[Taxacom] Paraphyletic species and paraphyletic higher taxa

[John Grehan]

We are back to the authority of the evidence (characters) rather than
just a 'what the heck' choice about groups.

John Grehan

-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Richard Jensen
Sent: Tuesday, December 14, 2010 1:43 PM
To: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Paraphyletic species and paraphyletic higher taxa

So, we're back to authority - I imagine (perhaps hypothesize) a 
phylogenetic group and my preferred method of classification yields that

group, thus my method is phylogenetically accurate?  Or, do I know ahead

of time that my preferred method will yield accurate phylogenetic
groups?

Besides, just because my analysis suggests that group A is a 
monophyletic, that doesn't mean it really is.  Just that the data on 
hand suggest it is.  By what criterion do I know that the reconstruction

is accurate?

Dick J

On 12/14/2010 1:16 PM, John Grehan wrote:
> Accurate in the sense that it denotes a phylogenetic group.
>
> If the goal of constructing groups is to represent groups comprising
all
> descendants of a unique common ancestor then that ability would be
> considered useful. If the goal of constructing groups is something
else
> then presumably usefulness would be defined in some other way.
>
> John Grehan
>
> -----Original Message-----
> From: taxacom-bounces at mailman.nhm.ku.edu
> [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Richard
Jensen
> Sent: Tuesday, December 14, 2010 1:10 PM
> To: taxacom at mailman.nhm.ku.edu
> Subject: Re: [Taxacom] Paraphyletic species and paraphyletic higher
taxa
>
> John Grehan wrote:
>
> "But the group would not be phylogenetically informative or accurate."
>
> I don't know how we can assess phylogenetic accuracy - accuracy
implies
> no error, or meeting a specified standard.  Given that we cannot know
> what the real phylogeny is, what standard is used to determine
accuracy?
>
> We also have to ask ourselves what we want the recognized group to
> convey.  That is, there is a notion of usefulness connected with any
> classification and while we may wish our classifications to be useful
as
> explanations of phylogeny, we may also wish them to be useful for
making
> predictions.  These two aspects of usefulness are not necessarily
> congruent.
>
> Dick J
>
>
>
> On 12/14/2010 12:49 PM, John Grehan wrote:
>> But the group would not be
>> phylogenetically informative or accurate.

-- 
Richard J. Jensen, Professor
Department of Biology
Saint Mary's College
Notre Dame, IN 46556
Tel: 574-284-4674


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