scholarly journals Morphological variation under domestication: how variable are chickens?

2018 ◽  
Vol 5 (8) ◽  
pp. 180993 ◽  
Author(s):  
Madlen Stange ◽  
Daniel Núñez-León ◽  
Marcelo R. Sánchez-Villagra ◽  
Per Jensen ◽  
Laura A. B. Wilson
Keyword(s):  
Neural Crest ◽  
Geometric Morphometrics ◽  
Multivariate Statistics ◽  
Morphological Variation ◽  
Three Dimensional ◽  
Cranial Vault ◽  
Shape Variation ◽  
Skull Morphology ◽  
Variable Part ◽  
Brain Shape

The process of domestication has long fascinated evolutionary biologists, yielding insights into the rapidity with which selection can alter behaviour and morphology. Previous studies on dogs, cattle and pigeons have demonstrated that domesticated forms show greater magnitudes of morphological variation than their wild ancestors. Here, we quantify variation in skull morphology, modularity and integration in chickens and compare those to the wild fowl using three-dimensional geometric morphometrics and multivariate statistics. Similar to other domesticated species, chickens exhibit a greater magnitude of variation in shape compared with their ancestors. The most variable part of the chicken skull is the cranial vault, being formed by dermal and neural crest-derived bones, its form possibly related to brain shape variation in chickens, especially in crested breeds. Neural crest-derived portions of the skull exhibit a higher amount of variation. Further, we find that the chicken skull is strongly integrated, confirming previous studies in birds, in contrast to the presence of modularity and decreased integration in mammals.

How unique is unique? Quantifying geometric differences in stripe patterns of Cape mountain zebra, Equus zebra zebra (Perissodactyla: Equidae)

2020 ◽  
Author(s):  
Nicolas D Prinsloo ◽  
Martin Postma ◽  
P J Nico de Bruyn
Keyword(s):  
Geometric Morphometrics ◽  
Morphological Variation ◽  
Individual Animal ◽  
Shape Variation ◽  
Model Species ◽  
Degree Of Branching ◽  
Pattern Similarity ◽  
Surface Models ◽  
Coat Pattern ◽  
Study Population

Abstract Quantified coat pattern dissimilarity provides a visible surface for individual animal traceability to populations. We determined the feasibility in quantifying uniqueness of stripe patterns of Cape mountain zebra (CMZ; Equus zebra zebra) using geometric morphometrics. We photogrammetrically created dense surface models of CMZ (N = 56). Stripe edges were landmarked, superimposed and compared for shape variation across replicates and the population. Significant allometry in stripe patterns prompted allometric correction to remove increased curvature of stripes at the rump, belly and back with larger adult individuals, to facilitate equilibrated comparison between individuals. Re-landmarked replicates showed lower dissimilarity (Di) than non-replicates (Dp), representing minimal landmarking error. Individuals were 78.07 ± 1.79% unique (U=1−DiDp×100%) relative to the study population. Size, the number of torso stripes and degree of branching in four rear torso stripes described the most shape variation (36.79%) but a significant portion could only be distinguished with geometric morphometrics (41.82%). This is the first known use of geometric morphometrics to quantify coat pattern uniqueness, using a model species to provide baseline individual morphological variation. Measures of coat pattern similarity have a place in phenotypic monitoring and identification.

scholarly journals ShapeRotator: an R tool for standardised rigid rotations of articulated Three-Dimensional structures with application for geometric morphometrics

2017 ◽  
Author(s):  
Marta Vidal-García ◽  
Lashi Bandara ◽  
J. Scott Keogh
Keyword(s):  
Geometric Morphometrics ◽  
Phenotypic Diversity ◽  
Three Dimensional ◽  
R Package ◽  
Morphological Data ◽  
List Type ◽  
Shape Variation ◽  
Data Set ◽  
Articulated Structures ◽  
Shape And Size

SummaryThe quantification of complex morphological patterns typically involves comprehensive shape and size analyses, usually obtained by gathering morphological data from all the structures that capture the phenotypic diversity of an organism or object. Articulated structures are a critical component of overall phenotypic diversity, but data gathered from these structures are difficult to incorporate in to modern analyses because of the complexities associated with jointly quantifying 3D shape in multiple structures.While there are existing methods for analysing shape variation in articulated structures in Two-Dimensional (2D) space, these methods do not work in 3D, a rapidly growing area of capability and research.Here we describe a simple geometric rigid rotation approach that removes the effect of random translation and rotation, enabling the morphological analysis of 3D articulated structures. Our method is based on Cartesian coordinates in 3D space so it can be applied to any morphometric problem that also uses 3D coordinates (e.g. spherical harmonics). We demonstrate the method by applying it to a landmark-based data set for analysing shape variation using geometric morphometrics.We have developed an R tool (ShapeRotator) so that the method can be easily implemented in the commonly used R package geomorph and MorphoJ software. This method will be a valuable tool for 3D morphological analyses in articulated structures by allowing an exhaustive examination of shape and size diversity.

scholarly journals Sources of Intraspecific Morphological Variation in Vipera seoanei: Allometry, Sex, and Colour Phenotype

2020 ◽  
Author(s):  
Nahla Lucchini ◽  
Antigoni Kaliontzopoulou ◽  
Guillermo Aguado Val ◽  
Fernando Martínez-Freiría
Keyword(s):  
Geometric Morphometrics ◽  
Morphological Variation ◽  
Morphological Variability ◽  
Tail Length ◽  
Shape Variation ◽  
Body Proportions ◽  
Head Shape ◽  
Relative Contribution ◽  
Colour Morphs ◽  
Intraspecific Morphological Variation

AbstractSnakes frequently exhibit ontogenetic and sexual variation in head dimensions, as well as the occurrence of distinct colour morphotypes which might be fitness-related. In this study, we used linear biometry and geometric morphometrics to investigate intraspecific morphological variation related to allometry and sexual dimorphism in Vipera seoanei, a species that exhibits five colour morphotypes, potentially subjected to distinct ecological pressures. We measured body size (SVL), tail length and head dimensions in 391 specimens, and examined variation in biometric traits with respect to allometry, sex and colour morph. In addition, we analysed head shape variation by recording the position of 29 landmarks in 123 specimens and establishing a low-error protocol for implementing geometric morphometrics to European vipers. All head dimensions exhibited significant allometry, while sexual differences occurred for SVL, relative tail length and snout height. After considering size effects, we found significant differences in body proportions between the sexes and across colour morphs, which suggests an important influence of lowland and montane habitats in shaping morphological variation. By contrast, head shape did not exhibit significant variation across sexes or colour morphs. Instead it was mainly associated to allometric variation, where the supraocular and the rear regions of the head were the areas that varied the most throughout growth and across individuals. Overall, this study provides a thorough description of morphological variability in Vipera seoanei and highlights the relevance of combining different tools (i.e. linear and geometric morphometrics) and analyses to evaluate the relative contribution of different factors in shaping intraspecific variation.

scholarly journals Evolutionary versatility of the avian neck

2021 ◽  
Vol 288 (1946) ◽  
pp. 20203150
Author(s):  
Ryan D. Marek ◽  
Peter L. Falkingham ◽  
Roger B. J. Benson ◽  
James D. Gardiner ◽  
Thomas W. Maddox ◽  
...  
Keyword(s):  
Cervical Spine ◽  
Geometric Morphometrics ◽  
Multivariate Statistics ◽  
Three Dimensional ◽  
Morphological Diversity ◽  
Ecological Niches ◽  
Neck Length ◽  
Ecological Functions ◽  
Length Scales

Bird necks display unparalleled levels of morphological diversity compared to other vertebrates, yet it is unclear what factors have structured this variation. Using three-dimensional geometric morphometrics and multivariate statistics, we show that the avian cervical column is a hierarchical morpho-functional appendage, with varying magnitudes of ecologically driven osteological variation at different scales of organization. Contrary to expectations given the widely varying ecological functions of necks in different species, we find that regional modularity of the avian neck is highly conserved, with an overall structural blueprint that is significantly altered only by the most mechanically demanding ecological functions. Nevertheless, the morphologies of vertebrae within subregions of the neck show more prominent signals of adaptation to ecological pressures. We also find that both neck length allometry and the nature of neck elongation in birds are different from other vertebrates. In contrast with mammals, neck length scales isometrically with head mass and, contrary to previous work, we show that neck elongation in birds is achieved predominantly by increasing vertebral lengths rather than counts. Birds therefore possess a cervical spine that may be unique in its versatility among extant vertebrates, one that, since the origin of flight, has adapted to function as a surrogate forelimb in varied ecological niches.

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

2017 ◽  
Author(s):  
Lionel Hautier ◽  
Guillaume Billet ◽  
Benoit De Thoisy ◽  
Frédéric Delsuc
Keyword(s):  
Morphological Variation ◽  
Distinct Species ◽  
Morphological Characters ◽  
Molecular Data ◽  
Guiana Shield ◽  
Shape Variation ◽  
Skull Morphology ◽  
Geometric Morphometric ◽  
Skull Shape ◽  
Shape And Size

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 (D. novemcinctus). Methods. We present the first exhaustive 3D comparison of the skull morphology within the genus Dasypus, based on µCT-scans. 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 between Dasypus species, with D. pilosus representing a clear outlier compared to other long-nosed armadillos. The study of the cranial intraspecific variation in D. novemcinctus evidences clear links to the geographic distribution and argue in favour of a revision of past taxonomic delimitations. Our detailed morphometric comparisons detected previously overlooked morphotypes of nine-banded armadillo, especially a very distinctive unit circumscribed 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 D. novemcinctus should be regarded either as a polytypic species (with three to four subspecies) or as a complex of several distinct species.

Analysing morphological variation of appendages and labrum in 10 species of Heterocypris Claus, 1893 (Podocopida : Cyprididae) with additional description of Heterocypris exigua

2018 ◽  
Vol 32 (6) ◽  
pp. 1448
Author(s):  
Tamara Karan-Žnidaršič ◽  
Vukica Vujić ◽  
Ángel Baltanás
Keyword(s):  
Geometric Morphometrics ◽  
Morphological Variation ◽  
Relative Length ◽  
Interspecific Variation ◽  
Canonical Variate ◽  
Shape Variation ◽  
Males And Females ◽  
New Perspective ◽  
Relative Measurements ◽  
Post Hoc

Natural selection can lead to speciation, but its effects depend on amount of morphological variation within populations. In Ostracoda, the appendages enclosed within the calcified carapace are less influenced by environmental conditions in comparison with carapace valves. Here, we explored morphological variation of appendages and labrum in cosmopolitan genus Heterocypris, investigating the species occurring in Europe. With the aim to overcome taxonomical problems, both traditional and geometric morphometrics were applied. The relative lengths were analysed by one-way ANOVA and post-hoc tests to determine interspecific variation and sexual dimorphism. Significant traits were further analysed by Canonical Variate Analysis separately for males and females as segment width/length ratios and relative length of claws and setae ratios. Landmark-based geometric morphometrics were applied to analyse shape variation of the labrum and traits of the maxillular palp. From this, a new perspective on morphological variation within this genus emerged. Relative measurements of the second segment of the maxillular palp, and relative lengths of the natatory setae were found to be the characters that contribute most to discrimination among Heterocypris species. The most important discriminant traits in females are the relative lengths of the G2 and G1 claws. Heterocypris exigua is additionally described, as all findings demonstrated that this is the most distinctive species, the most similar to H. gevgelica. In conclusion, we found that in comparison with maxillular palp and other analysed characters, labrum traits showed as more reliable and deserve more attention in descriptions of new species.

scholarly journals Morphological convergence in ‘river dolphin’ skulls: a disparate grouping justified

2017 ◽  
Author(s):  
Charlotte E Page ◽  
Natalie Cooper
Keyword(s):  
Geometric Morphometrics ◽  
Convergent Evolution ◽  
Shape Variation ◽  
Skull Morphology ◽  
Feeding Mode ◽  
River Dolphin ◽  
Morphological Convergence ◽  
Inia Geoffrensis ◽  
Pontoporia Blainvillei ◽  
Future Work

Convergent evolution can provide insights into the predictability of, and constraints on, the evolution of biodiversity. One striking example of convergence is seen in the ‘river dolphins’. The four dolphin genera that make up the ‘river dolphins’ (Inia geoffrensis, Pontoporia blainvillei, Platanista gangetica and Lipotes vexillifer) do not represent a monophyletic group, despite being very similar in morphology. This has led many to using the ‘river dolphins’ as an example of convergent evolution. However, these morphological similarities have never been quantified. We investigate whether the skulls of the four ‘river dolphin’ genera are convergent when compared to other toothed dolphin taxa. We use geometric morphometrics to uncover shape variation in the skulls of the ‘river dolphins’ and then apply a number of phylogenetic techniques to test for convergence. We find significant convergence in the skull morphology of the ‘river dolphins’. The four genera seem to have experienced evolution in the same direction, leading to a convergent morphotype characterised by elongation of skull features. The cause of this morphological convergence remains unclear, but our results support hypotheses of shared feeding mode or diet and thus provide the foundation for future work into convergence within the Odontoceti.

scholarly journals Three-dimensional geometric morphometrics for studying floral shape variation

2010 ◽  
Vol 15 (8) ◽  
pp. 423-426 ◽  
Author(s):  
Timotheüs van der Niet ◽  
Christoph P.E. Zollikofer ◽  
Marcia S. Ponce de León ◽  
Steven D. Johnson ◽  
H. Peter Linder
Keyword(s):  
Geometric Morphometrics ◽  
Three Dimensional ◽  
Shape Variation
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