[Taxacom] cladistics (was: clique analysis in textbooks)
Richard.Zander at mobot.org
Thu Aug 18 14:33:27 CDT 2011
What I mean is that there is no one clade. A clade is a grouping of exemplar specimens on a cladogram. The morphology has a clade of (maybe)
((homo orang)(chimp gorilla)) gibbon, or something like that.
The DNA has a clade of ((homo chimp)gorilla)orang
Asking which is the true clade is nonsense because based on method not theory. Like "which is the true method?"
Both are based on clustering by present-day relationships, which are equivocal.
* * * * * * * * * * * *
Richard H. Zander
Missouri Botanical Garden, PO Box 299, St. Louis, MO 63166-0299 USA
Web sites: http://www.mobot.org/plantscience/resbot/ and http://www.mobot.org/plantscience/bfna/bfnamenu.htm
Modern Evolutionary Systematics Web site: http://www.mobot.org/plantscience/resbot/21EvSy.htm
From: taxacom-bounces at mailman.nhm.ku.edu [mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Kenneth Kinman
Sent: Wednesday, August 17, 2011 10:37 PM
To: taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] cladistics (was: clique analysis in textbooks)
Well, in this case, the consensus is that the orangutan clade is
actually "D", the first great ape to split off, and that ABC (however
those three are interrelated) is an exclusive clade separate from the
orangutan clade. If you are suggesting otherwise, which of the great
apes is the outlier (if not the orangutan)?
In any case, the morphology of the great apes has not remained
static (even if molecular evolution has tended to race ahead of
morphology). Perhaps we just have to look a lot harder for fundamental
morphological transitions within the presumed hominid-African ape clade
to challenge those of Schwartz and Grehan (which I still believe to be
Molecular analysis may not be able to "directly" refute and
reject the proposed orangutan-hominid clade in the near term, but I
believe it will help resolve whether the chimp-hominid clade is as
well-founded as most researchers seem to believe (and if it is not, that
opens the door to more intensive research into an exclusive
chimp-gorilla clade, which sadly has been relatively neglected by both
sides in this debate).
The fossil record of great apes is so fragmentary that it
generates more heat than light in this debate (much like the fragmentary
fossil record of angiosperms). Therefore, as with angiosperms,
molecular analysis will probably make break-throughs that allow a more
efficient search for true morphological synapomorphies. Only then will
congruency be found between molecular and morphological data sets. The
angiosperm researchers seem to be far ahead of great ape researchers in
this difficult process of reevaluation and new discoveries.
Richard Zander wrote:
Again, I suggest that morphological clades and molecular clades
can be different because they are based on different dimensions in
present-day relationships of evolution, thus the refutation of one clade
cannot be done by finding high probability that the other is correct.
Morphologically you can have ((AB)C,D and molecularly ((AC)B,D, and both
are correct if the morphological ancestor of both A and B is C.
C is then postulated as a morphologically primitive taxon surviving into
present time after generating the geographic isolate B then A. This
difference in clades is because DNA continues to mutate but the
morphology can remain in stasis.
Molecular analysis cannot refute or reject the orangutan-homo
morphological evolutionary relationship, assuming the morphological
relationship has been demonstrated by Grehan and Swartz, et al. A direct
analysis, using other data, that might reveal the morphology of the
ancestor of both man and whatever the sister group in morphology is, is
necessary. The present argument is just talking past each other, and
both analyses, if taken separately, are each sciolistic, that is, based
on only partial knowledge.
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