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Posted by vvvddd on December 10, 2002 at 13:39:35:
In Reply to: subspecies - useful or not? posted by troy h on December 10, 2002 at 12:00:43:
On how you use the taxonomy. Subspecies are extremely important to conservation because its easier to protect just the endangered population than the whole species, which may not be endangered (as a whole).
At the same time however, I think ssp is used far too often with regards to taxonomy and evolution. Burbrink's ratsnakes are a good example of eliminating ssp effectively (but not elevating them to species status). The lineages were separated by bodies of water and glaciers during the glaciated period of history. We would have legitimately (I think) called them subspecies then. Now, as the glaciers retreat and the bodies of water shrink to rivers, the subspecies come back into contact across rivers and mountain ridges to share genes once more, thus eliminating most reproductive restrictions and re-mixing the populations into one single species with some genetic difference still present due to the historical separations.
The remaining groups do have different external morphology (color pattern, maybe scale counts). But does that really constitute enough difference to make them subspecies? Internal morphologies and molecular data suggest that they're all pretty much the same.
Ecologically, the color patterns are somewhat restricted to certain habitats, but is this phenomenon ancestral or derived? In other words, were they restricted to those habitats by glacial separation and are now losing that restriction or are they just now separating in this manner? Its impossible to really predict what effects future evolution will have on the speciation of these groups, so why make them subspecies in terms of "future possible species"?
What exactly is a subspecies anyway? Species themselves are difficult to define with at least 4 different species concept definitions. Why complicate things by throwing an additional classification level below species that is even more difficult to define. Compare American subspecies, such as ratsnakes, kingsnakes, or milksnakes, that don't really have any large gaps in their populations (correct me if I'm wrong), to an example of Australian subspecies like Coastal Australian and New Guinea Taipans. Theres a huge gap between them but (as I've heard) they haven't been separated long enough to be true species morphologically or molecularly, so they are subspecies. Which subspecies definition is more correct? Ecologically, the Taipans would be different species all together. I don't know how they would rate in terms of the BSC and RSC.
I guess what I'm trying to say is that a standardized format using a combination of all the species concepts and as much information as possible (molecular, ecological, morphological, etc) for determining what species/subspecies are would be ideal. Using just one concept and one method and reaching a definitive conclusion cannot be the most useful way (as shown by Burbrink's ratsnakes and all the controversy they have generated). Unfortunately, I don't know how reliable a standard format would be in light of natural variations and deviations.
Again, I think subspecies is a fluid concept that is going to be used more often in ecology and conservation but less often in systematics. However, systematicists MUST utilize individuals from ALL ecotypes and populations of a species to be able to do their jobs most effectively.
Is it important to distinguish subspecies from populations or ecotypes? All separate populations are going to have lines of intergradation just like subspecies do. All will be adapted to their microhabitat, just like subspecies are. All must interbreed with other groups that are all part of a 'species-level' whole. What sets subspecies apart from populations? How different do they need to be to be worthy of a taxonomic classification? Why not just note them as geographical variations?
Here is an excellent example that will probably stir up some
emotions. DISCLAIMER- do not take this the wrong way, it is just an example of taxonomy and should not be related to cultural or racial prejudices in any way, shape or form.
Lets use your 3 rules on human populations.
1) the variation in pattern or scalation must be tied to geography
-I think this one holds true for humans (at least, before you take modern immigration/emigration into account).
2) intergrade zones must be narrow (geographically) and tied to changes in geography or vegetation
-This one you could probably argue either way. I don't know enough anthropology to really make a definitive statement, but I think it would hold true.
3) intergrade (intermediate) specimens must be common in the intergrade zone. if intermediates are rare, you're probably talking two species & a hybrid zone.
- Again, I don't think I'm qualified enough to definitively answer this, but I'd again agree with it applied to a human example.
My opinion, say what you may
To reiterate, nothing I said was meant in any kind of racial or prejudiced way. If anyone feels offended, I am truly sorry for that is NOT my intention. It is just an example of geographical variation.