Species as "Hypotheses"

Guy redeuilh redeuilh at CLUB-INTERNET.FR
Tue Jul 13 00:36:56 CDT 2004


I agree with these comments.
At the present time, the unsolved problem for me is : what is a taxon (a word curently used by cladists and phylogeneticists) in a purely phylogenetical - and especially cladistical - concept ?

I resume me too the concept of taxon in "linnean" systematics and nomenclature (ICBN) :
  - In a general definition, a taxon is a biological unit grouping organisms.
  - In linnean classical taxnomy and nomenclature (here ICBN) "taxon" have the same sense and is defined by 4 parameters :
     * Its circumscription (summ of his characters)
     * Its rank (the "vertical" floor in the pyramid of the classification)
     * Its ("horizontal") position in this pyramid in connection with the taxon immediatly superior, in which is included)
     * Its name (nomenclaturally ruled by the Code and taxonomically linked to its type - if have it).
           (the terms horizontal and vertical can be interverted  according to their definition)
Phylogeneticists cladists have "kidnapped" the term taxon (and others as such "species") for their use, but apparently with a different definition, who is unacceptable a priori.
Could someone give a clear definition of th word "taxon" in a purely phylogenetical and cladistical concept ?

G. Redeuilh 

----- Original Message ----- 
From: "Ron Gatrelle" <gatrelle at TILS-TTR.ORG>
To: <TAXACOM at LISTSERV.NHM.KU.EDU>
Sent: Monday, July 12, 2004 8:27 PM
Subject: Re: Species as "Hypotheses"


> ----- Original Message -----
> From: Paul van Rijckevorsel
> Subject: Re: Species as "Hypotheses"
> 
> 
> > Guy Redeuilh Wrote:
> > > This concept applies to a taxon better than a species only.
> 
> From: Richard Pyle <deepreef at BISHOPMUSEUM.ORG>
> > To maintain consistency with the point of my original question, I would
> have to qualify this as "ranked taxon".
> 
> + + +
> Seems to me that a taxon is ranked, by default. A taxon is a taxonomic
> grouping, the result of the application of taxonomy. It is the core business
> of taxonomy to make hierarchical classifications, and the units of the
> taxonomic process are ranked. This may be the big difference between
> taxonomy and systematics?
> 
> **********
> 
> The ICZN glossary has two interesting and useful catagorical definitions of
> taxon.
> 
> A  "zoological taxon" is:  "A natural taxon of animals (which may, or may
> not, have had a name applied to it)."
> 
> A "taxonomic taxon" is:  "A taxon (e.g. family, genus, species) including
> whatever nominal taxa and individuals a zoologist at any time considers it
> to contain in his or her endeavour to define the _boundaries_ of a
> zoological taxon (q.v.).  A taxonomic taxon is denoted by the valid name
> determined from the available names of its included nominal taxa."
> (Emphasis mine.)
> 
> So, for the zoologists here, Richard's term "ranked taxon" would be accurate
> as he applies this to the humanly defined taxa (our species inquiry).   By
> the two ICZN definitions of "taxon", a taxon is not ranked by default -
> unless it is  a taxonomic taxon.  So some hair splitting of terms is
> warranted.   Which brings us full circle into the original question.
> 
> A zoological taxon is simply an observed type of living animal, then, once
> we as humans propose its _boundaries_ and create a taxonomic taxon have we
> proposed a hypothesis or a definition?  That is, a definition (= delimited
> by recognizable boundaries) of the zoological taxon?   To me, it is as
> Richard stated, "...definitions that are followed or ignored based on
> subjective preference by other taxonomists?"   I don't see species as a
> hypotheses.   I see their systematic evolutionary relationships as
> hypotheses - but not their states as species, genera or families.   This is
> because the taxonomic taxon names we create are applied to snap shots taken
> from specific spatial and temporal locations - past or present.
> 
> We _collectively rank_ our taxonomic taxa in a hierarchy, which indicates
> their hypothetical evolutionary past.   But with each ranked entity itself
> we (should) have a taxon that is an observable product of the process, a
> definable reality know not by hypothesis or theory but observable factual
> _boundaries_.  Thus, this is why species are merely argued about and can not
> be put into some pragmatic, standardized, falsifiable formula.   Systematics
> is a quest/debate for/about origins and relationships - taxonomy is about
> subjectively perceived reality at a fixed point in time and space.  The
> reason we talk of "missing links" is because they are missing - thus the
> hypothesis.  Nothing is missing in an observable population of a zoological
> taxon - just let it sting or bit or flog or eat you if you question its
> factual reality.   Species are about tangible boundaries not hypotheses.
> Disagreement on which boundaries are "valid" or which to utilize does not a
> hypothesis make - it makes an opinion based position.   Of course,
> scientists always like to think of their opinions as analytical conclusions
> (by scientific means and methods) and not what they often are - mere
> personal bias.
> 
> Ron Gatrelle.
>




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