Perdiz arrow points from Caddo burial contexts aid in defining discrete behavioral regions

Recent research in the ancestral Caddo area yielded evidence for distinct _behavioral regions_, across which material culture from Caddo burials—bottles and Gahagan bifaces—has been found to express significant morphological differences. This inquiry assesses whether Perdiz arrow points from Caddo burials, assumed to reflect design intent, may differ across the same geography, and extend the pattern of shape differences to a third category of Caddo material culture. Perdiz arrow points collected from the geographies of the northern and southern Caddo _behavioral regions_ defined in a recent social network analysis were employed to test the hypothesis that morphological attributes differ, and are predictable, between the two communities. Results indicate significant between-community differences in maximum length, width, stem length, and stem width, but not thickness. Using the same traditional metrics combined with the tools of machine learning, a predictive model---support vector machine---was designed to assess the degree to which community differences could be predicted, achieving a receiver operator curve score of 97 percent, and an accuracy score of 94 percent. The subsequent geometric morphometric analysis identified significant differences in Perdiz arrow point shape, size, and allometry, coupled with significant results for modularity and morphological integration. These findings bolster recent arguments that established two discrete _behavioral regions_ in the ancestral Caddo area defined on the basis of discernible morphological differences across three categories of Caddo material culture.

‘Dinosaur-bird’ macroevolution, locomotor modules and the origins of flight

The dinosaurian origin of birds is one of the best documented events that palaeontology has contributed to the understanding of deep time evolution. This transition has been studied on multiple fossils using numerous multidisciplinary resources, including systematics, taxonomic, anatomical, morphological, biomechanical and molecular approaches. However, whereas deep time origins and phylogenetic relationships are robust, important nuances of this transition’s dynamics remain controversial. In particular, the fossil record of several maniraptoran groups clearly shows that aerial locomotion was developed before an ‘avialization’ (i.e., before the first divergence towards avialans), thus earlier than presumed. Although aspects as important as miniaturization and the acquisition of several anatomical and morphological modifications are key factors determining such evolutionary transition, understanding this macroevolutionary trend also involves to seize the evolution of developmental systems, which requires assessing the morphological expression of integration and modularity of the locomotor apparatus throughout time. This is so because, as it happened in other flying vertebrate taxa such as pterosaurs and bats, the transformation of the maniraptoran forelimbs into flying locomotor modules must not only have involved a gradual anatomical transformation, but also a complete developmental re-patterning of the integration scheme between them and the hindlimbs. Here, we review the most relevant aspects of limb morphological transformation during the so-called ‘dinosaur-bird’ transition to stress the importance of assessing the role of modularity and morphological integration in such macroevolutionary transition, which ultimately involves the origins of flight in dinosaurs.

Radial symmetry molding skull roundness: a human fetal MR study

The aim of this study consists in evaluating the morphological integration and molding shape of the human fetal craniofacial complex development on MR sagittal images. The sella point has been used as a reference point to build eleven dimensional parameters encompassing the craniofacial complex. Data and measurements obtained were statistically analyzed by PCA. The designed rays were significantly correlated, normally distributed and characterized by linearity over the overall fetal development. These findings showed that the craniofacial units are clustering together, whereas craniobasal and craniopharyngeal traits are spread. The data analysis supported the efficacy of specific morphological traits to evaluate differences emerging during the modeling growth processes. Skull modeling seems to be characterized by a rotational symmetry around the sella as inertial point. We firstly present the intriguing hypothesis through which the skull development grows along a dihedral angle symmetry made of a both rotational and reflection vector.

Morphological integration during postnatal ontogeny: implications for evolutionary biology

Understanding how development changes the genetic covariance of complex phenotypes is fundamental for the study of evolution. If the genetic covariance changes dramatically during postnatal ontogeny, one cannot infer confidently evolutionary responses based on the genetic covariance estimated from a single postnatal ontogenetic stage. Mammalian skull morphology is a common model system for studying the evolution of complex structures. These studies often involve estimating covariance between traits based on adult individuals. There is robust evidence that covariances changes during ontogeny. However, it is unknown whether differences in age-specific covariances can, in fact, bias evolutionary analyses made at subadult ages. To explore this issue, we sampled two marsupials from the order Didelphimorphia, and one precocial and one altricial placental at different stages of postnatal ontogeny. We calculated the phenotypic variance-covariance matrix (P-matrix) for each genus at these postnatal ontogenetic stages. Then, we compared within genus P-matrices and also P-matrices with available congeneric additive genetic variance-covariance matrices (G-matrices) using Random Skewers and the Krzanowsky projection methods. Our results show that the structural similarity between matrices is in general high (> 0.7). Our study supports that the G-matrix in therian mammals is conserved during most of the postnatal ontogeny. Thus it is feasible to study life-history changes and evolutionary responses based on the covariance estimated from a single ontogenetic stage. Our results also suggest that at least for some marsupials the G-matrix varies considerably prior to weaning, which does not invalidate our previous conclusion because specimens at this stage would experience striking differences in selective regimes than during later ontogenetic stages.

Sexual Dimorphism and Morphological Modularity in Acanthoscelides obtectus (Say, 1831) (Coleoptera: Chrysomelidae): A Geometric Morphometric Approach

Sexual dimorphism and specific patterns of development contribute in a great manner to the direction and degree of the sexual differences in body size and shape in many insects. Using a landmark-based geometric morpohometrics approach, we investigated sex-specific morphological size and shape variation in the seed beetle, Acanthoscelides obtectus. We also tested the functional hypothesis of the two morphological modules—thorax and abdomen in both sexes. Female-biased sexual dimorphism in size was shown, while differences in shape were reflected in the wider thorax and abdomen and shorter abdomen in females in comparison to males. The functional hypothesis of a two-module body was confirmed only in females before correction for size, and in both sexes after the allometry correction. Our results indicate that reproductive function has the central role in forming the patterns of modularity. We hypothesize that high morphological integration of the abdomen in females results from intense stabilizing selection, while the more relaxed integration in males is driven by the higher intensity of sexual selection.

Morphological integration of the human brain across adolescence and adulthood

Brain structural covariance norms capture the coordination of neurodevelopmental programs between different brain regions. We develop and apply anatomical imbalance mapping (AIM), a method to measure and model individual deviations from these norms, to provide a lifespan map of morphological integration in the human cortex. In cross-sectional and longitudinal data, analysis of whole-brain average anatomical imbalance reveals a reproducible tightening of structural covariance by age 25 y, which loosens after the seventh decade of life. Anatomical imbalance change in development and in aging is greatest in the association cortex and least in the sensorimotor cortex. Finally, we show that interindividual variation in whole-brain average anatomical imbalance is positively correlated with a marker of human prenatal stress (birthweight disparity between monozygotic twins) and negatively correlated with general cognitive ability. This work provides methods and empirical insights to advance our understanding of coordinated anatomical organization of the human brain and its interindividual variation.

Developmental instability and phenotypic evolution in a small and isolated bear population

We explored fluctuating asymmetry (FA) and morphological integration (MI) in the skull of the small, highly inbred and divergent Apennine bear ( Ursus arctos marsicanus ), to explore its uniqueness and investigate any potential effects of inbreeding depression. We used 3D geometric morphometrics contrasting Apennine bears with other two large outbred bear populations from Scandinavia and Kamchatka as controls. Shape divergence and variability were explored by a principal component analysis on aligned coordinates of 39 landmarks. Procrustes ANOVA, morphological disparity and the global integration index were used to explore FA, shape variance and MI. By remarking Apennine bears as a highly divergent phenotype, we recorded the highest FA and deviation from self-similarity compared with the other two control populations. We conclude that Apennine bears are likely facing developmental instability as a consequence of inbreeding depression, whereas the divergent trait covariance pattern may represent a potential source of evolutionary novelties. We discuss the implications for the conservation and management of this imperiled taxon.

Morphological variability of Betula pendula Roth leaves under conditions of technogenic transformation of the environment

The paper analyzes morphological characters variability of Betula pendula Roth leaves growing in the gradient of technogenic soil transformation. Biological material was collected in natural phytocoenoses and in the Pritagilskaya zone of the Middle Urals technogenically contaminated with heavy metals. In the gradient under study, a change in the shape of the leaf blade is observed: it is rounded, the base is straightened and the top is stretched. The sizes of leaf blades of Betula pendula are smaller under conditions of an average level of pollution than in the background and maximum polluted areas. The largest leaves are typical for B. pendula from the most polluted area. In the studied gradient of the technogenic transformation of the environment, four types of leaf blades forms were distinguished: 1) ovate with a rounded-wedge-shaped base and with a pointed apex; 2) triangular-broadly ovate with a rounded-wedge-shaped base and a pointed apex; 3) triangular-broadly ovate with a truncated base and a pointed apex; 4) triangular-broadly ovate with a truncated base and an elongated pointed apex. By the factor analysis the authors have identified the factors that explain 60% of the total variance of the leaf shape trait. The variables have large factor loads for the first factor (length and width of the leaf blade, length of the petiole, the distance from the tip of the leaf blade to the widest part) (42%) and smaller loads for the second one (leaf index) (18%). On the basis of these features, a discriminant analysis was carried out, the results of which indicate that the leaves of plants from the impact area differ from the rest. On the basis of the ratio of the general and consistent variability, morphological features were identified that are ecological indicators the distance between the bases of the first-second and second-third lateral veins of the first order, the distance from the widest part to the base of the leaf blade, IF (shape index sheet). The high overall and low consistent variability of these characteristics is determined to a greater extent by the influence of environmental factors. The analysis of changes patterns in the level of leaves morphological integration in the gradient of soils technogenic transformation showed that Betula pendula is characterized by a protective-stress developmental strategy.