revolution

Richard Jensen rjensen at SAINTMARYS.EDU
Thu Oct 3 10:34:07 CDT 1996


In reply to the remarks below, I suggest that you consult any reasonable
discourse on phenetic analysis.  A fundamental aspect of systemtics,
regardless of the preferred method, is that comparisons be made based on
homologous characters.  Sokal & Sneath and Sneath & Sokal provided
extensive discussion of the problem of homology.  As one who has used
phenetic methods, I can assure you that I used assumptions of homology in
constructing character information for generating character matrices.

Gee, I wasn't aware that everyone who conducted cladistic analyses used
_exactly_ the same procedures.  Or, have I missed something.  Parsimony
is a model for algorithms, but I wasn't aware there was a universally
agreed upon way to generate most parsimonious solutions.  In fact, I'm
not sure that there is universal acceptance of most parsimonious
approximations as the final arbiters for a cladistic reconstruction.

I hesitate to stir up the relatively peaceful waters in which most
systematists are treading, vis-a-vis phenetics, cladistics, etc.  What we
need to keep in mind is that, while the two approaches have the same
starting points (yes, right through the preparation of taxon by character
data matrices for input to a preferred algorithm), they have explicitly
different objectives.  I can apply a parsimony algorithm or a simple
cluster analysis to the same data matrix.  The answers may be the same,
they may be different.   I would not recommend interpreting the phenetic
analysis as a reflection of evolutionary relationships (although, it may
very well be an excellent reflection of same), nor would I recommend the
cladistic analysis as a reflection of overall similarity (again, it may
be a good reflection of this).

Richard J. Jensen      |   E-MAIL: rjensen at saintmarys.edu
Dept. of Biology       |   TELEPHONE: 219-284-4674
Saint Mary's College   |   FAX: 219-284-4716
Notre Dame, IN  46556  |

On Thu, 3 Oct 1996, Tom DiBenedetto wrote:

>
> I disagree absolutely with this, There is no concept of homology in
> phenetics, no vision of individual characters as marks of history,
> and a reliance on measures of overall similarity. I dont know what
> you mean that we "start at the same point",,,with organisms?
> ok....The two approaches do not generate the same kind of data, and
> in cladistics we do not analyze with a variety of procedures.
> ---------------------------------------------
> Tom DiBenedetto
> Fish Division
> Museum of Zoology
> University of Michigan
>




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