[Taxacom] Why character-tracking doesn't happen?
sdmanning at asub.edu
Sat Sep 13 17:55:36 CDT 2008
At 05:41 PM 9/13/2008, Steve Manning wrote:
>At 05:36 PM 9/12/2008, you wrote:
>>Thomas Lammers wrote:
>>...an excellent and concise description of my own views!
>>Neil Bell then wrote:
>> > Aggregations of individuals
>> > and populations (generally and eventually, if by no means
>> > always) become discrete units through the process of
>> > speciation. Incomplete lineage sorting and reticulation occur
>> > and should be identified, but they are not the dominant
>> > patterns in the relationships between phylogenetically
>> > distant eukaryotic organisms.
>>I'm not sure I buy that. It's hard enough characterizing an individual
>>multecellular organism as a "discrete unit" (considering turnover of cells,
>>let alone molecules, over the lifespan of the organism).
This reminds me of a perhaps apocryphal story
about a situation in which a taxonomist,
investigating herbarium specimens, placed three
different collections from the same individual
tree (not knowing they were from the same tree)
into three different genera. When this became
known, the taxonomist was derided and the butt of
jokes. But the take home lesson was that maybe
the taxonomist was right after all if what he saw
matched the type specimens of species in three
genera. Mutations, stages of development and phenotypic plasticity happen!
>> I regard it as
>>effectively impossible to characterize populations (let alone species) as
>>"discrete units", except to define an explicit set of individual organisms
>>at a particular moment in time.
>>Yes, yes, I know the arguments behind "species are real" (had a wonderful
>>conversation with Quentin Wheeler on this recently at a streetside café in
>>Paris), and maybe we're just quibbling over the degree of precision we
>>ascribe to words like "real" and "discrete".
>>Even at a very general level, though, I think there is a notion that there
>>is a "fuzzy" region during speciation events where the boundaries are not so
>>clear, but that these represent mere punctuations against a background of
>>generally stable "discrete species"; an equilibirum of sorts that dominates
>>the majorty of biodivesity. But the more I explore my own realm (coral-reef
>>fishes*), the more it appears that the landscape is dominated by the "fuzzy"
>>areas, so much so that they seem to overlap with and blend into each other
>>over the course of evolutionary history.
>>I see less and less the pattern represented by a maple tree,
>>...and more an more the pattern represented by a Banyon tree.
>>Thomas Lammers then wrote (after I composed the above):
>>...another, even *better* synopsis of the views I express above, with such
>>clarity that it renders what I have written above effectively moot (except
>>that I could quibble with the "individuals are real" statement by
>>Thomas...if I wanted to....which I don't). However, as I have already
>>written the above, and as it took a bit of time to track down the right
>>internet images for the maple tree and banyon tree, I'm sending it anyway...
>>*P.S. On the scale that spans from "things that fit the nice bifurcating
>>model of speciation/evolution" to "things that...errr....don't"; coral-reef
>>fishes are a lot closer to the former than angiosperms. Yet, the patterns
>>therein have let me to the same conclusion as those people who study those
>>nasty, non-conformist plant-thingies.
>>P.P.S. At the recent Linnaeus 250 Symposium, David (Paddy) Patterson used an
>>example that was much better than the maple/banyon tree example. He
>>compared a cladogram (i.e., our attempt to describe reality), to this:
>>(i.e., reality itself).
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