distance based DNA trees

[B.J.Tindall]

Rob,
Interesting comments, which can be explained. ALL methods of evaluation,
whether it be neighbor-joining, maximum parsimony, or even maximum
likelihood include an underlying assumption that "parsimony of evolution"
is operating. Thus both phenetic and cladistic approaches include some
underlying reference to parsimony, without which just anything would be
possible.
Brian

At 09:55 15.4.2004 +1200, Rob Smissen wrote:
>I was going to let this pass, but Curtis Clark has written it twice, and
>I find myself in dissent.
>
>"Modern DNA phylogenetic
>studies don't use distance measures. "Genetic similarity" is basically
>too
>crude a measure, and it's not what we are talking about here."
>
>I published a nucleotide substitution distance tree last year, I may do
>it again. I very seldom find neighbour-joining trees built using an
>appropriate substitution model differ significantly from parsimony
>trees. Ditto for least squares or minimum evolution trees. NJ has the
>advantage of speed. Distance trees seem to be rather more realistic in
>estimating internal branch lengths for ancient radiations as a bonus.
>Where they do differ, there is usually a lack of clear signal in the
>data and neither is at all reliable. Where different tree building
>methods do give different results there is usually a specific
>explanation - that is the disagreement reveals or at least illustrates
>important properties of the data. Sometimes it will then be possible to
>argue why one method is better in the specific case - I don't think you
>can do that generally and absolutely.
>
>Moreover, since I keep seeing those "we stopped the search after X days
>because the universe was going to collapse before it finished" parsimony
>trees in the literature, maybe an honest NJ tree would be preferable -
>at least it is locally optimal.
>
>There is a very handy beta version of MEGA3 available, and PAUP4b10 has
>numerous distance options.
>
>If I had the time to do all those big likelihood searches I could just
>watch evolution happen and take notes :)
>
>cheers
>Rob
>
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