[Taxacom] burn out (was: classification of Class Rosopsida)

Tue Apr 14 11:14:10 CDT 2009

Richard,
I pointed out logical fallacies in your statements, which you use to 
support your view that paraphyletic classifications are inherently 
better than phylogenetic ones.

You say that "alpha taxonomy [taxonomists?] has the best grip on 
evolution-generated groupings". This is necessarily a subjective 
statement, because it depends on what you consider "best". Seems to me 
that what you consider best are unchangeable classifications set only by 
alpha taxonomists.

However, classifications have been constantly modified over time, not 
just by molecular phylogeneticists; also by people using cladistic 
methods with morphological traits, and for an even longer time, 
exclusively by "alpha" taxonomists using no particular method of 
analysis. Not to mention that, by definition, alpha taxonomy focuses on 
species-level issues, not higher level classifications. You mean 
traditional systematists, which many taxonomists are.

Besides, many taxonomists are also phylogeneticists (molecular or not), 
or routinely collaborate with them; thus the distinction you want to 
make is not clear at all.

I still cannot understand the logic in your statement that phylogenetic 
classifications eliminate information on ancestor-descendant 
relationships. You always have to refer to a cladogram or some other 
type of evolutionary diagram to visualize these relationships. How does 
a paraphyletic classification have more of this information? A 
classification is just a series of names of taxa and associated ranks. 
You cannot see that one group descended from another just by looking at 
a list of names in a paraphyletic classification.

Mario

Richard Zander wrote:
> Mario:
> You cannot refute the points I am making by making true statements about
> other things. 
>
> Classification should be based on evolution, most of us agree. My
> central point is that alpha taxonomy has the best grip on
> evolution-generated groupings, and that molecular analysis can
> demonstrate direct evolutionary relationships (paraphyly-autophyly
> series) between such groups as ancestor-descendant relationships (that
> is, involving descent with modification of taxa). 
>
> Classification by holophyly eliminates this information. The "natural"
> taxa are already classified by alpha taxonomists, and are chock full of
> evolutionary information that molecular analysis can reveal. Molecular
> analysis can let one know when one taxon is in the wrong cluster and
> point out the right cluster but otherwise the classification is already
> there in the original evaluation by an alpha taxonomist.
>
> Discovery of paraphyly, "massive homoplasy," and "cryptic" taxa has been
> misinterpreted. These features are evolutionary information and should
> not be hidden by burying them (in synonymy or splitting into new names)
> in phylogenetic classifications.
>
> *****************************
> Richard H. Zander 
> Voice: 314-577-0276
> Missouri Botanical Garden
> PO Box 299
> St. Louis, MO 63166-0299 USA
> richard.zander at mobot.org
> Web sites: http://www.mobot.org/plantscience/resbot/
> and http://www.mobot.org/plantscience/bfna/bfnamenu.htm
> Non-post deliveries to:
> Missouri Botanical Garden, 4344 Shaw Blvd., St. Louis, MO 63110
> *****************************
>
>
> -----Original Message-----
> From: taxacom-bounces at mailman.nhm.ku.edu
> [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Mario Blanco
> Sent: Sunday, April 12, 2009 5:34 PM
> To: TAXACOM
> Subject: Re: [Taxacom] burn out (was: classification of Class Rosopsida)
>
> Richard Zander wrote (in brackets):
>
> [ The reason some of us insist on paraphyletic taxa is because
> evolution,
> if defined as descent with modification, is described only by
> paraphyletic-autophyletic series, where the paraphyletic taxon is the
> descendee (ancestor), and the autophyletic taxon is the descender. ]
>
>    Not true. Evolution does not require a classification to be 
> described. If you meant "represented" instead of "described", then your 
> statement is also erroneous. Evolutionary history can be represented by 
> a cladogram, and can be summarized by a series of monophyletic clades 
> nested in other (monophyletic) clades. You can circumscribe every clade 
> so they are all monophyletic.
>
> [ In a phylogenetic cladogram with paraphyly eliminated, we know what
> the
> descender is, it is the exemplar, but we don't know what the descendee
> is, it is only a node, without diagnosis or any real biological
> attribute. ]
>
>    A cladogram by itself does not have paraphyly or monophyly. Those are
>
> attributes of classifications. If you meant to say "phylogenetic 
> classification" instead of cladogram, then your are implying that in a 
> paraphyletic classification you know the "descendee" (I guess you mean 
> ancestor), which you do not know by just looking at the names of taxa in
>
> either type of classification. Just by looking at a group of names of 
> families in a paraphyletic classification, you cannot know if one of 
> them originated from another. In a phylogenetic classification, at least
>
> it is safe to assume that none of them originated from another taxon in 
> the same rank.
>
> [ The central stem of a phylogenetic lineage is a series of
> nothings. ]
>
>    It is a series of hypothesized ancestors. Same as in a paraphyletic 
> classification. Again, you are confusing cladograms with
> classifications.
>
> [ ONLY demonstration of descent with modification of taxa will
> demonstrate
> evolution. This may be done in several ways, but demonstration of
> paraphyly should be the one way systematists should try to preserve by
> not enforcing holophyly in circumscribing taxa. ]
>
>    Again, an explanation of the evolutionary process does not require a 
> pre-existing classification. You are stating your preference of 
> classification methodology as if it was a fact.
>
> Mario Blanco
>
>
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