[Taxacom] Elimination of paraphyly: sensible or not?

[John Grehan]

Yes, the common ancestor is the node - at least as I understand it.

John Grehan

On Sat, Feb 10, 2018 at 1:42 PM, Richard Zander <Richard.Zander at mobot.org>
wrote:

> 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
> <https://maps.google.com/?q=4344+Shaw+Blvd.+%E2%80%93+St.+Louis+%E2%80%93+Missouri+%E2%80%93+63110+%E2%80%93+USA&entry=gmail&source=g>
>
> 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>
> 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
> <https://maps.google.com/?q=4344+Shaw+Blvd.+%E2%80%93+St.+Louis+%E2%80%93+Missouri+%E2%80%93+63110+%E2%80%93+USA&entry=gmail&source=g>
>
> richard.zander at mobot.org
>
> Web sites: http://www.mobot.org/plantscience/bfna/bfnamenu.htm and
> http://www.mobot.org/plantscience/resbot/
>
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