[Taxacom] Why character-tracking doesn't happen?

Richard Pyle deepreef at bishopmuseum.org
Fri Sep 12 17:36:31 CDT 2008


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). 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, 
http://www.dkimages.com/discover/previews/838/25010916.JPG

...and more an more the pattern represented by a Banyon tree.
http://farm1.static.flickr.com/128/331038459_6136f090fe.jpg

*******
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...

Aloha,
Rich

*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:
http://www.pages.drexel.edu/~bko23/20061121091445_smoke%20for%20web.jpg
(i.e., reality itself).






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