nominal characters

[Alan Harvey]

At 8:10 AM 4/7/95, Richard Jensen wrote:
>
>Ordering of two state characters may be implicit, but unless we know the
>evolutionary origin (e.g., for my example of fruit maturation in oaks:
>annual vs. biennial), we can't be sure of the ordering.  Simply coding
>one as 0 and the other as 1 does not validate the "order."  Whic way is
>it, 1-->0  or 0-->1?  While the order is unchanged, the interpretation is
>quite different.  This will be important for cladistic analyses in which
>the transformation series needs to be included (of course, parsimony
>methods can be applied to unordered data).
>

I don't mean to nit-pick, but what Richard describes above as the "order"
of a two-state character is in fact its "polarity."  As Maddison, Donoghue
and Maddison (1984) and probably a slew of others have noted, polarity and
ordering are different concepts and need to be treated as such.

Alan Harvey


------------------------------------

Alan W. Harvey (aharvey at amnh.org)
Assistant Curator of Invertebrates
American Museum of Natural History
Central Park West at 79th Street
New York, NY 10024
(212) 769-5638