More on the 'cladistics' of sequences

[John Grehan]

At 01:24 PM 6/11/04 -0500, Richard Jensen wrote:

>That's my point - the character could be used in either a phenetic or a
>cladistic analysis.  The same data matrix can be analysed by a cladistic
>algorithm or a phenetic algorithm.

Well I can agree with this although I would say that the latter would not
be cladistics if the characters were not already limited to predicted
synapomorphies.

>The results will most likely be
>different, as will the interpretation, but that's a function of how the
>characters are analyzed, not how they are are coded.

I agree that the results may be different depending on what algorithm is
used, but I also assert that the results can be different depending on what
kind of characters are used. Using characters that are an undetermined mix
of primitive and derived characters is, to me, just a phenetic analysis
whether or not a cladistic algorithm is used on the data. So the lack of
correspondence between the huaman-orangutan morphology and DNA sequences
could be due (with respect to the DNA sequences) that:

1. The DNA sequence data only represents an overall similarity of DNA
sequences and is therefore not a necessary match for phylogeny;
2. And DNA sequences may not necessarily match the genetics connected with
speciation events that is represented in the morphological synapomorphies.

John Grehan


>Dick
>
>
>--
>Richard J. Jensen              | tel: 574-284-4674
>Department of Biology      | fax: 574-284-4716
>Saint Mary's College         | e-mail: rjensen at saintmarys.edu
>Notre Dame, IN 46556    | http://www.saintmarys.edu/~rjensen