-------- Original Message --------
Subject: cva question
Date: Wed, 30 Nov 2011 21:35:23 -0500
From: Jordan Mallon <[email protected]>
To: [email protected], PAST <[email protected]>
Dear all,
I've reached a bit of a dilemma with my morphometrics studies lately,
stemming from the hierarchical nature of variation. I've been studying
ecomorphology and how it varies within and between three dinosaur
families (each family contains two subfamilies). I've been using
canonical variates analysis to examine which variables best
discriminate the various taxa. The three families are perfectly
discriminated in CVA space.
Next, I would like to examine how the subfamilies differ, particularly
those that belong within the same family (i.e., looking at
intra-family variation). As far as I can tell, I have two options:
1) Place all six subfamilies into a single CVA and look for
intra-family clustering. The problem I see here is that most of the
variance captured by the CV axes will comprise inter-family
differences, rather than intra-family differences, because the
families are much more separate in space than sister subfamilies. In
other words, if families A and C are well-separated along axis 2, and
subfamilies Ai and Aii are only slightly separated along the same
axis, the loadings on that axis will tell me more about the separation
of families A and C than about subfamilies Ai and Aii. Right?
Hopefully I'm making myself clear.
2) Just run separate discriminant function analyses on all sister
subfamilies. I suppose this negates the problem above, but it
otherwise involves more work.
Has anyone run into a similar problem before? If so, how have you dealt
with it?
Thanks,
Jordan
