1,720,968 research outputs found
Morphological integration affects the evolution of midline cranial base, lateral basicranium, and face across primates
No full textObjectives The basicranium and face are two integrated bony structures displaying great morphological diversity across primates. Previous studies in hominids determined that the basicranium is composed of two independent modules: the midline basicranium, mostly influenced by brain size, and the lateral basicranium, predominantly associated with facial shape. To better assess how morphological integration impacts the evolution of primate cranial shape diversity, we test to determine whether the relationships found in hominids are retained across the order. Materials and methods Three-dimensional landmarks (29) were placed on 143 computed tomography scans of six major clades of extant primate crania. We assessed the covariation between midline basicranium, lateral basicranium, face, and endocranial volume using phylogenetically informed partial least squares analyses and phylogenetic generalized least squares models. Results We found significant integration between lateral basicranium and face and between midline basicranium and face. We also described a significant correlation between midline basicranium and endocranial volume but not between lateral basicranium and endocranial volume. Discussion Our findings demonstrate a significant and pervasive integration in the craniofacial structures across primates, differing from previous results in hominids. The uniqueness of module organization in hominids may explain this distinction. We found that endocranial volume is significantly integrated to the midline basicranium but not to the lateral basicranium. This finding underlines the significant effect of brain size on the shape of the midline structures of the cranial base in primates. With the covariations linking the studied features defined here, we suggest that future studies should focus on determining the causal links between them
Examining the effect of feralization on craniomandibular morphology in pigs, Sus scrofa (Artiodactyla: Suidae)
No full textBasicranium and face: Assessing the impact of morphological integration on primate evolution
No full textThe basicranium and facial skeleton are two integrated structures displaying great morphological diversity across primates. Previous studies focusing on limited taxonomic samples have demonstrated that morphological integration has a significant impact on the evolution of these structures. However, this influence is still poorly understood. A more complete understanding of craniofacial integration across primates has important implications for functional hypotheses of primate evolution. In the present study, we analyzed a large sample of primate species to assess how integration affects the relationship between basicranial and facial evolutionary pathways across the order. First, we quantified integration and modularity between basicranium and face using phylogenetically-informed partial least squares analyses. Then, we defined the influence of morphological integration between these structures on rates of evolution, using a time-calibrated phylogenetic tree, and on disparity through time, comparing the morphological disparity across the tree with that expected under a pure Brownian process. Finally, we assessed the correlation between the basicranium and face, and three factors purported to have an important role in shaping these structures during evolution: endocranial volume, positional behavior (i.e., locomotion and posture), and diet. Our findings show that the face and basicranium, despite being highly integrated, display significantly different evolutionary rates. However, our results demonstrate that morphological integration impacted shape disparity through time. We also found that endocranial volume and positional behavior are important drivers of cranial shape evolution, partly affected by morphological integration. (C) 2018 Elsevier Ltd. All rights reserved
How domestication, feralization and experience-dependent plasticity affect brain size variation in Sus scrofa
Full text linkAmong domestic species, pigs experienced the greatest brain size reduction, but the extent and factors of this reduction remain unclear. Here, we used the brain endocast volume collected from 92 adult skulls of wild, captive, feral and domestic Sus scrofa to explore the effects of domestication, feralization and captivity over the brain size variation of this species. We found a constant brain volume increase over 24 months, while body growth slowed down from month 20. We observed an 18% brain size reduction between wild boars and pigs, disagreeing with the 30%-40% reduction previously mentioned. We did not find significant sexual differences in brain volume, refuting the theory of the attenuation of male secondary sexual characteristics through the selection for reduced male aggression. Feralization in Australia led to brain size reduction-probably as an adaptation to food scarcity and drought, refuting the reversal to wild ancestral brain size. Finally, free-born wild boars raised in captivity showed a slight increase in brain size, potentially due to a constant and high-quality food supply as well as new allospecific interactions. These results support the need to further explore the influence of diet, environment and experience on brain size evolution during animal domestication
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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