Re: DNA news stories: bird and mammal evolution

["David Marjanovic" <david.marjanovic@gmx.at>]

> One question I have about DNA-DNA studies is: are they testable?  In a
> cladistic study of morphological characters, you can at least go back and
> see if you coded the characters properly.  In other words, what do you do
> if you get a DNA result that is, on the face of it, counter-intuitive
(like
> linking grebes and flamingos) and may not coincide with morphological
> features?  There seems to be some tendency to assume in such a case that
> the DNA results are "right", but how can you be sure?

Just wait for a newer study that uses more genes, more taxa, more reliable
genes etc.. Such things happen meanwhile. B-)

A good example is

Sandra L. Baldauf, A. J. Roger, I. Wenk-Siefert, W. F. Doolittle: A
Kingdom-Level Phylogeny of Eukaryotes Based on Combined Protein Data,
Science 290, 972 -- 977 (3 November 2000, directly following the description
of *Eudibamus*).

It uses four nuclear genes and demonstrates that more genes bring much more
resolution and support for clades. Apparently it has managed to eliminate
long-branch attraction, therefore it finds Microsporidia next to Fungi (and
doesn't include the really basal fungi...), a holophyletic Mycetozoa
(plasmodial + cellular slime molds), and the new Plantae (land plants +
green algae + red algae + Glaucophyta) as well as really big groupings.

>   For example, a recent DNA study on turtle origins put turtles near
> archosaurs, but also put Sphenodon closer to archosaurs than lepidosaurs -
> a result that flies in the face of the morphological evidence.  How do you
> assess such a result?

In the above way. Just found a paper in the newest Naturwissenschaften --
there is genetic evidence for the traditional placement of turtles (even
though that paper can't exclude placing them next to crocs). Of course, I've
forgot the ref... :-] It also says that mtDNA is generally less reliable,
though I forgot why.

BTW, just to show off =8-) , I've got PDW for birthday!

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I have never made predictions and will never do that.
        unknown