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

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5052 ◽  
Author(s):  
Marie R.G. Attard ◽  
Emma Sherratt ◽  
Paul McDonald ◽  
Iain Young ◽  
Marta Vidal-García ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Linear Measurement ◽  
Future Research ◽  
Species Variation ◽  
Shape Variation ◽  
Micro Computed Tomography ◽  
Finite Elements Analysis ◽  
Geometric Morphometric ◽  
Egg Shape ◽  
Precise Representation

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.

scholarly journals A developmentally descriptive method for quantifying shape in gastropod shells

2020 ◽  
Vol 17 (163) ◽  
pp. 20190721
Author(s):  
J. Larsson ◽  
A. M. Westram ◽  
S. Bengmark ◽  
T. Lundh ◽  
R. K. Butlin
Keyword(s):  
Empirical Studies ◽  
Three Dimensional ◽  
Shell Shape ◽  
Large Set ◽  
Littorina Saxatilis ◽  
Shape Variation ◽  
Gastropod Shell ◽  
Geometric Morphometric ◽  
Wide Range ◽  
Descriptive Method

The growth of snail shells can be described by simple mathematical rules. Variation in a few parameters can explain much of the diversity of shell shapes seen in nature. However, empirical studies of gastropod shell shape variation typically use geometric morphometric approaches, which do not capture this growth pattern. We have developed a way to infer a set of developmentally descriptive shape parameters based on three-dimensional logarithmic helicospiral growth and using landmarks from two-dimensional shell images as input. We demonstrate the utility of this approach, and compare it to the geometric morphometric approach, using a large set of Littorina saxatilis shells in which locally adapted populations differ in shape. Our method can be modified easily to make it applicable to a wide range of shell forms, which would allow for investigations of the similarities and differences between and within many different species of gastropods.

scholarly journals Heterochronic Shifts Mediate Ecomorphological Convergence in Skull Shape of Microcephalic Sea Snakes

2019 ◽  
Vol 59 (3) ◽  
pp. 616-624 ◽  
Author(s):  
Emma Sherratt ◽  
Kate L Sanders ◽  
Amy Watson ◽  
Mark N Hutchinson ◽  
Michael S Y Lee ◽  
...  
Keyword(s):  
Morphological Changes ◽  
Shape Variation ◽  
Micro Computed Tomography ◽  
Trophic Specialization ◽  
Evolutionary Patterns ◽  
Dietary Specialization ◽  
Geometric Morphometric ◽  
Sea Snakes ◽  
Morphometric Methods ◽  
Cranial Shape

Abstract Morphological variation among the viviparous sea snakes (Hydrophiinae), a clade of fully aquatic elapid snakes, includes an extreme “microcephalic” ecomorph that has a very small head atop a narrow forebody, while the hind body is much thicker (up to three times the forebody girth). Previous research has demonstrated that this morphology has evolved at least nine times as a consequence of dietary specialization on burrowing eels, and has also examined morphological changes to the vertebral column underlying this body shape. The question addressed in this study is what happens to the skull during this extreme evolutionary change? Here we use X-ray micro-computed tomography and geometric morphometric methods to characterize cranial shape variation in 30 species of sea snakes. We investigate ontogenetic and evolutionary patterns of cranial shape diversity to understand whether cranial shape is predicted by dietary specialization, and examine whether cranial shape of microcephalic species may be a result of heterochronic processes. We show that the diminutive cranial size of microcephalic species has a convergent shape that is correlated with trophic specialization to burrowing prey. Furthermore, their cranial shape is predictable for their size and very similar to that of juvenile individuals of closely related but non-microcephalic sea snakes. Our findings suggest that heterochronic changes (resulting in pedomorphosis) have driven cranial shape convergence in response to dietary specializations in sea snakes.

Averaging v. outlier removal. Decrypting variance among cryptic Lejeunea species (Lejeuneaceae: Jungermanniopsida) using geometric morphometrics

2013 ◽  
Vol 26 (1) ◽  
pp. 13 ◽  
Author(s):  
Matt A. M. Renner ◽  
Elizabeth A. Brown ◽  
Glenda M. Wardle
Keyword(s):  
Cryptic Species ◽  
Individual Variation ◽  
Species Difference ◽  
Molecular Data ◽  
Species Variation ◽  
Shape Variation ◽  
Outlier Removal ◽  
Geometric Morphometric ◽  
Size And Shape ◽  
Developmental Capacity

Molecular data have revealed many morphologically cryptic species. More surprising than lack of difference, however, is that morphological variation and complex patterns of overlapping features can mask cryptic species. We employ geometric morphometric methods (GMM) to explore patterns of variation within four liverwort species, three of which were previously attributed to Lejeunea tumida Mitt. Each species exhibited considerable variation within, and overlap among, species in size and shape, independent of degree of relatedness. Most variation was expressed within individuals, suggesting that the observed breadth of variation was within the developmental capacity of single genotypes. Size and shape variation within, and consequently overlap among, individuals resulted primarily from variance in growth of shoots. Inter-specific differences were swamped by intra- and inter-individual variation. We coupled GMM with multivariate methods for outlier removal, and simple averaging of individuals to explore whether intra-individual variation could be reconciled to maximise the inter-species difference, facilitating resolution of cryptic species despite extensive morphological continuity and overlap. Unfortunately, outlier removal did not achieve separation among species, because removing extremes failed to eliminate overlap resulting from within-species variation. Individual averaging was partially successful in extracting L. tumida as a discrete entity but did not segregate the remaining three species. Although the challenges for morphology-based identification of cryptic species are significant, GMM provide one of the best sets of methods for identifying and communicating any subtle morphological differences that may exist.

scholarly journals Phylogeny and adaptation shape the teeth of insular mice

2016 ◽  
Vol 283 (1824) ◽  
pp. 20152820 ◽  
Author(s):  
Ronan Ledevin ◽  
Pascale Chevret ◽  
Guila Ganem ◽  
Janice Britton-Davidian ◽  
Emilie A. Hardouin ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Size Variation ◽  
Wood Mouse ◽  
Relative Role ◽  
Resource Exploitation ◽  
Shape Variation ◽  
Geometric Morphometric ◽  
Competition Level ◽  
History Of

By accompanying human travels since prehistorical times, the house mouse dispersed widely throughout the world, and colonized many islands. The origin of the travellers determined the phylogenetic source of the insular mice, which encountered diverse ecological and environmental conditions on the various islands. Insular mice are thus an exceptional model to disentangle the relative role of phylogeny, ecology and climate in evolution. Molar shape is known to vary according to phylogeny and to respond to adaptation. Using for the first time a three-dimensional geometric morphometric approach, compared with a classical two-dimensional quantification, the relative effects of size variation, phylogeny, climate and ecology were investigated on molar shape diversity across a variety of islands. Phylogeny emerged as the factor of prime importance in shaping the molar. Changes in competition level, mostly driven by the presence or absence of the wood mouse on the different islands, appeared as the second most important effect. Climate and size differences accounted for slight shape variation. This evidences a balanced role of random differentiation related to history of colonization, and of adaptation possibly related to resource exploitation.

A three-dimensional geometric morphometric analysis of variation in cranial size and shape in tammar wallaby (Macropus eugenii) populations

2009 ◽  
Vol 57 (5) ◽  
pp. 337 ◽  
Author(s):  
Claire Hadley ◽  
Nick Milne ◽  
Lincoln H. Schmitt
Keyword(s):  
Three Dimensional ◽  
Tammar Wallaby ◽  
Shape Variation ◽  
Isolated Populations ◽  
Geometric Morphometric ◽  
Island Populations ◽  
Macropus Eugenii ◽  
Size And Shape ◽  
Geographic Separation ◽  
Analysis Of Variation

This study uses geometric morphometric techniques to examine cranial size and shape variation in nine isolated populations of the tammar wallaby (Macropus eugenii). A set of 36 three-dimensional landmarks were digitised on 143 tammar crania from two mainland and seven island populations. While there was no evidence of island dwarfism or gigantism, cranial size increased with both increasing island size and increasing latitude. As latitude increased, the palate narrowed relative to the nasal bones, cranial flexion and nasal height increased, and the zygomatic arches spread out laterally from the cranium. Overall, the anterior nasal aperture (nares) narrowed with increasing latitude. Mean shapes were calculated for each population, and pair-wise comparisons were made; most of these were significantly different. There was a clear tendency for island populations and those with greater geographic separation to show greater shape differentiation. Thus, regional and population differences in the cranial size and shape of tammar wallabies provide examples of selection, founder effect and random genetic drift.

scholarly journals Cranial integration in the ring-necked parakeet, Psittacula krameri (Psittaciformes: Psittaculidae)

2021 ◽  
Vol 133 (1) ◽  
pp. 47-56
Author(s):  
Matthew J Mitchell ◽  
Anjali Goswami ◽  
Ryan N Felice
Keyword(s):  
Invasive Species ◽  
Significant Influence ◽  
Three Dimensional ◽  
Shape Variation ◽  
Geometric Morphometric ◽  
Functional Relationships ◽  
Psittacula Krameri ◽  
Beak Shape ◽  
Native Populations ◽  
Parrot Species

Abstract The study of integration and modularity aims to describe the organization of components that make up organisms, and the evolutionary, developmental and functional relationships among them. Both have been studied at the interspecific (evolutionary) and intraspecific (phenotypic and ontogenetic) levels to different degrees across various clades. Although evolutionary modularity and integration are well-characterized across birds, knowledge of intraspecific patterns is lacking. Here, we use a high-density, three-dimensional geometric morphometric approach to investigate patterns of integration and modularity in Psittacula krameri, a highly successful invasive parrot species that exhibits the derived vertical palate and cranio-facial hinge of the Psittaciformes. Showing a pattern of nine distinct cranial modules, our results support findings from recent research that uses similar methods to investigate interspecific integration in birds. Allometry is not a significant influence on cranial shape variation within this species; however, within-module integration is significantly negatively correlated with disparity, with high variation concentrated in the weakly integrated rostrum, palate and vault modules. As previous studies have demonstrated differences in beak shape between invasive and native populations, variation in the weakly integrated palate and rostrum may have facilitated evolutionary change in these parts of the skull, contributing to the ring-necked parakeet’s success as an invasive species.

scholarly journals Beyond the carapace: skull shape variation and morphological systematics of long-nosed armadillos (genus Dasypus)

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3650 ◽  
Author(s):  
Lionel Hautier ◽  
Guillaume Billet ◽  
Benoit de Thoisy ◽  
Frédéric Delsuc
Keyword(s):  
Morphological Variation ◽  
Distinct Species ◽  
Morphological Characters ◽  
Molecular Data ◽  
Shape Variation ◽  
Micro Computed Tomography ◽  
Dasypus Novemcinctus ◽  
Skull Morphology ◽  
Geometric Morphometric ◽  
Skull Shape

Background The systematics of long-nosed armadillos (genus Dasypus) has been mainly based on a handful of external morphological characters and classical measurements. Here, we studied the pattern of morphological variation in the skull of long-nosed armadillos species, with a focus on the systematics of the widely distributed nine-banded armadillo (Dasypus novemcinctus). Methods We present the first exhaustive 3D comparison of the skull morphology within the genus Dasypus, based on micro-computed tomography. We used geometric morphometric approaches to explore the patterns of the intra- and interspecific morphological variation of the skull with regard to several factors such as taxonomy, geography, allometry, and sexual dimorphism. Results We show that the shape and size of the skull vary greatly among Dasypus species, with Dasypus pilosus representing a clear outlier compared to other long-nosed armadillos. The study of the cranial intraspecific variation in Dasypus novemcinctus evidences clear links to the geographic distribution and argues in favor of a revision of past taxonomic delimitations. Our detailed morphometric comparisons detected previously overlooked morphotypes of nine-banded armadillos, especially a very distinctive unit restricted to the Guiana Shield. Discussion As our results are congruent with recent molecular data and analyses of the structure of paranasal sinuses, we propose that Dasypus novemcinctus should be regarded either as a polytypic species (with three to four subspecies) or as a complex of several distinct species.

Salinity and Egg Shape Variation: A Geometric Morphometric Analysis

2013 ◽  
Vol 47 (1) ◽  
pp. 15-23 ◽  
Author(s):  
Christopher M. Murray ◽  
Kyle R. Piller ◽  
Mark Merchant ◽  
Amos Cooper ◽  
Michael E. Easter
Keyword(s):  
Morphometric Analysis ◽  
Shape Variation ◽  
Geometric Morphometric ◽  
Egg Shape ◽  
Geometric Morphometric Analysis

scholarly journals Three-dimensional geometric morphometric studies of modern human occipital variation

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245445
Author(s):  
Yameng Zhang ◽  
Lynne A. Schepartz
Keyword(s):  
Three Dimensional ◽  
Principal Component ◽  
Modern Human ◽  
Foramen Magnum ◽  
European Ancestry ◽  
Shape Variation ◽  
Geometric Morphometric ◽  
Phylogenetic Studies ◽  
Males And Females ◽  
Ct Data

Objectives To investigate three-dimensional morphological variation of the occipital bone between sexes and among populations, to determine how ancestry, sex and size account for occipital shape variation and to describe the exact forms by which the differences are expressed. Methods CT data for 214 modern crania of Asian, African and European ancestry were compared using 3D geometric morphometrics and multivariate statistics, including principal component analysis, Hotelling’s T2 test, multivariate regression, ANOVA, and MANCOVA. Results Sex differences in average occipital morphology are only observed in Europeans, with males exhibiting a pronounced inion. Significant ancestral differences are observed among all samples and are shared by males and females. Asian and African crania have smaller biasterionic breadths and flatter clivus angles compared to Europeans. Asian and European crania are similar in their nuchal and occipital plane proportions, nuchal and occipital angles, and lower inion positions compared to Africans. Centroid size significantly differs between sexes and among populations. The overall allometry, while significant, explains little of the shape variation. Larger occipital bones were associated with a more curved occipital plane, a pronounced inion, a narrower biasterionic breadth, a more flexed clivus, and a lower and relatively smaller foramen magnum. Conclusions Although significant shape differences were observed among populations, it is not recommended to use occipital morphology in sex or population estimation as both factors explained little of the observed variance. Other factors, relating to function and the environment, are suggested to be greater contributors to occipital variation. For the same reason, it is also not recommended to use the occiput in phylogenetic studies.

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