Re: Dino cladistics - long with requotations

["Jonathan R. Wagner" <znc14@ttacs1.ttu.edu>]

[S.F.: Changes from the version of this message I sent you are in square
brackets.]
Stanley Friesen wrote:
>The consistency index is a measure of how well the data support the
>reported cladogram.
[next message]
>This says nothing about how likely it is to be the true cladogram, or how
>likely it is that a particular alternative cladogram is closer to reality.

        If my reading of the Gauthier paper was accurate in its
representation of Consistancy index as # characters/ # steps, then it is not
really a measure of how well the data support the cladogram, nor how close
the cladogram represents reality. It is simply a measure of the degree of
homoplaisy in the phylogenetic hypothesis.
        If this is the case, a cladogram with a higher CI is not necessarily
any better than one with a lower CI using a *different* dataset. If they are
derived from the same dataset, however, the higher CI is de facto more
parsimonious, and [is] thus to be favored.
        I believe this illustrates the meaning of minimizing assumed
homoplaisy [by trying to get the lowest CI for a dataset] versus assuming
homoplaisy is minimal [by looking for the lowest overall CI from any dataset].
        Sorry for going so far off dinosaurs, folks...
+--------------------------------------------------------------------------+
| Jonathan R. Wagner                    "You can clade if you want to,     |
| Department of Geosciences              You can leave your friends behind |
| Texas Tech University                  Because your friends don't clade  |
| Lubbock, TX 79409                               and if they don't clade, |
|       *** wagner@ttu.edu ***           Then they're no friends of mine." |
|           Web Page:  http://faraday.clas.virginia.edu/~jrw6f             |
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