Geometric Morphometric Methods Research Articles

Mining tailings alter insects: revealing fluctuating asymmetry in the caddisfly Smicridea coronata.

The Samarco/Vale/BHP mine tailing dam breach that took place in Minas Gerais, southeastern Brazil, in 2015, deposited high concentrations of metals and metalloids in the Rio Doce basin, severely impacting freshwater and riverine forest ecosystems. To assess developmental instability of caddisflies in response to the environmental impacts of the dam breach, we investigated the fluctuating asymmetry (FA) in the species Smicridea (Rhyacophylax) coronata (Trichoptera: Hydropsychidae). FA was assessed at individual and populational scales using geometric morphometric methods in the cephalic capsule and mandibles of larvae and also on the forewings of adults, both collected under the impacted condition, and under the least disturbed condition. The levels of FA increased in response to stressors on the forewings at the populational scale, and on the mandibles, at individual scale. These morphological variations in the larval and adult stages may lead to detrimental effects and result in high mortality rates as well as lower adult fitness. Trichoptera forewings are revealed as suitable traits for assessing FA, holding potential for applications in biomonitoring programs. Directional asymmetry levels were higher than FA levels for all traits, and this correlation could be explained by a transition from fluctuating to directional asymmetry in the presence of heightened disturbance. Our results validate the relationship between the impacts from the dam breach and increased developmental instability in this species with likely cascade effects on the insect community.

Skull asymmetry in various sheep breeds: Directional asymmetry and fluctuating asymmetry.

Sheep (Ovis aries) play an important role in the economy of Turkey and the Balkan Peninsula due to their use in farming. As a domesticated species, sheep's morphometric and morphological diversity is likely determined by selective breeding practices rather than geographic distribution. This study aimed to analyse four different sheep breed skulls and reveal skull asymmetry using geometric morphometric methods. For this purpose, 2D images of 52 sheep skulls from different breeds were analysed from the dorsal view of the skull, using 28 landmarks. In the comparison of sheep skulls from the dorsal view, the first principal components for directional asymmetry (DA) and fluctuating asymmetry (FA) were 32.98% and 39.62% of the total variation, respectively. Sharri and Ivesi (Awassi) sheep breeds had the broadest distribution of skull shapes among the breeds, while Lara e Polisit was the most conservative breed. DA was used as a measure of biomechanical constraints, and FA was used as an indicator of environmental stress. Consistent with DA, both differences in centroid size and shape between breeds were statistically significant. No differences between males and females related to asymmetry were revealed. Ivesi sheep revealed the highest fluctuating asymmetry. Geometric morphometric methods proved to be a useful tool for distinguishing differences in the shape of the skull of different sheep breeds and also can be useful for taxonomic purposes.

Geometric morphometric evaluation of mandibles of four sheep breeds: Bardoka, İvesi, Polish Mountain sheep and Turcana.

The enduring relationship between humans and domestic sheep has evolved over millennia, showcasing diverse uses such as meat, milk, wool, leather and fur, shaped by geographical, historical, cultural and social factors. The sheep breeds discussed include the Ivesi from Southeastern Anatolia, known for its varied animal products; the resilient Turcana breed of Romania; Kosovo's Bardoka, valued for its triple-purpose characteristics; and Poland's Polish Mountain Sheep, uniquely utilized for milk production in cheese making. Sheep, with their enduring relationship with humans and significant economic importance, have attracted scientific interest in morphometric studies of their mandibles, yielding valuable data applicable across various fields including basic anatomy, veterinary clinical anatomy, zooarchaeology and veterinary forensic medicine. Traditional morphometric studies rely on statistical methods to compare length, depth and angular ratios between anatomical formations, often highlighting differences between specific points but not fully revealing shape variations between distinct groups. Geometric morphometric analysis has emerged as a preferred method in recent years, enabling shape analyses using coordinate data from various imaging techniques, facilitating a comprehensive examination of mandibular morphometrics among sheep breeds across different countries. This study involved four sheep breeds from different countries, namely İvesi from Turkey, Bardoka from Kosovo, Polish Mountain Sheep from Poland and Turcana from Romania, with a total of 70 mandibles sourced from various veterinary faculties. Mandibular photographs were meticulously captured, focusing on the right side of mandible pairs and placing landmarks and semi-landmarks along the entire edge, enabling geometric morphometric analysis using tpsUtil, tpsDig2 and MorphoJ software. The analysis included principal component analysis, canonical variate analysis and discriminant function analysis for pairwise comparisons, facilitating a comprehensive examination of mandibular shape variations among the different sheep breeds. Using geometric morphometric methods, this study analysed mandibles from four distinct sheep breeds sourced from different countries, revealing notable variations in regions such as the ramus mandibula, angulus mandibula and incisive areas, attributed to genetic, geographical and dietary influences, highlighting the importance of continued research to better comprehend these shape differences.

Ontogenetic changes in jaw leverage and skull shape in tufted and untufted capuchins.

The ontogeny of feeding is characterized by shifting functional demands concurrent with changes in craniofacial anatomy; relationships between these factors will look different in primates with disparate feeding behaviors during development. This study examines the ontogeny of skull morphology and jaw leverage in tufted (Sapajus) and untufted (Cebus) capuchin monkeys. Unlike Cebus, Sapajus have a mechanically challenging diet and behavioral observations of juvenile Sapajus suggest these foods are exploited early in development. Landmarks were placed on three-dimensional surface models of an ontogenetic series of Sapajus and Cebus skulls (n = 53) and used to generate shape data and jaw-leverage estimates across the tooth row for three jaw-closing muscles (temporalis, masseter, medial pterygoid) as well as a weighted combined estimate. Using geometric morphometric methods, we found that skull shape diverges early and shape is significantly different between Sapajus and Cebus throughout ontogeny. Additionally, jaw leverage varies with age and position on the tooth rowand is greater in Sapajus compared to Cebus when calculated at the permanent dentition. We used two-block partial least squares analyses to identify covariance between skull shape and each of our jaw muscle leverage estimates. Sapajus, but not Cebus, has significant covariance between all leverage estimates at the anterior dentition. Our findings show that Sapajus and Cebus exhibit distinct craniofacial morphologies early in ontogeny and strong covariance between leverage estimates and craniofacial shape in Sapajus. These results are consistent with prior behavioral and comparative work suggesting these differences are a function of selection for exploiting mechanically challenging foods in Sapajus, and further emphasize that these differences appear quite early in ontogeny. This research builds on prior work that has highlighted the importance of understanding ontogeny for interpreting adult morphology.

Variety is the spice: the role of morphological variation of Triatoma infestans (Hemiptera, Reduviidae) at a macro-scale§

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi (Chagas, 1909). One of the primary vectors of T. cruzi in South America is Triatoma infestans (Klug, 1834). This triatomine species is distributed across a huge latitudinal gradient, inhabiting domiciliary , peridomiciliary , and wild environments. Its wide geographic distribution provides an excellent opportunity to study the relationships between environmental gradients and intraspecific morphological variation. In this study, we investigated variations in wing size and shape in T. infestans across six ecoregions. We aimed to address the following questions: How do wing size and shape vary on a regional scale, does morphological variation follow specific patterns along an environmental or latitudinal gradient, and what environmental factors might contribute to wing variation? Geometric morphometric methods were applied to the wings of 162 females belonging to 21 T. infestans populations, 13 from Argentina (n = 105), 5 from Bolivia (n = 42), and 3 from Paraguay (n = 15). A comparison of wing centroid size across the 21 populations showed significant differences. Canonical Variate Analysis (CVA) revealed significant differences in wing shape between the populations from Argentina, Bolivia, and Paraguay, although there was a considerable overlap, especially among the Argentinian populations. Well-structured populations were observed for the Bolivian and Paraguayan groups. Two analyses were performed to assess the association between wing size and shape, geographic and climatic variables: multiple linear regression analysis (MRA) for size and Partial Least Squares (PLS) regression for shape. The MRA showed a significant general model fit. Six temperature-related variables, one precipitation-related variable, and the latitude showed significant associations with wing size. The PLS analysis revealed a significant correlation between wing shape with latitude, longitude, temperature-related, and rainfall-related variables. Wing size and shape in T. infestans populations varied across geographic distribution. Our findings demonstrate that geographic and climatic variables significantly influence T. infestans wing morphology.

Sex‐specific consequences of host shift for morphology and fluctuating asymmetry in a seed beetle: an experimental evolution approach

AbstractMorphological plasticity may be induced by altering host plants and commonly it is sex‐specific in phytophagous insects. It is hypothesized that stress in insects caused by a host shift leads to morphological changes and developmental destabilization, which may be identified by fluctuating asymmetry. We performed reciprocal transplant experiments in eight replicated populations of the seed beetle Acanthoscelides obtectus (Say) (Coleoptera: Chrysomelidae, Bruchinae) adapted to common bean (Phaseolus vulgaris L., Fabaceae) as its ancestral host and chickpea (Cicer arietinum L., Fabaceae) as a suboptimal host. Using methods of geometric morphometrics we assessed the effects of the short‐ and long‐term host shift on size and shape variation of beetles of both sexes. We also tested the hypothesis that fluctuating asymmetry is lower when the beetles develop within seeds of the ancestral host. Our results showed that females respond more plastically related to their body size and shape of the abdomen, particularly during a short‐term host shift, suggesting that females have a greater importance in maintaining the population on a new host. The level of fluctuating asymmetry is lowest in males that have evolved for generations on bean indicating that they have the most canalized development, so we suggested that symmetry in A. obtectus is maintained by sexual selection. Even if the beetles are adapted to a suboptimal host over many generations, they stabilize their development after returning to the ancestral host. Our work indicates that host shifts may change morphological aspects of the beetles in a sex‐specific manner and consequently influence their developmental trajectories.

Capturing the cervical spine shape: Angular measurements versus geometric morphometric methods.

The cervical spine manifests a wide shape variation. However, the traditional methods to evaluate the cervical spine curve were never tested against its actual shape. The study's main aim was to determine whether the shape classification of the cervical spine, based on traditional angular measurements, coincides with each other and with the shape captured by the 2D landmark-based geometric morphometric method. The study's second aim was to reveal the associations between the cervical spine shape and the demographic parameters, the head's position, and the spine's sagittal balance. CT scans of the cervical spine of 163 individuals were evaluated to achieve these goals. The shape was assessed by measuring the C2-C7 Cobb angle (CA), the C2-C7 posterior tangent angle (PTA), the curvedness of the arch, and by a 2D landmark-based geometric morphometric method. The position of the head and the sagittal balance of the spine were evaluated by measuring the foramen magnum-C2 Cobb angle (FMCA) and the T1 slope angle (T1SA), respectively. Based on the size of the angle measured, each individual was classified into one of the three cervical 'shape groups' (lordotic, straight, and kyphotic). We found that cervical lordosis was the dominant shape regardless of the measuring methods utilized (46.6%-54.6%), followed by straight neck (28.2%-30.1%), and kyphosis (15.3%-25.2%); however, about a third of the 163 individuals were classified into a different shape group using the CA and PTA methods. The cervical spine angle was sex-independent and age-dependent. The T1SA was significantly correlated with CA and PTA (r = 0.640 and r = 0.585, respectively; p < 0.001). In conclusion, the cervical spine shape evaluation is method-dependent and varies with age.

Cranial variation in species and subspecies of kangaroo rats (Dipodomys, Dipodomyinae, Rodentia) according to geometric morphometrics.

Traditional Dipodomys (sub)species identification uses geography, phenotype, and external/skull measurements. Such measurements are correlated with size and thus redundant. I assessed the value of scaled cranial shape, based on two-dimensional landmarks (analyzed using geometric morphometric methods) in distinguishing Dipodomys taxa, and in summarizing their variation. My dataset includes 601 adult specimens from 20 species (49 operational taxonomic units - OTUs) across 190 localities. Cranial shape was highly useful in classifying Dipodomys taxa without considering geography. The auditory bulla was the most variable region-taxa differed in its hypertrophy, accompanied by different degrees of nearby structure crowding. Cranial shape was weakly allometric, with no significant sexual dimorphism. Weak size dimorphism was detected. (Sub)specific taxonomy is not reflective of shape variation, as the number of subspecies per species is not associated with disparity. Shape had significant phylogenetic signal, but subspecies did not always cluster with conspecifics and species did not always cluster according to phylogenetic relationship/taxonomy. Shape variation was correlated with climate, and species differed in morphological disparity and degree of specialization, which may contribute to divergence in shape variation patterns from phylogeny. D. deserti was the most specialized species, diverging greatly from the genus mean; D. heermanni was the least specialized. This study provides new insights into morphological variation of North American keystone species, several of conservation interest, for example, D. heermanni berkeleyensis, D. h. dixoni, D. nitratoides brevinasus, and D. n. nitratoides.

Variation in the shape and size of the scale of the Tigris bream (Acanthobrama marmid, Heckel, 1843) from the Tigris River, Türkiye attributed to Seasonality, Age and Sex: A geometric morphometric study

In this study, the Tigris bream Acanthobrama marmid individuals (44 females and 31 males) were captured from the Tigris River. The scale size (as centroid size) and shape were analyzed separately using 2–dimensional geometric morphometric methods. Procrustes ANOVA revealed significant differences in scales size between sexes, while no difference in shape was observed. Groups based on season and age showed significant differences in both size and shape. Female individuals had larger scale sizes than males, with the scales of the Autumn group being larger than those of the Spring and Summer groups. Scale size also increased with age groups. PCA analysis showed variation in the first five components when examined by age, season, and gender. CVA and DFA results indicated significant differences in shape between different age groups and seasonal groups, but no significant differences between sexes were observed.

Morphological and molecular data combined reveal inter- and intraspecific cranial shape variations in bats of Artibeus Leach, 1821 (Chiroptera: Phyllostomidae)

Abstract Since morphological traits may overlap among species within a complex, the integration of morphological and mitochondrial data could provide crucial insights for distinguishing species, as observed in fruit-eating bats of the genus Artibeus. Therefore, the application of geometric morphometric (GM) techniques could yield more refined and robust analyses of inter- and intraspecific variations. In this study, we generated two datasets: one with molecular delimitation data based on the barcode region (COI) and the other with cranial size and shape data using GM methods. Our aims were to investigate variations between large and small species within the genus Artibeus, as well as to explore potential factors influencing such variations. The results from species delimitation revealed molecular operational taxonomic units (MOTUs) supporting the morphological identification. Analyses using GM techniques demonstrated significant inter- and intraspecific variations in cranial size and shape among Artibeus species. The combined outcomes suggest the absence of a significant phylogenetic signal influencing skull variation. This scenario indicates that potential historical ecological factors may have directly influenced the cranial morphology of these species, acting as significant selection forces in geographical space and generating intraspecific variations in Artibeus planirostris.

Relationship between genetic diversity and morpho-functional characteristics of flight-related traits in Triatoma garciabesi (Hemiptera: Reduviidae)

BackgroundTriatoma garciabesi, a potential vector of the parasitic protozoan Trypanosoma cruzi, which is the causative agent of Chagas disease, is common in peridomestic and wild environments and found throughout northwestern and central Argentina, western Paraguay and the Bolivian Chaco. Genetic differentiation of a species across its range can help to understand dispersal patterns and connectivity between habitats. Dispersal by flight is considered to be the main active dispersal strategy used by triatomines. In particular, the morphological structure of the hemelytra is associated with their function. The aim of this study was to understand how genetic diversity is structured, how morphological variation of dispersal-related traits varies with genetic diversity and how the morphological characteristics of dispersal-related traits may explain the current distribution of genetic lineages in this species.MethodsMales from 24 populations of T. garciabesi across its distribution range were examined. The cytochrome c oxidase I gene (coI) was used for genetic diversity analyses. A geometric morphometric method based on landmarks was used for morpho-functional analysis of the hemelytra. Centroid size (CS) and shape of the forewing, and contour of both parts of the forewing, the head and the pronotum were characterised. Length and area of the forewing were measured to estimate the aspect ratio.ResultsThe morphometric and phylogenetic analysis identified two distinct lineages, namely the Eastern and Western lineages, which coincide with different ecological regions. The Eastern lineage is found exclusively in the eastern region of Argentina (Chaco and Formosa provinces), whereas the Western lineage is prevalent in the rest of the geographical range of the species. CS, shape and aspect ratio of the hemelytra differed between lineages. The stiff portion of the forewing was more developed in the Eastern lineage. The shape of both portions of the hemelytra were significantly different between lineages, and the shape of the head and pronotum differed between lineages.ConclusionsThe results provide preliminary insights into the evolution and diversification of T. garciabesi. Variation in the forewing, pronotum and head is congruent with genetic divergence. Consistent with genetic divergence, morphometry variation was clustered according to lineages, with congruent variation in the size and shape of the forewing, pronotum and head.Graphical

Beyond the dominant narratives: Identifying Indigenous and African individuals in Quebec St-Lawrence Valley colonial cemeteries by three-dimensional morphometrical analysis of the temporal bone

In Quebec, written accounts of free or enslaved Indigenous and African individuals during colonial times are few and limited. Three-dimensional geometric morphometric methods applied on 214 temporal bones individuals are used to explore intra-cemetery population variation throughout three centuries (1683–1878), to identify plausible non-European or admixed individuals. First, Principal Component Analysis (PCA) was generated from populations originated from Africa, North-America (Indigenous) and Europe where colonial cemeteries are projected to assess their degree of overlap with the reference groups. Second, Discriminant Function Analysis (DFA) based on typicality probabilities also allowed to assign unknown individuals to the three reference groups. Our results highlighted discrepancy between PCA and DFA. With the PCA, Quebec colonial groups overlap with the Europeans except for three individuals. For the DFA, 64 % (n = 136) were classified as typical to one group and 36 % as atypical (n = 77). Most were European, (82 %; n = 112), followed by those as Indigenous (7 %; n = 10), intermediate between Africans and Indigenous (6 %; n = 8) and Africans (5 %; n = 7). Compared with previous research, one individual from the first Protestant cemeteries of St-Matthew in Quebec could be assessed as plausible African or admixed origin. Two others need further analysis: one from St-Matthew and one from the first Catholic cemetery of Notre-Dame in Montreal. Finally, in response to dominant narratives that focused mainly on Euro-colonists, this research provided for the first time a new snapshot of several colonial population diversity in Quebec, underlining the presence of marginalized groups -especially those of African origin, who are absent from the archaeological reports under study.

Geometric morphometrics of silky pocket mice (Perognathus: Perognathinae: Rodentia) crania reveals new insights into their variation, evolution, and taxonomy

Abstract We used cranial geometric morphometric methods (GMM) to explore interspecific variation in Perognathus (silky pocket mice). We digitized 67 cranial landmarks on photographs of 305 adult voucher specimens (10 species and 33 subspecies, 121 localities). After summarizing variation patterns, we explored their association with biological, ecological, and climatic factors, and how (and why) shape evolved through time. Phenotypic clusters did not accord with phylogenetic clades, and we found instances of convergence, divergence, and increased rates of shape change. These are discussed in terms of shared selective pressures (e.g. habitat substrate and burrowing plus historic shifts in habitat/climate and desert adaptation). We also used variation patterns and phenetics to address ongoing taxonomic issues. While pocket mice are difficult to distinguish externally, GMM allowed us to precisely characterize interspecific cranial variation. Species significantly differed and could be classified based on their shape. We find P. alticola to be the most cranially distinct species and suggest raising the P. alticola + P. parvus (including P. mollipilosus) cluster/clade to subgenus status (=Cricetodipus). Cranial GMM found differences among taxa that seemed similar (i.e. cryptic) when previously explored using linear measurements (e.g. P. parvus vs. P. mollipilosus).

Geometric morphometric methods for identification of oyster species based on morphology.

Both genetic and environmental factors affect the morphology of oysters. Molecular identification is currently the primary means of species identification, but it is inconvenient and costly. In this research, we evaluated the effectiveness of geometric morphometric (GM) techniques in distinguishing between two oyster species, Crassostreagigas and C.ariakensis. We used traditional morphometric and GM methods, including principal component analysis (PCA), thin-plate spline analysis (TPS) and canonical variable analysis (CVA), to identify specific features that distinguish the two species. We found that differences in shape can be visualised using GM methods. The Procrustes analysis revealed significant differences in shell morphology between C.gigas and C.ariakensis. The shells of C.ariakensis are more prominent at the widest point and are more scattered and have a greater variety of shapes. The shells of C.gigas are more oval in shape. PCA results indicated that PC1 explained 45.22%, PC2 explained 22.09% and PC3 explained 10.98% of the variation between the two species, which suggests that the main morphological differences are concentrated in these three principal components. Combining the TPS analysis function plots showed that the shell shape of C.ariakensis is mainly elongated and spindle-shaped, whereas the shell shape of C.gigas is more oval. The CVA results showed that the classification rate for the two species reached 100% which means that C.ariakensis and C.gigas have distinct differences in shell morphology and can be completely separated, based on morphological characteristics. Through these methods, a more comprehensive understanding of the morphological characteristics of different oyster populations can be obtained, providing a reference for oyster classification and identification.

Advances in the Clinical Diagnostics to Equine Back Pain: A Review of Imaging and Functional Modalities.

Back pain is common in ridden horses. Back diseases in horses include Impinging Dorsal Spinous Processes, Ventral Spondylosis, Osteoarthritis of Articular Process, Intervertebral Discs Disease, Vertebral Fractures, Conformational Abnormalities, Desmopathy of the Supraspinous Ligament, Desmopathy of the Intraspinous Ligament, and Longissimus Muscle Strain. Back pain may also develop as a result of lameness (particularly hindlimb lameness). A poorly fitting saddle and an unbalanced rider are also considered important factors influencing the development of back pain in horses. The conventional diagnosis of equine back pain includes a clinical examination and diagnostic imaging examination using ultrasound, radiography, and thermography. Advanced diagnostic modalities of equine back pain involve the objectification of standard procedures through the use of algometers, a lameness locator, biometric mats, and the geometric morphometrics method. In addition to modern diagnostic methods, such as computed tomography and scintigraphy, advances in the diagnosis of equine back pain include the use of electromyography and functional electrical stimulation. The aim of this review article is to familiarize clinicians with the usefulness and capabilities of conventional diagnostic protocols and advanced diagnostic modalities. Although orthopedic examination and traditional diagnostic methods will remain the foundation of the diagnosis of back diseases, modern methods meet the growing expectations towards high-performance horses and allow for deeper diagnostics and objective monitoring of rehabilitation and training progress.

Maxillary first premolar shape (and not size) as an indicator of sexual dimorphism: A 2D geomorphometric study.

The primary aim of the study is to evaluate the morphological form of the maxillary first premolar using 2D geomorphometry and evaluate the sexually dimorphic characteristics. The present study was carried out on standardized photographs of right Maxillary first premolar from 120 dental casts (60 male and 60 females). Twenty landmarks (based on geometric and anatomic evidence) were marked on the tooth using TPSdig software and analysed using Morpho J applying procrustes analysis and discriminant function analysis. The results showed similar centroid sizes between gender (p = 0.541). Procrustes ANOVA for shape analysis showed a greater dimorphism between sexs (f value of 1.35; p value=0.0793). Discriminant function analysis based on the procrustes coordinates showed an overall accuracy of 74.2 % in classifying sex based on the landmark coordinates with correct classification of 48/60 (80.00%) females and 41/60 (68.33) males. Shape of the tooth can be measured objectively using geometric morphometric methods which can be utilized to identify the sex of an individual. The enamel is derived from ectoderm and once formed does not change during the life. The tooth's structure and shape are determined by the sex chromosomes, which is well represented as sexual dimorphism. The study evaluates the occlusal and contact area morphology of premolars. These are important parameters considered during restorative treatment, functional rehabilitation and forensic investigations.

Bill shape reflects divergent prey consumption for island compared to mainland American kestrels (Falco sparverius)

Abstract Feeding morphology permits animals to adapt to changing environments and is often under strong selection. We evaluated if bill shape varies according to differences in dietary prey taken across geographical ranges (North America, Central America, South America, and Caribbean islands) in a ubiquitous, New World raptor species, the American kestrel (Falco sparverius). Specifically, we predicted that bills in geographies where kestrels consumed a larger proportion of vertebrates would be shorter and wider, with a larger tomial tooth. We reviewed the literature on kestrel diets across their range and quantified potential differences in bill shape using geometric morphometric methods for 245 museum specimens. The literature review revealed that most prey consumed by kestrels in North, South, and Central America were invertebrates (51.6–69.1%), whereas Caribbean kestrels consumed mostly vertebrates (61.4%), most of which were reptiles (77.3%). Morphometric analyses agreed with these findings; bill shape differed for island versus mainland kestrels but not among mainland regions. Bill shape on islands reflected a more robust bill with a larger tomial tooth, but had a longer hook, which we suggest is adaptive for consumption of lizard prey, more available on islands due to reduced competition with other raptors compared to mainland regions.

Geometry of posterior larval spiracles to identify medically and forensically important calliphorids in Thailand

Fly identification is the primary step of analysis in forensic entomology. Although morphology and molecular techniques are considered satisfactory methods, some constraints may arise from a financial or even human point of view. Over the past decade, the geometric morphometric approach has been increasingly advocated for the classification and identification of arthropods. This study explored the method for species identification of 800 third-instar larvae of eight blow fly species of medical and forensic importance: Chrysomya chani Kurahashi, Chrysomya megacephala (Fabricius), Chrysomya (Ceylonomyia) nigripes Aubertin, Chrysomya pinguis (Walker), Chrysomya (Achoetandrus) rufifacies (Macquart), Hemipyrellia ligurriens (Wiedemann), Lucilia cuprina (Wiedemann), and Lucilia porphyrina (Walker). Based on the posterior spiracles geometry, the cross-validation revealed a relatively high percentage of correct classification in most species, ranking from 86% to 100%. The results of this study confirmed that the geometric morphometric (GM) analysis of posterior spiracles might be utilized as a larva identification tool. Therefore, this GM method represents one way of overcoming difficulties with the identification of blow fly larvae and can support further studies of these flies.

Species identification through deep learning and geometrical morphology in oaks (Quercus spp.): Pros and cons.

Plant phenotypic characteristics, especially leaf morphology of leaves, are an important indicator for species identification. However, leaf shape can be extraordinarily complex in some species, such as oaks. The great variation in leaf morphology and difficulty of species identification in oaks have attracted the attention of scientists since Charles Darwin. Recent advances in discrimination technology have provided opportunities to understand leaf morphology variation in oaks. Here, we aimed to compare the accuracy and efficiency of species identification in two closely related deciduous oaks by geometric morphometric method (GMM) and deep learning using preliminary identification of simple sequence repeats (nSSRs) as a prior. A total of 538 Asian deciduous oak trees, 16 Q. aliena and 23 Q. dentata populations, were firstly assigned by nSSRs Bayesian clustering analysis to one of the two species or admixture and this grouping served as a priori identification of these trees. Then we analyzed the shapes of 2328 leaves from the 538 trees in terms of 13 characters (landmarks) by GMM. Finally, we trained and classified 2221 leaf-scanned images with Xception architecture using deep learning. The two species can be identified by GMM and deep learning using genetic analysis as a priori. Deep learning is the most cost-efficient method in terms of time-consuming, while GMM can confirm the admixture individuals' leaf shape. These various methods provide high classification accuracy, highlight the application in plant classification research, and are ready to be applied to other morphology analysis.

Maxillary morphology of chimpanzees: Captive versus wild environments.

Morphological studies typically avoid using osteological samples that derive from captive animals because it is assumed that their morphology is not representative of wild populations. Rearing environments indeed differ between wild and captive individuals. For example, mechanical properties of the diets provided to captive animals can be drastically different from the food present in their natural habitats, which could impact cranial morphology and dental health. Here, we examine morphological differences in the maxillae of wild versus captive chimpanzees (Pan troglodytes) given the prominence of this species in comparative samples used in human evolution research and the key role of the maxilla in such studies. Size and shape were analysed using three-dimensional geometric morphometric methods based on computed tomography scans of 94 wild and 30 captive specimens. Captive individuals have on average larger and more asymmetrical maxillae than wild chimpanzees, and significant differences are present in their maxillary shapes. A large proportion of these shape differences are attributable to static allometry, but wild and captive specimens still differ significantly from each other after allometric size adjustment of the shape data. Levels of shape variation are higher in the captive group, while the degree of size variation is likely similar in our two samples. Results are discussed in the context of ontogenetic growth trajectories, changes in dietary texture, an altered social environment, and generational differences. Additionally, sample simulations show that size and shape differences between chimpanzees and bonobos (Pan paniscus) are exaggerated when part of the wild sample is replaced with captive chimpanzees. Overall, this study confirms that maxillae of captive chimpanzees should not be included in morphological or taxonomic analyses when the objective is to characterise the species.