Fwd: Re: [TAXACOM] genetic vs morphological trace of phylogeny

[John Grehan]

At 04:11 PM 4/9/2004 -0600, Derek Sikes wrote:
>John,
>
>I think the question of whether DNA data can be considered "cladistic" can
>be simply answered by reading papers published in Cladistics, the top
>journal of the field 'cladistics'.

Hmm - so its the 'top' journal in the subject now? (Interesting in that I
understand the field of cladistics is fractionalized and if you are in the
wrong faction you do not get published in this journal).

>If one were to do this, one would notice that a large percentage of the
>papers deal with DNA data. I'm sorry, but there is *absolutely no question*
>about whether DNA data can be used in cladistic analyses. None.

If publication of DNA data in a 'cladistic' journal is the criterion.

>Anyone who thinks otherwise cannot be a practicing systematist.

Really?

>There are differences between morphology & DNA, yes,

Thanks for the agreement on that (to contrast with others)

>but as I've said before, both types of datacan be analyzed the same way
>and often are - using parsimony, and now (>2001) maximum likelihood.

I guess I do not see these methods making the phylogeny 'cladistic' in the
sense of Hennig, Rosa etc. As Curtis has so kindly pointed out, I appear to
be out of step with 'informed' opinion (informed being by definition the
majority).

>Taxacom is a good place for expressing views, exploration of ideas and
>learning from each other. But I'm wondering if learning is actually
>happening...

That can go in anyone's direction.

As I have said before, there seem to be different opinions about the nature
of DNA characters being cladistic or not, and different opinions about
whether DNA characters may be misleading about phylogeny (from problems
such as homology, phenetic vs cladistic status) no matter how many are
stacked up in favour of a particular pattern - and this by people who do
cladistics and molecular work.

And of course, there is that vexing question of fossils. If, as some say,
molecules are the only reliable source, fossils become meaningless without
molecular corroboration. There is still the problem of Lucy and her
relatives looking just like the very ape supposed to be least related, and
even sharing some apparent synapomorphies with that ape (cheekbone
structure, palate thickness). There is a real incongruence here that may
not just go away.

John Grehan

Dr. John Grehan
Director of Science and Collections
Buffalo Museum of Science
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