Felsenstein versus Ockham?

R. Zander bryo at PARADOX.NET
Mon Jan 25 15:00:05 CST 1999


Tom:
To some extent we can simply repeat our philosophical stances endlessly, and I think we've explained them well enough in this
forum.

Tom DiBenedetto wrote:

> R. Zander wrote:
> >In the case of parsimony, I recommend a high Bremer support value for a clade before a cladistic hypothesis can be
> >seen as a genuine probabilistic reconstruction that is better than any other method of grouping taxa by characters
> >influenced by evolutionary processes.
>
> I have no argument with the notion that better-supported trees are a good thing to have. And I agree that Bremer
> support is a relevant and useful metric. And I agree that a weakly supported tree is not one on which anyone should
> base susbequent dependant studies. But I dont think many people do that anyway. And I dont think it has anything to
> do with probabilism.

We agree, essentially, about whether or not to use weakly supported trees in future studies. And yes, I see few studies using
past studies to determine, say outgroups, for the new study. On the other hand, this kind of house of cards is coming, you can
be sure of it.


> But you will agree, will you not, that one of the alternative toplogies for a given set of taxa MUST BE guilty, no?

Yes, given a few assumptions, one of them is the true tree. That statement is much like saying there is a confidence or
credible interval there. I am content with the credible interval and feel no compulsion to select one tree as "best" when the
chance that the true tree is somewhere among sum of the alternatives is so high. What does "best" mean anyway, when you cannot
act upon it?


I appreciate your considered responses, Tom, to what I believe are critical problems in phylogenetic analysis.

Richard

--


Richard H. Zander, Curator of Botany
Patricia M. Eckel, Research Fellow in Botany
Buffalo Museum of Science
1020 Humboldt Pkwy, Buffalo, NY 14211 USA
bryo at paradox.net   voice: 716-896-5200 ext. 351




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