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.
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).
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