedius-Lesser Black-backed Gulls?

 

[njlarsen]

There is an "Ornithology Monograph" (publication series from AOU, the predecessor of AOS) in 2010 on the topic of subspecies validity. I could find the chapters using this search in SORA:

Advanced Search Results | Searchable Ornithological Research Archive

sora.unm.edu

You will see all sorts of arguments for or against subspecies as concept, and also some agreement that some subspecies should be synonymized with others.
Niels

 

[mjh73]

I think the importance is less in how identifiable they are in the field, and more that we have subspecies as a tool to differentiate between important populations in some way that recognizes their distinctiveness in a broader population sense and helps with conservation efforts.

The more we smoosh things up the easier it is to say 'we can lose that habitat and the species that use it because there are more of the same in that habitat over there.'
This is of course what happens anyway but the harder we make it the better IMHO.

 

[Mysticete]

Subspecies traditionally have had very little rigor applied to assessing and identifying them, often being named using very small sample sizes and subjective assessments of morphological variation. I think subspecies are useful, but a lot of the recognized ones probably are not.

 

[jts1882]

Traditionally subspecies were just regional variants with minimal morphological differences, often described on the basis of few specimens. When there is a clear difference they tend to be promoted to species. The total number of bird species + subspecies hasn't changed significantly over time while the number of species had increased substantially (there's a table somewhere, possibly in the IOC update thread).

P.S. I think the traditional leopard and tiger subspecies were mostly described on the basis of surprisingly few skins (just one in several cases).

 

[Kirk Roth]

The definition/opinions of what a "valid" subspecies is has changed quite a bit since the 1700s so it may depend on what is meant and how many people will adopt it.

I've been surprised to see some mammal publications which refuse to recognize anything with clinal variation as a subspecies (essentially subspecies are defined as PSC species in their view). This is the opposite (I think) of the classic early Ernst Myer definition which used clinal variation as the defining reason that organisms would be subspecies instead of outright species - they have "intergrades."

In American herpetology, the philosophical pendulum has been in the opposite corner recently- I have been told that "the BSC doesn't make sense in herpetology" due to limited mobility of those animals, and that integration/hybridization is no barrier to a species concept. In that scheme, subspecies designations are similarly discouraged in favor of what I guess I would call "morphotype species" with extended hybrid zones. Check out the recent Peterson Guides to reptiles and amphibians for some interesting examples and range maps.

Personally, I think its worthwhile to have a name for anything that is different, if possible. In other words, if a morphotype (geographically correlated or otherwise) is not called a subspecies, then what do we call it? Do we really want publications burdened with having to refer to "the big darker plumaged Song Sparrows from coastal Alaska" when we could have an easy shorthand? I agree that the diagnosis of some subspecies can be kind of a stretch, so to speak - when they are defined only by something like bill length, or a slighter shade of brown. But if these are real differences, I see no problem with naming them. And if those differences have a geographic correlation - those are subspecies... at least according to some of us.

 

[Maffong]

I'm not arguing against subspecies as a whole concept. For example the Yellow Wagtails taxa are clearly very different even when they hybridise in small contact zones.

But subspecies of birds like Willow Tit, Bearded Reedling or the Bean Geese (both Tundra and Taiga) don't make much sense to me, as there's no way to verify our current classification as differing subspecies, because the ID criteria are too weakly differentiated and the distribution is likely clinal.

 

[cajanuma]

What's the use of subspecies that are not diagnosable (except perhaps by range) or only by minute characteristics? Do we need fewer subspecies?
And how should we treat subspecies that are morphologically identical to conspecifics but differ drastically in life history, such as vulpinus- and buteo-Common Buzzards or fuscus- and intermedius-Lesser Black-backed Gulls?

I like Kirk Roth's answer to your broader question above, but as concerns vulpinus vs buteo Common Buzzard or fuscus vs intermedius LBBG, I would not consider them morphologically identical, in fact they are quite distinct for the most part. Not all individuals can be safely identified, especially out of range, but this does not mean that they aren't different taxa (and I think fuscus LBBG was treated as a full species for some time by the Dutch, right?)

 

[Mysticete]

The definition/opinions of what a "valid" subspecies is has changed quite a bit since the 1700s so it may depend on what is meant and how many people will adopt it.

I've been surprised to see some mammal publications which refuse to recognize anything with clinal variation as a subspecies (essentially subspecies are defined as PSC species in their view). This is the opposite (I think) of the classic early Ernst Myer definition which used clinal variation as the defining reason that organisms would be subspecies instead of outright species - they have "intergrades."

In American herpetology, the philosophical pendulum has been in the opposite corner recently- I have been told that "the BSC doesn't make sense in herpetology" due to limited mobility of those animals, and that integration/hybridization is no barrier to a species concept. In that scheme, subspecies designations are similarly discouraged in favor of what I guess I would call "morphotype species" with extended hybrid zones. Check out the recent Peterson Guides to reptiles and amphibians for some interesting examples and range maps.

Personally, I think its worthwhile to have a name for anything that is different, if possible. In other words, if a morphotype (geographically correlated or otherwise) is not called a subspecies, then what do we call it? Do we really want publications burdened with having to refer to "the big darker plumaged Song Sparrows from coastal Alaska" when we could have an easy shorthand? I agree that the diagnosis of some subspecies can be kind of a stretch, so to speak - when they are defined only by something like bill length, or a slighter shade of brown. But if these are real differences, I see no problem with naming them. And if those differences have a geographic correlation - those are subspecies... at least according to some of us.

Birds are almost the perfect organisms for BSC...which is very hard to test in most other groups. You can readily notice differences in display, display structures, and calls which are virtually impossible to notice with the naked eye in most herps and mammals. Also birds are generally a lot easy to just observe in the wild. I mean there is a reason why birding is more popular than mammalwatching!

I personally tend to like Remsen's view of treating phylogenetic species as subspecies and biological species as species. It provides a less vague for what a subspecies actually represents and integrates two different popular species concepts into bird taxonomy.

 

[Mono]

Reading through the early editions of British Birds much of the drive to identify new sub-species seem to be nationalistic. There seemed to be a craze to have a British sub-species of every bird they could. Few to none of these sub-species seem to have survived modern rigour.

 

[Tom Schulenberg]

a good number of subspecies probably would not withstand rigorous re-analysis (even recognizing that plenty already have been synonymized). it's a lot of work to assembly all relevant specimens and document that differences between a particular set of subspecies are trivial or non-existent, however, and I suspect that there's also not a great deal of glory in publishing that kind of a paper. that's my take on how we remain stuck with so many zombie subspecies.