A new, three-dimensional geometric morphometric approach to assess egg shape

PeerJ

article

Marie R.G. Attard¹  Emma Sherratt¹  Paul McDonald¹  Iain Young¹  Marta Vidal-García⁵  Stephen Wroe¹ 

[1]Zoology Department, School of Environmental and Rural Science, University of New England

[2]Department of Animal and Plant Sciences, University of Sheffield

[3]Department of Ecology and Evolutionary Biology, School of Biological Sciences, The University of Adelaide

[4]School of Life and Environmental Sciences, Faculty of Science, University of Sydney

[5]Ecology and Evolution, Research School of Biology, Australian National University

关键词: Egg shape;    Geometric morphometrics;    Morphospace;    Three-dimensional;    Curvature;    Clutch;    Bird egg;    Passerine;   

DOI  :  10.7717/peerj.5052

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

This paper proposes a new methodology to quantify patterns of egg shape variation using geometric morphometrics of three-dimensional landmarks captured on digitally reconstructed eggshells and demonstrates its performance in capturing shape variation at multiple biological levels. This methodology offers unique benefits to complement established linear measurement or two-dimensional (2D) contour profiling techniques by (i) providing a more precise representation of eggshell curvature by accounting for variation across the entire surface of the egg; (ii) avoids the occurrence of correlations from combining multiple egg shape features; (iii) avoids error stemming from projecting a highly-curved three-dimensional (3D) object into 2D space; and (iv) enables integration into 3D workflows such as finite elements analysis. To demonstrate, we quantify patterns of egg shape variation and estimate morphological disparity at multiple biological levels, within and between clutches and among species of four passerine species of different lineages, using volumetric dataset obtained from micro computed tomography. The results indicate that species broadly have differently shaped eggs, but with extensive within-species variation so that all four-focal species occupy a range of shapes. Within-species variation is attributed to between-clutch differences in egg shape; within-clutch variation is surprisingly substantial. Recent comparative analyses that aim to explain shape variation among avian taxa have largely ignored potential biases due to within-species variation, or use methods limited to a narrow range of egg shapes. Through our approach, we suggest that there is appreciable variation in egg shape across clutches and that this variation needs to be accounted for in future research. The approach developed in this study to assess variation in shape is freely accessible and can be applied to any spherical-to-conical shaped object, including eggs of non-avian dinosaurs and reptiles through to other extant taxa such as poultry.

【 授权许可】

CC BY