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.File | Dimensione | Formato | |
---|---|---|---|
2016 cardini one side only mirroring point of view.pdf
Open access
Descrizione: articolo
Tipologia:
VOR - Versione pubblicata dall'editore
Dimensione
436.72 kB
Formato
Adobe PDF
|
436.72 kB | Adobe PDF | Visualizza/Apri |
Pubblicazioni consigliate
I metadati presenti in IRIS UNIMORE sono rilasciati con licenza Creative Commons CC0 1.0 Universal, mentre i file delle pubblicazioni sono rilasciati con licenza Attribuzione 4.0 Internazionale (CC BY 4.0), salvo diversa indicazione.
In caso di violazione di copyright, contattare Supporto Iris