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1
Stevens, William P. "Hierarchical factor analysis and the derivation of phylogenetic skull shape characters in canids". Paleontological Society Special Publications 6 (1992): 281. http://dx.doi.org/10.1017/s2475262200008418.
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Character independence is an important assumption in parsimony-based phylogenetic analysis. For taxa with extant representatives, the analysis of within-species covariation of quantitative characters provides a basis for assessing character independence. One promising approach is to use mean species scores on factors of within-species covariation as phylogenetic characters, but the use of common morphometric factor models leads to problems with either the independence or the interpretability of such characters. Principal components and principal factors, whether rotated or not, may be constrained to be orthogonal but may be difficult to interpret since the effects of each factor are spread over all variables. In Wright-style factor analysis the restriction of secondary factors to subsets of variables facilitates their interpretation, but the factors may be highly correlated.An alternative approach is to adopt a hierarchical factor model in which correlated first-order factors are restricted to subsets of the variables. Size is modelled as a second-order factor inducing correlation of the primary factors, in contrast to the common morphometric procedure of attempting to partial out size in the first stage of analysis. The size-independent components of the primary factors provide shape characters which are interpretable as the deviations of regional growth from their predictions based on size. Hierarchical factor models have been widely used in psychometric studies since their introduction by Thurstone in the 1930's, but have been little used in morphometric analyses.The hierarchical model is applied to the covariances of interlandmark trusses measured on skulls of extant canids using a video-based stereophotogrammetric system. Preliminary results indicate that the canid skull may be partitioned into discrete regions of relatively independent local growth.
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Paoloni, Valeria, Roberta Lione, Francesca Farisco, Demetrios J. Halazonetis, Lorenzo Franchi y Paola Cozza. "Morphometric covariation between palatal shape and skeletal pattern in Class II growing subjects". European Journal of Orthodontics 39, n.º 4 (14 de marzo de 2017): 371–76. http://dx.doi.org/10.1093/ejo/cjx014.
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Ruiz, Ferdinando, Pietro Venezia, Vincenzo Ronsivalle, Calogero Lacagnina, Cristina Conforte, Gaetano Isola, Rosalia Leonardi y Antonino Lo Giudice. "Geometric Morphometric Analysis of Mandibular Symphysis Growth between 12 and 15 Years of Age in Class II Malocclusion Subjects". Life 13, n.º 2 (15 de febrero de 2023): 543. http://dx.doi.org/10.3390/life13020543.
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The aim of the present paper was to evaluate the morphology changes of the mandibular symphysis (MS) in a longitudinal retrospective cohort of class II untreated subjects. The study sample included 120 subjects followed during normal growth and examined at the age of 12 (T0) and 15 (T1) years. MS was traced using two landmarks and ten sliding semi-landmarks. The acquired morphological data were processed via Procrustes superimposition that allowed to study variation and covariation in MS’form according to specific variables such as age, gender, and skeletal pattern. The first two principal components (PCs) described more than 90 % of the total morphological variation. Both types of form changes of the symphysis could be associated with the different skeletal vertical growth patterns. Age and sex did not interfere with the form of chin symphysis. Moreover, there was no significant covariation between initial MS morphology and form modifications. Clinicians should not expect to be faced with spontaneous changes of the form of the symphysis during the orthodontic treatment of adolescents.
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Alisauskas, Ray T. "Morphometric Correlates of Age and Breeding Status in American Coots". Auk 104, n.º 4 (1 de octubre de 1987): 640–46. http://dx.doi.org/10.1093/auk/104.4.640.
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Abstract I studied morphometric variation in 13 linear measurements from 228 American Coots (Fulica americana) collected in southern Manitoba. Univariate and multivariate techniques revealed differences in size and shape among adult coots that were 1, 2, and =2 yr old. In addition to the obvious differences in size between males and females, the morphometry of older birds differed from that of younger birds in two ways. First, older coots were of larger body size than younger coots of the same sex. Second, older coots had proportionately larger feet and claws relative to the size of their tarsi, and proportionately wider bills and heads relative to other head measurements, than did younger birds. Multivariate dispersion matrices within age/sex cohorts were less variable for older coots. In an analysis of 1-yr-old males, breeders did not differ from nonbreeders in overall body size, but breeders had relatively longer claws and wings than nonbreeders. Age-related differences in morphology may have relevance to the social structure of nesting coots, which involves highly aggressive territorial behavior. Part of the age-related variation in nesting phenology that has been documented elsewhere for coots may be a consequence of covariation in body size and shape.
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Neaux, Dimitri, Franck Guy, Emmanuel Gilissen, Walter Coudyzer, Patrick Vignaud y Stéphane Ducrocq. "Facial Orientation and Facial Shape in Extant Great Apes: A Geometric Morphometric Analysis of Covariation". PLoS ONE 8, n.º 2 (18 de febrero de 2013): e57026. http://dx.doi.org/10.1371/journal.pone.0057026.
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Klingenberg, Christian Peter y Jesús Marugán-Lobón. "Evolutionary Covariation in Geometric Morphometric Data: Analyzing Integration, Modularity, and Allometry in a Phylogenetic Context". Systematic Biology 62, n.º 4 (31 de mayo de 2013): 591–610. http://dx.doi.org/10.1093/sysbio/syt025.
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Torres‐Tamayo, Nicole, Sandra Martelli, Stefan Schlager, Daniel García‐Martínez, Juan Alberto Sanchis‐Gimeno, Federico Mata‐Escolano, Shahed Nalla, Naomichi Ogihara, Motoharu Oishi y Markus Bastir. "Assessing thoraco‐pelvic covariation in Homo sapiens and Pan troglodytes : A 3D geometric morphometric approach". American Journal of Physical Anthropology 173, n.º 3 (30 de agosto de 2020): 514–34. http://dx.doi.org/10.1002/ajpa.24103.
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DeLorenzo, Leah, Victoria DeBrock, Aldo Carmona Baez, Patrick Ciccotto, Erin Peterson, Clare Stull, Natalie Roberts, Reade Roberts y Kara Powder. "Morphometric and Genetic Description of Trophic Adaptations in Cichlid Fishes". Biology 11, n.º 8 (3 de agosto de 2022): 1165. http://dx.doi.org/10.3390/biology11081165.
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Since Darwin, biologists have sought to understand the evolution and origins of phenotypic adaptations. The skull is particularly diverse due to intense natural selection on feeding biomechanics. We investigated the genetic and molecular origins of trophic adaptation using Lake Malawi cichlids, which have undergone an exemplary evolutionary radiation. We analyzed morphological differences in the lateral and ventral head shape among an insectivore that eats by suction feeding, an obligate biting herbivore, and their F2 hybrids. We identified variation in a series of morphological traits—including mandible width, mandible length, and buccal length—that directly affect feeding kinematics and function. Using quantitative trait loci (QTL) mapping, we found that many genes of small effects influence these craniofacial adaptations. Intervals for some traits were enriched in genes related to potassium transport and sensory systems, the latter suggesting co-evolution of feeding structures and sensory adaptations for foraging. Despite these indications of co-evolution of structures, morphological traits did not show covariation. Furthermore, phenotypes largely mapped to distinct genetic intervals, suggesting that a common genetic basis does not generate coordinated changes in shape. Together, these suggest that craniofacial traits are mostly inherited as separate modules, which confers a high potential for the evolution of morphological diversity. Though these traits are not restricted by genetic pleiotropy, functional demands of feeding and sensory structures likely introduce constraints on variation. In all, we provide insights into the quantitative genetic basis of trophic adaptation, identify mechanisms that influence the direction of morphological evolution, and provide molecular inroads to craniofacial variation.
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Martin, Meg L., Kenny J. Travouillon, Emma Sherratt, Patricia A. Fleming y Natalie M. Warburton. "Covariation between forelimb muscle anatomy and bone shape in an Australian scratch‐digging marsupial: Comparison of morphometric methods". Journal of Morphology 280, n.º 12 (22 de octubre de 2019): 1900–1915. http://dx.doi.org/10.1002/jmor.21074.
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Neaux, Dimitri, Franck Guy, Emmanuel Gilissen, Walter Coudyzer y Stéphane Ducrocq. "Covariation Between Midline Cranial Base, Lateral Basicranium, and Face in Modern Humans and Chimpanzees: A 3D Geometric Morphometric Analysis". Anatomical Record 296, n.º 4 (5 de febrero de 2013): 568–79. http://dx.doi.org/10.1002/ar.22654.
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Farina, S. C., E. A. Kane y L. P. Hernandez. "Multifunctional Structures and Multistructural Functions: Integration in the Evolution of Biomechanical Systems". Integrative and Comparative Biology 59, n.º 2 (5 de junio de 2019): 338–45. http://dx.doi.org/10.1093/icb/icz095.
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Abstract Integration is an essential feature of complex biomechanical systems, with coordination and covariation occurring among and within structural components at time scales that vary from microseconds to deep evolutionary time. Integration has been suggested to both promote and constrain morphological evolution, and the effects of integration on the evolution of structure likely vary by system, clade, historical contingency, and time scale. In this introduction to the 2019 symposium “Multifunctional Structures and Multistructural Functions,” we discuss the role of integration among structures in the context of functional integration and multifunctionality. We highlight articles from this issue of Integrative and Comparative Biology that explore integration within and among kinematics, sensory and motor systems, physiological systems, developmental processes, morphometric dimensions, and biomechanical functions. From these myriad examples it is clear that integration can exist at multiple levels of organization that can interact with adjacent levels to result in complex patterns of structural and functional phenotypes. We conclude with a synthesis of major themes and potential future directions, particularly with respect to using multifunctionality, itself, as a trait in evolutionary analyses.
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Mallard, Samantha y C. J. Barnard. "Food stress, fluctuating asymmetry and reproductive performance in the gryllid crickets Gryllus bimaculatus and Gryllodes sigillatus". Behaviour 141, n.º 2 (2004): 219–32. http://dx.doi.org/10.1163/156853904322890825.
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AbstractWhile associations between sexual selection, developmental stress and fluctuating asymmetry (FA) remain controversial, this does not necessarily undermine the more general hypothesis that FA reflects developmental instability and functional competence. This applies as much to reproductive processes as to any other. If this is the case, however, we should expect FA and measures of performance to covary under conditions of developmental stress. Using an established association between morphometric FA and reproductive performance in the gryllid crickets Gryllus bimaculatus and Gryllodes sigillatus, we looked at the effect of food stress on covariation between FA and measures of performance (vigour of locomotion and interaction, mating speed, sperm transfer, egg production and offspring weight). The results showed a clear effect of food treatment in males and females of both species, with composite measures reflecting greater FA and reduced performance being greatest when crickets were reared on impoverished food. Inspection of independent means suggested FA may have been most influenced by a relaxation of food stress under high quality feeding conditions, while reproductive performance was more susceptible to the reduction in food quality under low quality conditions.
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Riede, Tobias, Megan Coyne, Blake Tafoya y Karen L. Baab. "Postnatal Development of the Mouse Larynx: Negative Allometry, Age-Dependent Shape Changes, Morphological Integration, and a Size-Dependent Spectral Feature". Journal of Speech, Language, and Hearing Research 63, n.º 8 (10 de agosto de 2020): 2680–94. http://dx.doi.org/10.1044/2020_jslhr-20-00070.
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Purpose The larynx plays a role in swallowing, respiration, and voice production. All three functions change during ontogeny. We investigated ontogenetic shape changes using a mouse model to inform our understanding of how laryngeal form and function are integrated. We understand the characterization of developmental changes to larynx anatomy as a critical step toward using rodent models to study human vocal communication disorders. Method Contrast-enhanced micro-computed tomography image stacks were used to generate three-dimensional reconstructions of the CD-1 mouse ( Mus musculus ) laryngeal cartilaginous framework. Then, we quantified size and shape in four age groups: pups, weanlings, young, and old adults using a combination of landmark and linear morphometrics. We analyzed postnatal patterns of growth and shape in the laryngeal skeleton, as well as morphological integration among four laryngeal cartilages using geometric morphometric methods. Acoustic analysis of vocal patterns was employed to investigate morphological and functional integration. Results Four cartilages scaled with negative allometry on body mass. Additionally, thyroid, arytenoid, and epiglottic cartilages, but not the cricoid cartilage, showed shape change associated with developmental age. A test for modularity between the four cartilages suggests greater independence of thyroid cartilage shape, hinting at the importance of embryological origin during postnatal development. Finally, mean fundamental frequency, but not fundamental frequency range, varied predictably with size. Conclusion In a mouse model, the four main laryngeal cartilages do not develop uniformly throughout the first 12 months of life. High-dimensional shape analysis effectively quantified variation in shape across development and in relation to size, as well as clarifying patterns of covariation in shape among cartilages and possibly the ventral pouch. Supplemental Material https://doi.org/10.23641/asha.12735917
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Ismail, Tarek G. "Effect of geographic location and sexual dimorphism on shield shape of the Red Sea hermit crab Clibanarius signatus using the geometric morphometric approach". Canadian Journal of Zoology 96, n.º 7 (julio de 2018): 667–79. http://dx.doi.org/10.1139/cjz-2017-0050.
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The hermit crab Clibanarius signatus Heller, 1861 inhabits varied intertidal habitats of the Red Sea coast, such as rocky shores and mangrove littoral salt marshes. Shield-shape variation among three populations of C. signatus was analyzed with geometric morphometric methods. Shape variation was studied through multivariate analyses using configurations aligned by the generalized Procrustes analysis. Shape variation was explored through principal component analysis. The ordination of the populations and the sexes was investigated using discriminant analysis of canonical variables. Centroid size, as a measure of overall size, was used to estimate size variation among the three populations and the sexes. The results revealed the presence of shield-size variation among the three populations and confirmed the size sexual dimorphism in two populations. Moreover, the analysis revealed the occurrence of two morphotypes based on a covariation between shield shape and shape of occupied shells. The geographic distance was not a good predictor of shield shape. Cross-validation analyses correctly reclassified more than 70% of individuals and 66% of sexes to their correct group. It was suggested that association in shield-shell shape could be the result of the phenotypic plasticity of this species.
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Rapson, G. L. y Jack Maze. "Variation and integration in the rare grass Achnatherum (Oryzopsis) hendersonii: phenotypic comparison with parapatric common congeners". Canadian Journal of Botany 72, n.º 5 (1 de mayo de 1994): 693–700. http://dx.doi.org/10.1139/b94-090.
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Phenotypic properties indicating levels of variation and integration were compared among three populations of a rare bunch grass, Achnatherum (Oryzopsis) hendersonii (tribe Stipeae), and one parapatric population of each of its common relatives Achnatherum (Stipa) lemmonii and Achnatherum (Stipa) thurberiana, sampled from the Colockum Pass area of central Washington, U.S.A. Twenty-five randomly selected plants from each population were measured for both vegetative and spikelet features. The vegetative features were represented by morphometric measurements taken from one leaf on a tiller and the flag leaf on a flowering culm. The spikelet features were based on two to eight spikelets per plant. The three data sets were analyzed separately to compare population level variation both among individuals and among variables (variable covariation). Phenotypic variation among individuals is lowest for A. hendersonii in estimators of both size and shape; within-individual phenotypic variation, as evaluated through among-variable correlation coefficients, is highest for A. hendersonii and lowest for A. thurberiana. The lower level of among-individual variation for A. hendersonii is consistent with biological beliefs about rare species; its higher among-variable variation may indicate less precise control of integration. Key words: rarity, morphological variation and integration, Poaceae, Achnatherum.
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Hand, S. y A. York. "Morphological Variation in the Dentition and Skull of the Australian Ghost Bat, Macroderma-Gigas (Microchiroptera, Megadermatidae)". Australian Journal of Zoology 38, n.º 3 (1990): 263. http://dx.doi.org/10.1071/zo9900263.
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Morphological variation in the dentition and some cranial characters of the Australian ghost bat, Macroderma gigas, is reviewed by means of univariate and multivariate analyses. Specimens examined are drawn from existing populations across northern Australia; also included for parts of this study are mummified remains from southern central South Australia and late Pleistocene subfossil specimens from south-western Western Australia. No clear-cut geographic pattern in morphological variation in M. gigas is indicated by multivariate anlysis (i.e. principal components analysis), although there is some evidence for clinal variation from univariate analysis (i.e. Scheffe's multiple-comparions procedure). Northern Australian ghost bats (with the exception of north-eastern Australian indiv~duals) tend to be smaller than their southern counterparts. Sexual dimorphism appears to be low. Independent patterns of covariation among characters are extracted by principal components analysis: cheek tooth widths cluster separately from lengths; lengths and widths of the same teeth cluster separately from those of occluding teeth; and cranial measurements cluster separately from tooth measurements. Patterns in the data suggest that the number of characters needed to be examined in future morphometric studies of the vulnerable ghost bat can be significantly reduced.
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Yuan, Michael L., Catherine Jung, Marvalee H. Wake y Ian J. Wang. "Habitat use, interspecific competition and phylogenetic history shape the evolution of claw and toepad morphology in Lesser Antillean anoles". Biological Journal of the Linnean Society 129, n.º 3 (22 de enero de 2020): 630–43. http://dx.doi.org/10.1093/biolinnean/blz203.
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Abstract Ecologically functional traits are the product of several, at times opposing, selective forces. Thus, ecomorphological patterns can be disrupted locally by biotic interactions, such as competition, and may not be consistent across lineages. Here, we studied the evolution of claws and toepads in relationship to macrohabitat (vegetation), use of structural microhabitat (perch height) and congeneric competition for two distantly related Lesser Antillean anole clades: the Anolis bimaculatus and Anolis roquet series. We collected univariate and geometric morphometric data from 254 individuals across 22 species to test the hypotheses that functional morphology should covary with both vegetation and perch height and that the presence of a competitor may disrupt such covariation. Our data showed predictable associations between morphology and macrohabitat on single-species islands but not when a congeneric competitor was present. The outcomes of competition differed between series, however. In the A. bimaculatus series, species with a sympatric congener diverged in claw and toepad traits consistent with functional predictions, whereas A. roquet series anoles showed either no association between habitat and morphology or the opposite pattern. Our results demonstrated that ecomorphological patterns across macrohabitats can be disrupted by competition-driven microhabitat partitioning and that specific morphological responses to similar ecological pressures can vary between lineages.
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Lallensack, Jens N., Anneke H. van Heteren y Oliver Wings. "Geometric morphometric analysis of intratrackway variability: a case study on theropod and ornithopod dinosaur trackways from Münchehagen (Lower Cretaceous, Germany)". PeerJ 4 (8 de junio de 2016): e2059. http://dx.doi.org/10.7717/peerj.2059.
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A profound understanding of the influence of trackmaker anatomy, foot movements and substrate properties is crucial for any interpretation of fossil tracks. In this case study we analyze variability of footprint shape within one large theropod (T3), one medium-sized theropod (T2) and one ornithopod (I1) trackway from the Lower Cretaceous of Münchehagen (Lower Saxony, Germany) in order to determine the informativeness of individual features and measurements for ichnotaxonomy, trackmaker identification, and the discrimination between left and right footprints. Landmark analysis is employed based on interpretative outline drawings derived from photogrammetric data, allowing for the location of variability within the footprint and the assessment of covariation of separate footprint parts. Objective methods to define the margins of a footprint are tested and shown to be sufficiently accurate to reproduce the most important results. The lateral hypex and the heel are the most variable regions in the two theropod trackways. As indicated by principal component analysis, a posterior shift of the lateral hypex is correlated with an anterior shift of the margin of the heel. This pattern is less pronounced in the ornithopod trackway, indicating that variation patterns can differ in separate trackways. In all trackways, hypices vary independently from each other, suggesting that their relative position a questionable feature for ichnotaxonomic purposes. Most criteria commonly employed to differentiate between left and right footprints assigned to theropods are found to be reasonably reliable. The described ornithopod footprints are asymmetrical, again allowing for a left–right differentiation. Strikingly, 12 out of 19 measured footprints of the T2 trackway are stepped over the trackway midline, rendering the trackway pattern a misleading left–right criterion for this trackway. Traditional measurements were unable to differentiate between the theropod and the ornithopod trackways. Geometric morphometric analysis reveals potential for improvement of existing discriminant methods.
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Shadrina, Elena, Nina Turmukhametova, Victoria Soldatova, Yakov Vol'pert, Irina Korotchenko y Galina Pervyshina. "Fluctuating Asymmetry in Morphological Characteristics of Betula Pendula Roth Leaf under Conditions of Urban Ecosystems: Evaluation of the Multi-Factor Negative Impact". Symmetry 12, n.º 8 (6 de agosto de 2020): 1317. http://dx.doi.org/10.3390/sym12081317.
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The fluctuating asymmetry (FA) in Betula pendula Roth was estimated as an integrated measure of five morphometric characteristics of a lamina. Samples were collected in seven cities that differ both in climatic conditions, moderately to sharply continental. In total, 33 ecotopes were distinguished with various level of anthropogenic load. The statistical data processing involved correlation, one-way and factorial ANOVA, regression analyses, and principal component analysis (PCA). The impact of 25 climatic and anthropogenic factors on the FA value was considered. In most urban ecotopes, the integrated fluctuating asymmetry (IFA) value was higher than in natural biotopes of the same region. No significant inter-annual differences in IFA values were found. FA dependence on traffic load is noted to be statistically significant. The covariation analysis of IFA, climatic, and anthropogenic variables in various urban ecotopes revealed the impact of three groups of factors that together explain 93% of the variance in environmental parameters. The complex analysis clearly arranged the studied ecotopes by pollution gradient and climatic patterns. The primary effect of the total anthropogenic load on the developmental stability of B. pendula results in an IFA increase. IFA can play a key role in bioindication assessment of environmental quality. The climatic factors have no significant effect on the developmental stability of B. pendula in urban conditions.
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Hallgrímsson, Benedikt, David C. Katz, Jose D. Aponte, Jacinda R. Larson, Jay Devine, Paula N. Gonzalez, Nathan M. Young, Charles C. Roseman y Ralph S. Marcucio. "Integration and the Developmental Genetics of Allometry". Integrative and Comparative Biology 59, n.º 5 (14 de junio de 2019): 1369–81. http://dx.doi.org/10.1093/icb/icz105.
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Abstract Allometry refers to the ways in which organismal shape is associated with size. It is a special case of integration, or the tendency for traits to covary, in that variation in size is ubiquitous and evolutionarily important. Allometric variation is so commonly observed that it is routinely removed from morphometric analyses or invoked as an explanation for evolutionary change. In this case, familiarity is mistaken for understanding because rarely do we know the mechanisms by which shape correlates with size or understand their significance. As with other forms of integration, allometric variation is generated by variation in developmental processes that affect multiple traits, resulting in patterns of covariation. Given this perspective, we can dissect the genetic and developmental determinants of allometric variation. Our work on the developmental and genetic basis for allometric variation in craniofacial shape in mice and humans has revealed that allometric variation is highly polygenic. Different measures of size are associated with distinct but overlapping patterns of allometric variation. These patterns converge in part on a common genetic basis. Finally, environmental modulation of size often generates variation along allometric trajectories, but the timing of genetic and environmental perturbations can produce deviations from allometric patterns when traits are differentially sensitive over developmental time. These results question the validity of viewing allometry as a singular phenomenon distinct from morphological integration more generally.
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MacLeod, Norman y David Steart. "Automated leaf physiognomic character identification from digital images". Paleobiology 41, n.º 4 (septiembre de 2015): 528–53. http://dx.doi.org/10.1017/pab.2015.13.
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AbstractResearch into the relationship between leaf form and climate over the last century has revealed that, in many species, the sizes and shapes of leaf characters exhibit highly structured and predictable patterns of variation in response to the local climate. Several procedures have been developed that quantify covariation between the relative abundance of plant character states and the states of climate variables as a means of estimating paleoclimate parameters. One of the most widely used of these is the Climate Leaf Analysis Multivariate Program (CLAMP). The consistency, accuracy and reliability with which leaf characters can be identified and assigned to CLAMP character-state categories is critical to the accuracy of all CLAMP analyses. Here we report results of a series of performance tests for an image-based, fully automated at the point of use, leaf character scoring system that can be used to generate CLAMP leaf character state data for: leaf bases (acute, cordate and round), leaf apices (acute, attenuate), leaf shapes (ovate, elliptical and obovate), leaf lobing (unlobed, lobed), and leaf aspect ratios (length/width). This image-based system returned jackknifed identification accuracy ratios of between 87% and 100%. These results demonstrate that automated image-based identification systems have the potential to improve paleoenvironmental inferences via the provision of accurate, consistent and rapid CLAMP leaf-character identifications. More generally, our results provide strong support for the feasibility of using fully automated, image-based morphometric procedures to address the general problem of morphological character-state identification.
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Romaniuk, A. "Functional and Phylogenetic Aspect in Modularity of Palearctic Mustelids (Carnivora, Mustelidae) Mandible". Vestnik Zoologii 52, n.º 2 (1 de abril de 2018): 165–76. http://dx.doi.org/10.2478/vzoo-2018-0018.
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Abstract Geometric morphometrics was used to investigate morphological integration and modularity in mustelid mandible. A set of 16 two-dimensional landmarks was digitized on the mandibles of 14 extant species of Palearctic Mustelidae (genera Enhydra, Gulo, Meles, Lutra, Martes, Mustela). The original data size-corrected data and phylogenetically independent contrasts (PICs) were analyzed. Several hypotheses were tested: two and three-modules with the masseteric fossa included in corpus or ramus of the mandible. As a result, the two-module hypothesis (subdivision into the alveolar region and the ascending ramus) with masseteric fossa included in corpus for all sets of data was supported. A clear modularity in mustelid mandible is seen at interspecific level, whereas there was large within species covariation between mandibular corpus and ramus. The allometry correction reduces estimates of covariation for the mustelid mandibles. Due to the analysis of PICs the shape changes with maximum evolutionary covariation were found: elongated, sloped backward ramus and thick corpus.
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Hopkins, William D., Robert D. Latzman, Mary Catherine Mareno, Steven J. Schapiro, Aida Gómez-Robles y Chet C. Sherwood. "Heritability of Gray Matter Structural Covariation and Tool Use Skills in Chimpanzees (Pan troglodytes): A Source-Based Morphometry and Quantitative Genetic Analysis". Cerebral Cortex 29, n.º 9 (11 de octubre de 2018): 3702–11. http://dx.doi.org/10.1093/cercor/bhy250.
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Abstract Nonhuman primates, and great apes in particular, possess a variety of cognitive abilities thought to underlie human brain and cognitive evolution, most notably, the manufacture and use of tools. In a relatively large sample (N = 226) of captive chimpanzees (Pan troglodytes) for whom pedigrees are well known, the overarching aim of the current study was to investigate the source of heritable variation in brain structure underlying tool use skills. Specifically, using source-based morphometry (SBM), a multivariate analysis of naturally occurring patterns of covariation in gray matter across the brain, we investigated (1) the genetic contributions to variation in SBM components, (2) sex and age effects for each component, and (3) phenotypic and genetic associations between SBM components and tool use skill. Results revealed important sex- and age-related differences across largely heritable SBM components and associations between structural covariation and tool use skill. Further, shared genetic mechanisms appear to account for a heritable link between variation in both the capacity to use tools and variation in morphology of the superior limb of the superior temporal sulcus and adjacent parietal cortex. Findings represent the first evidence of heritability of structural covariation in gray matter among nonhuman primates.
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Evans, Kory M., Olivier Larouche, Sara-Jane Watson, Stacy Farina, María Laura Habegger y Matt Friedman. "Integration drives rapid phenotypic evolution in flatfishes". Proceedings of the National Academy of Sciences 118, n.º 18 (30 de abril de 2021): e2101330118. http://dx.doi.org/10.1073/pnas.2101330118.
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Evolutionary innovations are scattered throughout the tree of life, and have allowed the organisms that possess them to occupy novel adaptive zones. While the impacts of these innovations are well documented, much less is known about how these innovations arise in the first place. Patterns of covariation among traits across macroevolutionary time can offer insights into the generation of innovation. However, to date, there is no consensus on the role that trait covariation plays in this process. The evolution of cranial asymmetry in flatfishes (Pleuronectiformes) from within Carangaria was a rapid evolutionary innovation that preceded the colonization of benthic aquatic habitats by this clade, and resulted in one of the most bizarre body plans observed among extant vertebrates. Here, we use three-dimensional geometric morphometrics and a phylogenetic comparative toolkit to reconstruct the evolution of skull shape in carangarians, and quantify patterns of integration and modularity across the skull. We find that the evolution of asymmetry in flatfishes was a rapid process, resulting in the colonization of novel trait space, that was aided by strong integration that coordinated shape changes across the skull. Our findings suggest that integration plays a major role in the evolution of innovation by synchronizing responses to selective pressures across the organism.
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Vanhoof, Marie J. M., Lorenzo Galletta, Isabelle De Groote y Evie E. Vereecke. "Functional signals and covariation in triquetrum and hamate shape of extant primates using 3D geometric morphometrics". Journal of Morphology 282, n.º 9 (20 de julio de 2021): 1382–401. http://dx.doi.org/10.1002/jmor.21393.
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Webster, Mark y H. David Sheets. "A Practical Introduction to Landmark-Based Geometric Morphometrics". Paleontological Society Papers 16 (octubre de 2010): 163–88. http://dx.doi.org/10.1017/s1089332600001868.
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Landmark-based geometric morphometrics is a powerful approach to quantifying biological shape, shape variation, and covariation of shape with other biotic or abiotic variables or factors. The resulting graphical representations of shape differences are visually appealing and intuitive. This paper serves as an introduction to common exploratory and confirmatory techniques in landmark-based geometric morphometrics. The issues most frequently faced by (paleo)biologists conducting studies of comparative morphology are covered. Acquisition of landmark and semilandmark data is discussed. There are several methods for superimposing landmark configurations, differing in how and in the degree to which among-configuration differences in location, scale, and size are removed. Partial Procrustes superimposition is the most widely used superimposition method and forms the basis for many subsequent operations in geometric morphometrics. Shape variation among superimposed configurations can be visualized as a scatter plot of landmark coordinates, as vectors of landmark displacement, as a thin-plate spline deformation grid, or through a principal components analysis of landmark coordinates or warp scores. The amount of difference in shape between two configurations can be quantified as the partial Procrustes distance; and shape variation within a sample can be quantified as the average partial Procrustes distance from the sample mean. Statistical testing of difference in mean shape between samples using warp scores as variables can be achieved through a standard Hotelling's T2 test, MANOVA, or canonical variates analysis (CVA). A nonparametric equivalent to MANOVA or Goodall's F-test can be used in analysis of Procrustes coordinates or Procrustes distance, respectively. CVA can also be used to determine the confidence with which a priori specimen classification is supported by shape data, and to assign unclassified specimens to pre-defined groups (assuming that the specimen actually belongs in one of the pre-defined groups).Examples involving Cambrian olenelloid trilobites are used to illustrate how the various techniques work and their practical application to data. Mathematical details of the techniques are provided as supplemental online material. A guide to conducting the analyses in the free Integrated Morphometrics Package software is provided in the appendix.
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Chen, Z., W. Deng, Q. Gong, C. Huang, L. Jiang, M. Li, Z. He et al. "Extensive brain structural network abnormality in first-episode treatment-naive patients with schizophrenia: morphometrical and covariation study". Psychological Medicine 44, n.º 12 (20 de enero de 2014): 2489–501. http://dx.doi.org/10.1017/s003329171300319x.
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BackgroundAlterations in gray matter (GM) are commonly observed in schizophrenia. Accumulating studies suggest that the brain changes associated with schizophrenia are distributed rather than focal, involving interconnected networks of areas as opposed to single regions. In the current study we aimed to explore GM volume (GMV) changes in a relatively large sample of treatment-naive first-episode schizophrenia (FES) patients using optimized voxel-based morphometry (VBM) and covariation analysis.MethodHigh-resolution T1-weighted images were obtained using 3.0-T magnetic resonance imaging (MRI) from 86 first-episode drug-naive patients with schizophrenia and 86 age- and gender-matched healthy volunteers. Symptom severity was evaluated using the Positive and Negative Syndrome Scale (PANSS). GMV was assessed using optimized VBM and in 16 regions of interest (ROIs), selected on the basis of a previous meta-analysis. The relationships between GMVs in the ROIs were examined using an analysis of covariance (ANCOVA).ResultsThe VBM analysis revealed that first-episode patients showed reduced GMV in the hippocampus bilaterally. The ROI analysis identified reductions in GMV in the left inferior frontal gyrus, bilateral hippocampus and right thalamus. The ANCOVA revealed different patterns of regional GMV correlations in patients and controls, including of inter- and intra-insula, inter-amygdala and insula–postcentral gyrus connections.ConclusionsSchizophrenia involves regional reductions in GMV and changes in GMV covariance in the insula, amygdala and postcentral gyrus. These findings were evident at the onset of the disorder, before treatment, and therefore cannot be attributable to the effects of chronic illness progression or medication.
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Evans, Kory M., Marta Vidal-García, Victor A. Tagliacollo, Samuel J. Taylor y Dante B. Fenolio. "Bony Patchwork: Mosaic Patterns of Evolution in the Skull of Electric Fishes (Apteronotidae: Gymnotiformes)". Integrative and Comparative Biology 59, n.º 2 (9 de mayo de 2019): 420–31. http://dx.doi.org/10.1093/icb/icz026.
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Abstract Mosaic evolution refers to the pattern whereby different organismal traits exhibit differential rates of evolution typically due to reduced levels of trait covariation through deep time (i.e., modularity). These differences in rates can be attributed to variation in responses to selective pressures between individual traits. Differential responses to selective pressures also have the potential to facilitate functional specialization, allowing certain traits to track environmental stimuli more closely than others. The teleost skull is a multifunctional structure comprising a complex network of bones and thus an excellent system for which to study mosaic evolution. Here we construct an ultrametric phylogeny for a clade of Neotropical electric fishes (Apteronotidae: Gymnotiformes) and use three-dimensional geometric morphometrics to investigate patterns of mosaic evolution in the skull and jaws. We find strong support for a developmental, three-module hypothesis that consists of the face, braincase, and mandible, and we find that the mandible has evolved four times faster than its neighboring modules. We hypothesize that the functional specialization of the mandible in this group of fishes has allowed it to outpace the face and braincase and evolve in a more decoupled manner. We also hypothesize that this pattern of mosaicism may be widespread across other clades of teleost fishes.
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Brassard, Colline, Marilaine Merlin, Claude Guintard, Elodie Monchâtre-Leroy, Jacques Barrat, Nathalie Bausmayer, Stéphane Bausmayer et al. "Bite force and its relationship to jaw shape in domestic dogs". Journal of Experimental Biology 223, n.º 16 (25 de junio de 2020): jeb224352. http://dx.doi.org/10.1242/jeb.224352.
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ABSTRACTPrevious studies based on two-dimensional methods have suggested that the great morphological variability of cranial shape in domestic dogs has impacted bite performance. Here, we used a three-dimensional biomechanical model based on dissection data to estimate the bite force of 47 dogs of various breeds at several bite points and gape angles. In vivo bite force for three Belgian shepherd dogs was used to validate our model. We then used three-dimensional geometric morphometrics to investigate the drivers of bite force variation and to describe the relationships between the overall shape of the jaws and bite force. The model output shows that bite force is rather variable in dogs and that dogs bite harder on the molar teeth and at lower gape angles. Half of the bite force is determined by the temporal muscle. Bite force also increased with size, and brachycephalic dogs showed higher bite forces for their size than mesocephalic dogs. We obtained significant covariation between the shape of the upper or lower jaw and absolute or residual bite force. Our results demonstrate that domestication has not resulted in a disruption of the functional links in the jaw system in dogs and that mandible shape is a good predictor of bite force.
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Torres-Tamayo, Nicole, Stefan Schlager, Daniel García-Martínez, Juan Alberto Sanchis-Gimeno, Shahed Nalla, Naomichi Ogihara, Motoharu Oishi, Sandra Martelli y Markus Bastir. "Three-dimensional geometric morphometrics of thorax-pelvis covariation and its potential for predicting the thorax morphology: A case study on Kebara 2 Neandertal". Journal of Human Evolution 147 (octubre de 2020): 102854. http://dx.doi.org/10.1016/j.jhevol.2020.102854.
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Guenser, Pauline, Louise Souquet, Sylvain Dolédec, Michele Mazza, Manuel Rigo y Nicolas Goudemand. "Deciphering the roles of environment and development in the evolution of a Late Triassic assemblage of conodont elements". Paleobiology 45, n.º 3 (16 de mayo de 2019): 440–57. http://dx.doi.org/10.1017/pab.2019.14.
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AbstractTo assess evolutionary processes in deep time, it is essential to understand the roles of development and environment, both recorded through the morphological variability of fossil assemblages. Thanks to their great abundance and the high temporal resolution of their fossil record, conodont elements are ideal to address this issue. In this paper, we present the first quantitative study of a Carnian–Norian (Late Triassic) assemblage of closely related P1 conodont elements. Using geometric morphometrics (landmarks, sliding landmarks, and elliptic Fourier analysis), we explore the main axes of phenotypic variation and relate them to classically used taxonomic characters. We show that some important taxonomic features follow laws of covariation, hence highlighting developmental constraints. Furthermore, the intraspecific variation within all considered species, either Carnian or Norian forms, is similarly restricted, emphasizing, for the first time in conodont P1 elements, a common line of least resistance to evolution, which means that similar intrinsic (developmental) factors were acting on these taxa and likely biased the evolutionary trajectories of all these taxa in a similar way. Because the evolution between Carnian and Norian forms is known to have followed a trajectory that is significantly different from the line of least resistance, strong extrinsic pressures, such as environmental disturbances, were probably at play around the Carnian/Norian boundary to counteract the effects of these intrinsic, developmental constraints.
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Hou, Jiancheng, Andrew CN Chen, Bei Song, Changan Sun y Theodore P. Beauchaine. "Neural correlates of absolute pitch: A review". Musicae Scientiae 21, n.º 3 (4 de agosto de 2016): 287–302. http://dx.doi.org/10.1177/1029864916662903.
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Absolute pitch (AP) is the ability to identify and/or produce specific music notes without a reference tone from the Western tonal system. Functional imaging studies show that AP is subserved by a network of interconnected neural structures including the left posterior dorsolateral frontal cortex (DLFC), the bilateral planum temporale (PT), and other brain regions. Neurophysiological studies show that AP possessors do not always require context updating during pitch identification due to possible “tonal templates”, and that AP appears to emerge at a late processing stage that is associated with multiple cognitive strategies and is facilitated by music training at early ages. Morphometry studies show decreased cortical thickness and gray matter concentration among those with AP, which may reflect increased efficiency of AP skill. Graph theoretical analyses of cortical thickness covariations show involvement of higher-order auditory processing, working memory, and semantic memory processes. Diffusion tensor imaging studies provide evidence for a neural pathway between the left posterior DLFC and the left PT, which establishes retrieval and manipulation of verbal-tonal associations. Compared to AP musicians, quasi-AP (QAP) musicians have an extensive right hemisphere network implicated in auditory working memory and show the bilateral structural characteristics of PT morphometry. Future research should confirm the definition of PT boundary and the role of (bi)lateralization of PT in AP ability, develop a standard AP test, identify genetic bases of AP, and describe relations between AP, tonal languages, and associated neural functions and structures among non-musicians with AP ability.
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Tomášek, Oldřich, Jana Albrechtová, Martina Němcová, Pavlína Opatová y Tomáš Albrecht. "Trade-off between carotenoid-based sexual ornamentation and sperm resistance to oxidative challenge". Proceedings of the Royal Society B: Biological Sciences 284, n.º 1847 (25 de enero de 2017): 20162444. http://dx.doi.org/10.1098/rspb.2016.2444.
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It has been hypothesized that carotenoid-based sexual ornamentation signals male fertility and sperm competitive ability as both ornamentation and sperm traits may be co-affected by oxidative stress, resulting in positive covariation (the ‘redox-based phenotype-linked fertility hypothesis’; redox-based PLFH). On the other hand, the ‘sperm competition theory’ (SCT) predicts a trade-off between precopulatory and postcopulatory traits. Here, we manipulate oxidative status (using diquat dibromide) and carotenoid availability in adult zebra finch ( Taeniopygia guttata ) males in order to test whether carotenoid-based beak ornamentation signals, or is traded off against, sperm resistance to oxidative challenge. Initial beak colouration, but not its change during the experiment, was associated with effect of oxidative challenge on sperm velocity, such that more intense colouration predicted an increase in sperm velocity under control conditions but a decline under oxidative challenge. This suggests a long-term trade-off between ornament expression and sperm resistance to oxidative challenge. Shortening of the sperm midpiece following oxidative challenge further suggests that redox homeostasis may constrain sperm morphometry. Carotenoid supplementation resulted in fewer sperm abnormalities but had no effect on other sperm traits. Overall, our data challenge the redox-based PLFH, partially support the SCT and highlight the importance of carotenoids for normal sperm morphology.
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Stoessel, Alexander, Romain David, Philipp Gunz, Tobias Schmidt, Fred Spoor y Jean-Jacques Hublin. "Morphology and function of Neandertal and modern human ear ossicles". Proceedings of the National Academy of Sciences 113, n.º 41 (26 de septiembre de 2016): 11489–94. http://dx.doi.org/10.1073/pnas.1605881113.
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The diminutive middle ear ossicles (malleus, incus, stapes) housed in the tympanic cavity of the temporal bone play an important role in audition. The few known ossicles of Neandertals are distinctly different from those of anatomically modern humans (AMHs), despite the close relationship between both human species. Although not mutually exclusive, these differences may affect hearing capacity or could reflect covariation with the surrounding temporal bone. Until now, detailed comparisons were hampered by the small sample of Neandertal ossicles and the unavailability of methods combining analyses of ossicles with surrounding structures. Here, we present an analysis of the largest sample of Neandertal ossicles to date, including many previously unknown specimens, covering a wide geographic and temporal range. Microcomputed tomography scans and 3D geometric morphometrics were used to quantify shape and functional properties of the ossicles and the tympanic cavity and make comparisons with recent and extinct AMHs as well as African apes. We find striking morphological differences between ossicles of AMHs and Neandertals. Ossicles of both Neandertals and AMHs appear derived compared with the inferred ancestral morphology, albeit in different ways. Brain size increase evolved separately in AMHs and Neandertals, leading to differences in the tympanic cavity and, consequently, the shape and spatial configuration of the ossicles. Despite these different evolutionary trajectories, functional properties of the middle ear of AMHs and Neandertals are largely similar. The relevance of these functionally equivalent solutions is likely to conserve a similar auditory sensitivity level inherited from their last common ancestor.
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Vicari, Deborah, Eline D. Lorenzen, Mikkel Skovrind, Paul Szpak, Marie Louis, Morten T. Olsen, Richard P. Brown et al. "Skull ecomorphological variation of narwhals (Monodon monoceros, Linnaeus 1758) and belugas (Delphinapterus leucas, Pallas 1776) reveals phenotype of their hybrids". PLOS ONE 17, n.º 8 (12 de agosto de 2022): e0273122. http://dx.doi.org/10.1371/journal.pone.0273122.
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Narwhals and belugas are toothed whales belonging to the Monodontidae. Belugas have a circumpolar Arctic and sub-Artic distribution while narwhals are restricted to the Atlantic Arctic. Their geographical ranges overlap during winter migrations in the Baffin Bay area (Canada/West Greenland) and successful interbreeding may occur. Here, we employed geometric morphometrics on museum specimens to explore the cranium and mandible morphology of a known hybrid (NHMD MCE 1356) and the cranium morphology of a putative hybrid (NHMD 1963.44.1.4) relative to skull morphological variation in the parental species. Specifically, we used 3D models of skulls from 69 belugas, 86 narwhals, and the two known/putative hybrids and 2D left hemi-mandibles from 20 belugas, 64 narwhals and the known hybrid. Skull shape analyses allowed clear discrimination between species. Narwhals are characterised by a relatively short rostrum and wide neurocranium while belugas show a more elongated and narrower cranium. Sexual size dimorphism was detected in narwhals, with males larger than females, but no sexual shape dimorphism was detected in either species (excluding presence/absence of tusks in narwhals). Morphological skull variation was also dependent on different allometric slopes between species and sexes in narwhals. Our analyses showed that the cranium of the known hybrid was phenotypically close to belugas but its 2D hemi-mandible had a narwhal shape and size morphology. Both cranium and mandible were strongly correlated, with the pattern of covariation being similar to belugas. The putative hybrid was a pure male narwhal with extruded teeth. Comparison of genomic DNA supported this result, and stable carbon and nitrogen isotope values suggested that the putative hybrid had a more benthic foraging strategy compared to narwhals. This work demonstrates that although the known hybrid could be discriminated from narwhals and belugas, detection of its affinities with these parental species was dependent on the part of the skull analysed.
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Boivin, Myriam, Alicia Álvarez y Marcos D. Ercoli. "Integration patterns of cheek teeth and ecomorphological evolution in grinding herbivores: the case of caviine rodents (Caviomorpha: Caviidae)". Zoological Journal of the Linnean Society, 12 de marzo de 2022. http://dx.doi.org/10.1093/zoolinnean/zlac005.
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Abstract Caviid rodents have peculiar craniomandibular specializations toward masticatory propalinal movements and grinding, in relation to a grass-rich diet. The aim of this study is to: (1) analyse the variation of cheek tooth shape in the Caviinae and, (2) quantify the covariation relations between caviine cheek teeth. For this purpose, we perform the first geometric morphometric analysis on cheek teeth of fossil and extant caviids, ancestral shape reconstructions and covariation analyses. Our results show that caviine dentition is strongly integrated with a higher covariation between teeth of the same row than between opposite teeth, differing from mammals with complex interlocking. Each series acts as a single functional unit integrated during grinding action obtained by mainly propalinal movements. However, p4 shows more plasticity, allowing its morphology to differentiate from the common pattern of molars. Morphologically homogeneous cheek tooth series are ancestral in crown caviids and highly marked in Cavia, while stronger morphological differences between tooth pieces are observed in Microcavia and Galea. These differences are probably driven by diet changes. The tendency towards alignment of main masticatory movements with the tooth row axes seems to be a key factor in understanding cheek tooth covariation patterns in this and other rodent clades.
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Bardo, Ameline, Marie-Hélène Moncel, Christopher J. Dunmore, Tracy L. Kivell, Emmanuelle Pouydebat y Raphaël Cornette. "The implications of thumb movements for Neanderthal and modern human manipulation". Scientific Reports 10, n.º 1 (26 de noviembre de 2020). http://dx.doi.org/10.1038/s41598-020-75694-2.
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AbstractMuch research has debated the technological abilities of Neanderthals relative to those of early modern humans, with a particular focus on subtle differences in thumb morphology and how this may reflect differences in manipulative behaviors in these two species. Here, we provide a novel perspective on this debate through a 3D geometric morphometric analysis of shape covariation between the trapezial and proximal first metacarpal articular surfaces of Neanderthals (Homo neanderthalensis) in comparison to early and recent humans (Homo sapiens). Results show a distinct pattern of shape covariation in Neanderthals, consistent with more extended and adducted thumb postures that may reflect habitual use of grips commonly used for hafted tools. Both Neanderthals and recent humans demonstrate high intraspecific variation in shape covariation. This intraspecific variation is likely the result of genetic and/or developmental differences, but may also reflect, in part, differing functional requirements imposed by the use of varied tool-kits. These results underscore the importance of holistic joint shape analysis for understanding the functional capabilities and evolution of the modern human thumb.
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Miola, Alessandro, Nicolò Trevisan, Arcangelo Merola, Francesco Folena Comini, Daniele Olivo, Matteo Minerva, Silvia Valeggia et al. "Gray matter volume covariance networks are associated with altered emotional processing in bipolar disorder: a source-based morphometry study". Brain Imaging and Behavior, 21 de septiembre de 2021. http://dx.doi.org/10.1007/s11682-021-00541-5.
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AbstractWidespread regional gray matter volume (GMV) alterations have been reported in bipolar disorder (BD). Structural networks, which are thought to better reflect the complex multivariate organization of the brain, and their clinical and psychological function have not been investigated yet in BD. 24 patients with BD type-I (BD-I), and 30 with BD type-II (BD-II), and 45 controls underwent MRI scan. Voxel-based morphometry and source-based morphometry (SBM) were performed to extract structural covariation patterns of GMV. SBM components associated with morphometric differences were compared among diagnoses. Executive function and emotional processing correlated with morphometric characteristics. Compared to controls, BD-I showed reduced GMV in the temporo-insular-parieto-occipital cortex and in the culmen. An SBM component spanning the prefrontal-temporal-occipital network exhibited significantly lower GMV in BD-I compared to controls, but not between the other groups. The structural network covariance in BD-I was associated with the number of previous manic episodes and with worse executive performance. Compared to BD-II, BD-I showed a loss of GMV in the temporal-occipital regions, and this was correlated with impaired emotional processing. Altered prefrontal-temporal-occipital network structure could reflect a neural signature associated with visuospatial processing and problem-solving impairments as well as emotional processing and illness severity in BD-I.
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Polychronis, Georgios, Panagiotis Christou, Maria Mavragani y Demetrios J. Halazonetis. "Geometric morphometric 3D shape analysis and covariation of human mandibular and maxillary first molars". American Journal of Physical Anthropology, septiembre de 2013, n/a. http://dx.doi.org/10.1002/ajpa.22340.
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Park, Haeme R. P., Yann Quidé, Peter R. Schofield, Leanne M. Williams y Justine M. Gatt. "Grey matter covariation and the role of emotion reappraisal in mental wellbeing and resilience after early life stress exposure". Translational Psychiatry 12, n.º 1 (26 de febrero de 2022). http://dx.doi.org/10.1038/s41398-022-01849-6.
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AbstractResilience is a process of adaptive recovery crucial in maintaining mental wellbeing after stress exposure. A psychological factor known to buffer stress and promote positive wellbeing outcomes is the ability to regulate emotions. However, the neural networks underlying resilience, and the possible mediating role of emotion regulation, remain largely unknown. Here, we examined the association between resilience and grey matter covariation (GMC) in healthy adults with and without early life stress (ELS) exposure, and whether emotion regulation mediated this brain-resilience association. Source-based morphometry was used to identify spatial patterns of common GMC in 242 healthy participants. Wellbeing was measured using the COMPAS-W Wellbeing Scale. Linear mixed models were run to establish associations between GMC and wellbeing scores. Moderated mediation models were used to examine a conditional mediating effect of emotion regulation on the brain-wellbeing relationship, moderated by ELS exposure. Distinct ELS-related morphometric patterns were found in association with resilience. In participants without ELS exposure, decreased GMC in the temporo-parietal regions was associated with wellbeing. In participants with ELS exposure, we observed increased patterns of covariation in regions related to the salience and executive control networks, and decreased GMC in temporo-parietal areas, which were associated with resilience. Cognitive reappraisal mediated the brain-wellbeing relationship in ELS-exposed participants only. Patterns of stronger GMC in regions associated with emotional and cognitive functioning in ELS-exposed participants with high levels of wellbeing may indicate possible neural signatures of resilience. This may be further heightened by utilising an adaptive form of emotion regulation.
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MacLeod, Norman, Benjamin Price y Zackary Stevens. "What you sample is what you get: ecomorphological variation in Trithemis (Odonata, Libellulidae) dragonfly wings reconsidered". BMC Ecology and Evolution 22, n.º 1 (11 de abril de 2022). http://dx.doi.org/10.1186/s12862-022-01978-y.
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Abstract Background The phylogenetic ecology of the Afro-Asian dragonfly genus Trithemis has been investigated previously by Damm et al. (in Mol Phylogenet Evol 54:870–882, 2010) and wing ecomorphology by Outomuro et al. (in J Evol Biol 26:1866–1874, 2013). However, the latter investigation employed a somewhat coarse sampling of forewing and hindwing outlines and reported results that were at odds in some ways with expectations given the mapping of landscape and water-body preference over the Trithemis cladogram produced by Damm et al. (in Mol Phylogenet Evol 54:870–882, 2010). To further explore the link between species-specific wing shape variation and habitat we studied a new sample of 27 Trithemis species employing a more robust statistical test for phylogenetic covariation, more comprehensive representations of Trithemis wing morphology and a wider range of morphometric data-analysis procedures. Results Contrary to the Outomuro et al. (in J Evol Biol 26:1866–1874, 2013) report, our results indicate that no statistically significant pattern of phylogenetic covariation exists in our Trithemis forewing and hindwing data and that both male and female wing datasets exhibit substantial shape differences between species that inhabit open and forested landscapes and species that hunt over temporary/standing or running water bodies. Among the morphometric analyses performed, landmark data and geometric morphometric data-analysis methods yielded the worst performance in identifying ecomorphometric shape distinctions between Trithemis habitat guilds. Direct analysis of wing images using an embedded convolution (deep learning) neural network delivered the best performance. Bootstrap and jackknife tests of group separations and discriminant-function stability confirm that our results are not artifacts of overtrained discriminant systems or the “curse of dimensionality” despite the modest size of our sample. Conclusion Our results suggest that Trithemis wing morphology reflects the environment’s “push” to a much greater extent than phylogeny’s “pull”. In addition, they indicate that close attention should be paid to the manner in which morphologies are sampled for morphometric analysis and, if no prior information is available to guide sampling strategy, the sample that most comprehensively represents the morphologies of interest should be obtained. In many cases this will be digital images (2D) or scans (3D) of the entire morphology or morphological feature rather than sparse sets of landmark/semilandmark point locations.
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Parcha, Eleni, Elias Bitsanis y Demetrios J. Halazonetis. "Morphometric covariation between palatal shape and skeletal pattern in children and adolescents: a cross-sectional study". European Journal of Orthodontics, 30 de septiembre de 2016, cjw063. http://dx.doi.org/10.1093/ejo/cjw063.
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Paoloni, V., G. Gastaldi, L. Franchi, F. C. De razza y P. Cozza. "Evaluation of the morphometric covariation between palatal and craniofacial skeletal morphology in class III malocclusion growing subjects". BMC Oral Health 20, n.º 1 (27 de mayo de 2020). http://dx.doi.org/10.1186/s12903-020-01140-4.
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Winkler, Lennart, Anna K. Lindholm, Steven A. Ramm y Andreas Sutter. "The baculum affects paternity success of first but not second males in house mouse sperm competition". BMC Ecology and Evolution 21, n.º 1 (12 de agosto de 2021). http://dx.doi.org/10.1186/s12862-021-01887-6.
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AbstractThe vast variation observed in genital morphology is a longstanding puzzle in evolutionary biology. Studies showing that the morphology of the mammalian baculum (penis bone) can covary with a male’s paternity success indicate a potential impact of baculum morphology on male fitness, likely through influencing sperm competition outcomes. We therefore measured the size (measurements of length and width) and shape (geometric morphometric measurements) of the bacula of male house mice used in previously published sperm competition experiments, in which two males mated successively with the same female in staged matings. This enabled us to correlate baculum morphology with sperm competition success, incorporating potential explanatory variables related to copulatory plugs, male mating behavior and a selfish genetic element that influences sperm motility. We found that a wider baculum shaft increased a male’s paternity share when mating first, but not when mating second with a multiply-mating female. Geometric morphometric shape measurements were not clearly associated with fertilization success for either male. We found limited evidence that the effect of baculum morphology on male fertilization success was altered by experimental removal of the copulatory plug. Furthermore, neither genetic differences in sperm motility, nor covariation with male mating behavior mediated the effect of baculum morphology on male fertilization success. Taken together with previous findings, the mating-order effects we found here suggest that baculum-mediated stimulation by the first male might be particularly important for fertilization.
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Dashti, Zainab, Hasan Alhaddad y Bader H. Alhajeri. "A geometric morphometric analysis of geographic variation in the Cape Short-eared gerbil, Desmodillus auricularis (Rodentia: Gerbillinae)". Mammalia, 12 de julio de 2022. http://dx.doi.org/10.1515/mammalia-2022-0019.
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Abstract The genus Desmodillus is monospecific, consisting of only the Cape short-eared gerbil (Desmodillus auricularis). Despite being widely distributed across southern Africa, previous studies did not find evidence of intraspecific phenotypic geographic differentiation. The objectives of this study is to use geometric morphometrics to investigate if and how the skull of D. auricularis varies spatially. It examines the covariation of skull morphology with broad spatial (latitude and longitude) and climatic variables, based on a sample of 580 specimens from southern Africa (Botswana, Namibia, and South Africa). The results did not support the differentiation of D. auricularis populations into distinct geographically isolated phenotypic groups. However, there is strong evidence for clinal variation in skull morphology; the most prominent pattern being a decrease in size from the west (closest to the South Atlantic coast) to the east (towards the continent’s interior). Shape variation was not localized in any skull region and seem to be driven mostly by size (allometry), although it also covaried significantly with latitude and longitude. Statistically significant skull shape sexual dimorphism was also detected, with males having larger crania than females. Spatial clinal variation in skull morphology was mostly associated with differences in the aridity of the habitats relative to their distance from the coast as evidenced by precipitation-related bioclimatic variables—annual precipitation (BIO12), precipitation of driest month (BIO14), and precipitation of driest quarter (BIO17)—covarying the most with skull morphology. This could be driven by either the climate influencing local resources available to populations or by the climate directly instigating phenotypic climatic adaptations.
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Llambrich, Sergi, Rubèn González, Julia Albaigès, Jens Wouters, Fopke Marain, Uwe Himmelreich, James Sharpe et al. "Multimodal in vivo Imaging of the Integrated Postnatal Development of Brain and Skull and Its Co-modulation With Neurodevelopment in a Down Syndrome Mouse Model". Frontiers in Medicine 9 (11 de febrero de 2022). http://dx.doi.org/10.3389/fmed.2022.815739.
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The brain and skeletal systems are intimately integrated during development through common molecular pathways. This is evidenced by genetic disorders where brain and skull dysmorphologies are associated. However, the mechanisms underlying neural and skeletal interactions are poorly understood. Using the Ts65Dn mouse model of Down syndrome (DS) as a case example, we performed the first longitudinal assessment of brain, skull and neurobehavioral development to determine alterations in the coordinated morphogenesis of brain and skull. We optimized a multimodal protocol combining in vivo micro-computed tomography (μCT) and magnetic resonance imaging (μMRI) with morphometric analyses and neurodevelopmental tests to longitudinally monitor the different systems' development trajectories during the first postnatal weeks. We also explored the impact of a perinatal treatment with green tea extracts enriched in epigallocatechin-3-gallate (GTE-EGCG), which can modulate cognition, brain and craniofacial development in DS. Our analyses quantified alterations associated with DS, with skull dysmorphologies appearing before brain anomalies, reduced integration and delayed acquisition of neurodevelopmental traits. Perinatal GTE-EGCG induced disparate effects and disrupted the magnitude of integration and covariation patterns between brain and skull. Our results exemplify how a longitudinal research approach evaluating the development of multiple systems can reveal the effect of morphological integration modulating the response of pathological phenotypes to treatment, furthering our understanding of complex genetic disorders.
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Valge, Markus, Richard Meitern y Peeter Hõrak. "Mothers of small-bodied children and fathers of vigorous sons live longer". Frontiers in Public Health 11 (25 de enero de 2023). http://dx.doi.org/10.3389/fpubh.2023.1057146.
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Life-history traits (traits directly related to survival and reproduction) co-evolve and materialize through physiology and behavior. Accordingly, lifespan can be hypothesized as a potentially informative marker of life-history speed that subsumes the impact of diverse morphometric and behavioral traits. We examined associations between parental longevity and various anthropometric traits in a sample of 4,000–11,000 Estonian children in the middle of the 20th century. The offspring phenotype was used as a proxy measure of parental genotype, so that covariation between offspring traits and parental longevity (defined as belonging to the 90th percentile of lifespan) could be used to characterize the aggregation between longevity and anthropometric traits. We predicted that larger linear dimensions of offspring associate with increased parental longevity and that testosterone-dependent traits associate with reduced paternal longevity. Twelve of 16 offspring traits were associated with mothers' longevity, while three traits (rate of sexual maturation of daughters and grip strength and lung capacity of sons) robustly predicted fathers' longevity. Contrary to predictions, mothers of children with small bodily dimensions lived longer, and paternal longevity was not linearly associated with their children's body size (or testosterone-related traits). Our study thus failed to find evidence that high somatic investment into brain and body growth clusters with a long lifespan across generations, and/or that such associations can be detected on the basis of inter-generational phenotypic correlations.
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Gigena, Gisel V., Claudia S. Rodríguez, Federico G. Fiad, María Laura Hernández, Ana Laura Carbajal-de-la-Fuente, Romina V. Piccinali, Paz Sánchez Casaccia et al. "Phenotypic variability in traits related to flight dispersal in the wing dimorphic species Triatoma guasayana". Parasites & Vectors 16, n.º 1 (9 de enero de 2023). http://dx.doi.org/10.1186/s13071-022-05570-7.
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Abstract Background Triatoma guasayana is considered an emerging vector of Chagas disease in the Southern Cone of South America. The presence of a triatomine population with brachypterous individuals, in which both wings are reduced, has recently been reported for this species. The aim of the present study was to determine if flight-related traits varied across populations, if these traits could explain differences in flight capacity across populations and if flight-related traits are associated with geographic and/or climatic variation. Methods The study involved 66 male T. guasayana specimens from 10 triatomine populations. Digital images of wing, head and pronotum were used to estimate linear and geometric morphometric variables. Variations in size and shape were analysed using one-way analysis of variance and canonical variate analysis (CVA), respectively. Mantel tests were applied to analyse the relationship between morphometric and geographic distances, and the association between size measurements was analysed using Pearson’s correlation. We explored covariation between size and shape variables using partial least square analyses (PLS). The association of geographic and climatic variables with size measurements was tested using linear regression analyses. We performed PLS analyses for shape measurements. Results Wing size differed significantly across triatomine populations. The CVA showed that wing shape of the brachypterous population is well discriminated from that of the other populations. The Mantel test showed a positive and significant association between wing shape and geographic distances. The heads of the brachypterous population were significantly larger than those of the other populations. Similar to wing shape, the head shape of the brachypterous population was well discriminated from those of the other populations. Pronotum width did not show significant differences across populations. Geographic and climatic factors were associated with size and shape of both the wing and head, but not with pronotum width. Conclusions Most of the traits related to flight dispersal varied across populations. Wing shape and head shape were found to be better markers for differentiated morphological variation across populations. Head measurements also varied in accordance with this condition. Geographic and climatic variables were associated with most of the flight-related traits. Graphical Abstract
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Brassard, Colline, Marilaine Merlin, Elodie Monchâtre-Leroy, Claude Guintard, Jacques Barrat, Hélène Garès, Arnaud Larralle et al. "Masticatory system integration in a commensal canid: interrelationships between bones, muscles and bite force in the red fox". Journal of Experimental Biology 224, n.º 5 (1 de marzo de 2021). http://dx.doi.org/10.1242/jeb.224394.
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ABSTRACT The jaw system in canids is essential for defence and prey acquisition. However, how it varies in wild species in comparison with domestic species remains poorly understood, yet is of interest in terms of understanding the impact of artificial selection. Here, we explored the variability and interrelationships between the upper and lower jaws, muscle architecture and bite force in the red fox (Vulpes vulpes). We performed dissections and used 3D geometric morphometric approaches to quantify jaw shape in 68 foxes. We used a static lever model and bite force estimates were compared with in vivo measurements of 10 silver foxes. Our results show strong relationships exist between cranial and mandible shape, and between cranial or mandible shape on the one hand and muscles or estimated bite force on the other hand, confirming the strong integration of the bony and muscular components of the jaw system. These strong relationships are strongly driven by size. The functional links between shape and estimated bite force are stronger for the mandible, which probably reflects its greater specialisation towards biting. We then compared our results with data previously obtained for dogs (Canis lupus familiaris) to investigate the effect of domestication. Foxes and dogs differ in skull shape and muscle physiological cross-sectional area (PCSA). They show a similar amount of morphological variation in muscle PCSA, but foxes show lower variation in cranial and mandible shape. Interestingly, the patterns of covariation are not stronger in foxes than in dogs, suggesting that domestication did not lead to a disruption of the functional links of the jaw system.
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Haas, S. S., G. E. Doucet, S. Garg, S. N. Herrera, C. Sarac, Z. R. Bilgrami, R. B. Shaik y C. M. Corcoran. "Linking language features to clinical symptoms and multimodal imaging in individuals at clinical high risk for psychosis". European Psychiatry 63, n.º 1 (2020). http://dx.doi.org/10.1192/j.eurpsy.2020.73.
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Abstract Background. Abnormalities in the semantic and syntactic organization of speech have been reported in individuals at clinical high-risk (CHR) for psychosis. The current study seeks to examine whether such abnormalities are associated with changes in brain structure and functional connectivity in CHR individuals. Methods. Automated natural language processing analysis was applied to speech samples obtained from 46 CHR and 22 healthy individuals. Brain structural and resting-state functional imaging data were also acquired from all participants. Sparse canonical correlation analysis (sCCA) was used to ascertain patterns of covariation between linguistic features, clinical symptoms, and measures of brain morphometry and functional connectivity related to the language network. Results. In CHR individuals, we found a significant mode of covariation between linguistic and clinical features (r = 0.73; p = 0.003), with negative symptoms and bizarre thinking covarying mostly with measures of syntactic complexity. In the entire sample, separate sCCAs identified a single mode of covariation linking linguistic features with brain morphometry (r = 0.65; p = 0.05) and resting-state network connectivity (r = 0.63; p = 0.01). In both models, semantic and syntactic features covaried with brain structural and functional connectivity measures of the language network. However, the contribution of diagnosis to both models was negligible. Conclusions. Syntactic complexity appeared sensitive to prodromal symptoms in CHR individuals while the patterns of brain-language covariation seemed preserved. Further studies in larger samples are required to establish the reproducibility of these findings.