Re: Tree of Life

On Wed, 9 Apr 2008 19:51:34 +0100, Ernest Major
<{$to$}@meden.demon.co.uk> wrote:

In message <fq0qv3dse9kjsb1jtbn12allov5mot544k@xxxxxxx>, r norman
<r_s_norman@xxxxxxxxxxxx> writes
On 9 Apr 2008 10:17:10 -0700, TomS <TomS_member@xxxxxxxxxxx> wrote:

The latest issue of "Nature" magazine features on the cover
an article on the animal branch of the tree of life:

CW Dunn et al.
Broad phylogenomic sampling improves resolution of the animal
tree of life
Nature 452 (10 April 2008) 745-750
doi:10.1038/nature06614

Is there anything in the paper that is of particular or special
interest we should take note of? The 'editor's summary' of its
contents

http://www.nature.com/nature/journal/v452/n7188/edsumm/e080410-01.html
says: "The conclusions confirm ideas long established by anatomy,"

That is unless you really want us to pay special attention to the fact
that "New and interesting evolutionary relationships are also
uncovered, including a single origin for spiral cleavage of the early
embryo."

Or perhaps you mean the support for "velvet worms rather than
tardigrades as the sister group of arthropods." OK, proposing a
"clade that unites annelids (including sipunculans and echiurans) with
nemerteans, phoronids and brachiopods" is really quite an exciting
development. I eagerly await the sequel. (These last two citations
from the paper, itself)
http://www.nature.com/nature/journal/v452/n7188/abs/nature06614.html

This was discussed a little in the blogosphere a month ago when it came
out on Nature advanced publication. See
<URL:http://nimravid.wordpress.com/2008/03/06/the-metazoan-tree-of-life-i
mproved/>.

I looked at the supplementary information at the time. The most
surprising result is ctenophores (two taxa studied), rather than
sponges, as the sister group to other animals.

I'd worry about this being the result of a long branch artefact (adding
base pairs doesn't always correct long branch artefacts), but they've
done about as well as reasonable with outgroups - they include a
capsasporid amoeba and a choanoflagellate, though a nuclearid amoeba
would have been nice. However they only included one sponge. (A second
sponge was not included in the Bayesian analysis.)

Yes, I did see that point about the Ctenophora. But I didn't read the
entire paper to see how it might be discussed. I can't see how the
diploblastic body structure with a gastrovascular cavity could easily
have originated quite independently of the embryonic development of
the rest of the animals (sponges excepted).

.

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