polarized and unpolarized

[taxacom]

Sorry, Pierre, for misunderstanding (weighting of 'changes' instead of
characters). I never felt the necessity for such an operation in my
practical work and did associate the term weighting only with characters.

Larissa

----- Original Message -----
From: "Pierre Deleporte" <Pierre.Deleporte at UNIV-RENNES1.FR>
To: <TAXACOM at USOBI.ORG>
Sent: Tuesday, January 15, 2002 3:48 AM
Subject: Re: polarized and unpolarized


> At 17:02 09/01/2002 +1000, Larissa Vasilyeva wrote:
>
> >2. He   [Pierre Deleporte]   wrote that different states are given a
> >different weight, but, actually, states of the same character are of
equal
> >weight since 'weight' of a character means its position in a hierarchy.
>
> In fact I wrote:
> "In phylogenetic inference, ordering characters is a coding procedure
> consisting in giving a different weight to changes between different
states
> of a character".
>
> The key word is "changes". I was speaking of weight of transitions between
> character states, i.e. weight of "steps" for parsimony analysis, but
> neither "weight of characters" nor "weight of character states" properly.
>
> >  (If two genera differ in some character, and one genus possesses a
> > primitive state of this character, while another genus has an advanced
> > state, one can trace a phylogenetic line but both states are equal in
> > level, consequently in weight).
>
> I did not mean this at all, but  "weighting changes" (steps). Character
> ordering, in cladistic jargon, consist in giving increasing weight to
steps
> between character states more distant in the "order" (=unpolarized
sequence
> of states).
> "Unordered" characters mean that for such characters all changes (= steps)
> between any two states are given equal weight for calculating tree length.
>
> Talking of "character weighting" instead of "character steps weighting"
may
> be misleading.
>
> Best wishes,
> Pierre
>
>
> Pierre Deleporte
> CNRS UMR 6552 - Station Biologique de Paimpont
> F-35380 Paimpont   FRANCE
> Téléphone : 02 99 61 81 66
> Télécopie : 02 99 61 81 88
>
>