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Overuse of 'subspecies'


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Posted by vvvddd on September 26, 2002 at 19:08:50:

Hello,

I've been kicking an idea around lately concerning the overuse of a so-called taxonomic classification known as 'subspecies'. What exactly is a subspecies? The book "Evolutionary Biology", by Douglas J. Futuyma, defines a biological species as "a population, or group of populations, among which there is interbreeding (gene exchange). Two individual organisms might not be able to interbreed, but they are members of the same species (conspecific) if they are part of the same gene pool (Chihuahuas and Great Danes are an example)."

Ecologically speaking, species are broken down into numerous populations across the entire range. Here is a (linear) diagram using letters of a multiple-population species over some range:

A-B-C-D-E-F-G

Now, assume the range of this species to be similar to the north-south populations of an east coast species such as L. getula or E. obsoleta, where A is the northern-most population and G is the southern-most population. Each population is generally able to interbreed with sympatric populations (B will share genes with A and C). However, A and G (getula getula and getula floridana) do not directly interbreed in the wild and may be so evolved for their own specific range that they cannot willfully interbreed in captive conditions.

Does this mean that A and G are different species? According to Futuyma, the answer is no, because A and G are still sharing genes (tell me if I'm wrong) through a succession of populations. This means that A through G are a single species and should be classified as such.

So what exactly is a subspecies? Subspecies are (again, Futuyma)"populations of a species that are distinguishable by one or more characteristics and are equivalent to 'geographic races' No criteria specify how different populations must be to warrant designation as subspecies, so some systematists have argued that the practice of naming subspecies should be abandoned."

So why aren't subspecies abandoned? Some argue that subspecies are populations that are currently evolving and will, one day, be an entirely different species. That is probably true, but the rate of evolution will be different for all every population depending on the rate of change of its environment. It would be logical to classify organisms in the 'now' rather than the 'then' because it is impossible to know what may happen to those organisms in the future.

In the end, it seems to me that the only valid 'subspecies' is a reproductively isolated population (i.e. does not share geneflow of any kind from other populations) but still retains enough similarity to a 'parent' species that individuals willfully breed in captivity. But again, it may become its own species in a few hundred/thousand years, or it may just go extinct, or it may re-establish geneflow with the parent species.

Why so many subspecies classified in Reptilia in general and serpentes in particular?

Easy answer- Money!

Subspecific classification justifies herpetoculturists, breeders, and dealers to charge more money for a rarer population of a species that may be slightly different (especially in color) from the rest of the species. Popular examples are Elaphe, Lampropeltis, Morelia, Pituophis, Epicrates, and Boa (off the top of my head).

Please note I'm not trying to blame or label anyone, just speaking my mind. Please tell me if I'm off my rocker, but PLEASE EXPLAIN WHY!

James (Van) Van Dyke


PS If I am mistaken about getula getula and getula floridana, replace them with any other sympatric subspecific populations that DO interbreed. If sympatric populations do not interbreed, then they should be different species, not subspecies.


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