B.J. Tindal, logics and terminology

[Gurcharan Singh]

-----Original Message-----
From: Pierre Deleporte <Pierre.Deleporte at UNIV-RENNES1.FR>
To: <TAXACOM at USOBI.ORG>
Date: 05 November, 1999 4:35 PM
Subject: Re: B.J. Tindal, logics and terminology


B. J. Tindall <bti at DSMZ.DE>  wrote (no title):

(...)
>Thus I can sort organisms into groups by overall
>similarity, or based on character sets, but neither the resulting
>phenogram, nor the resulting cladogram is the "phylogenetic tree" unless I
>start to try to explain the resulting dendrogram in terms of evolution.


>>As for the ambiguity of many terms designating the different methods in
>>systematics, you are right again. These terms have both a general
>>acception, and a restricted meaning when naming a particular school in


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
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Our aim of using diverse methods is to ultimately develop phylogenetic
systems of classification. Till this is achieved we should attempt to
maintain the identity of different terms and approaches.
Phenogram as all of agree is a dendrogram constructed through taximetric
methods based on different character-states of a particular character.
Cladogram has been the most confused term often used for phylogenetic trees
or even diagrams representing putative relationships between groups ( as
line diagrams: Classification of Hutchinson for flowering plants, or as
bubble diagrams: classifications of Cronquist, Takhtajan, Thorne, etc; It is
logical to call these diagrams as phylograms as suggested by Stace, 1989).
It is useful to restrict term cladogram to a diagram constructed through
cladistic methods ( similar to taximetric methods in general methodology)
based on distinction between plesiomorphic and apomorphic states of a
particular character, using principle of parsimony and some specialised
procedures. The line diagrams and bubble diagrams are merely diagrammatic
representation of phylogenetic relationship where the length (or distance) a
group reaches is roughly correlated with its degree of apomorphy. They are
better differentiated as phylograms. A phylogenetic tree be better
understood in the traditional sense, i.e. vertical axis representing the
geological time scale.

Gurcharan Singh

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