what is a species et al.

Mark BROWN brown.mark@wanadoo.fr
Thu, 13 Dec 2007 12:20:13 PST

Dear Mr McKenny,
What a wonderful clear and calm view.Thank-you for your viewpoint.I am making a fairly comprehensive study of primitive angiosperms.And cladistics the best way forward,are our best hope of being as objective as possible,are so valuable because they use all traits and not just genetics to make as clear a picture as possible.Plant fossils are wonderful eye openers too.They contain bizarre mixes of modern plant traits and thus are a lesson for all who try to understand plants today,which as you quite rightly say are only snapshots in time.Paleobotany is a humbling science for overzealous taxonomists.We must always tread some middle path of reason between "lumpers and splitters" anyway.
Mark W.Brown

> Message du 13/12/07 15:45
> De : "Jim McKenney" 
> A : "'Pacific Bulb Society'" 
> Copie à : 
> Objet : [pbs] what is a species et al.
> Warning: ranting old guy alert!
> Dylan wrote: "Whatever the evidence employed, once substantiated
> monophyletic groups are worked out then the rank of those groups becomes
> "academic". Hence the subjective nature of taxonomic schemes and hence the
> everlasting hope of armchair botanists for more suitable arrangements."
> Well said, Dylan, although I want to quibble about one aspect of this
> statement. 
> First, let's take another look at this concept species. Here's my version of
> the history of the concept in a nutshell: from the time of Plato and his
> concept of eidos (form) up until not quite a century ago, gross morphology
> was the only criterion generally considered in delimiting species. 
> Then, as biologists began to realize the implications of what studies in
> genetics were telling them, the concept of population genetics arose and
> from it the idea that species were delimited by breeding behavior. In this
> view, two entities were members of the same species if they shared the same
> gene pool. The beauty of this concept is that it is relatively objective.
> Whereas in the old system based on morphology all of the traditional
> Linnaean ranks (species no more or less than the others) were determined
> subjectively, the "species as an interbreeding population" concept was not
> subjective in the same way: membership, so-to-speak, in a species was not
> subjectively determined by a taxonomist but rather by the breeding behavior
> of the entity in question. Those studying populations didn't determine what
> the breeding arrangements would be, the simply reported what they observed.
> This approach seemed to eliminate the main objection to traditional taxonomy
> - namely that it was subjective. 
> I like to contrast the differences in these two approaches in this aphorism:
> two entities are not members of the same species because they look alike
> (that's the old taxonomic approach); it's the other way around - they look
> alike because they are members of the same species (i.e. they share the same
> gene pool). That's the insight derived from genetic studies. 
> Although the gene pool concept resolved the main objection to traditional
> taxonomy (i.e. that it was blatantly subjective) and seemed to provide a
> modern, objective species concept which could be used for all sexually
> reproducing populations, it did not resolve the challenge posed by
> evolutionary studies. The problem, if it is one, with the gene pool concept
> is that it portrays species as a snap-shot of real life - the species so
> delimited is valid for only an instant. 
> And what are the challenges posed by evolutionary studies? Unless you
> believe in special creation, then all existing species evolved from other
> species. When one species evolves from another, it's a gradual process.
> There is probably never a clear break. It's not as if the new species
> suddenly separates from the existing one; the ancestral species merges
> imperceptibly over time into the new species. Think about that for a moment:
> there is no boundary separating the ancestral and derived species. There has
> been an unbroken succession of parents and progeny over time. That they are
> distinct "species" is an illusion. Darwin himself seems to have been aware
> of this- and I cite Darwin only because he wrote a century and a half ago
> and some people still don't seem to have caught on. 
> There really is no such thing as species in a purely objective sense except
> in the momentary sense - the gene pool concept does give us an objective
> view of species, but because natural populations are constantly shifting and
> changing, that view is valid only at the moment it is made. 
> It's a lot like the conundrum posed by analytic a priori knowledge: the more
> certain you can be about something, the less relevance it has to the real
> world. 
> As you can see, I take the view that species is as much a philosophical
> question as a purely scientific one. I don't expect DNA studies to resolve
> the species question. Every generation has had those who look to the latest
> technological innovations to solve the "species question". When I was a kid
> it was chromosome studies. Technological innovations provide wonderful
> insight, but they won't solve the species problem. 
> We old guys sure do go on, don't we! I'm 64 now, and for the first time in
> my life I have that vague feeling that I wish I were younger, not just
> younger but at the beginning of my intellectual life. Why? Because of all
> the amazing technological innovations: where is it all going? I so envy
> those of you who can look forward to another fifty years: I can't even
> imagine what that world will be like. 
> Thanks Joe for providing some links to broaden our horizons. 
> One final thing. Dylan mentioned "the everlasting hope of armchair botanists
> for more suitable arrangements." But really, Dylan, isn't that what we all
> want? You can rest assured that the DNA guys will be making arrangements
> which suit them.
> I'm all for things making sense. 
> Jim McKenney
> jimmckenney@jimmckenney.com
> Montgomery County, Maryland, USA, USDA zone 7 where Iris unguicularis
> continues to bloom. 
> My Virtual Maryland Garden http://www.jimmckenney.com/
> BLOG! http://mcwort.blogspot.com/
> Webmaster Potomac Valley Chapter, NARGS 
> Editor PVC Bulletin http://www.pvcnargs.org/ 
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