[Taxacom] Defining polyphyly

[Richard Jensen]

John,

For someone who has argued that definitions are irrelevant, you surely 
take advantage of every opportunity to obfuscate (is this deliberate, or 
do you simply not understand what is meant?).  Let's try "informed 
estimate"; would that be OK?  Or, how about "informed hypothesis"?  Or, 
is the latter redundant?

I think we all know what Richard intended, just as we all know what 
we'll get if we order "jumbo shrimp"!

Dick J

On 12/15/2010 8:10 AM, John Grehan wrote:
> "informed guess"? Seems a bit like an oxymoron.
>
> John grehan
>
> -----Original Message-----
> From: taxacom-bounces at mailman.nhm.ku.edu
> [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Richard Zander
> Sent: Tuesday, December 14, 2010 8:07 PM
> To: Kenneth Kinman; taxacom at mailman.nhm.ku.edu
> Subject: Re: [Taxacom] Defining polyphyly
>
> Students should note that definitions by cladists are ALWAYS in terms of
> patterns of nested exemplars, never in terms of process-based theory of
> descent-with-modification with informed guesses on which was the
> progenitor and which the descendant. Thus paraphyly and phylogenetic
> polyphyly can be anything represented by these simple patterns that turn
> up in patterns of evidence. Evolutionary polyphyly is when the same
> taxon is generated by an ancestor taxonomically different from the
> ancestor of a different but similar line. Phylogenetic polyphyly could
> be this, or it could signal what Ken Kinman refers to as paraphyly with
> multiple exgroups.
>
> _______________________
> Richard H. Zander
> Missouri Botanical Garden
> PO Box 299
> St. Louis, MO 63166 U.S.A.
> richard.zander at mobot.org
>
>
> ________________________________
>
> From: taxacom-bounces at mailman.nhm.ku.edu on behalf of Kenneth Kinman
> Sent: Tue 12/14/2010 5:55 PM
> To: taxacom at mailman.nhm.ku.edu
> Subject: [Taxacom] Defining polyphyly
>
>
>
> Dear All,
>           As I said in my last post, I agreed with how
> Chris defined a paraphyletic group (specifically, a singly paraphyletic
> group). However, I think that he misspoke in defining a polyphyletic
> group as "clade A minus clades B. C., etc." Actually that defines a
> paraphyletic group with multiple exgroups (doubly paraphyletic, etc.).
> But if you then combine those exgroups together, you do get a
> polyphyletic group. Creating a paraphyletic group is a subtractive
> process, while creating a polyphyletic group is an unnatural additive
> process.
>              For instance, Class Reptilia is a
> doubly paraphyletic group: Clade A (Amniota) minus Clades B and C
> (exgroups Aves and Mammalia). However, if you combine the two exgroups
> (B plus C), you do get a polyphyletic taxon (namely Haemothermia).
> Polyphyletic taxa are unnatural, while paraphyletic and holophyletic
> taxa are natural.
>                      ----------Ken
> ----------------------------------------------
> Chris Thompson wrote:
>        Not exactly as a paraphyletic group is merely clade A
> minus clade B. A polyphletic group is merely clade A minus clades B, C,
> etc. So, it is not argument by authority.
>
>
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-- 
Richard J. Jensen, Professor
Department of Biology
Saint Mary's College
Notre Dame, IN 46556
Tel: 574-284-4674