----- Forwarded message from
Alfonso Caetta
Date: Tue, 14 Aug
2012 13:41:23 -0400
From: Alfonso Caetta
Reply-To: Alfonso Caetta
Subject:
help
To: [email protected]
----- End forwarded message
-----
Hi,
we are trying to use landmarks to
analyze the effect of some genetic and environmental variables on the
developmental instability of the fly wing. We are using MorphoJ with landmarks
obtained using TPSdig.
We want to measure size
variation between genotypes/temps (using centroid size variation) and shape
variation (using procrustes fit variation). We wanted to use both fluctuating
asymmetry, and total within-group variation, as our measures of developmental
instability.
As newcomers to this field, we have a
couple of basic questions:
1) Can raw centroid size
difference (R minus L) be used to gauge wing size variation, or must these
values be corrected somehow to account for allometry or overall size differences
that may exist between genotypes? i.e., how do we normalize the R-L values so
that they are comparable across genotypes and
treatments?
2) When doing procrustes fit to estimate
fluctuating asymmetry values, must we perform an individual procrustes fit for
the two wings of EACH individual fly, followed by an estimation of procrustes
distance between the two wings' landmark profiles? Or, alternatively, can we
perform a single procrustes fit for ALL wings of each genotype say, and then
using an L vs R classifier in MorphoJ, estimate procrustes distances between
wing pairs?
I hope these questions make
sense!!
thanks
--
Alfonso
Caetta
Columbia University, NY
