nominal characters

Richard Jensen rjensen at SAINTMARYS.EDU
Fri Apr 7 08:10:06 CDT 1995

The ordering of mutistate qualitative characters is critical if they are
to be used in ordination or for the calculation of distances.  The
"ordering" of two-state characters is of no consequence, except that
reordering changes the sign of the correlation/covariance.

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 know the pin/thrum literature that well.  There are taxa in which
the mature anthers are at two different levels within a single flower and
I seem to recall examples in which there are three states for anther

I was going to suggest life history strategies as nominal characters for
some groups: i.e., self-compatible, self-incompatible.  For some taxa,
these two seem reasonably well-marked.  For others, both states occur in
a single population.  But, this is not morphological.

How about the morphology of starch grains in the cotyledons of peas?  As
I recall, there are two clearly differentiated morphologies for starch
grains, both of which can occur in a single individual; other
individuals, however, uniformly produce one or the other type.  This was
once viewed as a simple Mendelian trait, reflecting a dominant/recessive
condition.  But recent work has revealed that the determination of starch
grain shape is much more complex than the effects of a single Mendelian gene.


Richard J. Jensen      |   E-MAIL: rjensen at
Dept. of Biology       |   TELEPHONE: 219-284-4674
Saint Mary's College   |   FAX: 219-284-4716
Notre Dame, IN  46556  |

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