Characters.

[Don.Colless at CSIRO.AU]

John Grehan belongs to an ancient school that claims there is no difference between a character and a character state. I suggest that those who do not share this quaint belief give up arguing with him. I learned long ago that it's a waste of time!

Don Colless,
Div of Entomology, CSIRO,
GPO Box 1700,
Canberra. 2601.
Email: don.colless at csiro.au
Tuz li munz est miens envirun



-----Original Message-----
From:   Taxacom Discussion List on behalf of Richard Jensen
Sent:   Tue 6/22/2004 12:09 AM
To:     TAXACOM at LISTSERV.NHM.KU.EDU
Cc:	
Subject:             Re: Characters.
John Grehan wrote:

> At 08:42 PM 6/18/04 +0200, pierre deleporte wrote:
> >OK you restate your view, but it is simply wrong as cladistics goes. If we
> >have surmounted the semantic problem about "phenetic" (concerns analysis,
> >not characters) and we do agree on what "overall similarity" means (i.e.
> >between taxa, not characters), hence your statement is still wrong.
>
> We will just have to agree to disagree. I view phenetic characters as
> characters that individually represent overall similarity of a feature. To
> me that's phenetic.

Here, perhaps, is a major part of the problem.  Overall similarity is not a
function of a single character - I don't know how a single character can
illustrate overall similarity.  Overall similarity refers to a measure of
similarity (e.g., a simple matching coefficient, Manhattan distance, Pearson
correlation) between all pair-wise comparisons of taxa (e.g., A vs. B; A vs. C;
B vs. C) "over all characters in the data matrix."

This is why definitions are important!

Dick
--
Richard J. Jensen              | tel: 574-284-4674
Department of Biology      | fax: 574-284-4716
Saint Mary's College         | e-mail: rjensen at saintmarys.edu
Notre Dame, IN 46556    | http://www.saintmarys.edu/~rjensen