angiosperm enigma

John Grehan jgrehan at SCIENCEBUFF.ORG
Mon Jan 26 13:06:45 CST 2004


Just to add the usual off-the-wall comment on angiosperms phylogeny
(probably a repeat from a posting a long time back) I can't help but wonder
if angiosperm phylogeny is a potential problem as much as that of humans
and orangutans. If Croizat was right about his assertion, for example, that
the flower of a birch is homologous with an ovule of the Magnolia flower,
the popular tree model of angiosperm phylogeny becomes problematic.

Admittedly I've been out of touch with angiosperm phylogeny for a couple of
years, but up to that time there was a lot of the genetic tree construction
that created relationships all over the place with great confidence while
usually nothing was said or understood about the morphology (one
practitioner even considered the morphology completely irrelevant to
phylogeny reconstruction and therefore informative about angiosperm evolution).

As for the Nymphaceae - Croizat (Principia Botanica, 1961) placed it along
with the Magnoleaceae as one of three principal basal nodes in the
transition between pre-angiospermy and angiospermy, along with the
Monimiaceae/Ulmaceae and Betulaceae/Hamamelidaceae (with the podostemaceous
alliance being a lesser node).

John Grehan


At 07:45 PM 1/13/2004 -0800, Ken Kinman wrote:
>Dear All,
>       I should perhaps clarify that I am not
>suggesting the removal of Amborellaceae from the basal
>"ANITA" grade (3 clades?) at the base of angiosperms,
>but just the possible removal of Amborellaceae as the
>FIRST extant clade to split off.  But this has
>extremely important implications for the nature of the
>first flowering plants.
>       The big story for several years now has been:
>Amborella is the first to split off (or the somewhat
>less popular suggestion that an Amborella +
>Nymphaeales clade split off first).  I am actually
>beginning to feel more comfortable with the neglected
>possibility that Nymphaeales (Nymphaeaceae sensu lato
>in my classification) split off alone as the basal
>clade of flowering plants.  Given this possibility,
>whether Amborellaceae then split off before or after
>the "Austrobaileyales" clade is less clear to me at
>this point, or even if the later clade is truly
>holophyletic (strictly monophyletic) or not.  In any
>case, if Amborella is NOT part of that first clade of
>extant flowering plants, the whole picture of
>angiosperm origins could change dramatically.
>          ---- Cheers,
>                  Ken Kinman
>
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Dr. John Grehan
Director of Science and Collections
Buffalo Museum of Science
1020 Humboldt Parkway
Buffalo, New York 14211-1293
Voice 716-896-5200 x372
Fax 716-897-6723
jgrehan at sciencebuff.org
http://www.sciencebuff.org/biogeography/Panbiogeography/Panbiogeography-Gate.htm
http://www.sciencebuff.org/HepialidaeGate.htm




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