Subspecies (1 Viewer)

Remsen, J. V. 2010.
Subspecies as a meaningful taxonomic rank in avian classification.
Ornithological Monographs 67: 62–78

Abstract.—Dissatisfaction with the subspecies unit of classification is, in part, a consequence of the failure of many of those who have described subspecies to follow the conceptual definition of the subspecies, namely that it should represent diagnosable units. The antiquity of the descriptions of most subspecies (median year of description of currently recognized subspecies estimated to be 1908–1909) means that the majority predated any statistical tools for assessing diagnosability. The traditional subspecies concept, as originally construed, identifies minimum diagnosable units as terminal taxa, and I suggest that it is thus essentially synonymous with the phylogenetic species concept. Therefore, both must deal with the fundamental difficulties inherent in using diagnosability as a criterion. Application of monophyly as a criterion for taxon rank at the population level has inherent difficulties. An advantage of the biological species concept is that it incorporates, in its classification of taxa, assessments of gene flow and reproductive isolation, which are critical components of the evolutionary process. Critics of the biological species concept persistently overlook the fact that it includes the subspecies rank as a necessary component of that concept for distinct populations within biological species. Analyses that require terminal taxa can, with care, be conducted under the biological species concept using subspecies plus monotypic species. Critics of the biological species concept with respect to its application have missed the biological and political disadvantages of treating minimum diagnosable units as the primary unit of conservation concern. Human perception is in accord with ranking such minimum diagnosable units below the species rank; socially and scientifically, humans consider diagnosable units of other humans as distinct groups but not separate species.

Usefulness of subspecies as an evolutionary unit and a conservation unit

Hi,

I understand from the abstract that this article discusses the usefulness of the subspecies unit for taxonomy in birds, and the author is somehow in favour of the biological species concept. But what about the debate about the combination of the usefulness of subspecies as an evolutionary unit of classification but also as a conservation unit. I found these articles some time ago, all freely accessible, and you probably already seen them:

Phillimore & Owens (2006) found that 36% of avian subspecies are indeed phylogenetically distinct lineages. They concluded that, contrary to the low levels of genetic differentiation among continental subspecies from North America and Eurasia, more than 50% of traditional subspecies are phylogenetically distinct in other regions. So, they stressed the conservation utility of subspecies in the Equatorial and Southern Hemisphere regions where the absence or scarcity of molecular data is the norm. I think that this study is a sort of response to an earlier analysis by Zink (2004).

Zink (2004) found that only 3% (7 out of 230) of traditional avian subspecies were distinct phylogenetic units, but the subspecies sampled are largely from the continental Nearctic and Palearctic. Thus Zink (2004) argued against the traditional subspecies nomenclature. He stated that this can misrepresent the true geographical pattern of intraspecific differentiation and can misdirect conservation effort as in the case of dusky seaside sparrow (Ammodramus maritimus nigrescens) in North America, and other taxa that he cited.

I think that the case of the Cape Verde Kite (Milvus milvus fasciicauda) should be cited as an example of this as well. Johnson et al (2005) found that historical Cape Verde kites (museum specimens collected between 1897 and 1924), including the type specimen, were non-monophyletic and scattered within a larger red kite clade. The recently trapped (August 2002) kites from the Cape Verde Islands were all phylogenetically diagnosed as black kites. So, they concluded that the traditional Cape Verde kite is not a distinctive evolutionary unit. Therefore, their study does not support neither the distinctiveness of the Cape Verde kite nor the conservation effort (a captive breeding program) devoted to it.

Johnson J.A., Watson R.T. & Mindell D.P. 2005. Prioritizing species conservation: does the Cape Verde kite exist? Proc. R. Soc. B 272: 1365–1371.

Phillimore A.B. & Owens I.P.F. 2006. Are subspecies useful in evolutionary and conservation biology? Proc. R. Soc. B 273:1049-1053.

Zink, R. M. 2004. The role of subspecies in obscuring avian biological diversity and misleading conservation policy. Proc. R. Soc. B 271: 561–564.


Regards

But what about the debate about the combination of the usefulness of subspecies as an evolutionary unit of classification but also as a conservation unit.

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I can't say much about conservation efforts in other countries, but here in the states, subspecies are very much a "conservation unit," as far as the Endangered Species Act goes.

However, an endangered species vs. endangered subspecies makes little, if any difference as far as real conservation goes (again, at least in the U.S.), and press coverage is far more consequential. A good exercise is to compare the conservation efforts for the northern subspecies of the Spotted Owl vs. any of several Hawaiian honeycreepers, some of which have recently gone extinct due to "neglect," for lack of a better term.

Acrocephalus said:

Hi,

I understand from the abstract that this article discusses the usefulness of the subspecies unit for taxonomy in birds, and the author is somehow in favour of the biological species concept. But what about the debate about the combination of the usefulness of subspecies as an evolutionary unit of classification but also as a conservation unit.

Click to expand...

This is what the paper has to say on that topic. The risk he cautions against in the second paragraph seems to me a very real one - but of course any law or policy that seeks to conserve every subspecies on the basis that it's a conservation unit worthy of preservation runs exacly the same risk.

A particularly disingenuous criticism of the
biological species concept as an impediment to
conservation is the claim that it masks biodiversity.
For example, Peterson (2006) denounced the
biological species concept for overlooking numerous
distinct populations but did not mention
that under this concept all of those populations
are named, as subspecies, and overlooked only
if one restricts an analysis to the species rank.
Thus, Peterson (2006) found much higher levels
of species richness and unrecognized or underappreciated
patterns of endemism by application
of a diagnosability-based species concept; however,
he did not point out that an analysis that included
subspecies would have revealed the same
patterns that he “discovered.”

Application of the phylogenetic species concept
produces two potentially severe problems
for conservation. First, opponents of conservation
would quickly discover that the definition of
species had been changed to elevate more taxa to
higher threat levels, with accusations of manipulation
of the rules. Changing the definition would
only fuel the suspicions of conservation opponents
that scientists have abandoned objectivity
in favor of a pro-conservation agenda. Second,
elevating to species rank many taxa diagnosable
only by characters that conservation opponents,
the general public, and most biologists would
justifiably label as trivial could diminish confidence
in conservation science, undermine the
credibility of taxonomists, and erode support for
programs to protect threatened species.​

The ornithological monograph that Daniel references one part of in post one is now available at Caliber according to an Email I just received: 200 pages all about subspecies!

Niels

Here's the URL for the whole publication:

http://caliber.ucpress.net/toc/om/67/1

Chapter 6 is at:

http://caliber.ucpress.net/doi/abs/10.1525/om.2010.67.1.62

The problem with all these species concepts and why the argument wont be resolved is that there are too many agendas on how by using a particular species concepts can be used to push a particular barrow. We, as people use species as a way of identifying recognisable taxa (for personal or scientific purposes) and that is fine. Systematics, however, want to define species as a biological unit by defining species limits and thereby putting each bird into a particular box. Unfortunately species just don't fit that easily into a box. Hence the plethora of species concepts in attempts to do so and the use of sub-species, clines, morphs, ecological units etc. all of which muddy the boundaries for the ordinary person and for the animal itself, is irrelevant.

So, use whatever system that suits your purpose. You'd have to be dreaming that you can argue a species concept that will achieve broad agreement, let alone resolve the issue.

Chris Shaw

I would argue that scientists are quite aware that many species just don't fit into the neat boxes; even Charles Darwin commented on it. I guess what it comes down to is what concept is useful for a given research group and a given research question. BSC was developed by ornithologists and is quite applicable to birds, but fails with other groups. I really don't see, in the long run, subspecies being maintained for anything but birds or perhaps mammals. Even then, how often do you see new subspecies being described or delimited?

Do you anticipate PSC in other groups or which other alternative to the BSC?

Niels

The reason the BSC is successful is that it maps onto a biological reality which is digital, not analog. If there were no such thing as biological species, then all individuals would be able to reproduce with every other individual. Elephants could hybridize with mushrooms. What would such a world look like. It's really absurd to deny that there are biological entities which prefer to mate with their own kind. Nor should the existence of positive assortative mating be taken for granted. It is not something we humans made up so we could catalog birds the way we catalog rocks.

This is not to say that there are not cases of evolutionary intermediacy. If speciation is an evolutionary process, that is not unexpected. But to focus on the borderline cases at the expense of the vast array of unique biological entities is not particularly productive.

I will admit that the BSC does not work all that well for asexually reproducing organisms and that other species concepts may do a better job at describing such situations.

The Herp community has almost completely switched over to Evolutionary Species Concept, and I think you see a similar pattern in fish workers.

BSC works so well for birds because it is so easy to test and so important to birds. Birds rely on vocal and display mate recognition systems, which are amendable to human observation. Also the majority of species are relatively easy to do field studies on in nature (at least compared to shrews and salamanders). Biological recognition might also be more important just because birds have greater (intentional or accidental) dispersal capabilities compared to most organisms.

In contrast, many species may rely on scent or similar chemical cues that might be too subtle for human detection as a speciation recognition. Similarly, allopatry, habitat selection, and even "culture" may be more important in selection than any sort of barriers to interspecies mating. There are plenty of examples of this, even within my subarea of interest (marine mammals).

Mysticete said:

Even then, how often do you see new subspecies being described or delimited?

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Well, two new avian subspecies were described in the first issue of BBOC this year, and another three are being considered for publication in the pages of the same journal, which compared to the number of new bird species being described these days, seems like a fair rate, especially when you consider also the percentage of avian taxonomists who, unlike Van Remsen, have abandoned BSC and therefore are only going to describe new taxa as species.

Chapter 12 is there

Personally I think if biologists stopped arguing about subspecies...alot of biologists would be out of work.

Fundamentally though (my opinion), this is something I have seen get worse from the eighties on, alot of the problem results from trying to mix cladistics (at least as a thought process) with Linnean rank based approaches.

Herpetology is a good example, cladistics is wonderful at showing relationships, but as humans, snakes and lizards are much easier to understand.

That might seem a bit off topic, but what I am getting at is a push to reconcile an evolutionary approach to systematics to a more intuitive approach (which admittedly is often wrong but works). "I saw a snake" is much easier for most people than I saw a highly developed monitor lizard (Varanidae - from memory) that lost it's legs - is much easier.

So to me it is simple using the right tool for the job, once that hurdle is overcome then there is no problem with subspecies. But trying to fit square pegs into round holes never works.

Once you get away from trying to force too much on a rank system it is fine. Subspecies makes sense since it is just a description of the current state of things. With no real information on past or future. The danger is just trying to read too much into it. So it is simply a matter of keeping it in context.

As scientists it makes sense to record - and organise - as much information as possible, eg. blue balls in the blue container, red in the red container. Ignoring phenotype arguments for now... So if you have a red ball with a touch of blue - do you make a new container for it? Throw them in the red container? or say they are almost red, so they must be closer to red...put them in a little box in the red container.

That makes sense to most people, but if you use a phylogenetic approach and try that, suddenly all the balls are in the same container. You have learnt a great deal more scientifically about your balls, but have gained nothing in terms of communication.

To me it is just a matter of using the right tool for the job. Elevation of everything to species level is scientifically ambiguous - or plain wrong. And dropping the subspecies loses too much information.

If I see a good picture of Malurus cyaneus - Superb Fairy-wren, I can normally spot where it is from straight away based on phenotype. To say they are all the same is a disservice and to elevate them all to species would be absurd.

Well that made sense to me, but I doubt anyone else.

End incoherent ranting...

Scott.

jmorlan said:

Here's the URL for the whole publication:

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and here the pdfs

Daniel Philippe said:

and here the pdfs

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Great! Thanks for sharing.

Avian subspecies

On the ABA Blog today, the first of a four-part series by Steve Howell: On Avian Subspecies: Buyer Beware? - Part 1.

Avian subspecies - 2

On Avian Subspecies: Buyer Beware? - Part 2.

Howell is clearly unconvinced by Banks 2011 (Taxonomy of Greater White-fronted Geese).
www.birdforum.net/showthread.php?t=213378

I wonder where these posts are ultimately going. Endorsement of PSC? recognition of some sort of class of field-identifiable form that doesn't correspond to subspecies? Implications for how field guides should treat subspecies?

Mysticete said:

I wonder where these posts are ultimately going. Endorsement of PSC? recognition of some sort of class of field-identifiable form that doesn't correspond to subspecies? Implications for how field guides should treat subspecies?

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I guess we'll know by Thursday...