[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: cladobabble


Kendall,
This is just a suggestion, but if you really want to challenge your students (and perhaps your own thinking as well), I would suggest exploring the possibility that Lophotrochozoa is paraphyletic to the clades Deuterostomia and Ecdysozoa. Specifically, are the genes (and Hox genes in particular) of Lophotrochozoa really synapomorphies, or just plesiomorphies??? This question has not only *not* been answered, but few have even thought to ask this question at all.
-------Ken
P.S. I would also note that I have long believed that platyhelminths are secondarily simplified from other "lophotrochozoans". And I also agree that poriferans and cnidarians are probably paraphyletic as well (in addition to lophotrochozoans, each in succession).
******************************************************** 
From: Kendall Clements <k.clements@auckland.ac.nz>
To: Ken Kinman <kinman@hotmail.com>
CC: dinosaur@usc.edu
Subject: Re: cladobabble
Date: Mon, 16 Oct 2000 17:01:47 +1200

On Mon, 16 Oct 2000 01:23:03 GMT Ken Kinman <kinman@hotmail.com> wrote:

>
> Kendall,
>       I'm wondering which tripartite bilaterian phylogeny you are
referring > to.  Did any of your students question whether one of the
three "clades" > might be paraphyletic?


Dear Ken

The tripartite phylogeny I was referring to is summarised in several
papers over the past few years, e.g.

Adoutte, A., G. Balavoine, N. Lartillot, O. Lespinet, B. PrudÕhomme and
R. de Rosa (2000) The new animal phylogeny: reliability and
implications.  PNAS 97: 4453-4456

Balavoine, G., and A. Adoutte (1998)  One or three Cambrian radiations?
Science 280: 397-398

Conway Morris, S. (1998) Metazoan phylogenies: falling into place or
falling to pieces? A palaeontological perspective. Curr. Opin. Gen.
Devel. 8: 662-667

de Rosa, R., J.K. Grenier, T. Andreeva, C.E. Cook, A. Adoutte, M. Akam,
S.B. Carroll and G.  Balavoine  (1999)  Hox genes in brachiopods and
priapulids and protostome evolution.  Nature 399: 772-776

Knoll, A.H., and S.B. Carroll (1999)  Early animal evolution: emerging
views from comparative biology and geology.  Science 284: 2129-2137

Peterson, K.J., and E.H. Davidson (2000) Regulatory evolution and the
origin of the bilaterians.  PNAS 97: 4430-4433


None of the students questioned whether any of the three clades were
paraphyletic. If they were they wouldn't be clades, would they? I have
read that it is possible that cnidarians are paraphyletic, and that
poriferans (sponges) are PROBABLY paraphyletic. However, as far as I am
aware results to date suggest Deuterostomes, Lophotrochozoa and
Ecdysozoa are all clades. Analyses that place Platyhelminthes outside
Lophotrochozoa have been questioned.

Cheers

Kendall

----------------------
Kendall Clements
k.clements@auckland.ac.nz

_________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.

Share information about yourself, create your own public profile at http://profiles.msn.com.