Home About us Contact
|
Home About us Contact | ||
|
|
||
Geometric Morphometrics (geometric + morphometric)
Terms modified by Geometric Morphometrics Selected AbstractsGeometric morphometrics of corpus callosum and subcortical structures in the fetal-alcohol-affected brainBIRTH DEFECTS RESEARCH, Issue 1 2001Fred L. Bookstein Background Although experienced clinicians have been diagnosing fetal alcohol syndrome (FAS) for nearly 30 years, the rest of the spectrum of fetal alcohol damage is not being classified effectively. This article describes a quantification of neuroanatomical structure that may supply a useful discriminator of prenatal brain damage from alcohol. It is demonstrated in a data set of adults of both sexes. Methods Ninety adults (45 males) were examined by magnetic resonance imaging (MRI). These subjects were group-matched for age and ethnicity across three diagnoses: FAS, fetal alcohol effects (FAE), and normals. All FAS and FAE were heavily alcohol-exposed in utero; normals were not. From T1 -weighted MR brain images, we extracted 3D morphometric representations of shape for 33-landmark point configurations and 40-point outlines of the corpus callosum along its midline (a slightly nonplanar structure). Results There are striking differences between exposed and unexposed in the statistical distributions of these two shapes. The differences are better characterized by excess variance in the exposed group than by any change in average landmark or outline shape. For each sex, combining the callosal outline data with the landmark data leads to a powerful quadratic discriminator of exposed from unexposed. The discriminating features include the relationship of brain stem to diencephalon, and localized variabilities of callosal outline shape, but not diagnosis (FAS vs. FAE). Conclusions Statistical analysis of brain shape is a powerful new source of information relevant to fetal alcohol spectrum nosology and etiology. Patients with FAS and FAE do not differ in these brain shape features, but both differ from the unexposed. The aspects of brain shape that are especially variable may be entailed in the underlying neuroteratogenetic mechanisms. Teratology 64:4,32, 2001. © 2001 Wiley-Liss, Inc. [source] Differential correlates of diet and phylogeny on the shape of the premaxilla and anterior tooth in sparid fishes (Perciformes: Sparidae)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2004M. Linde Abstract We explore the correlational patterns of diet and phylogeny on the shape of the premaxilla and anterior tooth in sparid fishes (Perciformes: Sparidae) from the western Mediterranean Sea. The premaxilla is less variable, and in spite of the presence of species-specific features, a common structural pattern is easily recognizable in all species (i.e. the ascending and the articular processes are fused in a single branch, as in many percoid fishes). In contrast, tooth shape is more variable, and different structural types can be recognized (e.g. canine-like or incisive). Coupling geometric morphometric and comparative methods we found that the relationship between shape, diet and phylogeny also differs between premaxilla and tooth. Thus, the shape of the premaxilla is significantly correlated with food type, whereas the shape of the teeth is not correlated with diet, and probably reflects the species phylogenetic relationships. Two biological roles, resistance against compressive forces generated in the buccal cavity and the size of the oral gape, would explain the ecomorphological patterns of the premaxilla. The premaxilla and anterior tooth appear to evolve at different rates (mosaic evolution) and represent an example of morphological traits belonging to the same functional unit but following uncoupled evolutionary pathways. [source] Chondrocranial development in larval Rana sylvatica (Anura: Ranidae): Morphometric analysis of cranial allometry and ontogenetic shape changeJOURNAL OF MORPHOLOGY, Issue 2 2002Peter M. Larson Abstract This study provides baseline quantitative data on the morphological development of the chondrocranium in a larval anuran. Both linear and geometric morphometric methods are used to quantitatively analyze size-related shape change in a complete developmental series of larvae of the wood frog, Rana sylvatica. The null hypothesis of isometry was rejected in all geometric morphometric and most linear morphometric analyses. Reduced major axis regressions of 11 linear chondrocranial measurements on size indicate a mixture of allometric and isometric scaling. Measurements in the otic and oral regions tend to scale with negative allometry and those associated with the palatoquadrate and muscular process scale with isometry or positive allometry. Geometric morphometric analyses, based on a set of 11 chondrocranial landmarks, include linear regression of relative warp scores and multivariate regression of partial warp scores and uniform components on log centroid size. Body size explains about one-quarter to one-third of the total shape variation found in the sample. Areas of regional shape transformation (e.g., palatoquadrate, otic region, trabecular horns) are identified by thin-plate spline deformation grids and are concordant with linear morphometric results. Thus, the anuran chondrocranium is not a static structure during premetamorphic stages and allometric patterns generally follow scaling predictions for tetrapod cranial development. Potential implications regarding larval functional morphology, cranial development, and chondrocranial evolution in anurans are discussed. J. Morphol. 252:131,144, 2002. © 2002 Wiley-Liss, Inc. [source] Technical note: A new method for measuring long bone curvature using 3D landmarks and semi-landmarksAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2010Isabelle De Groote Abstract Here we describe and evaluate a new method for quantifying long bone curvature using geometric morphometric and semi-landmark analysis of the human femur. The technique is compared with traditional ways of measuring subtense and point of maximum curvature using either coordinate calipers or projection onto graph paper. Of the traditional methods the graph paper method is more reliable than using coordinate calipers. Measurement error is consistently lower for measuring point of maximum curvature than for measuring subtense. The results warrant caution when comparing data collected by the different traditional methods. Landmark data collection proves reliable and has a low measurement error. However, measurement error increases with the number of semi-landmarks included in the analysis of curvature. Measurements of subtense can be estimated more reliably using 3D landmarks along the curve than using traditional techniques. We use equidistant semi-landmarks to quantify the curve because sliding the semi-landmarks masks the curvature signal. Principal components analysis of these equidistant semi-landmarks provides the added benefit of describing the shape of the curve. These results are promising for functional and forensic analysis of long bone curvature in modern human populations and in the fossil record. Am J Phys Anthropol, 2010. © 2010 Wiley-Liss, Inc. [source] Comparative morphometrics of embryonic facial morphogenesis: Implications for cleft-lip etiologyTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 1 2007Nathan M. Young Abstract Cleft lip (CL) with or without cleft palate (CL[P]) has a complex etiology but is thought to be due to either genetic or environmentally induced disruptions of developmental processes affecting the shape and size of the facial prominences (medial nasal, lateral nasal, and maxilla). Recent advances in landmark-based morphometrics enable a rigorous reanalysis of phenotypic shape variation associated with facial clefting. Here we use geometric morphometric (GM) tools to characterize embryonic shape variation in the midface and head of six strains of mice that are both cleft-liable (A, A/WySn, CL/Fr) and normal (BALB/cBy, C57BL, CD1). Data were comprised of two-dimensional landmarks taken from frontal and lateral photographs of embryos spanning the time period in which the facial prominences fuse (GD10-12). Results indicate that A/- strain mice, and particularly A/WySn, have overall smaller midfaces compared to other strains. The A/WySn strain also has significant differences in facial shape related to retarded development. Overall, CL/Fr strain mice are normal-sized, but tend to have undersized maxillary prominences that do not project anteriorly and have a small nasal contact area. These results suggest that the etiology of clefting differs in A/WySn and CL/Fr strains, with the former strain suffering disruptions to developmental processes affecting overall size (e.g., neural crest migration deficiencies and lower mitotic activity), while the latter strain has defects restricted to the shape and size of the maxilla. A combination of molecular experimentation and phenotypic analysis of shape is required to test these hypotheses further. Anat Rec, 290:123,139, 2007. © 2006 Wiley-Liss, Inc. [source] EVOLUTION OF SCAPULA SIZE AND SHAPE IN DIDELPHID MARSUPIALS (DIDELPHIMORPHIA: DIDELPHIDAE)EVOLUTION, Issue 9 2009Diego Astúa The New World family Didelphidae, the basal lineage within marsupials, is commonly viewed as morphologically conservative, yet includes aquatic, terrestrial, scansorial, and arboreal species. Here, I quantitatively estimated the existing variability in size and shape of the Didelphidae scapula (1076 specimens from 56 species) using geometric morphometrics, and compared size and shape differences to evolutionary and ecologic distances. I found considerable variation in the scapula morphology, most of it related to size differences between species. This results in morphologic divergence between different locomotor habits in larger species (resulting from increased mechanical loads), but most smaller species present similarly shaped scapulae. The only exceptions are the water opossum and the short-tailed opossums, and the functional explanations for these differences remain unclear. Scapula size and shape were mapped onto a molecular phylogeny for 32 selected taxa and ancestral size and shapes were reconstructed using squared-changed parsimony. Results indicate that the Didelphidae evolved from a medium- to small-sized ancestor with a generalized scapula, slightly more similar to arboreal ones, but strikingly different from big-bodied present arboreal species, suggesting that the ancestral Didelphidae was a small scansorial animal with no particular adaptations for arboreal or terrestrial habits, and these specializations evolved only in larger-bodied clades. [source] QUANTITATIVE GENETICS OF PLASTRON SHAPE IN SLIDER TURTLES (TRACHEMYS SCRIPTA)EVOLUTION, Issue 3 2006Erin M. Myers Abstract Shape variation is widespread in nature and embodies both a response to and a source for evolution and natural selection. To detect patterns of shape evolution, one must assess the quantitative genetic underpinnings of shape variation as well as the selective environment that the organisms have experienced. Here we used geometric morphometrics to assess variation in plastron shell shape in 1314 neonatal slider turtles (Trachemys scripta) from 162 clutches of laboratory-incubated eggs from two nesting areas. Multivariate analysis of variance indicated that nesting area has a limited role in describing plastron shape variation among clutches, whereas differences between individual clutches were highly significant, suggesting a prominent clutch effect. The covariation between plastron shape and several possible maternal effect variables (yolk hormone levels and egg dimensions) was assessed for a subset of clutches and found to be negligible. We subsequently employed several recently proposed methods for estimating heritability from shape variables, and generalized a univariate approach to accommodate unequal sample sizes. Univariate estimates of shape heritability based on Procrustes distances yielded large values for both nesting populations (h2, 0.86), and multivariate estimates of maximal additive heritability were also large for both nesting populations (h2max, 0.57). We also estimated the dominant trend in heritable shape change for each nesting population and found that the direction of shape evolution was not the same for the two sites. Therefore, although the magnitude of shape evolution was similar between nesting populations, the manner in which plastron shape is evolving is not. We conclude that the univariate approach for assessing quantitative genetic parameters from geometric morphometric data has limited utility, because it is unable to accurately describe how shape is evolving. [source] Facial surface analysis by 3D laser scanning and geometric morphometrics in relation to sexual dimorphism in cerebral,craniofacial morphogenesis and cognitive functionJOURNAL OF ANATOMY, Issue 3 2005Robin J. Hennessy Abstract Over early fetal life the anterior brain, neuroepithelium, neural crest and facial ectoderm constitute a unitary, three-dimensional (3D) developmental process. This intimate embryological relationship between the face and brain means that facial dysmorphogenesis can serve as an accessible and informative index of brain dysmorphogenesis in neurological and psychiatric disorders of early developmental origin. There are three principal challenges in seeking to increase understanding of disorders of early brain dysmorphogenesis through craniofacial dysmorphogenesis: (i) the first, technical, challenge has been to digitize the facial surface in its inherent three-dimensionality; (ii) the second, analytical, challenge has been to develop methodologies for extracting biologically meaningful shape covariance from digitized samples, making statistical comparisons between groups and visualizing in 3D the resultant statistical models on a ,whole face' basis; (iii) the third, biological, challenge is to demonstrate a relationship between facial morphogenesis and brain morphogenesis not only in anatomical,embryological terms but also at the level of brain function. Here we consider each of these challenges in turn and then illustrate the issues by way of our own findings. These use human sexual dimorphism as an exemplar for 3D laser surface scanning of facial shape, analysis using geometric morphometrics and exploration of cognitive correlates of variation in shape of the ,whole face', in the context of studies relating to the early developmental origins of schizophrenia. [source] Quantifying temporal bone morphology of great apes and humans: an approach using geometric morphometricsJOURNAL OF ANATOMY, Issue 6 2002Charles A. Lockwood Abstract The hominid temporal bone offers a complex array of morphology that is linked to several different functional systems. Its frequent preservation in the fossil record gives the temporal bone added significance in the study of human evolution, but its morphology has proven difficult to quantify. In this study we use techniques of 3D geometric morphometrics to quantify differences among humans and great apes and discuss the results in a phylogenetic context. Twenty-three landmarks on the ectocranial surface of the temporal bone provide a high level of anatomical detail. Generalized Procrustes analysis (GPA) is used to register (adjust for position, orientation and scale) landmark data from 405 adults representing Homo, Pan, Gorilla and Pongo. Principal components analysis of residuals from the GPA shows that the major source of variation is between humans and apes. Human characteristics such as a coronally orientated petrous axis, a deep mandibular fossa, a projecting mastoid process, and reduced lateral extension of the tympanic element strongly impact the analysis. In phenetic cluster analyses, gorillas and orangutans group together with respect to chimpanzees, and all apes group together with respect to humans. Thus, the analysis contradicts depictions of African apes as a single morphotype. Gorillas and orangutans lack the extensive preglenoid surface of chimpanzees, and their mastoid processes are less medially inflected. These and other characters shared by gorillas and orangutans are probably primitive for the African hominid clade. [source] Morphometric comparison of the cephalic region of cultured Acipenser baerii (Brandt, 1869), Acipenser naccarii (Bonaparte, 1836) and their hybrid,JOURNAL OF APPLIED ICHTHYOLOGY, Issue 1 2006C. Costa Summary Geometric morphometric techniques were used in the characterization of morphological differences of the cranial region in cultured Acipenser baerii and A. naccarii and their hybrid. Species identification in sturgeons sometimes is difficult, because of the morphological plasticity of individual variability and the small differences between taxa. Identification is also complicated by human intervention and manipulation (e.g. aquaculture, hybridization, pollution). This study indicates how the differences between two species and their hybrids can be quantified and accurately visualized via geometric morphometrics. This technique may serve as a useful methodology to supplement analytical studies on morphometrics and systematics in Acipenseridae. [source] Adaptive radiation in African weakly electric fish (Teleostei: Mormyridae: Campylomormyrus): a combined molecular and morphological approachJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 1 2007P. G. D. FEULNER Abstract We combined multiple molecular markers and geometric morphometrics to revise the current taxonomy and to build a phylogenetic hypothesis for the African weakly electric fish genus Campylomormyrus. Genetic data (2039 bp DNA sequence of mitochondrial cytochrome b and nuclear S7 genes) on 106 specimens support the existence of at least six species occurring in sympatry. We were able to further confirm these species by microsatellite analysis at 16 unlinked nuclear loci and landmark-based morphometrics. We assigned them to nominal taxa by comparisons to type specimens of all Campylomormyrus species recognized so far. Additionally, we showed that the shape of the elongated trunk-like snout is the major source of morphological differentiation among them. This finding suggests that the radiation of this speciose genus might have been driven by adaptation to different food sources. [source] Morphological differences between two ecologically similar sympatric fishesJOURNAL OF FISH BIOLOGY, Issue 10 2009I. P. Helland Morphological differentiation and microhabitat segregation of two ecologically similar populations of pelagic planktivorous fishes, Coregonus albula and the smaller Coregonus fontanae, were studied in Lake Stechlin (northern Germany). Both populations performed diel vertical migrations, although C. fontanae was always situated in deeper pelagic water than C. albula both during day and night. Landmark-based geometric morphometrics revealed that sympatric C. albula and C. fontanae differ in external morphology, with main differences found in head length and eye position, as well as in length and width of the caudal peduncle. Moreover, while C. albula has a similar morphology over all sizes, the shape of C. fontanae changes with size. Accordingly, the morphology of the two is most different at smaller size. Although the morphological differences may reflect adaptations to the slightly differing microhabitats of the two populations, there is no conclusive evidence that this correspondence between ecology and morphology is the main mechanism behind the coexistence of the closely related coregonids in Lake Stechlin. [source] Multivariate and geometric morphometrics in the analysis of sexual dimorphism variation in Podarcis lizardsJOURNAL OF MORPHOLOGY, Issue 2 2007Antigoni Kaliontzopoulou Abstract Podarcis bocagei and P. carbonelli are two closely related lacertid species, very similar morphologically and ecologically. We investigated sexual dimorphism patterns presented by both species in allopatry and in sympatry. Sexual size and shape dimorphism patterns were analyzed using both multivariate and geometric morphometric techniques. Multivariate morphometrics revealed a marked sexual dimorphism in both species,males being larger with more robust habitus and females presenting a longer trunk. General patterns of sexual size dimorphism are not modified in sympatry, although there is evidence for some morphological change in male head size. The application of geometric morphometrics offered a more detailed image of head shape and revealed that males present a more developed tympanic area than do females, while females have a more rounded head. Differences in the degree of sexual shape dimorphism were detected in sympatry, but no consistent patterns were observed. From the results of the study, and based on previous knowledge on the populations studied, we conclude that the morphological differences observed are probably not caused by exploitative competition between the species, but rather appear attributable to the modification of the relative influence of sexual and natural selection on both sexes. J. Morphol., 2007. © 2007 Wiley-Liss, Inc. [source] Morphological evolution of the lizard skull: A geometric morphometrics surveyJOURNAL OF MORPHOLOGY, Issue 1 2005C. Tristan Stayton Abstract Patterns of diversity among lizard skulls were studied from a morphological, phylogenetic, and functional perspective. A sample of 1,030 lizard skulls from 441 species in 17 families was used to create a lizard skull morphospace. This morphospace was combined with a phylogeny of lizard families to summarize general trends in the evolution of the lizard skull. A basal morphological split between the Iguania and Scleroglossa was observed. Iguanians are characterized by a short, high skull, with large areas of attachment for the external adductor musculature, relative to their sister group. The families of the Iguania appear to possess more intrafamilial morphological diversity than families of the Scleroglossa, but rarefaction of the data reveals this to be an artifact caused by the greater number of species represented in Iguanian families. Iguanian families also appear more dissimilar to one another than families of the Scleroglossa. Permutation tests indicate that this pattern is real and not due to the smaller number of families in the Iguanidae. Parallel and convergent evolution is observed among lizards with similar diets: ant and termite specialists, carnivores, and herbivores. However, these patterns are superimposed over the more general phylogenetic pattern of lizard skull diversity. This study has three central conclusions. Different clades of lizards show different patterns of disparity and divergence in patterns of morphospace occupation. Phylogeny imposes a primary signal upon which a secondary ecological signal is imprinted. Evolutionary patterns in skull metrics, taken with functional landmarks, allow testing of trends and the development of new hypotheses concerning both shape and biomechanics. J. Morphol. 263:47,59, 2005. © 2004 Wiley-Liss, Inc. [source] Advances in insectivore and rodent systematics due to geometric morphometricsMAMMAL REVIEW, Issue 2 2009LENKA BAR ABSTRACT 1Morphometrics, the study of the variation and change in form amongst organisms, serves as a basic methodological tool in various fields of biological research, including systematics. Because it includes information about spatial relationships amongst anatomical landmarks, geometric morphometrics is more suitable for analyzing morphometric variation than methods based on distance measurements. 2Geometric morphometrics allows us to answer general ecological and evolutionary questions about shape. 3In this paper, landmark-based methods are described and illustrated, based on a dataset of measurements from 295 Apodemus mandibles, and the applications of such methods in the systematics of insectivores (Eulipotyphla) and rodents (Rodentia) are summarized. [source] The Ordovician Trilobite Carolinites, A Test Case for Microevolution in A Macrofossil LineagePALAEONTOLOGY, Issue 2 2002Tim McCormick We use geometric morphometrics to test a claim that the Ordovician trilobite Carolinites exhibits gradualistic evolution. We follow a previously proposed definition of gradualism, and define the criteria an ideal microevolutionary case study should satisfy. We consider the Lower,Middle Ordovician succession at Ibex, western Utah to meet these criteria. We discovered examples of: (1) morphometric characters which fluctuate with little or no net change; (2) characters which show abrupt ,step' change; (3) characters which show transitional change through intermediate states. Examples belonging to (2) and (3) exhibit reversals. The transitional characters were tested against a null hypothesis of symmetrical random walk. The tests indicated that they were not changing under sustained directional selection. Two alternative interpretations are possible. (1) The characters are responding to random causes (genetic drift or rapidly fluctuating selection pressures) or to causes that interact in so complex a way that they appear random. This observation may be applicable to most claimed cases of gradualistic evolution in the literature. (2) Sampling was at too poor a resolution to allow meaningful testing against the random walk. If so, then this situation is likely to apply in most evolutionary case studies involving Palaeozoic macrofossils. [source] A comparison of the ontogeny of shape variation in the anthropoid scapula: Functional and phylogenetic signalAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2008Nathan M. Young Abstract This article compares ontogenetic shape variation in the scapula of 17 anthropoid species using three-dimensional landmark-based geometric morphometrics. These data are used to investigate functional and phylogenetic signal in the major components of scapular variation and to evaluate the degree to which postnatal growth contributes to interspecific differences in shape. Results indicate that the shape of the infant and adult scapula is primarily associated with positional behavior (e.g., orthograde suspensory nonquadrupeds versus pronograde quadrupeds), but within this functional structure there is phylogenetic signal, particularly at infant stages. Growth most closely correlates with infant/adult shape and locomotor function. These results suggest that the shape of the infant scapula drives the pattern of postnatal scapular growth and adult morphology. As such, variation in postnatal growth is not the primary source of interspecific variation in adult shape. Instead, interspecific differences in scapular morphology are hypothesized to be the result of selection for variation in embryonic developmental processes that affect shape. Am J Phys Anthropol, 2008. © 2008 Wiley-Liss, Inc. [source] The promise of geometric morphometricsAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue S35 2002Joan T. Richtsmeier Abstract Nontraditional or geometric morphometric methods have found wide application in the biological sciences, especially in anthropology, a field with a strong history of measurement of biological form. Controversy has arisen over which method is the "best" for quantifying the morphological difference between forms and for making proper statistical statements about the detected differences. This paper explains that many of these arguments are superfluous to the real issues that need to be understood by those wishing to apply morphometric methods to biological data. Validity, the ability of a method to find the correct answer, is rarely discussed and often ignored. We explain why demonstration of validity is a necessary step in the evaluation of methods used in morphometrics. Focusing specifically on landmark data, we discuss the concepts of size and shape, and reiterate that since no unique definition of size exists, shape can only be recognized with reference to a chosen surrogate for size. We explain why only a limited class of information related to the morphology of an object can be known when landmark data are used. This observation has genuine consequences, as certain morphometric methods are based on models that require specific assumptions, some of which exceed what can be known from landmark data. We show that orientation of an object with reference to other objects in a sample can never be known, because this information is not included in landmark data. Consequently, a descriptor of form difference that contains information on orientation is flawed because that information does not arise from evidence within the data, but instead is a product of a chosen orientation scheme. To illustrate these points, we apply superimposition, deformation, and linear distance-based morphometric methods to the analysis of a simulated data set for which the true differences are known. This analysis demonstrates the relative efficacy of various methods to reveal the true difference between forms. Our discussion is intended to be fair, but it will be obvious to the reader that we favor a particular approach. Our bias comes from the realization that morphometric methods should operate with a definition of form and form difference consistent with the limited class of information that can be known from landmark data. Answers based on information that can be known from the data are of more use to biological inquiry than those based on unjustifiable assumptions. Yrbk Phys Anthropol 45:63,91, 2002. © 2002 Wiley-Liss, Inc. [source] The Relationship Between Cephalic Scales and Bones in Lizards: A Preliminary Microtomographic Survey on Three Lacertid SpeciesTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 2 2010David Costantini Abstract In the last two decades, there has been a great deal of interest in the morphology and anatomy of the lizard skull in an ecological and evolutionary perspective. However, the relationship between variations in many key anatomical features remains largely unknown. Using microtomography and geometric morphometrics, we examined the relationship between bones and scales associated with the parietal foramen in the three lizards species most common in the Italian peninsula: Podarcis muralis, P. sicula, and Lacerta bilineata. The imprints of the scales are clearly recognizable on the outer bone surface, and this may suggest a structural interaction between these elements. The temporal osteoderms are visible in the larger males and in the larger females of L. bilineata, but they are absent in the smaller specimens of L. bilineata and in all Podarcis specimens. Two parallel rows of pterygoid teeth are present in all the specimens of L. bilineata and are absent in the smaller male of L. bilineata and in both Podarcis species. Cheek osteoderms occurred only in the largest specimens of our sample (i.e., large L. bilineata), being possibly related to hyperostotic processes and densitometric thresholds more than to phylogeny. Minor differences may be also associated with the form of the parietal foramen. In absolute terms the parietal foramen tends to be largest in L. bilineata but in relation to skull length the foramen tends to be larger in P. muralis. In this latter species the foramen is also more elongated. In all three species the fronto-parietal suture occupies a similar location relatively to the scale spatial organization. A shared allometric pattern shows that the main vault enlargement can be localised at the areas anterior to the fronto-parietal suture, providing further information on the possible morphogenetic dynamics associated with the interaction between scales and bones around this structure. Anat Rec, 2010. © 2009 Wiley-Liss, Inc. [source] Cranial allometry, phylogeography, and systematics of large-bodied papionins (primates: Cercopithecinae) inferred from geometric morphometric analysis of landmark dataTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 2 2003Stephen R. Frost Abstract The cranial morphology of the African Old World monkeys Mandrillus, Papio, and Theropithecus (i.e., baboons) has been the subject of a number of studies investigating their systematic relationships, patterns of scaling, and growth. In this study, we use landmark-based geometric morphometrics and multivariate analysis to assess the effects of size, sex, taxonomy, and geographic location on cranial shape. Forty-five landmarks were digitized in three dimensions on 452 baboon crania and subjected to generalized Procrustes analysis (GPA), which standardizes geometric size but leaves scaling-based shape differences in the data. The resulting shape coordinates were submitted to regression analysis, principal components analysis (PCA), partial least-squares (PLS) analysis, and various clustering techniques. Scaling (shape differences correlated with size) was the largest single factor explaining cranial shape variation. For instance, most (but not all) of the shape differences between the sexes were explained by size dimorphism. However, central tendencies of shape clearly varied by taxon (both specific and subspecific) even after variations in size and sex were adjusted out. Within Papio, about 60% of the size- and sex-adjusted shape variations were explained by the geographic coordinates of the specimen's provenance, revealing a stepped cline in cranial morphology, with the greatest separation between northern and southern populations. Based on evidence from genetic studies, and the presence of at least two major hybrid/interbreeding zones, we interpret the phylogeographic pattern of cranial variation as indicating that these populations are best ranked as subspecies of a single species, rather than as two or more distinct biological species. This objective approach can be applied to other vertebrate species or species groups to help determine the taxonomic rank of problematic taxa. Anat Rec Part A 275A:1048,1072, 2003. © 2003 Wiley-Liss, Inc. [source] Satyrinae butterflies from Sardinia and Corsica show a kaleidoscopic intraspecific biogeography (Lepidoptera, Nymphlidae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010LEONARDO DAPPORTO The Mediterranean islands of Sardinia and Corsica are known for their multitude of endemics. Butterflies in particular have received much attention. However, no comprehensive studies aiming to compare populations of butterflies from Sardinia and Corsica with those from the neighbouring mainland and Sicily have been carried out. In the present study, the eleven Satyrinae species inhabiting Sardinia and Corsica islands were examined and compared with continental and Sicilian populations by means of geometric morphometrics of male genitalia. Relative warp computation, discriminant analyses, hierarchical clustering, and cross-validation tests were used to identify coherent distributional patterns including both islands and mainland populations. The eleven species showed multifaceted distributional patterns, although three main conclusions can be drawn: (1) populations from North Africa and Spain are generally different from those belonging to the Italian Peninsula; (2) populations from Sardinia and Sicily often resemble the North Africa/Spain ones; Corsica shows transitional populations similar to those from France; and (3) sea barriers represent filters to dispersal, although their efficacy appears to be unrelated to their extension. Indeed, the short sea straits between Sardinia and Corsica and between Sicily and the Italian Peninsula revealed a strong effectiveness with respect to preventing faunal exchanges; populations giving onto sea channels between Corsica and Northern Italy and between Sicily and Tunisia showed a higher similarity. A comparison of island and mainland distributions of the eleven taxa have helped to unravel the complex co-occurrence of historical factors, refugial dynamics, and recent (post-glacial) dispersal with respect to shaping the populations of Mediterranean island butterflies. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 195,212. [source] Morphological variation in house mice from the Robertsonian polymorphism area of BarcelonaBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2009MARIA ASSUMPCIÓ SANS-FUENTES Morphometric variation in the Robertsonian polymorphism zone of Barcelona of Mus musculus domesticus was studied by geometric morphometrics. This system is characterized by populations of reduced diploid number (2n = 27,39) surrounded by standard populations (2n = 40). We investigated the morphological variation in mice from this area, as well as the effect of geographical distance and karyotype on this variation. We also investigated the degree of co-variation between the two functional units of the mandible to explore the origin of this system (primary intergradation or secondary contact). The size and shape of the cranium, mandible and scapula were analysed for 226 specimens grouped by population, chromosome number and structural heterozygosity. Size was estimated as the centroid size, and shape was estimated after Procrustes superimposition. No significant differences in size between populations or chromosomal groups were detected. Diploid number, structural heterozygosity and local geographical isolation contributed to the differentiation in shape. Morphological differentiation between standard mice and Robertsonian specimens was observed, suggesting genetic isolation between these groups. Co-variation between the ascending ramus and alveolar region of the mandible was quantified by the trace correlation between landmark subsets of these modules. The trace values showed an ascending trend, correlated with the distance from the centre of the polymorphism area, a pattern consistent with a primary intergradation scenario. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 555,570. [source] Insect wing shape evolution: independent effects of migratory and mate guarding flight on dragonfly wingsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009FRANK JOHANSSON Although, in some insect taxa, wing shape is remarkably invariant, the wings of Anisopteran dragonflies show considerable variation among genera. Because wing shape largely determines the high energetic costs of flight, it may be expected that interspecific differences are partly due to selection. In the present study, we examined the roles of long-distance migration and high-manoeuvrability mate guarding in shaping dragonfly wings, using a phylogeny-based comparative method, and geometric morphometrics to quantify wing shape. The results obtained show that migration affects the shape of both front and hind wings, and suggest that mate guarding behaviour may also have an effect, especially on the front wing. These effects on front wing shape are at least partly independent. Our findings are interesting when compared with the geographically widespread and ecologically diverse dipterans Acalyptratae (including the genus Drosophila). The wings in that group are similar in function and structure, but show strikingly low levels of interspecific variation. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 362,372. [source] Genetic and morphological divergence reveals local subdivision of perch (Perca fluviatilis L.)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009SARA BERGEK The level of gene flow is an important factor influencing genetic differentiation between populations. Typically, geographic distance is considered to be the major factor limiting dispersal and should thus only influence the degree of genetic divergence at larger spatial scales. However, recent studies have revealed the possibility for small-scale genetic differentiation, suggesting that the spatial scale considered is pivotal for finding patterns of isolation by distance. To address this question, genetic and morphological differentiation were studied at two spatial scales (range 2,13 km and range 300 m to 2 km) in the perch (Perca fluviatilis L.) from the east coast archipelago of Sweden, using seven microsatellite loci and geometric morphometrics. We found highly significant genetic differentiation between sampled locations at both scales. At the larger spatial scale, the distance per se was not affecting the level of divergence. At the small scale, however, we found subtle patterns of isolation by distance. In addition, we also found morphological divergence between locations, congruent with a spatial separation at a microgeographic scale, most likely due to phenotypic plasticity. The present study highlights the importance of geographical scale and indicates that there might be a disparity between the dispersal capacity of a species and the actual movement of genes. Thus, how we view the environment and possible barriers to dispersal might have great implications for our ability to fully understand the evolution of genetic differentiation, local adaptation, and, in the end, speciation. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 746,758. [source] Intraspecific taxonomy and ecology characterize morphological divergence among cutthroat trout (Oncorhynchus clarkii ssp.BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2009Richardson) populations We compared the proportion of morphological variation accounted for by subspecies categories with the proportion encompassed by ecologically based categories in cutthroat trout (Oncorhynchus clarkii ssp.), as a means of assessing the relative importance of each approach in identifying intraspecific diversity. We used linear and geometric morphometrics to compare measures of body shape, fin length, and head features between and within subspecies of cutthroat trout. Both categories accounted for a significant proportion of the variation between and within the subspecies; however, the larger proportion was explained by subspecific differences, with the greatest morphological divergence between coastal cutthroat trout (Oncorhynchus clarkii clarkii) and interior subspecies. Ecotypic categories within each subspecies also explained significant morphological differences: stream populations had longer fins and deeper, more robust bodies than lake populations. The largest ecotypic differences occurred between stream and lake populations of Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri). Given that many cutthroat trout subspecies are of conservation concern, our study offers a better understanding of intraspecific variation existing within the species, providing precautionary evidence of incipient speciation, and a framework of describing phenotypic diversity that is correlated with ecological conditions. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 266,281. [source] Combining geometric morphometrics and pattern recognition to identify interspecific patterns of skull variation: case study in sympatric Argentinian species of the genus Calomys (Rodentia: Cricetidae: Sigmodontinae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2008PEDRO CORDEIRO-ESTRELA Sympatric species of vesper mice Calomys laucha and Calomys musculinus are difficult to discriminate, especially in natural history collections where they are identified by external body measurements and cranial characteristics. Accurate identification of these two species can be important because only one of them, C. musculinus, is a Junin virus reservoir, the aetiological agent of the Argentine Hemorragic Fever. Research has focused into the development of molecular techniques to unambiguously identify these species. We apply statistical procedures from the field of pattern recognition to three-dimensional geometric morphometric data based on skull landmarks to identify sympatric species C. laucha, C. musculinus and Calomys venustus. Pattern recognition techniques correctly identified the three species without any prior information on specimen identity. By contrast to expectations, C. venustus differed from the other two species mainly on the basis of shape and not by its centroid size. The main sources of difference between C. laucha and C. musculinus were of shape, specifically localized at the landmarks defined by: (1) the sutures between the premaxillaries, the nasals and the frontals; (2) the sutures between the parietals, the frontals and the squamosals; and (3) the suture between the parietals and the interparietal. Nevertheless, allometries dominate the patterns of interspecific variation between these latter species and may partly explain past identification difficulties. Morphological evolution is discussed. The need for objective methods to define phenotypic clusters is highlighted with respect to the need for fast and precise biodiversity assessments. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 94, 365,378. [source] Patterns of cryptic hybridization revealed using an integrative approach: a case study on genets (Carnivora, Viverridae, Genetta spp.) from the southern African subregionBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2005PHILIPPE GAUBERT Recent years have seen the development of molecular-based methodologies to investigate hybridization and its impact on the evolutionary process. However, morphological characterization of hybrid zones has only scantily been considered, especially in zootaxa. Thus, the level of congruence between molecular and morphological characters when attempting to detect hybrids remains a poorly tackled area. The genets (genus Genetta) provide an ideal case study for further investigation of the respective contribution of morphology and DNA in hybrid zone characterization because (1) their morphology has recently been exhaustively explored and (2) the existence of hybrid zones in southern Africa was proposed in the literature. We assessed levels of hybridization among the southern African genets, and questioned the role of ecological factors on the hybridization patterns detected. We used an integrative approach involving nine discrete morphological characters and a diagnostic discriminant function, geometric morphometrics and sequences of cytochrome b including collection specimens. The combination of independent materials allowed us to accurately reassess the level of hybridization in southern African genets, and revealed cryptic, interspecific gene flows. Morphology unambiguously detected a low number of G. maculata × G. tigrina hybrids and rejected the hypothesis of a large intergradation zone in KwaZulu-Natal, thus supporting the species status of the two genets. Cytochrome b analyses revealed: (1) cryptic, massive hybridization between G. tigrina and the sympatric G. felina, and (2) a trace of reticulation (one sequence) between G. tigrina and the allopatric G. genetta. The type specimen of G. mossambica Matschie, 1902 is considered to be a morphological hybrid between G. maculata and G. angolensis. Remarkably, the morphological approaches (discrete characters and morphometrics) proved complementary to conclusions derived from cytochrome b sequences. Whilst morphometrics was generally unable to accurately identify all putative hybrids, this approach revealed diagnostic cranial shape differences between recognized species as well as the cryptic G. ,letabae' (included in the super-species G. maculata). Morphometrics also confirmed the diagnostic value and age dependency of discrete characters. Our integrative approach appeared necessary to the detection of cryptic hybridizations and to the comprehensive characterization of hybrid zones. The recurrent detection of hybrids exhibiting tigrina -like coat patterns may suggest (1) asymmetric hybridization of G. tigrina males to females of other species and (2) positive selection for tigrina -like phenotype in South African habitats, but these hypotheses will have to be further tested using other sources of evidence. Despite the precise mosaic of hybrid zones identified in southern African genets, the environmental factors that shape patterns of distribution of hybrids remain unclear. Nevertheless, in the light of our range reassessment, it appears that seasonality of precipitation and periods of annual frost may play stringent roles in the distribution of genets. The complementarity of our results based on morphology and molecules is regarded as encouraging for the further development of integrative approaches in order to better understand the complex phenomena that underlie hybridization processes. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 86, 11,33. [source] | |||||||||||||||||||||||||