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Re: The validity of cladograms (was Re: giant birds)
Tracy Ford wrote:
> The answer is an overwhelming yes!!! In the majority of cases
> cladograms of extant organisms based on morphological characters are
> congruent with those based on morphologicl characters. I have mentioned
> this a couple of times to support my view that cladistics is the best
> method we have for reconstructing the phylogenies of extinct organisms.
> Your message implies that phylogenetic analysis of DNA is somehow
> "different" to that of morphological characters. Molecular characters
> (DNA) can be analysed using exactly he same methods as morphologicl
> characters (i.e. parsimony). Molecular characters can also be analysed
> using a modelling approach (i.e. maximum likelihood), and by a
> clustering approach (neighbour joining). The latter is not usually
> considered reliable enough on its own for evolutionary reconstructions.
> If yes, then why is it in paleontology, 90 % of the time, different authors
> come up with different cladograms? Why isn't there more of a consensus?
Are they "different" 90 % of the time? Tom "Captain Clade" Holtz
presented a good poster at SVP this year showing that, statistically,
the "different" theropod trees out there aren't so "different" after all
- certain select groups are bouncing around in different analyses, but
the general pattern is stable and uniform.
Christopher A. Brochu
Department of Geology
Field Museum of Natural History
Roosevelt Road at Lake Shore Drive
Chicago, IL 60605
voice: 312-665-7633 (NEW)
fax: 312-665-7641 (NEW)