Data from: Geometric morphometrics of nested symmetries unravels hierarchical inter- and intra-individual variation in biological shapes

Symmetry is a pervasive feature of organismal shape and the focus of a
large body of research in Biology. Here, we consider complex patterns of
symmetry where a phenotype exhibits a hierarchically structured
combination of symmetries. We extend the Procrustes ANOVA for the analysis
of nested symmetries and the decomposition of the overall morphological
variation into components of symmetry (among-individual variation) and
asymmetry (directional and fluctuating asymmetry). We illustrate its use
with the Aristotle’s lantern, the masticatory apparatus of ‘regular’ sea
urchins, a complex organ displaying bilateral symmetry nested within
five-fold rotational symmetry. Our results highlight the importance of
characterising the full symmetry of a structure with nested symmetries.
Higher order rotational symmetry appears strongly constrained and
developmentally stable compared to lower level bilateral symmetry. This
contrast between higher and lower levels of asymmetry is discussed in
relation to the spatial pattern of the lantern morphogenesis. This
extended framework is applicable to any biological object exhibiting
nested symmetries, regardless of their type (e.g., bilateral, rotational,
translational). Such cases are extremely widespread in animals and plants,
from arthropod segmentation to angiosperm inflorescence and corolla shape.
The method therefore widens the research scope on developmental
instability, canalization, developmental modularity and morphological
integration.