Paraphyly

Thomas G. Lammers lammers at FMPPR.FMNH.ORG
Fri Jun 13 09:40:17 CDT 1997


At 10:17 AM 06-13-97 -0400, Robert J. Soreng wrote:

>Take a close look at Cronquist's argument for Cyperales (Cyperaceae +
>Poaceae) especially page 1135 An Integrated System of Classification of
>Flowering Plants, 1981, and ask yourself if he willingly accepted
>polyphyletic groups.  I think it is pretty clear that he was willing to
>if they had converged enough and were closely related.  Subsequent
>anatomical and molecular evidence have bolstered the position that
>Joinvilleaceae is the sistergroup to Poaceae and that Cyperaceae and
>Juncaceae are sistergroups.  But even in 1981 the placement of Poaceae
>with Cyperaceae was on shaky ground, and Cronquist knew it.

Well, it's not EXACTLY polyphyly.  To me, polyphylly is the old
Pachydermata, with elephants, hippos, and rhinos all in an order together,
yet actually branches of three seperate trees within the mammals.  I think
what Cronquist is talking about in loc. cit. is a very "diffuse" monophyly,
where several closely related things collectively give rise to a derivative
group.  I don't think it was a case of convergence, exactly.  Rather a
matter of degree, not kind.    After all, if we were really compulsive about
our definition of monophyly, we should insist that ever sexual species, for
example, be traceable to an original breeding pair.  Somewhere, Cronquist
argues (I believe) that organisms with a roughly similar genetic makeup,
when confronted by similar challenges, may give rise to similar descendents.
This is what he means by "close parallelism".   Isn't something like this
being postulated for the rise of Homo sapiens from H. erectus on a global
scale?  That within a given species, similar adaptive shifts or mutations
happened repeatedly in disparate populations, eventually creating something
new and distinct along a broad front?  Isn't it known that this has indeed
happened with certainly recently evolved species, e.g., Tragopogon mirus and
T. miscellus in the nw. USA?

I guess the point is, that some of us feel it is silly to swear allegience
to a methodology that demands we ignore biological reality.  We must make
our classifications accomodate nature, and not the reverse.


Thomas G. Lammers

Classification, Nomenclature, Phylogeny and Biogeography
of the Campanulaceae, s. lat.

Department of Botany
Field Museum of Natural History
Roosevelt Road at Lake Shore Drive
Chicago, Illinois 60605-2496 USA

e-mail:     lammers at fmppr.fmnh.org
voice mail: 312-922-9410 ext. 317

*******************************************************************
"He uses statistics as a drunken man uses lampposts
 -- for support rather than illumination."
                                            -- Andrew Lang




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