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nomenclature vs. identification key
I think we're beginning to run in circles about this, so these will
be my last thoughts on this series of threads.
Besides, I actually have stuff to do.
Ken Kinman wrote:
Using a military hierarchy as an analogy, Reptilia was like a big land
army in which only a single company specialized in airplane duties in the
early years---- but then the "air force" company expanded rapidly
and becomes a separate branch ("Class" Air Force) that rivaled the
importance and diversity of the "Class" Army from which it was
removed. A crude analogy, but you get the idea.
Crude enough to be inaccurate. Fixed ranks and divisions in the
military have meaning beyond a natural hierarchy; last time I
checked, organismal taxa weren't all that concerned about
congressional funding or chain of command.
Steve Salisbury wrote:
> Why? We're working in an evolutionary framework, Owen worked on a
typlogical framework. Different frameworks.
Ah. A penny has dropped! Why should you assume that everyone is working in
your evolutionary framework?
It's not MY evolutionary framework. Evolution provides a hierarchy
that we discover (or estimate, or hypothesize, or whatever). It has
nothing to do with me, you, or anyone else.
(in another post,)
The truly important point is that phylogenetically-defined names have
stability in meaning; stability in content, in diagnosis, and in time
of origin can never be stable (under ANY taxonomic system)
Eh? How can a cladistically defined name have meaning in a
non-cladistically based taxonomic system? The truly important point is that
there is more than one set of rules. There's also more than one game, and
no one should be telling us which one we have to play.
I disagree. What's the point of using taxon names if there are as
many meanings floating about as there are systematists? And I hardly
think phylogenetic nomenclature is at fault for creating a set of
rules everyone is expected to use - I've got a rather dense copy of
the ICZN on my desk.
At the end of the day (and hopefully this chain!)
it all depends on whether
you believe taxonomies should reflect phylogenies. I don't think taxonomic
categorisations have anything to do with phylogeny or, for that matter,
evolutionary transformations. To my mind, taxonomic definitions that rely
on assumptions of relationship are therefore meaningless (sorry Chris).
They're conclusions (or hypotheses) - patterns derived from an
analysis are post hoc and are hence not assumptions. And if they're
meaningless, how come we get so much from them? (I know some people
find them useless - but I would argue that such opinions derive from
not REALLY using them, or from finding that a phylogenetic analysis
clashes with one's preconceived notions of what must have happened.)
Taxonomies are much easier to defend when they don't involve phylogenetic
But without phylogeny, there is precious little TO defend. So I
guess you're right - if there's nothing left to defend, one's job
suddenly becomes very easy.
I think, ultimately, part of the difference between Steve's approach
and mine is that for some people, a taxonomic system should serve a
direct utilitarian function as an identification key. ID keys are
certainly useful things (and are true classifications in the
strictest sense of the word), but they are not (and cannot be)
taxonomies, because they are operating from the standpoint that
groups of organisms are classes with static defining properties and
not the historical products of ancestry and descent - which is
precisely what taxonomies are. This is why a phylogenetic
nomenclatural system is not a classification - it operates with
objects understood to be individuals rather than classes.
And I know darned well that phylogenetic nomenclature will not
stabilize everything. What it stabilizes is the meaning of the name
- this is why I was very surprised at the paper by Dominguez and
Wheeler that Ollie cited. "My gosh! This will only stabilize name
meaning!" Yes! That's the whole point! They seem to have
independently figured out what the central strength of the method is,
and in their surprise regard it as some sort of fault. The only way
we can establish content stability is to have perfect knowledge of
biodiversity and its history - something we can only achieve
(hopefully) when we croak. (A few moleculoids and I have a case of
Steenbrugge riding on the resolution of the Gavialis issue.
Unfortunately, if I'm to collect, I have to die.)
Another point to emphasize (though independent of the above
discussion) - phylogenetic nomenclature is not tied to parsimony
analysis. I know there are many reading these threads who advocate
alternative methods (e.g. stratocladistics, likelihood); whether I
accept these methods or not is irrelevant to whether these methods
will yield a hierarchical pattern amenable to translation into a
phylogenetic hypothesis. Any such hypothesis can be used to derive a
Christopher A. Brochu
Department of Geoscience
University of Iowa
Iowa City, IA 52242