[Taxacom] The Reality (or not) of Species (again!)`

Curtis Clark jcclark-lists at earthlink.net
Sun Sep 14 10:25:45 CDT 2008


On 2008-09-13 17:58, Richard Pyle wrote:
> Sorry, Curtis -- I stand by my assertion that the image of the billowing
> smoke is a MUCH closer representation of the "reality" of the contunuum of
> life through the ages than the stick-figure cladograms we see so often.

I didn't say it wasn't a representation, I said it wasn't reality. As a 
representation of evolutionary history (in contrast to it also being a 
representation of smoke), I find it un-useful, since it generates no 
hypotheses.

With respect to your essay about species, I think our differences *are* 
semantic, but no less important for the way they shape our views of 
evolution.

Consider the cells in a metazoan or land plant. With some exceptions 
(cardiac muscle comes to mind), most of us have a clear conception of 
cells as "real" objects. There's an entire field, cell biology, that 
assumes they are.

Nevertheless, it's somewhat of an arbitrary exercise to say when during 
mitosis one cell becomes two, and in some cases, such as endosperm 
formation in many flowering plants, it can be rather fuzzy for a while.

What I am saying is that it's not necessary to be discrete in order to 
be "real".

I consider species to be real because I (used to) study their origins. 
As I pointed out to Tom, that would be pretty silly if species were 
imaginary. I consider species and individuals both to be real because 
both genealogy and phylogeny seem to be useful models of specific parts 
of evolutionary history, and yet they consist of different patterns, 
which implies a difference in process.

And I consider the fuzzy parts to be the most interesting. Sometimes it 
turns out that they aren't fuzzy at all (at least among land plants, 
"intermediate" forms tend to be over-represented in museum collections, 
since they are the ones most often brought back to be keyed out). 
Sometimes within-species variation can be maintained over long periods 
of time, through ecoclines and the like. Sometimes the fuzziness is the 
result of unusual breeding systems (for example, agamospermy rarely 
interrupted by sexual reproduction in some plant groups). And sometimes 
the fuzziness is the early stage of a speciation event, or perhaps a 
failed speciation event.

Despite there being a lot more tools for studying these things, such 
studies are less popular that they used to be. But the questions are 
still out there.

-- 
Curtis Clark                  http://www.csupomona.edu/~jcclark/
Director, I&IT Web Development                   +1 909 979 6371
University Web Coordinator, Cal Poly Pomona




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