Home About us Contact
|
Home About us Contact | ||
|
|
||
Shape Differences (shape + difference)
Selected AbstractsDetecting corpus callosum abnormalities in autism subtype using planar conformal mappingINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 2 2010Ye Duan Abstract A number of studies have documented that autism has a neurobiological basis, but the anatomical extent of these neurobiological abnormalities is largely unknown. In this paper, we apply advanced computational techniques to extract 3D models of the corpus callosum (CC) and subsequently analyze local shape variations in a homogeneous group of autistic children. Besides the traditional volumetric analysis, we explore additional phenotypic traits based on the oriented bounding rectangle of the CC. In shape analysis, a new conformal parameterization is applied in our shape analysis work, which maps the surface onto a planar domain. Surface matching among different individual meshes is achieved by aligning the planar domains of individual meshes. Shape differences of the CC between autistic patients and the controls are computed using Hotelling T2 two-sample metric followed by a permutation test. The raw and corrected p -values are shown in the results. Additional visualization of the group difference is provided via mean difference map. Copyright © 2009 John Wiley & Sons, Ltd. [source] A geometric morphometric approach to the quantification of population variation in sub-Saharan African craniaAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 1 2010Daniel Franklin We report here on new data examining cranial variation in 18 modern human sub-Saharan African populations. Previously, we investigated variation within southern Africa; we now extend our analyses to include a series of Central, East, and West African crania, to further knowledge of the relationships between, and variation and regional morphological patterning in, those populations. The sample comprises 377 male individuals; the three-dimensional coordinates of 96 landmarks are analyzed using Procrustes-based methods. Interpopulation variation is examined by calculating shape distances between groups, which are compared using resampling statistics and parametric tests. Phenotypic variance, as a proxy for genetic variance, is measured and compared across populations. Principal components and cluster analyses are employed to explore relationships between the populations. Shape differences are visualized using three-dimensional rendered models. Observed disparity patterns imply a mix of differences and similarities across populations, with no apparent support for genetic bottlenecks, which is likely a consequence of migrations that may have influenced differences in cranial form; supporting data are found in recent molecular studies. The Pygmy sample had the most distinctive cranial morphology; characteristically small in size with marked prognathism. These features characterized, although less strongly, the neighboring Bateke, and are possibly related to similar selective pressures in conjunction with interbreeding. Small cranial size is also involved in the considerable distinctiveness of the San and Khoikhoi. The statistical procedures applied in this study afford a powerful and robust means of quantifying and visualizing the magnitude and pattern of cranial variation between sub-Saharan African populations. Am. J. Hum. Biol., 2010. © 2009 Wiley-Liss, Inc. [source] Influence of genotype and geography on shell shape and morphometric trait variation among North Atlantic blue mussel (Mytilus spp.) populationsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009JONATHAN P. A. GARDNER The influence of geography and genotype on shell shape (outline) and trait (morphometric) variation among North Atlantic blue mussels and their hybrids has been examined. Shape differences among reference taxa (Mytilus trossulus, Mytilus edulis and Mytilus galloprovincialis) were consistent with an association between taxon-specific genes and shape genes. Newfoundland M. edulis × M. trossulus populations and northern Quebec M. trossulus populations exhibited an uncoupling of taxon-specific genes from shape genes, whereas Nova Scotia M. trossulus populations and SW England M. edulis × M. galloprovincialis populations exhibited an association between taxon-specific genes and shape genes. We found no evidence of a geographic effect (NE versus NW Atlantic) for shape variation, indicating that the genotype effect is stronger than any geographic effect at macrogeographic scales. Pronounced differences were observed in trait variability consistent with an association between taxon-specific genes and trait genes in European populations, and trait divergence of New York M. edulis from all European mussels. Trait variability in mussels from Newfoundland, Nova Scotia and northern Quebec indicated an uncoupling of taxon genes from trait genes, whereas trait variability in SW England M. edulis × M. galloprovincialis populations was consistent with background genotype, indicating a strong association between taxon genes and trait genes. A pronounced macrogeographic split (NE versus NW Atlantic) regardless of taxonomy was observed, indicating that geography exerts a greater influence than genotype on trait variation at the macrogeographic scale. This is consistent with pronounced within-taxon genetic divergence, indicative of different selection regimes or more likely of different evolutionary histories of mussels on either side of the North Atlantic. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 875,897. [source] Shape difference visualization for ancient bronze mirrors through 3D range imagesCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 4 2003Tomohito Masuda Abstract Japanese archaeologists have paid special attention to ancient Chinese bronze mirrors because the mirrors may provide a key for the exact location of Yamatai State, which is one of the major archaeological controversies. Currently, archaeologists visually analyse ancient Chinese bronze mirrors for their shape difference. The practice requires a huge amount of time and effort. In this paper, we propose an automatic method for detecting the shape difference between a pair of ancient mirrors. The 3D data of the mirrors are obtained using a laser range scanner. Our algorithm then aligns them into the same coordinate and visualizes their shape differences. Our proposed algorithm provides fast and non-damaging analysis for shape difference. Further analysis can be evaluated on our data instead of the actual mirror, so it can be performed by more than one group of archaeologists. Copyright © 2003 John Wiley & Sons, Ltd. [source] Food abundance affects both morphology and behaviour of juvenile perchECOLOGY OF FRESHWATER FISH, Issue 2 2008J. Borcherding Abstract,,, Behaviour and morphology were both shown to differ between 1+ perch from two lakes that in earlier studies showed differences in size-specific predation risk. As the level of nourishment is known to affect behaviour and morphology, we fed perch of the two lakes in tanks for 40 days with two food levels, to study whether observed differences remain stable with changes in food availability. The perch fed in excess grew significantly, while the perch at the low food conditions lost weight, clearly indicating undernourishment. In aquarium experiments, the starved perch from both lakes were much bolder in the trade-off between foraging and predator avoidance than their well-fed conspecifics. In addition, the shape of perch differed significantly between feeding treatments. At low food levels perch got a more slender body, while at high food levels they developed a deeper body and a relatively smaller head. Independent of feeding level, the comparison between the two lakes revealed a clearly deeper body and a larger head area for one population, a shape difference that remained stable after the feeding period. The results give evidence that the level of nourishment is an important factor that quickly alters risk-taking behaviour. In body morphology, however, more stable shape characteristics must be distinguished from more flexible ones. Consequently, the level of nourishment is a potential factor that may quickly hide other proximate cues and must be considered attentively in studies, in which shape changes and behaviour are related to environmental factors like diet, predation pressure or habitat diversity. [source] Use of evaporative light scattering detector in the detection and quantification of enantiomeric mixtures by HPLCJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10 2006Tong Zhang Abstract Routinely used in our laboratories at analytical scale, an evaporative light scattering detector (ELSD) has proved to be versatile in the detection of enantiomeric resolution using chiral stationary phases by HPLC. Though this kind of detector has been widely used in various domains, its application in enantiomeric resolution has not been discussed in the literature and is found to have very specific features especially in the quantitative perspective. In contrast with the UV detection, the peak area from ELSD for both enantiomers of a racemic mixture may not be the same. This complicates the assessment of the enantiomeric purity of unknown samples. This current work deals with some practical aspects in the detection of enantiomers and in accurate quantitative determination of enantiomeric purity by ELSD. Effects of analyte nature (more precisely molecular weight and volatility), peak shape and peak shape difference between enantiomers on the quantitative integration by ELSD are discussed in connection with the UV-detection results. The calibration for quantitative enantiomeric analysis and its effectiveness are demonstrated. [source] Shape difference visualization for ancient bronze mirrors through 3D range imagesCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 4 2003Tomohito Masuda Abstract Japanese archaeologists have paid special attention to ancient Chinese bronze mirrors because the mirrors may provide a key for the exact location of Yamatai State, which is one of the major archaeological controversies. Currently, archaeologists visually analyse ancient Chinese bronze mirrors for their shape difference. The practice requires a huge amount of time and effort. In this paper, we propose an automatic method for detecting the shape difference between a pair of ancient mirrors. The 3D data of the mirrors are obtained using a laser range scanner. Our algorithm then aligns them into the same coordinate and visualizes their shape differences. Our proposed algorithm provides fast and non-damaging analysis for shape difference. Further analysis can be evaluated on our data instead of the actual mirror, so it can be performed by more than one group of archaeologists. Copyright © 2003 John Wiley & Sons, Ltd. [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] Geographical and taxonomic influences on cranial variation in red colobus monkeys (Primates, Colobinae): introducing a new approach to ,morph' monkeysGLOBAL ECOLOGY, Issue 2 2009Andrea Cardini ABSTRACT Aim, To provide accurate but parsimonious quantitative descriptions of clines in cranial form of red colobus, to partition morphological variance into geographical, taxonomic and structured taxonomic components, and to visually summarize clines in multivariate shape data using a method which produces results directly comparable to both univariate studies of geographical variation and standard geometric morphometric visualization of shape differences along vectors. Location, Equatorial Africa. Methods, Sixty-four three-dimensional cranial landmarks were measured on 276 adult red colobus monkeys sampled over their entire distribution. Geometric morphometric methods were applied, and size and shape variables regressed onto geographical coordinates using linear and curvilinear models. Model selection was done using the second-order Akaike information criterion. Components of variation related to geography, taxon or their combined effect were partitioned using partial regresssion. Multivariate trends in clinal shape were summarized using principal components of predictions from regressions, plotting vector scores on maps as for univariate size, and visualizing differences along main axes of clinal shape variation using surface rendering. Results, Significant clinal variation was found in size and shape. Clines were similar in females and males. Trend surface analysis tended to be more accurate and parsimonious than alternative models in predicting morphology based on geography. Cranial form was relatively paedomorphic in East Africa and peramorphic in central Africa. Most taxonomic variation was geographically structured. However, taxonomic differences alone accounted for a larger proportion of total explained variance in shape (up to 40%) than in size (, 20%). Main conclusions, A strong cline explained most of the observed size variation and a significant part of the shape differences of red colobus crania. The pattern of geographical variation was largely similar to that previously reported in vervets, despite different habitat preferences (arboreal versus terrestrial) and a long period since divergence (c. 14,15 Myr). This suggests that some aspects of morphological divergence in both groups may have been influenced by similar environmental, geographical and historical factors. Cranial size is likely to be evolutionarily more labile and thus better reflects the influence of recent environmental changes. Cranial shape could be more resilient to change and thus better reflects phylogenetically informative differences. [source] Mechanisms of Visual Object Recognition in Infancy: Five-Month-Olds Generalize Beyond the Interpolation of Familiar ViewsINFANCY, Issue 1 2007Clay Mash This work examined predictions of the interpolation of familiar views (IFV) account of object recognition performance in 5-month-olds. Infants were familiarized to an object either from a single viewpoint or from multiple viewpoints varying in rotation around a single axis. Object recognition was then tested in both conditions with the same object rotated around a novel axis. Infants in the multiple-views condition recognized the object, whereas infants in the single-view condition provided no evidence for recognition. Under the same 2 familiarization conditions, infants in a 2nd experiment treated as novel an object that differed in only 1 component from the familiar object. Infants' object recognition is enhanced by experience with multiple views, even when that experience is around an orthogonal axis of rotation, and infants are sensitive to even subtle shape differences between components of similar objects. In general, infants' performance does not accord with the predictions of the IFV model of object recognition. These findings motivate the extension of future research and theory beyond the limits of strictly interpolative mechanisms. [source] The importance of understanding the shape of diverse ethnic female consumers for developing jeans sizing systemsINTERNATIONAL JOURNAL OF CONSUMER STUDIES, Issue 2 2007Su-Jeong Hwang Shin Abstract This study has been conducted to investigate the fit issues related to the current apparel pants and jeans sizing system for diverse consumers, identifying body shape differences among ethnic groups. A total of 1335 women in a certain size range (Misses figure type sizes 2,20) were selected in the study. A Misses figure type size category is commonly used for adult women of average proportion and height. First, the body dimension differences among ethnic groups were examined with a single factor analysis of variance. Second, the fit of pants and jeans for the diverse consumers within the same size category was examined with the current standard sizing system, ASTM D5585 for adult female Misses figure type sizes 2,20. Three cases were programmed within a database: When each consumer selects a size for a pair of jeans based on (1) waist size; (2) hip size; and (3) waist height (usually pants length). And last, the results were analysed with fit comparison plots. Current jean consumers are racially diversified in the US and globally as well. This study revealed that ethnic groups had different fit problems and significant body shape differences. Even within the same figure type size category, a variety of body dimensions existed in each ethnic group. According to the fit problem assessment in this study, consumers within the same body figure type size category could not find the right fit of the pants and jeans within the current sizing system. Half of the female consumers could not find a garment to fit based on waist height (pants length) because the current sizing systems overlooked the effect of diverse consumers. This study will be useful for standardizing organizations to modify current sizing systems for diverse ethnic consumer groups as a demographic factor so that apparel companies could provide better quality of fit for their consumers in the global and local market. [source] Morphological changes in the shape of the non-pathological bony knee joint with age: a morphometric analysis of the distal femur and proximal tibia in three populations of known age at deathINTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 4 2008S. D. Stevens Abstract This study examines possible morphological variation in the knee joint of Homo sapiens with increasing age in ostensively healthy and non-pathological distal femora and proximal tibiae. Throughout the lifetime of each individual, the hard tissue of the knee undergoes considerable remodelling as a response to biomechanical stresses, changes in bone microarchitecture and reduction of bone mineral content as a concomitant of ageing. The knee is also subject to greater levels of degenerative joint disease than any other joint. If death occurs whilst such diseases are in the earliest stages, initial bone changes may not be visually obvious in museum specimens. If such specimens are used for comparative analyses, it is hypothesised that changes might render it problematic if all ages are conglomerated into discrete samples. This study therefore investigates the degree to which the distal femur and proximal tibia change shape during ageing and, if changes are present, whether they are expressed similarly in males and females. It also examines whether changes are of greater magnitude than those morphological differences which might exist between populations. In an example population of African-Americans, results indicate that there is a statistically significant difference in shape between age groups and those differences become progressively greater between the youngest and oldest adults. Results also show that although morphological variation caused by ageing is apparent, those shape differences attributable to sexual dimorphism are more powerful. When two additional populations are analysed jointly with the African-Americans (Caucasian Americans and the European Spitalfields sample), results indicate that inter-population shape differences are considerably greater than differences caused by increasing age. Results imply that it is justifiable to combine specimens of all ages into discrete samples for comparative purposes. Copyright © 2007 John Wiley & Sons, Ltd. [source] Evolutionary acceleration in the most endangered mammal of Canada: speciation and divergence in the Vancouver Island marmot (Rodentia, Sciuridae)JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2007A. CARDINI Abstract The Vancouver Island marmot is the most endangered mammal of Canada. Factors which have brought this population to the verge of extinction have not yet been fully elucidated, but the effects of deforestation and habitat fragmentation on survival rates, as well as those of variation in rainfall, temperature, snowpack depth and snowmelt strongly suggest that marmots on the island are struggling to keep pace with environmental changes. Genetic analyses, however, seem to indicate that the Vancouver Island marmot may merely represent a melanistic population of its parental species on the mainland. Were it not for its black pelage colour, it is unlikely that it would have attracted much attention as a conservation priority. Our study uses three-dimensional coordinates of cranial landmarks to further assess phenotypic differentiation of the Vancouver Island marmot. A pattern of strong interspecific divergence and low intraspecific variation was found which is consistent with aspects of drift-driven models of speciation. However, the magnitude of shape differences relative to the putatively neutral substitutions in synonymous sites of cytochrome b is too large for being compatible with a simple neutral model. A combination of bottlenecks and selective pressures due to natural and human-induced changes in the environment may offer a parsimonious explanation for the large phenotypic differentiation observed in the species. Our study exemplifies the usefulness of a multidisciplinary approach to the study of biological diversity for a better understanding of evolutionary models and to discover aspects of diversity that may be undetected by using only a few genetic markers to characterize population divergence and uniqueness. [source] Sexual Dimorphism in America: Geometric Morphometric Analysis of the Craniofacial Region,JOURNAL OF FORENSIC SCIENCES, Issue 1 2008Erin H. Kimmerle Ph.D. Abstract:, One of the four pillars of the anthropological protocol is the estimation of sex. The protocol generally consists of linear metric analysis or visually assessing individual skeletal traits on the skull and pelvis based on an ordinal scale of 1,5, ranging from very masculine to very feminine. The morphologic traits are then some how averaged by the investigator to estimate sex. Some skulls may be misclassified because of apparent morphologic features that appear more or less robust due to size differences among individuals. The question of misclassification may be further exemplified in light of comparisons across populations that may differ not only in cranial robusticity but also in stature and general physique. The purpose of this study is to further examine the effect of size and sex on craniofacial shape among American populations to better understand the allometric foundation of skeletal traits currently used for sex estimation. Three-dimensional coordinates of 16 standard craniofacial landmarks were collected using a Microscribe-3DX digitizer. Data were collected for 118 American White and Black males and females from the W.M. Bass Donated Collection and the Forensic Data Bank. The MANCOVA procedure tested shape differences as a function of sex and size. Sex had a significant influence on shape for both American Whites (F = 2.90; d.f. = 19, 39; p > F = 0.0024) and Blacks (F = 2.81; d.f. = 19, 37; p > F = 0.0035), whereas size did not have a significant influence on shape in either Whites (F = 1.69; d.f. = 19, 39; p > F = 0.08) or Blacks (F = 1.09; d.f. = 19, 37; p > F = 0.40). Therefore, for each sex, individuals of various sizes were statistically the same shape. In other words, while significant differences were present between the size of males and females (males on average were larger), there was no size effect beyond that accounted for by sex differences in size. Moreover, the consistency between American groups is interesting as it suggests that population differences in sexual dimorphism may result more from human variation in size than allometric variation in craniofacial morphology. [source] Pelvic growth: Ontogeny of size and shape sexual dimorphism in rat pelvesJOURNAL OF MORPHOLOGY, Issue 1 2007S. Berdnikovs Abstract The mammalian pelvis is sexually dimorphic with respect to both size and shape. Yet little is known about the differences in postnatal growth and bone remodeling that generate adult sexual dimorphism in pelvic bones. We used Sprague-Dawley laboratory rats (Rattus norvegicus), a species that exhibits gross pelvic size and shape dimorphism, as a model to quantify pelvic morphology throughout ontogeny. We employed landmark-based geometric morphometrics methodology on digitized landmarks from radiographs to test for sexual dimorphism in size and shape, and to examine differences in the rates, magnitudes, and directional patterns of shape change during growth. On the basis of statistical significance testing, the sexes became different with respect to pelvic shape by 36 days of age, earlier than the onset of size dimorphism (45 days), although visible shape differences were observed as early as at 22 days. Males achieved larger pelvic sizes by growing faster throughout ontogeny. However, the rates of shape change in the pelvis were greater in females for nearly all time intervals scrutinized. We found that trajectories of shape change were parallel in the two sexes until age of 45 days, suggesting that both sexes underwent similar bone remodeling until puberty. After 45 days, but before reproductive maturity, shape change trajectories diverged because of specific changes in the female pelvic shape, possibly due to the influence of estrogens. Pattern of male pelvic bone remodeling remained the same throughout ontogeny, suggesting that androgen effects on male pelvic morphology were constant and did not contribute to specific shape changes at puberty. These results could be used to direct additional research on the mechanisms that generate skeletal dimorphisms at different levels of biological organization. J. Morphol., 2006. © 2006 Wiley-Liss, Inc. [source] A morphometric approach to the geographic variation of the terrestrial isopod species Armadillo tuberculatus (Isopoda: Oniscidea)JOURNAL OF ZOOLOGICAL SYSTEMATICS AND EVOLUTIONARY RESEARCH, Issue 3 2009M. Kamilari Abstract The terrestrial isopod species Armadillo tuberculatus Vogl, 1876 (Crustacea, Isopoda, Oniscidea) is a widely polymorphic species distributed in the south-central Aegean region (Greece) with a different morph on each island. Variation consists in coloration, size of cuticular tubercules, shape of telson and the shape of the male first pleopod exopodite (secondary sexual character of taxonomic importance). We studied the allometric growth of a cuticular tubercule in 17 populations (for both male and female individuals) and the shape variation of the first male pleopod exopodite in 10 populations using Elliptic Fourier Analysis, in order to test for patterns of intraspecific variation and possible relationships between morphs. In addition, Thin Plate Spline analysis was used for the calculation of the minimum bending energy between different exopodite shapes, which was then used for estimating the minimum spanning network (MSN) connecting them. The different allometric growth rates of the tubercule among island groups were significantly related to island latitude and climatic factors. On the other hand, the clustering of islands and the MSN based on male exopodite shape differences were not related to the palaeogeography of the Aegean region or to the present geographic distances of islands. These results are interpreted as evidence for non-adaptive radiation of the morphs. Resumen El isópodo terrestre Armadillo tuberculatus Vogl, 1876 (Crustacea, Isopoda, Oniscidea) es una especie extensamente polimórfica distribuida por la región sur-central del piélago Egéo (Grecia), con una forma distinta en cada isla. Se trata de variaciones en la coloración, el tamaño de los tubérculos cuticulares y en la forma del primer exopodio masculino del pleopodo (carácter sexual secundario de importancia taxonómica). Estudiamos el crecimiento alométrico del tubérculo cuticular en 17 poblaciones (en individuos de ambos sexos) y la variación de la forma del primer exopodio masculino del pleopodo en 10 poblaciones según el análisis de Fourier elíptico (Elliptic Fourier Analysis) para detectar patrones de variación intraespecifica y relaciones posibles entre las formas de la especie. Además, el análisis Thin Plate Spline fue utilizado para el cálculo de la Energía de Flexión Mínima (Minimum Bending Energy) entre diversas formas del exopodio, que entonces fue utilizada para estimar la Mínima Red de Distancias (Minimum Spanning Network, MSN) que las conectaba. Detectamos una correlación significativa entre las diversas tasas de crecimiento alométrico del tubérculo entre los grupos de islas y la latitud de la isla. Por otro lado, la agrupación de las islas y la MSN, basada en las diferencias de la forma del exopodio, no fueron relacionados con la paleogeografía de la región del piélago Egéo ni con las actuales distancias geográficas de las islas. Estos resultados se interpretan como evidencia para la radiación non-adaptativa de las diversas formas de la especie. [source] A geometric morphometric analysis of the shape of the first upper molar in mice of the genus Mus (Muridae, Rodentia)JOURNAL OF ZOOLOGY, Issue 4 2006M. Macholán Abstract Phenotypic variation in the shape of the first upper molar among 595 mice, representing nine extant and three extinct taxa of the genus Mus, was studied with thin-plate spline analysis. The reliability of classification of individual specimens into known groups based on their molars varied from 75 to 100%, depending on group and method used. Including 13 sliding semilandmarks to the analysis improved the detection of different kinds of size and shape variation as well as visualization of shape differences between studied groups. Correlation between phylogenetic and morphometric distances suggested about 80% contribution of phylogenetic inertia to the molar shape variation; moreover, the importance of localized versus global shape changes was similar in the detection of phylogenetic signals. Finally, shape changes along individual evolutionary lineages were revealed, suggesting a few cases of reversals, convergence and/or retention of ancestral shape. The evolution of mouse molars has thus been driven by random effects of drift together with stabilizing selection and convergence. [source] Geometric morphometric study of population variation in indigenous southern African craniaAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 1 2007D. Franklin Much of our understanding of population variation in southern Africa is derived from traditional morphometric research. In the search for new perspectives, this paper reports on new geometric morphometric data examining cranial variation in 12 modern human populations from southern Africa. In total, 298 male Bantu-speaking individuals were studied. In addition, a small Khoisan (Khoikhoi and San) series was also examined. The purpose of this study was to investigate Khoisan-Bantu morphological similarities and differences, and to examine variation within both the Bantu-speaking and Khoisan populations. The three-dimensional coordinates of 96 landmarks were analyzed, using the shape-analysis software morphologika. Interpopulation variation was examined by calculating Procrustes distances between groups; a cluster analysis was then used to summarize phenetic relationships. A principal components analysis explored the relationships between populations; shape differences were visualized and explored using three-dimensional rendered models, and further interpreted using thin-plate splines. Morphological differences are present within and between the crania of Bantu-speaking and Khoisan individuals. The Khoisan demonstrate features (e.g., a pentagonoid vault, more rounded forehead contour, and a small and less prognathic face) that clearly distinguish them from Bantu-speaking populations. Although southern African Bantu-speaking populations are clearly closely related, they show population-specific features (e.g., the crania of more southerly populations (Xhosa, Southern Sotho, and Zulu) are characteristically more brachycephalic and less prognathic). This study suggests that differential admixture with adjacent Khoisan peoples has contributed to diversity within southern African Bantu-speaking populations. Am. J. Hum. Biol. 19:20,33, 2007. © 2006 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] Three-dimensional average-shape atlas of the honeybee brain and its applicationsTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 1 2005Robert Brandt Abstract The anatomical substrates of neural nets are usually composed from reconstructions of neurons that were stained in different preparations. Realistic models of the structural relationships between neurons require a common framework. Here we present 3-D reconstructions of single projection neurons (PN) connecting the antennal lobe (AL) with the mushroom body (MB) and lateral horn, groups of intrinsic mushroom body neurons (type 5 Kenyon cells), and a single mushroom body extrinsic neuron (PE1), aiming to compose components of the olfactory pathway in the honeybee. To do so, we constructed a digital standard atlas of the bee brain. The standard atlas was created as an average-shape atlas of 22 neuropils, calculated from 20 individual immunostained whole-mount bee brains. After correction for global size and positioning differences by repeatedly applying an intensity-based nonrigid registration algorithm, a sequence of average label images was created. The results were qualitatively evaluated by generating average gray-value images corresponding to the average label images and judging the level of detail within the labeled regions. We found that the first affine registration step in the sequence results in a blurred image because of considerable local shape differences. However, already the first nonrigid iteration in the sequence corrected for most of the shape differences among individuals, resulting in images rich in internal detail. A second iteration improved on that somewhat and was selected as the standard. Registering neurons from different preparations into the standard atlas reveals 1) that the m-ACT neuron occupies the entire glomerulus (cortex and core) and overlaps with a local interneuron in the cortical layer; 2) that, in the MB calyces and the lateral horn of the protocerebral lobe, the axon terminals of two identified m-ACT neurons arborize in separate but close areas of the neuropil; and 3) that MB-intrinsic clawed Kenyon cells (type 5), with somata outside the calycal cups, project to the peduncle and lobe output system of the MB and contact (proximate) the dendritic tree of the PE1 neuron at the base of the vertical lobe. Thus the standard atlas and the procedures applied for registration serve the function of creating realistic neuroanatomical models of parts of a neural net. The Honeybee Standard Brain is accessible at www.neurobiologie.fu-berlin.de/beebrain. J. Comp. Neurol. 492:1,19, 2005. © 2005 Wiley-Liss, Inc. [source] Square pegs in round holes , the implications of shell shape variation on the translocation of adult Margaritifera margaritifera (L.)AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 5 2010S. J. Preston Abstract 1.The freshwater pearl mussel Margaritifera margaritifera is endangered throughout Europe. 2.Historically, mussels were described on the basis of shell characteristics. In more recent years with the advent of molecular techniques many ,species' of molluscs have been found to be ecophenotypes. 3.The pearl mussel is found in numerous rivers throughout Ireland and the UK with varying degrees of superficial differences. It is has been thought that the most divergent form is found in the Nore River, Ireland, Margaritifera m. durrovensis. 4.The current investigation considers shell shape differences (using morphometrics , elliptic Fourier descriptors) in mussels from a variety of rivers in Ireland in relation to river pH. 5.Results suggest that M. margaritifera has a fairly plastic phenotype, with a gradient of shape change in relation to water pH. 6.Margaritifera m. durrovensis does not appear to be morphologically unique from other populations studied, instead occurring at one end of the shell shape gradient. 7.Findings also suggest that shell shape may be characteristic to individual rivers. The existence of phenotypically distinct groups of Margaritifera margaritifera has particularly important implications for the future conservation of the species. 8.Ex situ conservation and reintroduction efforts will need to consider both the genotypic and phenotypic suitability of mussels if translocation is to be used as a viable conservation tool in the future. Copyright © 2010 John Wiley & Sons, Ltd. [source] Inferring adaptation within shape diversity of the humerus of subterranean rodent CtenomysBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010FRANCISCO STEINER-SOUZA In subterranean rodents of the genus Ctenomys, excavation activity can be carried out with the claws and forelimbs (scratch-digging) as well as with the skull and incisor teeth (skull-tooth digging). Within the forelimb myoskeletal system, the humerus is a main bone concentrating a large number of muscles and bearing tensions during excavation. The genus Ctenomys is considered primarily a scratch-digger and secondarily a skull-tooth digger. We analysed the humerus (N = 165) of four species of Ctenomys from southern Brazil, in areas ranging from the soft soils of the first lines of coastal dunes (Ctenomys flamarioni, Ctenomys minutus), through the sandy fields of the coastal plains (Ctenomys minutus, Ctenomys lami), on to the hard soils of the southern pampas ,gaúchos' fields (Ctenomys torquatus). The differences in the form (size + shape) were quantified using geometric morphometrics methods and interpreted in the light of myological descriptions. As expected from a phylogenetic and ecological point of view, C. flamarioni had the most divergent shape and larger size among the species analysed, showing a more slender humerus, especially in the head region, than C. lami, C. minutus, and C. torquatus. Crossing the osteology data with the qualitative observations of the musculature, it was possible to detect large differences in the proximal portion of the humerus that could be related to the insertion of important extension muscles of the pectoral,shoulder joints, which could increase force. The comparison of shape differences between the three closely-related species (C. lami, C. minutus, and C. torquatus) revealed unexpected patterns because C. lami was the species phenetically more distant from C. flamarioni and not C. torquatus as expected from ecological data and phylogenetic relationships. A two-step adaptive path to humeral shapes better fit to digging is postulated where the deltoid crest and epicondylar crest increases precede an articular surface area increase. The absence of sexual dimorphism in C. torquatus is discussed with regard to the optimal size required to dig in hard soils. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 353,367. [source] Variation in the digging apparatus of the subterranean silvery mole-rat, Heliophobius argenteocinereus (Rodentia, Bathyergidae): the role of ecology and geographyBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009IOVÁ, LENKA BAR The skull of most subterranean tooth-digging rodents is markedly affected by their digging mode. In the present study, we investigated the cranial variation in a strictly subterranean, highly specialized Afrotropical tooth-digger, Heliophobius argenteocinereus (Bathyergidae, Rodentia), using a geometric morphometric approach and evaluated the effect of different factors on size and shape differences among four populations. No evidence for sexual dimorphism was found in skull size or shape. The cranial shape variation was large and influenced mainly by the type of habitat (miombo woodland versus farmland and grassland) and the latitudinal gradient. The dorsal side of the skull appears to be more plastic and adaptable to local environments, as well as more independent of size, than the ventral side. Only the shortening of the rostrum is presumably an adaptive process independent of size that leads to an increase of efficacy of the tooth-digging apparatus in Heliophobius, whereas the increase in the in-force and the more procumbent incisors both comprise size-related changes caused by ontogenetic allometric growth. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 822,831. [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] | |||||||||||||||||||||||||||||||