nomenclature vs. identification key

[chris brochu <cbrochu@blue.weeg.uiowa.edu>]

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!)

agreed.




> >  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
> > presuppositions.


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 
taxonomy.


chris



--
------------------------
Christopher A. Brochu
Assistant Professor
Department of Geoscience
University of Iowa
Iowa City, IA 52242

christopher-brochu@uiowa.edu
319-353-1808 phone
319-335-1821 fax

www.geology.uiowa.edu/faculty/brochu