Tools for quantitative form description : an evaluation of different software packages for semi-landmark analysis

The challenging complexity of biological structures has led to the development of several methods for quantitative analyses of form. Bones are shaped by the interaction of historical (phylogenetic), structural, and functional constrains. Consequently, bone shape has been investigated intensively in an evolutionary context. Geometric morphometric approaches allow the description of the shape of an object in all of its biological complexity. However, when biological objects present only few anatomical landmarks, sliding semi-landmarks may provide good descriptors of shape. The sliding procedure, mandatory for sliding semi-landmarks, requires several steps that may be time-consuming. We here compare the time required by two different software packages ('Edgewarp' and 'Morpho') for the same sliding task, and investigate potential differences in the results and biological interpretation. 'Morpho' is much faster than 'Edgewarp,' notably as a result of the greater computational power of the 'Morpho' software routines and the complexity of the 'Edgewarp' workflow. Morphospaces obtained using both software packages are similar and provide a consistent description of the biological variability. The principal differences between the two software packages are observed in areas characterized by abrupt changes in the bone topography. In summary, both software packages perform equally well in terms of the description of biological structures, yet differ in the simplicity of the workflow and time needed to performthe analyses

Interspecific variation in the limb long bones among modern rhinoceroses—extent and drivers

International audienceAmong amniotes, numerous lineages are subject to an evolutionary trend toward body mass and size increases. Large terrestrial species may face important constraints linked to weight bearing, and the limb segments are particularly affected by such constraints due to their role in body support and locomotion. Such groups showing important limb modifications related to high body mass have been called "graviportal." Often considered graviportal, rhinoceroses are among the heaviest terrestrial mammals and are thus of particular interest to understand the limb modifications related to body mass and size increase. Here, we present a morphofunctional study of the shape variation of the limb long bones among the five living rhinos to understand how the shape may vary between these species in relation with body size, body mass and phylogeny. We used three dimensional geometric morphometrics and comparative analyses to quantify the shape variation. Our results indicate that the five species display important morphological differences depending on the considered bones. The humerus and the femur exhibit noticeable interspecific differences between African and Asiatic rhinos, associated with a significant effect of body mass. The radius and ulna are more strongly correlated with body mass. While the tibia exhibits shape variation both linked with phylogeny and body mass, the fibula displays the greatest intraspecific variation. We highlight three distinct morphotypes of bone shape, which appear in accordance with the phylogeny. The influence of body mass also appears unequally expressed on the different bones. Body mass increase among the five extant species is marked by an increase of the general robustness, more pronounced attachments for muscles and a development of medial parts of the bones. Our study underlines that the morphological features linked to body mass increase are not similar between rhinos and other heavy mammals such as elephants and hippos, suggesting that the weight bearing constraint can lead to different morphological responses

The mark of captivity: plastic responses in the ankle bone of a wild ungulate (Sus scrofa)

International audienceDeciphering the plastic (non-heritable) changes induced by human control over wild animals in the archaeological record is challenging. We hypothesized that changes in locomotor behaviour in a wild ungulate due to mobility control could be quantified in the bone anatomy. To test this, we experimented with the effect of mobility reduction on the skeleton of wild boar (Sus scrofa), using the calcaneus shape as a possible © 2020 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited. phenotypic marker. We first assessed differences in shape variation and covariation in captive-reared and wild-caught wild boars, taking into account differences in sex, body mass, available space for movement and muscle force. This plastic signal was then contrasted with the phenotypic changes induced by selective breeding in domestic pigs. We found that mobility reduction induces a plastic response beyond the shape variation of wild boars in their natural habitat, associated with a reduction in the range of locomotor behaviours and muscle loads. This plastic signal of captivity in the calcaneus shape differs from the main changes induced by selective breeding for larger muscle and earlier development that impacted the pigs' calcaneus shape in a much greater extent than the mobility reduction during the domestication process of their wild ancestors

Sexual dimorphism among Mesoamerican turkeys: A key for understanding past husbandry

International audience"Few animals have been domesticated in Mesoamerica and the organization of husbandry practices in this part of the world remains little known. The turkey (Meleagris gallopavo), one of these few animals, shows an evident sexual dimorphism that allows for the analysis of past demographic structure from the study of archaeological bone remains. Here we document sexual dimorphism in turkey populations from the Classic to the Post classic (200–1521 CE) in northern Mesoamerica. We present a morphometric approach based on both size and shape that allows the distinction of two groups in the archaeological populations, corresponding to males and females. Group delimitation with no prior knowledge of their number and parameters is conducted with Gaussian mixture analyses. The accuracy of the method was first evaluated using bibliographic data from the Southwestern USA and then applied on 120 Mesoamerican bone remains of unknown sex coming from five archaeological sites. We point out an imbalanced sex-ratio in Mesoamerican turkey flocks that account for more females than males. We also show that there were no significant size variations between the different sites tested in this study even if they are situated in both lowlands and highlands." (source éditeur

Is vertebral form a valid species-specific indicator for salmonids? The discrimination rate of trout and Atlantic salmon from archaeological to modern times

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Distinguishing female, male and castrated sheep using linear metrics and geometric morphometrics: Application on an archaeological assemblage

Although as a species sheep are commonly found in archaeological deposits and occupy a major position in the history of animal husbandry, it remains difficult to discriminate the sexual type (male, female or castrate) of individuals from observation of the remains. However, understanding sheep husbandry through sex ratio analysis, contributes to a better understanding of the history of animal husbandry. Current criteria for determining are limited to visual characters on coxal and skull. This study explores the variability of sheep skeletons according to their sex to submit hypotheses for methods capable of individual sexing. Using 58 complete skeletons and 428 isolated Soay sheep bones from the collection of the Natural History Museum (UK), we initially tested the sexual distinction using the so-called classical methods: the estimates of shoulder heights and the slenderness index. We then evaluated the influence of sex on the shape and size of selected bones with geometric morphometric, using a protocol that we had previously developed and validated. Finally, we classified these data using the K-Nearest Neighbors (KNN) method, quantifying the reliability of sex attribution. We were able to test its application on an archaeological sample, after selecting bones with the best rate of sexual assignment. Our results demonstrate the difficulty of using traditional methods to sex sheep whilst proposing solutions for sex assignment (88% reliable) using geometric morphometric and KNN. In addition, we were able to highlight the influence of sex according to bone type, though this is strongly qualified by various criteria (such as the age of castration). By characterising and quantifying the sex ratio within archaeological assemblages, we may better understand herd management, procurement strategies and feeding habits, and therefore improve our global knowledge of animal husbandry history

How Can Phenotypic Evolution be Characterized Over Time and Through Environmental Changes?

International audienceRapid phenotypic evolution is observed in response to rapid environmental changes. These phenotypic variations can occur at different scales, from the population to the community. We intended to characterize these multiscale phenotypic responses in rodents from the archaeological site El Harhoura 2 (Rabat, Morocco), dated from the Late Pleistocene to the Holocene, and relate them to paleoenvironmental variations. Upper and lower first molars were used as proxies for phenotype. Their shape was quantified using a landmark-free method. To account for both intra- and interspecific variations, we used morphogroups as phenotypic units. Those morpho-groups were identified using unsupervised clustering. Three shape indicators were computed: number of morpho-groups, morpho-group disparity and changes in morpho-group mean shape over time. To evaluate this little-used approach on small mammals, we compared it to three widely used biodiversity indices: number of taxa, Shannon index, and Simpson index. Phenotypic evolution between and within species was highlighted. Morpho-groups seemed to be phenotypic response units representing ecological groups that transversed species. Variations in the morpho-group mean shapes were partly related to paleoenvironmental changes; however, variations in disparity were not. Thus, environmental changes deduced from fossil microvertebrate communities did not seem to be the main determinants of the characterized phenotypic variations

How Can Phenotypic Evolution be Characterized Over Time and Through Environmental Changes?

International audienceRapid phenotypic evolution is observed in response to rapid environmental changes. These phenotypic variations can occur at different scales, from the population to the community. We intended to characterize these multiscale phenotypic responses in rodents from the archaeological site El Harhoura 2 (Rabat, Morocco), dated from the Late Pleistocene to the Holocene, and relate them to paleoenvironmental variations. Upper and lower first molars were used as proxies for phenotype. Their shape was quantified using a landmark-free method. To account for both intra- and interspecific variations, we used morphogroups as phenotypic units. Those morpho-groups were identified using unsupervised clustering. Three shape indicators were computed: number of morpho-groups, morpho-group disparity and changes in morpho-group mean shape over time. To evaluate this little-used approach on small mammals, we compared it to three widely used biodiversity indices: number of taxa, Shannon index, and Simpson index. Phenotypic evolution between and within species was highlighted. Morpho-groups seemed to be phenotypic response units representing ecological groups that transversed species. Variations in the morpho-group mean shapes were partly related to paleoenvironmental changes; however, variations in disparity were not. Thus, environmental changes deduced from fossil microvertebrate communities did not seem to be the main determinants of the characterized phenotypic variations

Inside the head of snakes: influence of size, phylogeny, and sensory ecology on endocranium morphology

International audienceEnvironmental properties, and the behavioral habits of species impact sensory cues available for foraging, predator avoidance and inter/intraspecific communication. Consequently, relationships have been discovered between the sensory ecology and brain morphology in many groups of vertebrates. However, these types of studies have remained scare on snake. Here, we investigate 2 Our results thus demonstrate the value of utilizing endocranial shape as complementary information to size and volume in neurobiological studies

Influence of mass on tarsus shape variation: a morphometrical investigation among Rhinocerotidae (Mammalia: Perissodactyla)

International audienceMany tetrapod lineages show extreme increases in body mass in their evolutionary history, associated with important osteological changes. The ankle joint, essential for foot movement, is assumed to be particularly affected in this regard. We investigated the morphological adaptations of the astragalus and the calcaneus in Rhinocerotidae, and analysed them in light of a comparative analysis with other Perissodactyla. We performed 3D geometric morphometrics and correlated shape with centroid size of the bone and body mass of the species. Our results show that mass has an influence on bone shape in Rhinocerotidae and in Perissodactyla, but this is not as strong as expected. In heavy animals the astragalus has a flatter trochlea, orientated more proximally, associated with a more upright posture of the limb. The calcaneus is more robust, possibly to sustain the greater tension force exerted by the muscles during plantarflexion. Both bones show wider articular facets, providing greater cohesion and better dissipation of the loading forces. The body plan of the animals also has an influence. Short-legged Teleoceratina have a flatter astragalus than the other rhinocerotids. Paraceratherium has a thinner calcaneus than expected. This study clarifies adaptations to high body weight among Rhinocerotidae and calls for similar investigations in other groups with massive forms. ADDITIONAL KEYWORDS: ankle-astragalus-calcaneus-functional morphology-high body weight-geometric morphometrics-Perissodactyla-Rhinocerotidae