Terms: Disparity, modularity, integration...

Last week I was trying to analyse shape data with geomorph package in R. However, I’m unfamiliar with the terms used in geometric morphometrics literature so I decided to intentionally read “Geometric Morphometric for Biologists - A Primer” by Zelditch, Swiderski and Sheets (2nd edition 2012).

Here are a few terms I want to note for my future self:

Disparity - the variety of a group of species. Outcome of evolutionary processes. The increase in # of taxa does not always mean increase in mophological ‘disparity.’

Variation - Variety of individuals within a population (homogenous). This is what selection acts on.

Integration - tendency for different traits to vary in a coordinated manner throughout (morphology or even the whole organism).

Modularity - integrated ‘modules’ that are compartamentalised. E.g. flowers and compound leaevs are modules but themselves are modular stuructures consistenting multiple parts arranged in specific ways. Example of modular design is a personal computer where users can swap different hardwares and it will still work if they are compatible.

Other notes:

Definition of Shape (Kendall 1997) Shape - is all the geometrical information that remain when location, scale and rotational effects are filtered out from an object.

Configuration matrix defines a shape on a Cartesian coordinate.

Pleiotropy (pleion = ‘more’ tropos = ‘way’) - occurs when one gene influence multiple (seemingly) unrelated phenotypes. This is related to integration.

Variance-covariance matrix - “represents the expected covariance structure of the residuals from regression equation” (Garamszegi 2014). Essentially, this matrix is used to account for phylogenetic relationships when applying generalised least squares. I think I will have to make another post about this when I learn more about it.

The variance-covariance matrix represented by (Garamszegi 2014).

References:

Klingenberg. 2014. Studying morphological integration and modularity at multiple levels: concepts and analysis. Phil. Trans. R. Soc. B 369: 201302493. pp 276-285.

Garamszegi LZ (ed). 2014. Modern Phylogenetic Comparative Methods and Their Application in Evolutionary Biology: Concepts and Practice. Springer Berlin Heidelberg, Berlin, Heidelberg. pp 113-115

Zelditch ML, Swiderski DL, Sheets HD (2012) Geometric morphometrics for biologists: a primer. academic press

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Sarin 'Putter' Tiatragul
PhD Candidate

I’m a Thai PhD candidate at the Research School of Biology (ANU). I go by the name “Putter”.