re: Character State Choice - We Have a Long Way to Go

[david peters <davidrpeters@earthlink.net>]

Mickey Mortimer wrote:


There are far too many instances where characters are defined as a feature
being smaller or larger than some other feature. 

In actuality, of course, taxa show a continuously varying range of
proportions for any such character, and gaps made of proportions not filled
by any taxon will fill up as we discover new specimens.   Unfortunately,
given the limitations of PAUP, we need to break up such a range of
proportions into a few states.  This is problematic for a few reasons.  If
we use too few states, we'll lose potentially useful information.


>>>>>
I found in my cladistic analysis of the Pterosauria similar problems. Try 
statistics. Take all the data and ratios, then place the figures on a 
continuum. Let them fall, like pachinko pinballs, into natural groupings into a 
jagged sort of bell curve, (usually). At the 'breaks' you can place upper and 
lower limits on the various states. 

It's okay to expect and get homoplasy. Get enough data and those problems will 
work themselves out into natural groupings.  Perhaps this is what the original 
writers did, and that's why you might get states that are not halves, or 
quarters, but unanticipated fractions.

BTW ~ If anyone wants to play with 178 characters and 109 ingroup taxa within 
the Pterosauria, let me know if you have a PC or Mac and I'll send you my 
MacClade file. You'll also need a bit of freeware calld Stuffit Expander or 
WinZip to open the compressed files.

PAUP says the data produces a single most parsimonious tree. You'll see I used 
a number of multi-state characters following the statistically method above. 
And if you find any data point errors in the matrix, please let me know. I'm 
trying to get all the kinks out before publication.

Hope this helps,
David Peters