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Re: SICB Report



GJ Dyke wrote:
> 
> Apparently the
> > only way to find these is to compare them to the known control
> cladograms;
> > there is no algorithm that will tell you in advance that a cladogram
> is
> > incorrectly construl with it":
> cted (if there were, it would become
> part of the
> analysis,
> > of course). I was surprised to learn that the percentage was so high.
> 
> >>Also not entirely correct.  I agree that we can never *know* whether
> we have the One True Tree or not, but we can go beyond simply saying
> "Here's my tree - deal with it ">>>
> 
> Or we can expect to "converge" on the one true tree by the addition of
> characters and taxa - take the example of Mesozoic bird phylogeny,
> despite the dramatic increase in the numbers of taxa since 1986 (when
> Cracraft published his early work), overall topology appears to have
> remained the same, with no real changes in "shape" .... if you see what
> I mean ...

I absolutely do.  This is something John Wiens' paper deals with, though
not as directly.  One potential problem, though, is that some of John
Huelsenbeck's simulations suggest that if a given source of data is
positively misleading, the addition of more of it will only increase the
degree to which it misleads.  This makes all kinds of assumptions about
random sampling that don't really apply to morphology, and addresses
*character* data.  I'm sure you've seen the recent spate of papers
showing how taxon sampling can be more critical than character sampling.

Unfortunately, too many paleontologists are hung up on resolution - if
you add something and resolution drops, you've done something wrong. 
Most of the fossils we add are just going to force a local collapse, and
won't alter the topology.  I think Wiens misses it on this point  - he
sometimes uses the number of MPT's as a quasi-measure of accuracy,
something a Point of View in the same issue of Syst Biol calls him on.


chris