Paraphyly and names
tdib at OCEANCONSERVANCY.ORG
Mon Jan 28 12:06:00 CST 2002
From: SKÁLA Zdenek
That's the matter: "mono(holo)phyletic taxa (=clades) are best because
they are based on synapomorphies; synapomorphies are best because they
indicate clades". You really don't see any circularity?
Your statement is your statement, purposely designed to sound circular. My
statement is that monophyletic taxa are best becaue they are based on
synapomorphy, and synapomorphies are the preferred basis for classification
because they represent character states considered at their true historical
level of generality- and thus indicate complete groupings of species that
share descent from a common ancestor.
Well, I would ask you once again for the meaning of the words like
"natural", "useful", "real" etc. Apparently you still have in mind the
- information that supports them is then "natural, useful and real"
Yes. I use "natural" and "real" somewhat synonomously - referring to actual
events in the real world. Character states really transform within lineages.
Lineages really diverge. This has happened and continues to happen whether
we recognize it or not. Paraphyletic groups are not defined by real or
natural occurances - they are artificial in that their existence is wholly
an invention of human decisions, not a human recognition of a real world
>The eclectic classifications conflate lineage divergence and
Of course it does! It is inherent in the concept of loose monophyly
(incl.paraphyly) and enables the eclectic taxa to maximize the
information content and still being monophyletic....it is upon you Tom to
say why do you prefer the information on the cladogenetic events over the
information on the characters (states).
I strongly disagree that paraphyly maximizes character-based information
content. Paraphyletic groups FAIL to represent character information
accurately. I do not prefer information on cladogenic events OVER
information on character states. I want both - and I want both ACCURATELY.
Character information (or more precisely - reference to particular character
state transformation events) is inherently historical. These are events that
happened in specific lineages at specific times in the history of life. ALL
character information considered by systematists is accurately and
completely presented in a cladistic analysis. The characters are analyzed,
and used to make inferences as to lineage branching events, in a transparant
manner, and the character transformations are then associated with the
lineage branches on which they occured. This is a maximal use and
presentation of character information.
Eclectic classifications use character information in a non-transparant
manner for the purpose of imposing a subjective human judgement that is
allowed to overrides the inferences that are made as to the real-world
branching events in the lineages of life.
There is no way in which this use of character information can be considered
maximal - it does not represent a greater use of character information, it
merely represents an unscientific attempt to attribute greater importance to
some characters rather than others, and to use this subjective judgement to
mutilate the discovered real-world lineage hierarchy.
Aves are holophyletic (I guess being no zoologist), so perfectly
a taxon. In that case you will have still some feathered dinosaurs out
of Aves - even if you will split the "reptilia" into a series of
holophyletic taxa. Does it mean that feathers evolved twice ? ;-)
I think you are missing the point. Feathers are not an apomorphy of Aves,
although they once were considered to be so. For a cladist this means simply
that the character moves up a node or two, and indicates a somewhat higher
taxon. There is no way such a representation would cause anyone to be
confused about the number of times the character evovled. The absurd removal
of Aves from Reptilia, and the classification of the two taxa at equal
levels however does cause such confusion - at least for anyone so naive as
to think that the eclectic classification can teach them anything about the
history of character evolution.
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