Phenotypic variation of south-western Atlantic clam Mactra isabelleana (Bivalvia: Mactridae)

2012 ◽  
Vol 93 (2) ◽  
pp. 511-517 ◽  
Author(s):  
Javier H. Signorelli ◽  
Federico Márquez ◽  
Guido Pastorino
Keyword(s):  
Principal Component ◽  
Shell Shape ◽  
Physical Parameters ◽  
Buenos Aires Province ◽  
Shape Variation ◽  
Geometric Morphometric ◽  
Western Atlantic ◽  
Canonical Variates Analysis ◽  
Canonical Variates ◽  
Geometric Morphometric Method

The phenotypic shell shape variation of Mactra isabelleana was tested using the geometric morphometric method. Four localities were sampled along the Río de la Plata estuary and the coast of Buenos Aires province. Principal component analysis and canonical variates analysis of the first principal components were performed to reveal the shell variation and differences among localities, respectively. The specimens from different microhabitats mostly overlapped, although differences in shape were observed in the development of the umbo, the enlargement of the dorsoventral axes and the elongation of the posterior end. The ecological and physical parameters that could influence shell shape variation are discussed.

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 Individual variation of the masticatory system dominates 3D skull shape in the herbivory-adapted marsupial wombats

2019 ◽  
Author(s):  
Vera Weisbecker ◽  
Thomas Guillerme ◽  
Cruise Speck ◽  
Emma Sherratt ◽  
Hyab Mehari Abraha ◽  
...  
Keyword(s):  
Individual Variation ◽  
Principal Component ◽  
Individual Variability ◽  
Shape Variation ◽  
Mandibular Ramus ◽  
Geometric Morphometric ◽  
Skull Shape ◽  
Marsupial Species ◽  
Masticatory System ◽  
The Individual

AbstractBackgroundWithin-species skull shape variation of marsupial mammals is widely considered low and strongly size-dependent (allometric), possibly due to developmental constraints arising from the altricial birth of marsupials. However, species whose skulls are impacted by strong muscular stresses – particularly those produced through mastication of tough food items – may not display such intrinsic patterns very clearly because of the known plastic response of bone to muscle activity of the individual. In such cases, shape variation should not be dominated by allometry; ordination of shape in a geometric morphometric context through principal component analysis (PCA) should reveal main variation in areas under masticatory stress (incisor region/zygomatic arches/mandibular ramus); but this main variation should emerge from high individual variability and thus have low eigenvalues.ResultsWe assessed the evidence for high individual variation through 3D geometric morphometric shape analysis of crania and mandibles of thre species of grazing-specialized wombats, whose diet of tough grasses puts considerable strain on their masticatory system. As expected, we found little allometry and low Principal Component 1 (PC1) eigenvalues within crania and mandibles of all three species. Also as expected, the main variation was in the muzzle, zygomatic arches, and masticatory muscle attachments of the mandibular ramus. We then implemented a new test to ask if the landmark variation reflected on PC1 was reflected in individuals with opposite PC1 scores and with opposite shapes in Procrustes space. This showed that correspondence between individual and ordinated shape variation was limited, indicating high levels of individual variability in the masticatory apparatus.DiscussionOur results are inconsistent with hypotheses that skull shape variation within marsupial species reflects a constraint pattern. Rather, they support suggestions that individual plasticity can be an important determinant of within-species shape variation in marsupials (and possibly other mammals) with high masticatory stresses, making it difficult to understand the degree to which intrinsic constraint act on shape variation at the within-species level. We conclude that studies that link micro- and macroevolutionary patterns of shape variation might benefit from a focus on species with low-impact mastication, such as carnivorous or frugivorous species.

scholarly journals The use of the geometric morphometric method to illustrate shape difference in the skulls of different-aged horses

2020 ◽  
Vol 44 (3-4) ◽  
pp. 137-145
Author(s):  
Tiziana Liuti ◽  
Padraic M. Dixon
Keyword(s):  
Age Groups ◽  
Nasal Bone ◽  
Principal Component ◽  
Age Group ◽  
Shape Variation ◽  
Geometric Morphometric ◽  
Biological Studies ◽  
Potential Applications ◽  
Variation Explained ◽  
Ethmoid Sinuses

Abstract The geometric morphometrics method (GMM) is a technique to study scale and shape relationships of structures using Cartesian geometric coordinates rather than linear, areal (of area), or volumetric variables. GMM has been of great value in many biological studies, but does not appear to have been used to examine equine skulls. In this exploratory study, twenty-nine normal equine heads of three different age groups: <5 years old (N = 9), 6–15 years old (N = 10) and > 16 years old (N = 10) were examined. Computed tomography (CT) bone window DICOM images were reconstructed into isosurfaces (3-dimensional contoured surfaces), onto which landmarks were added using Stratovan Checkpoint® software. Data from 29 landmarks were analysed using MorphoJ analysis, which applies a Procrustes fit, prior to reducing data dimensionality through principal component (PC) analysis. PCs with and without allometry were considered. Allometric shape described by PC1 accounted for 27% of variance. Loading pertaining to: the pterygoid process, bilaterally; caudal aspect of hard palate; tip of nasal bone; ethmoid sinuses, bilaterally; caudal aspect of the ventral conchal bulla, bilaterally and caudal aspect of the vomer bone suggest that these anatomical structures are predictive of age group. When allometric effects (shape variation explained by size) were removed, PC1 was unable to distinguish horses by age group. Allometric shape differences could distinguish the youngest versus the two older age groups. The potential applications of GMM in equine diagnostic imaging are wide ranging and include the investigation of changes in the equine skull with respect to genetics and characterisation of conformation-related diseases affecting the teeth, jaws and sinonasal compartments.

scholarly journals Redescription and reassignment of Ondina semicingulata to the Pyramidellidae, with review of the occurrence of genus Evalea in the Western Atlantic (Gastropoda)

2018 ◽  
Vol 94 (2) ◽  
pp. 535-544
Author(s):  
Alexandre D. Pimenta ◽  
Franklin N. Santos ◽  
Carlo M. Cunha
Keyword(s):  
Atlantic Ocean ◽  
Original Description ◽  
Type Locality ◽  
Shell Shape ◽  
Shape Variation ◽  
Western Atlantic ◽  
Northeastern Atlantic

ActeonsemicingulatusDall, 1927, previously known only by its original description is reassigned to the Pyramidellidae, inOndina, based on the collecting of several new specimens along the coast of Brazil, in the same bathymetry as the type locality. Its shell shape variation is discussed and Odostomia (Evalea) ryclea Dall, 1927 is considered a synonymy. Other Western Atlantic species, previously allocated to other genera are transferred toOndina:AclisstriataVerrill, 1880, Odostomia (Iolaea) hendersoni Bartsch, 1909,EvaleastockiDe Jong &amp; Coomans, 1988 and Odostomia (Evalea) emeryi Bartsch, 1955 based on conchlogical comparison to the revison by Høisæter (2014), from Northeastern Atlantic. The genusEvaleais considered to be absent in the Atlantic Ocean.

scholarly journals Geometric morphometry of pupae to identify four medically important flies (Order: Diptera) in Thailand

2019 ◽  
Vol 20 (6) ◽  
Author(s):  
TANAWAT CHAIPHONGPACHARA ◽  
PATCHARAPRON TUBSAMUT
Keyword(s):  
Fourier Coefficients ◽  
Principal Component ◽  
Future Application ◽  
Size Analysis ◽  
Size Estimation ◽  
Shape Variation ◽  
Elliptic Fourier Analysis ◽  
Geometric Morphometric ◽  
Significance Level ◽  
Geometric Morphometry

Abstract. Chaiphongpachara T, Tubsamut P. 2019. Geometric morphometry of pupae to identify four medically important flies (Order: Diptera) in Thailand. Biodiversitas 20: 1504-1509. In this study, we evaluated an outline-based geometric morphometric (GM) approach for species identification from pupae of four common flies medically important in Thailand, Chrysomya megacephala, Lucilia cuprina, Musca domestica, and Boettcherisca nathani. For size estimation, mean perimeter length was used. For shape analysis, Elliptic Fourier Analysis was performed to produce the contour shape variables, which was calculated as Normalised Elliptic Fourier coefficients. Then, principal component analysis was performed on the Normalized Fourier coefficients for discriminant analysis, and used to estimate pupal shape variation among the species. The difference in size and shape between the fly species was analyzed using a non-parametric test based on 1000 permutations after Bonferroni correction for the significance level (p < 0.05). In the size analysis, the mean perimeter length for pupae of B. nathani was the largest (20.35 mm) followed by C. megacephala (14.73 mm), while that for M. domestica was the smallest (11.82 mm). The size differences were statistically significant between all species (p < 0.05). The contour shapes of all pupae were significantly different among all species. The results of this study can be used as a basis for the future application of GM to identify other types of flies via their pupae.

scholarly journals Shell shape variation of queen conch Strombus gigas (Mesograstropoda: Strombidae) from Southwest Caribbean

2016 ◽  
Vol 64 (4) ◽  
Author(s):  
Edna Judith Márquez ◽  
Natalia Restrepo-Escobar ◽  
Francisco Luis Montoya-Herrera
Keyword(s):  
Phenotypic Plasticity ◽  
Geometric Morphometrics ◽  
Genetic Background ◽  
Principal Component ◽  
Caribbean Region ◽  
Shell Shape ◽  
Shape Variation ◽  
Morphometric Variation ◽  
Strombus Gigas

The endangered species Strombus gigas is a marine gastropod of significant economic importance through the Greater Caribbean region. In contrast to phenotypic plasticity, the role of genetics on shell variations in S. gigas has not been addressed so far, despite its importance in evolution, management and conservation of this species. This work used geometric morphometrics to investigate the phenotypic variation of 219 shells of S. gigas from eight sites of the Colombian Southwest Caribbean. Differences in mean size between sexes and among sites were contrasted by analysis of variance. Allometry was tested by multivariate regression and the hypothesis of common slope was contrasted by covariance multivariate analysis. Differences in the shell shape among sites were analyzed by principal component analysis. Sexual size dimorphism was not significant, whereas sexual shape dimorphism was significant and variable across sites. Differences in the shell shape among sites were concordant with genetic differences based on microsatellite data, supporting its genetic background. Besides, differences in the shell shape between populations genetically similar suggest a role of phenotypic plasticity in the morphometric variation of the shell shape. These outcomes evidence the role of genetic background and phenotypic plasticity in the shell shape of S. gigas. Thus, geometric morphometrics of shell shape may constitute a complementary tool to explore the genetic diversity of this species.

Clonal structure and fertility in a sympatric population of the peat mosses Sphagnum rubellum and Sphagnum capillifolium

1996 ◽  
Vol 74 (9) ◽  
pp. 1375-1385 ◽  
Author(s):  
Nlls Cronberg
Keyword(s):  
Leaf Shape ◽  
Morphological Characters ◽  
Clonal Structure ◽  
Shape Variation ◽  
Canonical Variates Analysis ◽  
Hierarchical Structuring ◽  
Canonical Variates ◽  
Self Fertilization ◽  
The Mean ◽  
A Site

Data from isozyme and leaf shape variation are combined to explore the clonal structure at a site where hybridization between Sphagnum rubellum and Sphagnum capillifolium was previously indicated. Shoots of both species were sampled at 10-cm intervals along seven transects across different hummocks. Allelic data from 13 enzyme systems revealed 22 multilocus genotypes representing different clones, 18 being S. capillifolium and 4 being S. rubellum. The mean ± SE and maximum clonal length were 35 ± 8 cm and 160 cm, respectively. The sets of alleles found in the progeny of S. capillifolium were identical to the maternal complement of alleles in 78% of the material, indicating either self-fertilization or fertilization by a male with the same set of alleles at the screened loci. Outcrossing was detected in six cases. Patterns of differentiation and the hierarchical structuring of diversity among species, transects, and clones were analysed with canonical variates analysis using stem-leaf characters. A stronger relative differentiation was found between transects than between species. Clones identified by electrophoresis were usually morphologically well defined. Hybridization was indicated by morphological characters, occasional misplaced alleles, and signs of developmental instability. Keywords: allozymes, computerized image analysis, breeding system, clonal structure, Sphagnum rubellum, Sphagnum capillifolium.

scholarly journals Individual variation of the masticatory system dominates 3D skull shape in the herbivory-adapted marsupial wombats

2019 ◽  
Vol 16 (1) ◽  
Author(s):  
Vera Weisbecker ◽  
Thomas Guillerme ◽  
Cruise Speck ◽  
Emma Sherratt ◽  
Hyab Mehari Abraha ◽  
...  
Keyword(s):  
Individual Variation ◽  
Principal Component ◽  
Individual Variability ◽  
Shape Variation ◽  
Mandibular Ramus ◽  
Geometric Morphometric ◽  
Skull Shape ◽  
Marsupial Species ◽  
Masticatory System ◽  
The Individual

Abstract Background Within-species skull shape variation of marsupial mammals is widely considered low and strongly size-dependent (allometric), possibly due to developmental constraints arising from the altricial birth of marsupials. However, species whose skulls are impacted by strong muscular stresses – particularly those produced through mastication of tough food items – may not display such intrinsic patterns very clearly because of the known plastic response of bone to muscle activity of the individual. In such cases, allometry may not dominate within-species shape variation, even if it is a driver of evolutionary shape divergence; ordination of shape in a geometric morphometric context through principal component analysis (PCA) should reveal main variation in areas under masticatory stress (incisor region/zygomatic arches/mandibular ramus); but this main variation should emerge from high individual variability and thus have low eigenvalues. Results We assessed the evidence for high individual variation through 3D geometric morphometric shape analysis of crania and mandibles of three species of grazing-specialized wombats, whose diet of tough grasses puts considerable strain on their masticatory system. As expected, we found little allometry and low Principal Component 1 (PC1) eigenvalues within crania and mandibles of all three species. Also as expected, the main variation was in the muzzle, zygomatic arches, and masticatory muscle attachments of the mandibular ramus. We then implemented a new test to ask if the landmark variation reflected on PC1 was reflected in individuals with opposite PC1 scores and with opposite shapes in Procrustes space. This showed that correspondence between individual and ordinated shape variation was limited, indicating high levels of individual variability in the masticatory apparatus. Discussion Our results are inconsistent with hypotheses that skull shape variation within marsupial species reflects a constraint pattern. Rather, they support suggestions that individual plasticity can be an important determinant of within-species shape variation in marsupials (and possibly other mammals) with high masticatory stresses, making it difficult to understand the degree to which intrinsic constraints act on shape variation at the within-species level. We conclude that studies that link micro- and macroevolutionary patterns of shape variation might benefit from a focus on species with low-impact mastication, such as carnivorous or frugivorous species.

scholarly journals Multivariate discrimination of <i>Buryella</i> species from the Lower Eocene of the Outer Flysch Carpathians, Poland

2006 ◽  
Vol 25 (1) ◽  
pp. 45-54
Author(s):  
Marta Bak ◽  
Wanda Barwicz-Piskorz
Keyword(s):  
Principal Component Analysis ◽  
Cluster Analysis ◽  
Principal Component ◽  
Vertical Tube ◽  
Canonical Variates Analysis ◽  
Lower Eocene ◽  
External Wall ◽  
Flysch Carpathians ◽  
Canonical Variates ◽  
Varying Length

Abstract. Variegated shales in the Lower Eocene hemipelagic deposits of the Subsilesian Series, Polish part of the Western Carpathians, have yielded rich radiolarians with common representatives of the genus Buryella. Two new radiolarian species, Buryella spina sp. nov. and Buryella hannae sp. nov., are described, and two other species have been recognized: Buryella tetradica Foreman and Buryella clinata Foreman. Specimens have been measured, grouped and interpreted using cluster analysis, principal component analysis (PCA) and canonical variates analysis (CVA). Species attributed to Buryella have three or four segments, a fusiform or lobate outline, and a constricted, rather than flared, aperture. The cephalis always possesses an apical horn of varying length with a distinct vertical pore at the collar stricture. All specimens possess a pronounced vertical tube, rounded or elongate, that might extend to the base of apical horn. Near the base of the cephalis the parallel ridges observed on the external wall of the cephalis are ridges from the horn that diverge and extend to the collar stricture except ventrally, where two ridges rejoin to enclose the vertical pore and form an upwardly directed tube. These structure might be evidence of the presence of arches (A-Vbl, A-Vbr) and bars (Vbl, Vbr), which form the vertical tube.

scholarly journals Assessing species boundaries in the open sea: an integrative taxonomic approach to the pteropod genus Diacavolinia

2019 ◽  
Vol 187 (4) ◽  
pp. 1016-1040 ◽  
Author(s):  
Alice K Burridge ◽  
Remy Van Der Hulst ◽  
Erica Goetze ◽  
Katja T C A Peijnenburg
Keyword(s):  
Integrative Taxonomy ◽  
Species Boundaries ◽  
Shell Shape ◽  
Shape Variation ◽  
Geometric Morphometric ◽  
Integrative Framework ◽  
Rdna Sequences ◽  
Biogeographic Provinces ◽  
Taxonomic Approach ◽  
Species Specific

Abstract To track changes in pelagic biodiversity in response to climate change, it is essential to accurately define species boundaries. Shelled pteropods are a group of holoplanktonic gastropods that have been proposed as bio-indicators because of their vulnerability to ocean acidification. A particularly suitable, yet challenging group for integrative taxonomy is the pteropod genus Diacavolinia, which has a circumglobal distribution and is the most species-rich pteropod genus, with 24 described species. We assessed species boundaries in this genus, with inferences based on geometric morphometric analyses of shell-shape variation, genetic (cytochrome c oxidase subunit I, 28S rDNA sequences) and geographic data. We found support for a total of 13 species worldwide, with observations of 706 museum and 263 freshly collected specimens across a global collection of material, including holo‐ and paratype specimens for 14 species. In the Atlantic Ocean, two species are well supported, in contrast to the eight currently described, and in the Indo‐Pacific we found a maximum of 11 species, partially merging 13 of the described species. Distributions of these revised species are congruent with well-known biogeographic provinces. Combining varied datasets in an integrative framework may be suitable for many diverse taxa and is an important first step to predicting species-specific responses to global change.

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