[Taxacom] Elimination of paraphyly: sensible or not?

[Richard Zander]

What common ancestor? A node is not a common ancestor, it is a bifurcation in a cladogram or a space in a set of parentheses in a Newick formula.

If it were a common ancestor, and you imagine it to be a different taxon, then if you accept that a species must have at least two traits different from any other species, then the node would have two traits unaccounted for in the parsimony analysis. The two traits would have to reverse in the two descendants of the sister groups, which makes the cladogram not as parsimonious as simply saying one of the sister group gave rise to the other.

Not all pairs of branches on a cladogram have common ancestors. In fact, I suspect most are progenitor-descendant pairs.


-------
Richard H. Zander
Missouri Botanical Garden – 4344 Shaw Blvd. – St. Louis – Missouri – 63110 – USA
richard.zander at mobot.org<mailto:richard.zander at mobot.org>
Web sites: http://www.mobot.org/plantscience/bfna/bfnamenu.htm and http://www.mobot.org/plantscience/resbot/

From: John Grehan [mailto:calabar.john at gmail.com]
Sent: Friday, February 09, 2018 4:56 PM
To: Richard Zander
Cc: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Elimination of paraphyly: sensible or not?

I thought paraphyletic groups where those that did not include all descendants of the last common ancestor?

When it comes to "Classification should reflect what we know about evolution" the question is what do we 'know'?

John Grehan

On Fri, Feb 9, 2018 at 5:45 PM, Richard Zander <Richard.Zander at mobot.org<mailto:Richard.Zander at mobot.org>> wrote:
Paraphyly is not a process in nature. It models nothing real. It is a gimmick used by cladists because there is no innate taxon concept in cladistics.  It occurs when one taxon generates one or more other taxa of the same taxonomic level.



Phylogenetics is not the study of evolution. It is the study of dichotomous trees generated by non-ultrametric cluster analysis using character state changes. Cladistics is better at grouping evolutionarily related taxa than cluster analysis by overall similarity, but it does not model an evolutionary tree.



To study evolutionary trees you need to be aware of (have information about) radiation of descendants from progenitors. Trees restricted to sister groups do not allow hypotheses of serial evolution.



This discussion is about classification based on a particular kind of cluster analysis, not evolution. Classification should reflect what we know about evolution, not cluster analysis.



-------

Richard H. Zander

Missouri Botanical Garden – 4344 Shaw Blvd. – St. Louis – Missouri – 63110 – USA

richard.zander at mobot.org<mailto:richard.zander at mobot.org>

Web sites: http://www.mobot.org/plantscience/bfna/bfnamenu.htm and http://www.mobot.org/plantscience/resbot/
_______________________________________________
Taxacom Mailing List
Taxacom at mailman.nhm.ku.edu<mailto:Taxacom at mailman.nhm.ku.edu>,
http://mailman.nhm.ku.edu/cgi-bin/mailman/listinfo/taxacom
The Taxacom Archive back to 1992 may be searched at: http://taxacom.markmail.org

Send Taxacom mailing list submissions to taxacom at mailman.nhm.ku.edu<mailto:taxacom at mailman.nhm.ku.edu>
To subscribe or unsubscribe via the Web, visit: http://mailman.nhm.ku.edu/cgi-bin/mailman/listinfo/taxacom
You can reach the person managing the list at: taxacom-owner at mailman.nhm.ku.edu<mailto:taxacom-owner at mailman.nhm.ku.edu>

Nurturing Nuance while Assaulting Ambiguity for 31 Some Years, 1987-2018.