Re: Relating disparity with Semilandmark

[morphmet_moderator]

----- Forwarded message from Philipp Mitteröcker <mitte...@univie.ac.at> -----

Date: Mon, 21 Jan 2013 09:16:47 -0500
From: Philipp Mitteröcker <mitte...@univie.ac.at>
Reply-To: Philipp Mitteröcker <mitte...@univie.ac.at>
Subject: Re: Relating disparity with Semilandmark
To: morphmet@morphometrics.org

Sliding the semilandmarks in order to minimize Procrustes distance minimizes the total sample variance, which is one way to measure disparity. Minimizing bending energy hence will lead to a larger total variance, but bending energy is a more intuitively appealing homology criterion than Procrustes distance. 

However, for typical morphometric data sets I do not expect that the mode of sliding will influence the results considerably.

 

Changing the number of semilandmarks can have more severe effects on the results. Consider multiple measurements on skulls in two groups, and let's say group A is more variable in the face and group B is more variable in the neurocranium. When computing an overall measure of disparity for the whole skull, it will depend on the number of measurements (landmarks and semilandmarks) in the face and the neurocranium whether group A or group B will have a larger disparity measure. This ambiguity does not only apply to semilandmarks, but it is particularly obvious for them.

 

We discussed this in length in Huttegger & Mitteroecker (2011) Invariance and Meaningfulness in Phenotype spaces. Evolutionary Biology 38, 335–352 and Mitteroecker & Huttegger (2009) The Concept of Morphospaces in Evolutionary and Developmental Biology: Mathematics and Metaphors. Biological Theory 4(1), 54–67

 

Best,

 

Philipp

 

Am 16.01.2013 um 14:46 schrieb morphmet_modera...@morphometrics.org:

----- Forwarded message from Kalpana Das <kkalpanaa1...@gmail.com>-----

Date: Tue, 15 Jan 2013 02:38:02 -0500
From: Kalpana Das <kkalpanaa1...@gmail.com>
Reply-To: Kalpana Das <kkalpanaa1...@gmail.com>
Subject: Relating disparity with Semilandmark
To: morphmet@morphometrics.org

Hi all,

I am presently experimenting with how disparity value changes according to different no of semilandmark and also with two different sliding methods.I was wondering how to infer the results and relate disparity with semilandmarks.

Is there any such studies which deals with these topics together.

Any help in this regard will be appreciated.Looking forward fro your responses.

Thank you

Best,

Kalpana

-- 
Kalpana
Center for Ecological Sciences
Indian Institute of Science
Bangalore-560012 India

Email -kalp...@ces.iisc.ernet.in / 
          kkalpanaa1...@gmail.com

Phone(M)   + 919986701835

----- End forwarded message -----

 

___________________________________

 

Dr. Philipp Mitteroecker

Department of Theoretical Biology
University of Vienna
Althanstrasse 14
A-1090 Vienna, Austria

Tel: +43 1 4277 56705
Fax: +43 1 4277 9544
email: philipp.mitteroec...@univie.ac.at
homepage: http://theoretical.univie.ac.at/people/mitteroecker

----- End forwarded message -----