angiosperm origins

[Thomas G. Lammers]

At 10:19 PM 4/28/04, you wrote:
>       The "anthophyte hypothesis" (Gnetales as sister group to
> angiosperms) has been under repeated attack in recent years.  Various
> lines of molecular data have been used to argue that Gnetales are only
> convergently similar to angiosperms, and that gnetophytes are closer to
> conifers.  Some say Gnetales is sister group to Family Pinaceae
> ("gnepine" hypothesis), and others say Gnetales is sister group to all
> conifers (which I presume is what is called the "gnetifer"
> hypothesis).  Actually, if Pinaceae is sister group to all other
> conifers, then it would seem to me that the gnepine hypothesis is really
> only slightly different from the gnetifer hypothesis.  The really big
> question is whether we should abandon the anthophyte hypothesis.
>       But if Gnetales are not the immediate relatives of angiosperms,
> then which gymnosperms are?  Caytoniales?  Or perhaps Bennettitales?  And
> if the latter, are Bennettitales themselves also convergent to
> Gnetales?  Are there any other candidates for sister group to
> angiosperms?  Darwin's big "mystery" remains unsolved and I just wonder
> how long it will remain so.

Given the growing emphasis on molecular data in systematics, and the near
impossibility of extracting DNA from fossils, I suspect it will never be
answered with satisfaction.

FWIW, I'm betting on Caytoniales or Glossopteridales, though I haven't
spent much time looking into it.

A recent paper germane to this discussion is:
T. F. Stuessy, A trasnsitional-combinational theory for the origin of
angiosperms.  Taxon 53: 3-16 (Feb 2004).


Thomas G. Lammers, Ph.D.

Assistant Professor and Curator of the Herbarium (OSH)
Department of Biology and Microbiology
University of Wisconsin Oshkosh
Oshkosh, Wisconsin 54901-8640 USA

e-mail:       lammers at uwosh.edu
phone:      920-424-1002
fax:           920-424-1101

Plant systematics; classification, nomenclature, evolution, and
biogeography of the Campanulaceae s. lat.

Webpages:
http://www.uwosh.edu/departments/biology/Lammers.htm
http://www.uwosh.edu/departments/biology/herbarium/herbarium.html
http://www.geocities.com/TheTropics/Resort/7156/lammers.html
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