Use Of Geometric Morphometrics Research Articles

The pronotum shape of scelimenine grasshoppers (Orthoptera: Tetrigidae) likely represents an exaptation for heterogeneous niche colonization

Abstract Insects are suitable model organisms for functional morphology research, especially in the context of exaptation, when the same morphological trait represents an advantage in disparate niches. Phylogenetically distant groups of pygmy grasshoppers (Orthoptera: Tetrigidae) have various pronotal projections, defining their general appearance, i.e., body shape. However, pronotum shape has never been related to niche occupation in these insects, thus the aim of this study is to investigate the relationship between body shape and macrohabitat adaptation in Scelimeninae, a group of Asian and Papuan tetrigids encompassing amphibious and corticolous (bark-dwelling) representatives. With the use of geometric morphometrics and phylogenetic comparative methods, two morphological and functional groups were distinguished, with the body shape exhibiting a significant phylogenetic signal. The first group consists of elongated amphibious taxa (Scelimenini tribe) with highly uniform pronotum morphology, likely due to strong selection for streamlined body shape. Stouter corticolous taxa (Discotettigini tribe) exhibit more conspicuous body shape variability, possibly increasing camouflage efficiency in tree bark habitats. Ecological divergence associated with macrohabitat adaptation may thus have been the primary driver of speciation in this insect group, but the evolutionary constraints leading to this divergence are still to be identified.

Облик мужчин, склонных к риску, по данным геометрической морфометрии

The article presents the results of a facial anthropometric study suggesting markers of masculinity in motorcycle racers (n = 36), mountain climbers (n = 52), and students (n = 56). The use of geometric morphometrics on the basis of frontal photographs enabled the authors to describe and visualize the facial shapes of men from these three groups, and to reveal significant intergroup differences. Facial shapes of mountain climbers, racers, and students (control sample) were compared pairwise using multivariate regression analysis. The racers and climbers had more masculine facial features compared to the control group: larger, more elongated faces, with a large jaw, thin lips, and narrow eye shape. The differences identified by geometric morphometrics were also confirmed by an additional analysis of facial indices based on linear measurements of certain facial parameters. The findings prove the high efficiency of using a combination of geometric and classical morphometry methods to study full facial shape, as well as to quantify observed differences in certain facial areas.

Изменчивость лицевого скелета у носителей джетыасарской археологической культуры Восточного Приаралья по данным 3D геометрической морфометрии

Introduction. The origin of the Jetyasar culture’s population remains a subject of debate. It was generally accepted that the Xiongnu penetrated into the Aral Sea region and participated in the formation of the local population. Previous studies have shown a complex and admixed origin of the Jetyasar people. But the spread of the head deformation tradition in this population imposes serious limitations on the application of craniometric methods for studying Jetyasar samples. Those limitations can be potentially mitigated with the use of geometric morphometrics (GM). The purpose of this work was to assess the degree of variation in the facial skeleton of the Jetyasar people in comparison with populations of the Early Iron Age and the Hunno-Sarmatian period. Material and methods. Digital, three-dimensional models of the skulls were created. Ten landmarks were placed on each of the models and subjected to general Procrustes analysis (GPA) and principal component analysis (PCA). Results. The first PC of the analysis of the total male sample reflects variation in the height of the face, nasal bridge protrusion, and the relative width of the infraorbital region. The second component describes the height of the lateral part of the zygomatic process of the maxilla and the adjacent part of the zygomatic bone. The Kosasar 2 male sample is the most diverse morphologically. This burial ground, according to archeological data, belonged to a migrant population related to the Xiongnu. In the female total sample, high values of the first PC are associated with a tall face, a weak nasal bridge protrusion, and a long zygomatic-maxillary suture. The second PC describes the morphology of the zygomatic process of the upper jaw. The Jetyasar samples are morphologically distinct from the skulls from China, Mongolia, Western Siberia, and Southern Siberia. An exception are the crania from the burial grounds of Kosasar 2, 3, and Altyn-Asar 4t which are similar to the early Iron Age samples from China (inner Mongolia, Warring States period, 5 th – 3rd centuries BC), Mongolia (Xiongnu period), and Tuva (Arzhan-2). Discussion. The Xiongnu migration could become a catalyst for the admixture and ethnogenetic processes in the region. Conclusion. Our study shows that the population of the Jetyasar culture was morphologically heterogeneous at all stages of the culture’s development. The hypothesis about the migrant roots of a part of the population is confirmed by our data.

Geometric Morphometrics and Machine Learning Models Applied to the Study of Late Iron Age Cut Marks from Central Spain

Recently the incorporation of artificial intelligence has allowed the development of valuable methodological advances in taphonomy. Some studies have achieved great precision in identifying the carnivore that produced tooth marks. Additionally, other works focused on human activity have managed to specify what type of tool or raw material was used in the filleting processes identified at the sites. Through the use of geometric morphometrics and machine learning techniques, the present study intends to analyze the cut marks of the Ulaca oppidum (Solosancho, Ávila, Spain) in order to identify the type of tools used during carcass modification. Although the Ulaca oppidum is an Iron Age site, the results suggest that most of the cut marks were produced with flint tools.

Personalized statistical modeling of soft tissue structures in the knee.

Background and Objective: As in vivo measurements of knee joint contact forces remain challenging, computational musculoskeletal modeling has been popularized as an encouraging solution for non-invasive estimation of joint mechanical loading. Computational musculoskeletal modeling typically relies on laborious manual segmentation as it requires reliable osseous and soft tissue geometry. To improve on feasibility and accuracy of patient-specific geometry predictions, a generic computational approach that can easily be scaled, morphed and fitted to patient-specific knee joint anatomy is presented. Methods: A personalized prediction algorithm was established to derive soft tissue geometry of the knee, originating solely from skeletal anatomy. Based on a MRI dataset (n = 53), manual identification of soft-tissue anatomy and landmarks served as input for our model by use of geometric morphometrics. Topographic distance maps were generated for cartilage thickness predictions. Meniscal modeling relied on wrapping a triangular geometry with varying height and width from the anterior to the posterior root. Elastic mesh wrapping was applied for ligamentous and patellar tendon path modeling. Leave-one-out validation experiments were conducted for accuracy assessment. Results: The Root Mean Square Error (RMSE) for the cartilage layers of the medial tibial plateau, the lateral tibial plateau, the femur and the patella equaled respectively 0.32mm (range 0.14-0.48), 0.35mm (range 0.16-0.53), 0.39mm (range 0.15-0.80) and 0.75mm (range 0.16-1.11). Similarly, the RMSE equaled respectively 1.16mm (range 0.99-1.59), 0.91mm (0.75-1.33), 2.93mm (range 1.85-4.66) and 2.04mm (1.88-3.29), calculated over the course of the anterior cruciate ligament, posterior cruciate ligament, the medial and the lateral meniscus. Conclusion: A methodological workflow is presented for patient-specific, morphological knee joint modeling that avoids laborious segmentation. By allowing to accurately predict personalized geometry this method has the potential for generating large (virtual) sample sizes applicable for biomechanical research and improving personalized, computer-assisted medicine.

Classifying fossil Darwin wasps (Hymenoptera: Ichneumonidae) with geometric morphometrics of fore wings.

Linking fossil species to the extant diversity is often a difficult task, and the correct interpretation of character evidence is crucial for assessing their taxonomic placement. Here, we make use of geometric morphometrics of fore wings to help classify five fossil Darwin wasps from the Early Eocene Fur Formation in Denmark into subfamilies and often tribes. We compile a reference dataset with 342 fore wings of nine extant subfamilies and nine relevant fossil species. Since geometric morphometrics was mostly ignored in the past in Darwin wasp classification, the dataset is first used to examine differences and similarities in wing venation among subfamilies. In a next step, we used the reference dataset to inform the classification of the fossil species, which resulted in the description of one new genus and five new species, Crusopimpla weltii sp. nov., Ebriosa flava gen. et sp. nov., Entypoma? duergari sp. nov., Lathrolestes? zlatorog sp. nov., and Triclistus bibori sp. nov., in four different subfamilies. Carefully assessing data quality, we show that the fore wing venation of fossil Darwin wasps is surprisingly suitable to assign them to a subfamily or even lower taxonomic level, especially when used in conjunction with characters from other parts of the body to narrow down a candidate set of potential subfamilies and tribes. Our results not only demonstrate a fast and useful approach to inform fossil classification but provide a basis for future investigations into evolutionary changes in fore wings of ichneumonids. The high informativeness of wing venation for classification furthermore could be harvested for phylogenetic analyses, which are otherwise often hampered by homoplasy in this parasitoid wasp family.

Geometric Morphometrics Reveal Shape Differences in the Toes of Urban Lizards.

SynopsisUrbanization, despite its destructive effects on natural habitats, offers species an opportunity to colonize novel niches. Previous research found that urban Anolis lizards in Puerto Rico had increased adhesive toepad area and more ventral toepad scales, traits that are likely adaptive and genetically based. We further investigated these phenotypic changes using geometric morphometrics to measure differences in toe shape, toepad shape, and lamellar morphology. Our results indicate that the increased toepad area of urban Anolis cristatellus lizards in Puerto Rico is not simply an isometric increase in toe size. Toes of urban populations exhibit multiple disproportional changes compared to forest lizards, with a larger proportion of the toe length covered in adhesive toepad. In addition, the toepads of urban lizards increase more in length than width. Lastly, lizards in urban populations exhibit both increased number of lamellae as well as increased spacing between individual lamellae. We also observed regional variation, with urban specimens having significantly more disparity, suggesting similar processes of urban adaptation are likely happening in parallel across the island, yet with region-specific idiosyncrasies, possibly generating more variation in toepad morphology across urban specimens as compared to forest specimens. Considering the use of geometric morphometrics, we found that specimen preparation, specifically how flat and straight toes are during imaging, to be an important factor affecting our data, more so than specimen size or any other meaningful morphological variation. In addition, we found that landmark and semilandmark data can be used to directly estimate toepad area, offering the opportunity to streamline future studies. In conclusion, our results highlight the value of considering toepad morphology in more detail beyond adhesive pad area or number of lamellae. Geometric morphometrics tools may be employed to elucidate subtle differences in shape to better allow researchers to connect changes in morphology to ecology and adhesive performance.

Comparison of Donkey, Pony, and Horse Dorsal Profiles and Head Shapes Using Geometric Morphometrics.

Simple SummaryWith the increasing interest toward donkey breeding and equid welfare, the scales and methods of welfare assessment, which were successfully designed and validated for horses, are a starting point for the development of similar approaches for donkeys. As horses and donkeys are morphometrically different, the current study aimed to compare donkey, pony, and horse dorsal profiles and head shapes. Geometric morphometrics (GM) was applied to characterize the shapes and sizes of the studied equids based on the analysis of the photographs of 14 donkeys, 14 ponies, and 14 horses. The donkeys differed from ponies and horses in the shape of the dorsal profile and the head shape, but only from horses in the size of the evaluated centroids. Moreover, the ponies and horses differed in size but not in the shape of the investigated lines reflecting the posture and head contour. When both lines were compared, the GM distances (the Mahalanobis and Procrustes distances) were higher between donkeys and ponies and horses than between ponies and horses. GM revealed the differences in dorsal profiles and head shapes between equids, which should be considered when adapting scales and methods of welfare assessment from horses to donkeys.Since donkey breeding has increased due to their variety of uses, welfare evaluation has become more important. This study aimed to compare donkey, pony, and horse dorsal profiles and head shapes using geometric morphometrics (GM). Photographs of 14 donkeys, 14 ponies, and 14 horses were analyzed using GM, including the sliding semilandmarks method. The variations in the first three principal components (PCs) were PC1: 57.16%, PC2: 16.05%, and PC3: 8.31% for the dorsal profiles and PC1: 44.77%, PC2: 13.46%, and PC3: 7.66% for the head shapes. Both the dorsal profiles and head shapes differed between donkeys and horses (p < 0.0001) but not between donkeys and ponies (p > 0.05). Moreover, both the dorsal profiles and head shapes differed in size between ponies and horses (p < 0.0001) but not in shape (p > 0.05). Higher Mahalanobis and Procrustes distances were noted between donkeys and horses as well between donkeys and ponies than between ponies and horses. The use of geometric morphometrics revealed the differences in the dorsal profiles and head shapes between the studied equids. These differences should be taken into account when adapting welfare scales and methods from horses to donkeys.

Assessing the shape plasticity between Russian biotopes in Pterostichus dilutipes (Motschulsky, 1844) (Coleoptera: Carabidae) a geometric morphometric approach

Different biotopes or environments produce dissimilar stress level in insects, which can be reflected on the capacity of an individual to overcome these pressures and survive. Morphological plasticity of an organism is expressed by the ability of the species to produce different phenotypes depending on the environmental conditions. The following research evaluate the use of geometric morphometrics (GM) tool to evaluate the effect in the development of multiple phenotypes on a native beetle Pterostichus dilutipes Motschulsky, 1844 inhabiting different biotopes from the Baikal Lake coastal in Russia. GM results provided a powerful graphical visualization to detect small variation in morphology from beetles collected in an altitudinal gradient with a special plastic variation from warmer to colder biotopes. GM are very useful tool to future studies where the integration of research areas could allow researcher to identify with clarity of the morphological body plan product of natural selection.

Technical note: A technique to mount Sarcophagidae and Calliphoridae (Diptera) larvae for forensic identification using geometric morphometrics

Geometric morphometric analyses use landmark coordinates from images of specific areas on specimens. Therefore, to minimize differences arising from human preparation, preparation of the specimen is crucial. The application of geometric morphometrics has been used in entomology for identifying adult dipteran species, however, applying this technique to larval specimens requires the production of standard protocols which would allow specimens to be compared equally. This proposed protocol consists of a two-step process:1. using 15% potassium hydroxide (KOH) to clear the specimen, followed by rinsing the specimen with 80% ethanol;2. removal and spreading of the mouthhooks on a slide for imaging and analysis.The goal of this work is to standardize specimen preparation, which would reduce human error and facilitate use of geometric morphometrics to identify dipteran larvae.

Landmark-Based Shape Analysis on Middle Cerebral Intracranial Aneurysms: A Geometric Morphometrics Approach to Infer Natural History

Due to the scarcity of longitudinal data, the morphologic development of intracranial aneurysms (IAs) during their natural history remains poorly understood. However, longitudinal information can often be inferred from cross-sectional datasets as demonstrated by anatomists' use of geometric morphometrics to build evolutionary trees, reconstructing species inter-relationships based on morphologic landmarks. We adopted these tools to analyze cross-sectional image data and infer relationships between IA morphologies. On 3D reconstructions of 52 middle cerebral arteries (MCA) IAs (9 ruptured) and 10 IAfree MCAs (baseline geometries), 7 semi-automated landmarks were placed at the proximal parent artery and maximum height. From these, 64 additional landmarks were computationally generated to create a 71-landmark point cloud of 213 xyz coordinates. This data was normalized by Procrustes transformation and used in the principal component analysis, hierarchical clustering, and phylogenetic analyses. Principal component analysis showed separation of IA-free MCA geometries and grouping of ruptured IAs from unruptured IAs. Hierarchical clustering delineated a cluster of only unruptured IAs that were significantly smaller and more spherical than clusters that had ruptured IAs. Phylogenetic classification placed ruptured IAs more distally in the tree than unruptured IAs, indicating greater shape derivation. Groups of unruptured IAs were observed, but ruptured IAs were invariably found in mixed lineages with unruptured IAs, suggesting that some pathways of shape change may be benign while others are more associated with rupture. Geometric morphometric analyses of larger datasets may indicate particular pathways of shape change leading toward aneurysm rupture versus stabilization.

Effects of taphonomic deformation on geometric morphometric analysis of fossils: a study using the dicynodont Diictodon feliceps (Therapsida, Anomodontia).

Taphonomic deformation, the distortion of fossils as a result of geological processes, poses problems for the use of geometric morphometrics in addressing paleobiological questions. Signal from biological variation, such as ontogenetic trends and sexual dimorphism, may be lost if variation from deformation is too high. Here, we investigate the effects of taphonomic deformation on geometric morphometric analyses of the abundant, well known Permian therapsid Diictodon feliceps. Distorted Diictodon crania can be categorized into seven typical styles of deformation: lateral compression, dorsoventral compression, anteroposterior compression, “saddle-shape” deformation (localized collapse at cranial mid-length), anterodorsal shear, anteroventral shear, and right/left shear. In simulated morphometric datasets incorporating known “biological” signals and subjected to uniform shear, deformation was typically the main source of variance but accurate “biological” information could be recovered in most cases. However, in empirical datasets, not only was deformation the dominant source of variance, but little structure associated with allometry and sexual dimorphism was apparent, suggesting that the more varied deformation styles suffered by actual fossils overprint biological variation. In a principal component analysis of all anomodont therapsids, deformed Diictodon specimens exhibit significant dispersion around the “true” position of this taxon in morphospace based on undistorted specimens. The overall variance associated with deformation for Anomodontia as a whole is minor, and the major axes of variation in the study sample show a strong phylogenetic signal instead. Although extremely problematic for studying variation in fossil taxa at lower taxonomic levels, the cumulative effects of deformation in this study are shown to be random, and inclusion of deformed specimens in higher-level analyses of morphological disparity are warranted. Mean morphologies of distorted specimens are found to approximate the morphology of undistorted specimens, so we recommend use of species-level means in higher-level analyses when possible.

Lessons from Timor: Shells are poor taxonomic indicators in Asperitas land snails (Stylommatophora, Dyakiidae)

AbstractThe limacoid land snail Asperitas Gude, 1911 encompasses several vividly coloured, yet poorly known species that are distributed throughout the Lesser Sunda Islands, Sulawesi, and the Moluccas. We examined the variation in shell morphology, including the use of geometric morphometrics, and reproductive anatomy of snails from Timor and several adjacent islands. These studies revealed that none of the taxa described from Timor and considered to be endemic to this island could be reliably distinguished from any of the others. In addition to the systematic ambiguity of morphological characteristics, we uncovered rather low amounts of genetic differentiation in the mitochondrial marker cytochrome c oxidase subunit I that was not consistent with the current taxonomy. Based on these observations, we conclude that there is just a single Asperitas species on Timor that exhibits notable variability in shell characters and body colour. This variability is ascribed to the combined effects of polymorphic colour patterns with locally varying selection in different habitats and along altitudinal gradients. Individuals from the adjacent islands of Flores, Sumbawa, Solor and Romang, which are deemed to represent distinct species‐level taxa, exhibit similar amounts of variation in shell and body colour. They exhibit a consistent reproductive anatomy and overall negligible amounts of mitochondrial differentiation from the populations on Timor. Patterns in shell variation do not lend support to previously held ideas that different Sunda Islands harbour distinct radiations of polytypic Asperitas species. By contrast, we suggest that the taxonomic diversity of Asperitas has been overestimated for the over‐reliance on shell features and that many presently accepted taxa are likely mere synonyms of fewer and more widespread species.

Evaluating the effects of parallax in archaeological geometric morphometric analyses

Geometric morphometrics is a powerful set of techniques that can be used to visualize and analyze the shape of artifacts. With the growing use of geometric morphometrics in archaeology, it is important to understand and identify limitations in the method. One such limitation is the accumulation of measurement error. Here, we investigate the impact of parallax or the effect of the position of an object in relation to the camera. We designed an experiment to assess the effect of parallax on measurements of artifact morphology by photographing a sample of artifacts at close range (50 cm) and systematically shifting the fixed angle of the camera relative to the artifact in five steps: 90°, 95°, 100°, 105°, and 110°. We took digital images of geometric microliths from three Jordanian Epipalaeolithic sites at each of the camera angles. We then digitized the outline of each artifact using 24 sliding landmarks. Our subsequent analyses of microlith shapes grouped by camera angle show that they are statistically indistinguishable from each other, which suggests that within these parameters, parallax has little effect on geometric morphometric measurements. While taking digital images directly above artifacts is ideal, the angle at which previously published photographs of artifacts is sometimes unknown. Our findings suggest that small deviations of the camera angle (up to 20° from horizontal) will not significantly impact geometric morphometric analyses.

How unique is unique? Quantifying geometric differences in stripe patterns of Cape mountain zebra,Equus zebra zebra(Perissodactyla: Equidae)

AbstractQuantified coat pattern dissimilarity provides a visible surface for individual animal traceability to populations. We determined the feasibility in quantifying uniqueness of stripe patterns of Cape mountain zebra (CMZ; Equus zebra zebra) using geometric morphometrics. We photogrammetrically created dense surface models of CMZ (N = 56). Stripe edges were landmarked, superimposed and compared for shape variation across replicates and the population. Significant allometry in stripe patterns prompted allometric correction to remove increased curvature of stripes at the rump, belly and back with larger adult individuals, to facilitate equilibrated comparison between individuals. Re-landmarked replicates showed lower dissimilarity (Di) than non-replicates (Dp), representing minimal landmarking error. Individuals were 78.07 ± 1.79% unique (U=1−DiDp×100%) relative to the study population. Size, the number of torso stripes and degree of branching in four rear torso stripes described the most shape variation (36.79%) but a significant portion could only be distinguished with geometric morphometrics (41.82%). This is the first known use of geometric morphometrics to quantify coat pattern uniqueness, using a model species to provide baseline individual morphological variation. Measures of coat pattern similarity have a place in phenotypic monitoring and identification.

Objectifying processes: The use of geometric morphometrics and multivariate analyses on Acheulean tools

Nowadays, the fruitful discussion regarding the morphological variability of handaxes during the Middle Pleistocene has reached a decisive moment with the use of more accurate statistical methods, such as geometric morphometrics (GM) and multivariate analyses (MA). This paper presents a preliminary methodological approach for checking the utility of these new approaches on the analysis of the tools’ shape. It goes beyond the simple description of morphology and isolates the variables which define the final morphology of a tool. We compared two Middle Pleistocene sites, Boxgrove and Swanscombe, which are morphologically very different. Then, we applied the GM analysis on 1) 2D images, with two semi-landmark distributions: 28 semi-landmarks, specially concentrated on the tip and butt, and 60 equally spaced points; and 2) on 3D models using new software (AGMT3-D Software) including 5000 semi-landmarks. The more points used to define the tool’s outline, the more accurate will be the interpretation of the variables affecting shape. On the other hand, if the semi-landmarks are localized on specific sectors of the tool, a bias is created, by concentrating on those sectors, rather than the general tool shape. The 3D models offer a new dimension on the shape analysis, as their results mean the combination of plan-shape, profile-shape and the tool’s topography.

Epiplastral and geographic variation in &lt;em&gt;Echmatemys&lt;/em&gt;, a geoemydid turtle from the Eocene of North America: A multi-tiered analysis of epiplastral shape complexity

Author(s): Smith, Heather F.; Jager, Daniel; Hutchison, J. Howard; Adrian, Brent; Townsend, K.E. Beth | Abstract: Numerous geoemydid turtle fossils from the extinct genus Echmatemys have been recovered from the middle Eocene Uinta Formation, Uinta Basin, Utah over the past several decades. Here, we tested whether co-occurring Uintan species Echmatemys callopyge and E. uintensis can be reliably differentiated based on epiplastral morphology, and whether their geospatial distributions overlapped significantly. The geographic spatial and stratigraphic distributions of Uinta Basin E. callopyge and E. uintensis specimens were compared using ArcGIS and analysis of variance (ANOVA). The analysis revealed overlapping geographic distributions of these two species, and no significant differences in stratigraphic dispersal. This finding of extensive geospatial overlap between the two Uintan Echmatemys species highlights the need for accurate taxonomic identification, such as the gular scale morphology validated here. In addition, we sought to address a methodological question regarding the relative efficacy of data complexity in this context. Using epiplastra from three additional Eocene species of Echmatemys, we employed hierarchical analyses of increasing data complexity, from standard linear dimensions to 2D geometric morphometrics to 3D laser scans, to determine the degree to which data complexity contributes to taxonomic assessments within this genus. Uintan species E. callopyge and E. uintensis were found to differ significantly in epiplastral shape as captured by all three categories of data. These findings verify that these two co-occurring species can be differentiated consistently using the shape of the gular scale, and that the use of geometric morphometrics can improve identification of fragmentary specimens. Among the non-Uintan species, dorsal and ventral 2D landmark data reliably differentiated among species, but the linear dimensions were less useful.

The use of canid tooth marks on bone for the identification of livestock predation

Historically wolves and humans have had a conflictive relationship which has driven the wolf to extinction in some areas across Northern America and Europe. The last decades have seen a rise of multiple government programs to protect wolf populations. Nevertheless, these programs have been controversial in rural areas, product of the predation of livestock by carnivores. As a response to such issues, governments have presented large scale economic plans to compensate the respected owners. The current issue lies in the lack of reliable techniques that can be used to detect the predator responsible for livestock predation. This has led to complications when obtaining subsidies, creating conflict between landowners and government officials. The objectives of this study therefore are to provide a new alternative approach to differentiating between tooth marks of different predators responsible for livestock predation. Here we present the use of geometric morphometrics and Machine Learning algorithms to discern between different carnivores through in depth analysis of the tooth marks they leave on bone. These results present high classification rates with up to 100% accuracy in some cases, successfully differentiating between wolves, dogs and fox tooth marks.

Shaping up? A direct comparison between 2D and low-cost 3D shape analysis using African cichlid mandibles

Shape is a complex trait which can be investigated through a variety of methods that have been developed over the past century. Currently, ecologists and evolutionary biologists employ the use of geometric morphometrics on 2D images as their standard approach. Recently, there has been increased interest in the use of 3D methods. However, while low-cost 3D methods of data collection are becoming available their potential benefits are often more implied rather than quantified. Using the mandibles from two species of African cichlids (Maylandia zebra and Tropheops “Red Cheek”), this study aimed to evaluate the use of a low-cost 3D method of shape capture versus a range of 2D data sets (termed ‘standard’, ‘even’, and ‘extended’). Our findings indicated that while both 2D and 3D methods could discriminate differences in species and sexes there was only a slight improvement using 3D when landmark datasets were held even. Further, the standard approaches to data collection that would be taken by most researchers clearly outperformed our 3D approach. Therefore, as 3D methods become more accessible researchers should consider a cost/benefit ratio in terms of the time required to obtain 3D data versus shape information gained.

Geometric morphometrics of the forewing shape and size discriminate Plebeia species (Hymenoptera: Apidae) nesting in different substrates

AbstractHistorically, studies evaluating morphological diversity in stingless bees (Hymenoptera, Apidae: Meliponini) by geometric morphometrics have been used to successfully discriminate taxa and/or populations. Moreover, the use of geometric morphometrics to evaluate phylogenetic morphological variation among stingless bee species has received less attention. Here, we used geometric morphometrics to assess taxonomic discrimination and putative phylogenetic signals for six diapausing stingless bee species (Plebeia) occurring in southern Brazil. In all, 12 landmarks were captured from forewings of P. droryana, P. saiqui, P. emerina, P. remota, P. nigriceps and P. wittmanni. Our data show that the centroid size of the forewings reliably discriminated, for example, between P. droryana and P. emerina from P. saiqui. Moreover, this trait does not have a significant phylogenetic signal. In turn, we found that the overall accuracy in discriminating between the six Plebeia species according to forewing shape was 84%, while the confusion matrix achieved 71%. Interestingly, our discriminant analysis separated Plebeia species nesting in tree cavities from those nesting under granitic rocks. The latter group has second cubital (landmarks = 5, 6, 7), first medial (landmarks = 2, 3, 8) and first submarginal cells (landmarks = 3, 4, 9, 10) that are larger than those of species nesting in trees. The forewing shape showed a strong phylogenetic signal, therefore suggesting that its variation may be due to an evolutionary history shared between Plebeia species studied here rather than to environmental features. This work sheds light on the value of forewing size and shape attributes in discriminating Plebeia species within same genus. We suggest that landmarks separating different taxonomic groups could be incorporated into dichotomous keys to help in identifying clades of complex resolution.