Degree Of Morphological Integration Research Articles

Morphological integration and shape covariation between the trapezium and first metacarpal among extant hominids.

The shape of the trapezium and first metacarpal (Mc1) markedly influence thumb mobility, strength, and the manual abilities of extant hominids. Previous research has typically focused solely on trapezium-Mc1 joint shape. Here we investigate how morphological integration and shape covariation between the entire trapezium (articular and non-articular surfaces) and the entire Mc1 reflect known differences in thumb use in extant hominids. We analyzed shape covariation in associated trapezia and Mc1s across a large, diverse sample of Homo sapiens (n = 40 individuals) and other extant hominids (Pan troglodytes, n = 16; Pan paniscus, n = 13; Gorilla gorilla gorilla, n = 27; Gorilla beringei, n = 6; Pongo pygmaeus, n = 14; Pongo abelii, n = 9) using a 3D geometric morphometric approach. We tested for interspecific significant differences in degree of morphological integration and patterns of shape covariation between the entire trapezium and Mc1, as well as within the trapezium-Mc1 joint specifically. Significant morphological integration was only found in the trapezium-Mc1 joint of H. sapiens and G. g. gorilla. Each genus showed a specific pattern of shape covariation between the entire trapezium and Mc1 that was consistent with different intercarpal and carpometacarpal joint postures. Our results are consistent with known differences in habitual thumb use, including a more abducted thumb during forceful precision grips in H. sapiens and a more adducted thumb in other hominids used for diverse grips. These results will help to infer thumb use in fossil hominins.

The Vitruvian spider: Segmenting and integrating over different body parts to describe ecophenotypic variation.

Understanding what drives the existing phenotypic variability has been a major topic of interest for biologists for generations. However, the study of the phenotype may not be straightforward. Indeed, organisms may be interpreted as composite objects, comprising different ecophenotypic traits, which are neither necessarily independent from each othernor do they respond to the same evolutionary pressures. For this reason, a deep biological understanding of the focal organism is essential for any morphological analysis. The spider genus Dysdera provides a particularly well-suited system for setting up protocols for morphological analyses that encompass a suitof morphological structures in any nonmodel system. This genus has undergone a remarkable diversification in the Canary Islands, where different species perform different ecological roles, exhibiting different levels of trophic specialization or troglomorphic adaptations, which translate into a remarkable interspecific morphological variability. Here, we seek to develop a broad guide, of which morphological characters must be considered, to study the effect of different ecological pressures in spiders and propose a general workflow that will be useful whenever researchers set out to investigate variation in the body plans of different organisms, with data sets comprising a set of morphological traits. We use geometric morphometric methods to quantify variation in different body structures, all of them with diverse phenotypic modifications in their chelicera, prosoma, and legs. We explore the effect of analyzing different combined landmark (LM) configurations of these characters and the degree of morphological integration that they exhibit. Our results suggest that different LM configurations of each of these body parts exhibit a higher degree of integration compared to LM configurations from different structuresand that the analysis of each of these body parts captures different aspects of morphological variation, potentially related to different ecological factors.

Patterns of correlations and locomotor specialization in anuran limbs: association with phylogeny and ecology

As anuran saltatory locomotion has specific functional requirements achieved through certain intra- and inter-limb proportions, we analyzed pattern and degree of morphological integration in limbs of ten anuran species to reveal the relationship of shared developmental programs of serially homologous structures and locomotor specialization. Our main objectives were (1) to examine if morphological and functional differences in forelimb and hindlimb were associated with reduced covariation between limbs, (2) and to reveal patterns of correlation between species and the roles played by evolutionary history (phylogeny) and ecology (lifestyle and habitat use). Species with different locomotor behaviours (walking, jumping, hopping, running, climbing, swimming and burrowing) were used. Partial correlations showed that species shared similar patterns of functionally based morphological integration, with increased correlations in elements within limbs and reduced correlations between limbs. This was mainly based on strong correlations between proximal elements, humerus-radioulna and femur-tibiofibula. To test the influence of phylogenetic relationships and ecological demands we used different matrices (correlation similarity matrix, ecological similarity matrix, matrices of phylogenetic distance and morphological distance). The changes in correlation patterns are shown to be dissociated from phylogeny. On the other hand, they are to some extent shaped by habitat use and locomotion, as the species with similar locomotor behaviour also tend to have stronger similarity in integration patterns. The results from this study provide insight into the processes underlying the evolutionary change of anuran limbs, highlighting function as the main factor that shaped morphological integration of the examined species.

Morphological consequences of artificial cranial deformation: Modularity and integration.

The cranium is an anatomically complex structure. One source of its complexity is due to its modular organization. Cranial modules are distinct and partially independent units that interact substantially during ontogeny thus generating morphological integration. Artificial Cranial Deformation (ACD) occurs when the human skull is intentionally deformed, through the use of different deforming devices applied to the head while it is developing. Hence, ACD provides an interesting example to assess the degree to which biomechanical perturbations of the developing neurocranium impact on the degree of morphological integration in the skull as a whole. The main objective of this study was to assess how ACD affects the morphological integration of the skull. This was accomplished by comparing a sample of non-deformed crania and two sets of deformed crania (i.e. antero-posterior and oblique). Both developmental and static modularity and integration were assessed through Generalized Procrustes Analysis by considering the symmetric and asymmetric components of variation in adults, using 3D landmark coordinates as raw data. The presence of two developmental modules (i.e. viscero and neurocranium) in the skull was tested. Then, in order to understand how ACD affects morphological integration, the covariation pattern between the neuro and viscerocranium was examined in antero-posterior, oblique and non-deformed cranial categories using Partial Least-Squares. The main objective of this study was to assess how ACD affects the morphological integration of the skull. This was accomplished by comparing a sample of deformed (i.e. antero-posterior and oblique) and non-deformed crania. Hence, differences in integration patterns were compared between groups. The obtained results support the modular organization of the human skull in the two analyzed modules. The integration analyses show that the oblique ACD style differentially affects the static morphological integration of the skull by increasing the covariance between neuro and viscerocranium in a more constrained way than in antero-posterior and non-deformed skulls. In addition, the antero-posterior ACD style seems to affect the developmental integration of the skull by directing the covariation pattern in a more defined manner as compared to the other cranial categories.

The evolution of cranial base and face in Cercopithecoidea and Hominoidea: Modularity and morphological integration.

The evolutionary relationship between the base and face of the cranium is a major topic of interest in primatology. Such areas of the skull possibly respond to different selective pressures. Yet, they are often said to be tightly integrated. In this paper, we analyzed shape variability in the cranial base and the facial complex in Cercopithecoidea and Hominoidea. We used a landmark-based approach to single out the effects of size (evolutionary allometry), morphological integration, modularity, and phylogeny (under Brownian motion) on skull shape variability. Our results demonstrate that the cranial base and the facial complex exhibit different responses to different factors, which produces a little degree of morphological integration between them. Facial shape variation appears primarily influenced by body size and sexual dimorphism, whereas the cranial base is mostly influenced by functional factors. The different adaptations affecting the two modules suggest they are best studied as separate and independent units, and that-at least when dealing with Catarrhines-caution must be posed with the notion of strong cranial integration that is commonly invoked for the evolution of their skull shape.

Влияние антропогенной нагрузки на адаптациию <i>Betula pendula</i> Roth.

В качестве объекта исследования выбран широко распространенный вид берез Betula pendula Roth. Изучены механизмы приспособления листьев в условиях антропогенной нагрузки B. pendula лесополосы вдоль автодороги Р-240 «Уфа – Оренбург» на морфологическом уровне по двум показателям — флуктуирующая асимметрия и морфологическая интеграция структуры листа. Для оценки произведена выборка 250 листьев с 25 деревьев генеративного состояния в лесополосе, расположенной вдоль автодороги Р-240 «Уфа – Оренбург» с высоким уровнем антропогенной нагрузки. Определены 40 метрических признаков для оценки уровня морфологической интеграции, среди которых 19 парных признаков для оценки флуктуирующей асимметрии. Также с помощью метода геометрической морфометрии построен усредненный образ листьев B. pendula. При расчете балльных оценок качества среды по показателям флуктуирующей асимметрии по общепринятой методике выявлено, что все деревья формировались в условиях критического (V класс) состояния среды. Тип онтогенетической стратегии — защитно-стрессовый. С усилением антропогенной нагрузки уровень морфологической интеграции возрастает, что определяет защитную часть онтогенетической стратегии, а в последующем происходит снижение показателей морфологической интеграции — проявление стрессовой компоненты. Проведение однофакторного дисперсионного анализа показало значимое влияние фактора (антропогенная нагрузка) между группами внутри генеральной совокупности. Выявлены статистически значимые различия перехода между группами деревьев по уровню морфологической интеграции. Наиболее значимые различия характерны при переходе между группами 1 и 4, 2 и 3, 2 и 4, а также 4 и 5.

Patterns of morphological integration in the appendicular skeleton of mammalian carnivores.

We investigated patterns of evolutionary integration in the appendicular skeleton of mammalian carnivores. The findings are discussed in relation to performance selection in terms of organismal function as a potential mechanism underlying integration. Interspecific shape covariation was quantified by two-block partial least-squares (2B-PLS) analysis of 3D landmark data within a phylogenetic context. Specifically, we compared pairs of anatomically connected bones (within-limbs) and pairs of both serially homologous and functional equivalent bones (between-limbs). The statistical results of all the comparisons suggest that the carnivoran appendicular skeleton is highly integrated. Strikingly, the main shape covariation relates to bone robustness in all cases. A bootstrap test was used to compare the degree of integration between specialized cursorial taxa (i.e., those whose forelimbs are primarily involved in locomotion) and noncursorial species (i.e., those whose forelimbs are involved in more functions than their hindlimb) showed that cursors have a more integrated appendicular skeleton than noncursors. The findings demonstrate that natural selection can influence the pattern and degree of morphological integration by increasing the degree of bone shape covariation in parallel to ecological specialization.

Discontinuous negation in Hausa

Investigating the morphological and syntactic properties of discontinuous negative marking in Hausa, I shall suggest a constructional approach involving edge inflection, accounting simultaneously for the morphologically bound nature of the initial marker and its interaction with the TAM system, haplology of the final marker, and wide scope over coordination. I will argue that the degree of morphological integration of initial markers and haplology of final markers both favour an edge feature approach over phrasal affixation.

A comparative study of morphological integration in Apis mellifera (Insecta, Hymenoptera)

Morphometric correlation matrices from 11 Mediterranean and European honey bee races have been compared. The degree of integration, measured by the eigenvalue variance of the correlation matrix or by Cheverud's index of integration, varies considerably between races but covaries neither with overall body size nor with the variance of the respective sample. Hence, the degree of morphological integration does not depend on body size or the level of variability The patterns of morphometric correlation are significantly similar among all races, but some minor differences in the patterns could be detected: The similarity between the correlation matrices is independent of the degree of phylogenetic relatedness between the respective races. In all races characters belonin to the same functional and/or developmental unit (leg, wing, abdominal characters) have Eiter correlations than the average. Most of the variation in the pattern of correlation can be expfained as a side effect of variation in the degree of integration. Races with high levels of integration tend to have hiher correlations between the main groups of characters, and races with low levels of integration tave smaller correlations between the main grous of characters, while the basic pattern remains undisturbed. In summary, the comparative analysis of morphometric correlation matrices reveals a picture of stability with respect to the pattern of integration and of variation in the degree of integration, which is random with respect to body size, degree of variability, and phylogeny.

Morphological integration of cranium and postcranial skeleton during ontogeny of facultative paedomorphic European newts (Triturus vulgaris and T. alpestris)

AbstractThe patterns of ontogenetic and interspecific variation of morphological integration (the relationships and correlation patterns of functionally and developmentally related morphological traits) in facultative paedomorphic species of two European newts (Triturus vulgaris and T. alpestris) were examined. The degree of morphological integration differed among ontogenetic stages. Variation in the level of morphological integration of cranium and postcranial skeleton during ontogeny of paedomorphic newts had the same pattern in both analysed species. The lowest level of cranium morphological integration characterises the larvae and the juveniles. Individuals that follow alternative life-history path (paedomorphs) remain at a relatively low level of morphological integration, while integration highly increased in metamorphosed adult individuals. Limb skeleton also showed a lower level of integration in paedomorphs in comparison with metamorphosed individuals. The hypothesis of morphological integration was confirmed for all stages of T. vulgaris, while the same hypothesis was confirmed only for larval and paedomorphic stages of T. alpestris. In T. vulgaris, metamorphosis changes the pattern of correlation among the cranial traits, while in T. alpestris, the patterns of phenotypic correlation among the cranial traits remain substantially similar for all analysed ontogenetic stages.

Geometric morphometrics and the analysis of variations in facial form: robusticity of biological findings in relation to bilateral versus unilateral and missing landmarks

This paper reviews some recent advances in the analysis of form variability amongst objects described in terms of landmark configurations. Emphasis is given to the methods of geometric morphometrics that utilise the geometry of Kendall's shape space. This space has well understood and desirable statistical properties. Geometric morphometric methods preserve the geometry of the landmark configurations at every step of analysis and so enable ready visualisation of statistical findings. The methods are illustrated by reference to two example analyses of biological shape variability within growth series of facial skeletons. The first is a study of growth and sexual dimorphism in monkeys and the second is a study of human facial growth. Since the material is biological it is to be expected that its morphogenesis generates correlations amongst landmarks. Thus, the face is bilateral symmetrical, with bilateral as opposed to unilateral landmarks likely contributing little new information about underlying patterns of growth. Further, any one landmark is unlikely to be sited on a region that shows a completely uncorrelated pattern of a variation with the regions on which the other landmarks are sited. This paper investigates the effects of using bilateral as opposed to unilateral landmarks, and of missing landmarks, on the ultimate biological interpretation of analyses. Our empirical findings in these studies to indeed indicate considerable stability of biological findings when diverse landmark sets are chosen. These findings reflect on the degree of morphological integration amongst diverse anatomical regions in the face.