Systematists and evolutionary biologists have widely adopted Procrustes-based geometric morphometrics for measuring size and shape in biology. Many structures, and in fact most animals, are bilaterally symmetric with an internal plane of symmetry (also called object symmetry). Often, when quantifying asymmetric variation is not an aim, only one or the other side is measured and analyzed. This approach has been used in hundreds of studies. Its implicit assumption is that the information on the other side is redundant and a single side will, therefore, produce results mirroring those one would have obtained from the analysis of the entire structure with all its left and right landmarks. However, the extent to which this assumption is met has, to my knowledge, never been explored. Using two example data sets, I will show that congruence may be high in analyses at a macroevolutionary level but much lower at a microevolutionary one, and inaccuracies might especially affect shape. I will discuss some of the other factors that may influence results and will suggest a simple expedient that can improve both the visualization and accuracy of shape analyses in one-side-only studies.

Lost in the Other Half: Improving Accuracy in Geometric Morphometric Analyses of One Side of Bilaterally Symmetric Structures / Cardini, Andrea Luigi. - In: SYSTEMATIC BIOLOGY. - ISSN 1063-5157. - 65:6(2016), pp. 1096-1106. [10.1093/sysbio/syw043]

Lost in the Other Half: Improving Accuracy in Geometric Morphometric Analyses of One Side of Bilaterally Symmetric Structures

CARDINI, Andrea Luigi
2016

Abstract

Systematists and evolutionary biologists have widely adopted Procrustes-based geometric morphometrics for measuring size and shape in biology. Many structures, and in fact most animals, are bilaterally symmetric with an internal plane of symmetry (also called object symmetry). Often, when quantifying asymmetric variation is not an aim, only one or the other side is measured and analyzed. This approach has been used in hundreds of studies. Its implicit assumption is that the information on the other side is redundant and a single side will, therefore, produce results mirroring those one would have obtained from the analysis of the entire structure with all its left and right landmarks. However, the extent to which this assumption is met has, to my knowledge, never been explored. Using two example data sets, I will show that congruence may be high in analyses at a macroevolutionary level but much lower at a microevolutionary one, and inaccuracies might especially affect shape. I will discuss some of the other factors that may influence results and will suggest a simple expedient that can improve both the visualization and accuracy of shape analyses in one-side-only studies.
2016
10-giu-2016
65
6
1096
1106
Lost in the Other Half: Improving Accuracy in Geometric Morphometric Analyses of One Side of Bilaterally Symmetric Structures / Cardini, Andrea Luigi. - In: SYSTEMATIC BIOLOGY. - ISSN 1063-5157. - 65:6(2016), pp. 1096-1106. [10.1093/sysbio/syw043]
Cardini, Andrea Luigi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/1116709
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