Allometry and phylogenetic divergence: Correspondence or incongruence?

The potential connection between trends of within species variation, such as those of allometric change in morphology, and phylogenetic divergence has been a central topic in evolutionary biology for more than a century, including in the context of human evolution. In this study, I focus on size-related shape change in craniofacial proportions using a sample of more than 3200 adult Old World monkeys belonging to 78 species, of which 2942 specimens of 51 species are selected for the analysis. Using geometric morphometrics, I assess whether the divergence in the direction of static allometries increases in relation to phyletic differences. Because both small samples and taxonomic sampling may bias the results, I explore the sensitivity of the main analyses to the inclusion of more or less taxa depending on the choice of a threshold for the minimum sample size of a species. To better understand the impact of sampling error, I also use randomized subsampling experiments in the largest species samples. The study shows that static allometries vary broadly in directions without any evident phylogenetic signal. This variation is much larger than previously found in ontogenetic trajectories of Old World monkeys, but the conclusion of no congruence with phylogenetic divergence is the same. Yet, the effect of sampling error clearly contributes to inaccuracies and tends to magnify the differences in allometric change. Thus, morphometric research at the boundary between micro- and macro-evolution in primates, and more generally in mammals, critically needs very large and representative samples. Besides sampling error, I suggest other non-mutually exclusive explanations for the lack of correspondence between allometric and phylogenetic divergence in Old World monkeys, and also discuss why directions might be more variable in static compared to ontogenetic trajectories. Even if allometric variation may be a poor source of information in relation to phylogeny, the evolution of allometry is a fascinating subject and the study of size-related shape changes remains a fundamental piece of the puzzle to understand morphological variation within and between species in primates and other animals.

Phylogenetics, Molecular Species Delimitation and Geometric Morphometrics of All Reddish-Brown Species in the Genus Neotriplax Lewis, 1887 (Coleoptera: Erotylidae: Tritomini).

To date, five species of reddish-brown Neotriplax have been described, but their highly similar body color and other phenotypic traits make accurate taxonomy challenging. To clarify species-level taxonomy and validate potential new species, the cytochrome oxidase subunit I (COI) was used for phylogenetic analysis and the geometric morphometrics of elytron, pronotum, and hind wing were employed to distinguish all reddish-brown Neotriplax species. Phylogenetic results using maximum likelihood and Bayesian analyses of COI sequences aligned well with the current taxonomy of the Neotriplax species group. Significant K2P divergences, with no overlap between intra- and interspecific genetic distances, were obtained in Neotriplax species. The automatic barcode gap discovery (ABGD), assemble species by automatic partitioning (ASAP), and generalized mixed Yule coalescent (GMYC) approaches concurred, dividing the similar species into eight molecular operational taxonomic units (MOTUs). Geometric morphometric analysis using pronotum, elytron, hind wing shape and wing vein patterns also validated the classification of all eight species. By integrating these analytical approaches with morphological evidence, we successfully delineated the reddish-brown species of Neotriplax into eight species with three new species: N. qinghaiensis sp. nov., N. maoershanensis sp. nov., and N. guangxiensis sp. nov. Furthermore, we documented the first record of N. lewisii in China. This study underscores the utility of an integrative taxonomy approach in species delimitation within Neotriplax and serves as a reference for the taxonomic revision of other morphologically challenging beetles through integrative taxonomy.

Three-dimensional geometric morphometric shape analysis of chest wall kinematics in different breathing conditions.

Breathing motion is based on the differential activity of the thoracic, diaphragmatic and abdominal muscles. Muscle contributions differ between rest and exercise conditions and depend on posture and other factors. Traditionally, these changes are investigated on volumetric data using optoelectronic plethysmography (OEP). OEP offers insight into size variations of different chest wall (CW) compartments but does not provide three-dimensional visualization methods of CW breathing kinematics. Here we explore the use of three-dimensional geometric morphometrics to analyse size and shape changes caused by spontaneous breathing motion during quiet (QB), and recovery breathing (REC, immediately after heavy exercise) in two different postures (SIT, sitting on cycle ergometer; STA, standing position). Our findings show that size and shape differ significantly between inspiration and expiration and that differences are greater in REC than in QB. However, this is achieved by stronger expiration in SIT but by greater expiratory and inspiratory movements in STA. Shape analysis suggests that these differences may be attributed to constrained mobility of the shoulder girdle and a minor thoracic spine extension during inspiration owing to position on the ergometer. Breathing motion in STA seems biomechanically less constrained. Geometric morphometrics analyses can provide additional insights into data obtained by OEP.

On the wing: Morphological variation in the osteology of Mediterranean, Near Eastern, and European Anatidae (excluding Anserinae).

Accurate identification of waterfowl bones in archaeological and fossil assemblages has potential to unlock new methods of past environmental reconstruction, as species have differing habitat preferences and migration patterns. Therefore, identifying the presence of avian species with different ecological niches is key to determining past environments and ultimately how prehistoric people responded to climatic and environmental realignments. However, the identification of osteological remains of waterbirds such as ducks to species level is notoriously challenging. We address this by presenting a new two-dimensional geometric morphometric protocol on wing elements from over 20 duck species and test the utility of these shape data for correct species identification. This is an ideal starting point to expand utilization of these types of approaches in avifaunal research and test applicability to an extremely difficult taxonomic group.

Morphological and morphometric study of the hominin dental casts from Grotta-Riparo di Uluzzo C (Apulia, southern Italy).

OBJECTIVES: Grotta-Riparo di Uluzzo C (Apulia, southern Italy) is a pivotal site for investigating the evolution of the Middle Paleolithic and the earliest phases of the Upper Paleolithic in southern Italy, as the extensive stratigraphic record of this site includes a thick Mousterian sequence followed by the Uluzzian. Here, we investigate the taxonomic affinity of seven unpublished deciduous human teeth retrieved from the site of Uluzzo C in 1960. MATERIALS AND METHODS: The teeth are represented by seven plaster dental casts, which are housed at the Museo Civico di Paleontologia e Paletnologia in Maglie (Lecce, Apulia). The location of the original specimens remains unknown, rendering these casts the only human remains evidence yielded by Uluzzo C to date. Based on occlusal-view photographs and digital models of the casts, we examined the external morphology and morphometry of the teeth, comparing them to Homo sapiens and H. neanderthalensis samples. Through geometric morphometric methods and statistical analyses, we analyzed the crown outline of the deciduous molars. RESULTS: The teeth show morphological and morphometric features that are variably found in H. neanderthalensis, H. sapiens, or both. Specifically, crown outline analysis shows that all molars fall within H. neanderthalensis variability, except for Uluzzo 853 (lower right deciduous first molar), which falls within H. sapiens variability. DISCUSSION: This study provides the first taxonomic assessment of the hominin teeth from Uluzzo C. The results contribute additional insights into the Paleolithic peopling of southern Italy during a crucial period marked by the persistence of post-Tyrrhenian Neanderthal techno-complexes and the arrival of H. sapiens.

Functional data geometric morphometrics with machine learning for craniodental shape classification in shrews.

This work proposes a functional data analysis approach for morphometrics in classifying three shrew species (S. murinus, C. monticola, and C. malayana) from Peninsular Malaysia. Functional data geometric morphometrics (FDGM) for 2D landmark data is introduced and its performance is compared with classical geometric morphometrics (GM). The FDGM approach converts 2D landmark data into continuous curves, which are then represented as linear combinations of basis functions. The landmark data was obtained from 89 crania of shrew specimens based on three craniodental views (dorsal, jaw, and lateral). Principal component analysis and linear discriminant analysis were applied to both GM and FDGM methods to classify the three shrew species. This study also compared four machine learning approaches (naïve Bayes, support vector machine, random forest, and generalised linear model) using predicted PC scores obtained from both methods (a combination of all three craniodental views and individual views). The analyses favoured FDGM and the dorsal view was the best view for distinguishing the three species.

Genetic and morphometric differentiation between two morphs of Haematobosca sanguinolenta (Diptera: Muscidae) from Thailand.

Haematobosca is a genus of biting fly within the subfamily Stomoxyinae of the family Muscidae. It is currently recognized to include 16 species worldwide. These species, acting as ectoparasites, are considered to have significant importance in the veterinary and medical fields. To address the color polymorphism related to the genus Haematobosca in Thailand, herein, we focused on the normal (legs mainly black) and yellow (legs mainly yellow) morphs of Haematobosca sanguinolenta and examined them for genetic differences using three molecular markers: the cytochrome c oxidase subunit 1 (cox1) and cytochrome b (cytb) genes from the mitochondrial genome as well as the internal transcribed spacer 2 (ITS2) region from the nuclear ribosomal DNA. In addition, we analyzed wing differences between the two morphs using geometric morphometrics (GM). The genetic divergences between the two morphs showed that cytb gene showed the greatest divergence, for which the average distance was 5.6%. This was followed by the combination of cox1-cytb-ITS2, exhibiting an average divergence of 4.5%, ITS2 with a divergence of 4.1%, and finally cox1, showing the lowest divergence of 3.5%. Phylogenetic analyses distinctly separated the two morphs of H. sanguinolenta; this separation was supported by high bootstrap values (97-100%). These results were further corroborated by three species delimitation methods, i.e. assemble species by automatic partitioning (ASAP), automated barcode gap discovery (ABGD), and Poisson tree processes (PTP), all of which suggested that the two morphs likely represent separate species. In addition, a GM study identified a statistically significant difference in wing shape between the two morphs of H. sanguinolenta (P < 0.05). This combination of genetic and morphometric results strongly supports the existence of two distinct species within H. sanguinolenta in Thailand.

Shape variations of pelvis in different classes of dogs using geometric morphometry.

The ossa coxae are the bones that connect the hindlimbs to the axial skeleton. The right and left os coxae join at the median plane to form the pelvis. In this study, variations in pelvis shape and the asymmetric structure of the pelvis were investigated across different classes of dogs. To achieve this, computed tomography images of the pelvis were obtained from 35 dogs, and 3D modelling of the pelvis was created. Subsequently, 45 landmarks were identified on these models. As a result of the Principal Component Analysis, the shape variation was observed in the pelvic canal and crista iliaca. Directional asymmetry between Principal Component 1 and Principal Component 2 accounted for 33.84% of the total variation, while fluctuating asymmetry contributed 23.66%. Canonical variate analysis revealed that canonical variate (CV) 1 explained 56.56% of the total variation between groups, with CV 2 explained 28.98%. Male dogs exhibited greater pelvic variation than females. Procrustes ANOVA indicated that the greatest proportion of shape variation corresponds to the effect of differences among individuals. While directional asymmetry was statistically significant, fluctuating asymmetry was not. Male dogs displayed more pronounced pelvic shape asymmetry, typically towards the right. Gundogs had a narrower pelvic canal and a wide crista iliaca, whereas terriers had a wider pelvic canal and smaller crista iliaca in shape. Geometric morphometry enables statistical analysis and the derivation of average shapes from samples, making it a vital tool in veterinary anatomy. This study provides insights into pelvic geometric morphometry across different classes of dogs.

Changes in the wing shape and size in fruit flies exposed to micro and nanoplastics.

Geometric morphometrics analysis (GMA) is a well-known technique to identify minute changes in Drosophila wings. This study aimed to determine potential changes in Drosophila wings shape and size after exposure to polystyrene nanoplastics (NPs) (50 nm) and microplastics (MPs) (1 µm). Flies were exposed from eggs to pupal eclosion and analyzed using GMA. Results revealed a difference in shape and size between male and female wings, as expected, due to sexual dimorphism. Therefore, wings were analyzed by sex. Wings of MPs and NPs treated females were elongated compared to controls and had a constriction of the wing joint. Additionally, MPs treated female flies had the most dissimilar shape compared to controls. In male flies, NPs flies had smaller wings compared to MPs and control flies. Compared to control, NPs wings of males were shrunken at the joint and in the entire proximal region of the wing. However, male MPs wings had a narrower anal region and were slightly elongated. These results reveal that wing shape and size can change in a different way based on the sex of the flies and size of plastic particles that larvae interacted with. All the changes in the wings occurred only within the normally allowed wing variation and treatment with NPs/MPs did not cause development of the aberrant phenotypes. Results can pave the way for further understanding of how MPs and NPs can alter phenotypes of flies.

Craniofacial morphological variability in orthodontic patients with non-syndromic orofacial clefts: an approach using geometric morphometrics.

OBJECTIVES: Orofacial clefts are complex congenital anomalies that call for comprehensive treatment based on a thorough assessment of the anatomy. This study aims to examine the effect of cleft type on craniofacial morphology using geometric morphometrics. MATERIALS AND METHODS: We evaluated lateral cephalograms of 75 patients with bilateral cleft lip and palate, 63 patients with unilateral cleft lip and palate, and 76 patients with isolated cleft palate. Generalized Procrustes analysis was performed on 16 hard tissue landmark coordinates. Shape variability was studied with principal component analysis. In a risk model approach, the first nine principal components (PC) were used to examine the effect of cleft type. RESULTS: We found statistically significant differences in the mean shape between cleft types. The difference is greatest between bilateral cleft lip and palate and isolated cleft palate (distance of means 0.026, P = 0.0011). Differences between cleft types are most pronounced for PC4 and PC5 (P = 0.0001), which together account for 10% of the total shape variation. PC4 and PC5 show shape differences in the ratio of the upper to the lower face, the posterior mandibular height, and the mandibular angle. CONCLUSIONS: Cleft type has a statistically significant but weak effect on craniofacial morphological variability in patients with non-syndromic orofacial clefts, mainly in the vertical dimension. CLINICAL RELEVANCE: Understanding the effects of clefts on craniofacial morphology is essential to providing patients with treatment tailored to their specific needs. This study contributes to the literature particularly due to our risk model approach in lieu of a prediction model.

Bill shape variation in selected species in birds of prey.

At the top of many ecosystems, raptors, also known as birds of prey, hold major influence. They shape their surroundings through their powerful hunting skills and complex interactions with their environment. This study investigates the beak morphology of four prominent raptor species, Golden eagle (Aquila chrysaetos), Common buzzard (Buteo buteo), Peregrine falcon (Falco peregrinus) and Common kestrel (Falco tinnunculus), found in Türkiye. By employing geometric morphometric methods, we investigate shape variations in the beaks of these species to unravel the adaptive significance of their cranial structures. This analysis reveals distinct beak morphologies among the studied raptors, reflecting adaptations to their feeding habits, hunting techniques and ecological niches. The results from Principal component analysis and Canonical variate analysis demonstrate significant differences in beak morphology between the Falconiformes and Accipitriformes clades, as well as among all three groups. The overall mean beak shapes of Golden Eagles are quite similar to Common Buzzards, with both species having longer beaks. In contrast, Falcons exhibit a distinctly different beak morphology, characterized by wider and shorter beaks. Changes in beak shape can lead to changes depending on the skull. It is thought that skull shape variations among predator families may have an impact on beak shape. These findings highlight the importance of integrating morphometric analyses with ecological insights to enhance our understanding of the evolutionary processes shaping raptor beak morphology.

Beyond CREA: Evolutionary patterns of non-allometric shape variation and divergence in a highly allometric clade of murine rodents.

The shared functions of the skull are thought to result in common evolutionary patterns in mammalian cranial shape. Craniofacial evolutionary allometry (CREA) is a particularly prominent pattern where larger species display proportionally elongate facial skeletons and smaller braincases. It was recently proposed that CREA arises from biomechanical effects of cranial scaling when diets are similar. Thus, deviations from CREA should occur with changes in cranial biomechanics, for example due to dietary change. Here, we test this using 3D geometric morphometric analysis in a dataset of Australian murine crania, which are highly allometric. We contrast allometric and non-allometric variation in the cranium by comparing evolutionary mode, allometry, ordinations, as well as allometry, integration, and modularity in functional modules. We found evidence of stabilising selection in allometry-containing and size-free shape, and substantial non-allometric variation aligned with dietary specialisation in parallel with CREA. Integration among cranial modules was higher, and modularity lower, with size included, but integration between rostrum and cranial vault, which are involved in the CREA pattern, dropped dramatically after size removal. Our results thus support the hypothesis that CREA is a composite arising from selection on cranial function, with substantial non-allometric shape variation occurring alongside CREA where dietary specialisation impacts selection on gnawing function. This emphasises the need to research mammalian cranial evolution in the context of allometric and non-allometric selection on biomechanical function.

Osteon shape variation in the femoral diaphysis: A geometric-morphometric approach on human cortical bone microstructure in an elderly sample.

Geometric morphometrics (GMM) have been applied to understand morphological variation in biological structures. However, research studying cortical bone through geometric histomorphometrics (GHMM) is scarce. This research aims to develop a landmark-based GHMM protocol to depict osteonal shape variation in the femoral diaphysis, exploring the role of age and biomechanics in bone microstructure. Proximal, midshaft, and distal anatomical segments from the femoral diaphysis of six individuals were assessed, with 864 secondary intact osteons from eight periosteal sampling areas being manually landmarked. Observer error was tested using Procrustes ANOVA. Average osteonal shape and anatomical segment-specific variation were explored using principal component analysis. Osteon shape differences between segments were examined using canonical variate analysis (CVA). Sex differences were assessed through Procrustes ANOVA and discriminant function analysis (DFA). The impact of osteonal size on osteonal shape was investigated. High repeatability and reproducibility in osteon shape landmarking were reported. The average osteon shape captured was an elliptical structure, with PC1 reflecting more circular osteons. Significant differences in osteon shape were observed between proximal and distal segments according to CVA. Osteon shape differed between males and females, with DFA showing 52% cross-validation accuracies. No effect of size on shape was reported. Osteonal shape variation observed in this study might be explained by the elderly nature of the sample as well as biomechanical and physiological mechanisms playing different roles along the femoral diaphysis. Although a larger sample is needed to corroborate these findings, this study contributes to the best of our knowledge on human microanatomy, proposing a novel GHMM approach.

Sella turcica and facial bones: Morphological integration in the human fetal cranium.

OBJECTIVES: The cranial base plays a significant role in facial growth, and closer analyses of the morphological relationship between these two regions are needed to understand the morphogenesis of the face. Here, we aimed to study morphological integration between the sella turcica (ST) and facial bones during the fetal period using geometric morphometrics. MATERIALS AND METHODS: Magnetic resonance images of 47 human fetuses in the Kyoto Collection, with crown-rump lengths of 29.8-225 mm, were included in this study. Anatomical homologous landmarks and semilandmarks were registered on the facial bones and the midsagittal contour of the ST, respectively. The shape variations in the craniofacial skeleton and the ST were statistically investigated by reducing dimensionality using principal component analysis (PCA). Subsequently, the morphological integration between the facial bones and ST was investigated using two-block partial least squares (2B-PLS) analysis. RESULTS: PCA showed that small specimens represented the concave facial profile, including the mandibular protrusion and maxillary retrusion. The 2B-PLS showed a strong integration (RV coefficient = 0.523, r = .79, p < .01) between the facial bones and ST. The curvature of the anterior wall of the ST was highly associated with immature facial morphology characterized by a concave profile. CONCLUSION: The strong integration between the two regions suggested that the anterior ST may be associated with facial morphology. This result quantitatively confirms previous studies reporting ST deformities in facial anomalies and induces further research using postnatal subjects.

Integrating wing morphometrics and mitochondrial DNA analysis to assess the filaria vector Mansonia uniformis (Diptera: Culicidae) populations in Thailand.

Mansonia uniformis (Diptera: Culicidae) is recognized as a vector of Brugia malayi and has been reported to transmit Wuchereria bancrofti, both causing lymphatic filariasis in humans. This study employed geometric morphometrics (GM) to investigate wing shape variation and analyzed genetic diversity through cytochrome c oxidase subunit 1 (COI) gene analyses in Ma. uniformis populations across Thailand. Wing GM analyses indicated significant differences in wing shape based on Mahalanobis distances among nearly all population pairs (p < 0.05), with no significant correlation between wing shape and geographic distance (r = 0.210, p > 0.05). Genetic analyses identified 63 haplotypes and 49 polymorphic sites, with the overall population exhibiting a nucleotide diversity of 0.006 (± 0.001) and a haplotype diversity of 0.912 (± 0.017). Deviations from neutrality, as indicated by Tajima's D and Fu's FS tests for the overall Ma. uniformis populations in Thailand, were statistically significant and negative, suggesting population expansion (both p < 0.05). Analysis of molecular variance revealed no significant genetic structure when all populations were categorized based on collection sites and geographic regions. However, significant differences in FST values were observed between some populations. These findings enhance our understanding of the geographical and genetic factors influencing Ma. uniformis populations, which are crucial for developing effective control strategies in Thailand.

Face-brain correlates as potential sex-specific biomarkers for schizophrenia and bipolar disorder.

Given the shared ectodermal origin and integrated development of the face and the brain, facial biomarkers emerge as potential candidates to assess vulnerability for disorders in which neurodevelopment is compromised, such as schizophrenia (SZ) and bipolar disorder (BD). The sample comprised 188 individuals (67 SZ patients, 46 BD patients and 75 healthy controls (HC)). Using a landmark-based approach on 3D facial reconstructions, we quantified global and local facial shape differences between SZ/BD patients and HC using geometric morphometrics. We also assessed correlations between facial and brain cortical measures. All analyses were performed separately by sex. Diagnosis explained 4.1 % - 5.9 % of global facial shape variance in males and females with SZ, and 4.5 % - 4.1 % in BD. Regarding local facial shape, we detected 43.2 % of significantly different distances in males and 47.4 % in females with SZ as compared to HC, whereas in BD the percentages decreased to 35.8 % and 26.8 %, respectively. We detected that brain area and volume significantly explained 2.2 % and 2 % of facial shape variance in the male SZ - HC sample. Our results support facial shape as a neurodevelopmental marker for SZ and BD and reveal sex-specific pathophysiological mechanisms modulating the interplay between the brain and the face.

Eco-geographic and sexual variation of the ribcage in Homo sapiens.

Up to now, Allen and Bergmann's rules have been studied in modern humans by analyzing differences in limb length, height, or body mass. However, there are no publications studying the effects of latitude in the 3D configuration of the ribcage. To assess this issue, we digitally reconstructed the ribcages of a balanced sample of 109 adult individuals of global distribution. Shape and size of the ribcage was quantified using geometric morphometrics. Our results show that the ribcage belonging to tropical individuals is smaller and slenderer compared to others living in higher latitudes, which is in line with Allen and Bergmann's rules and suggests an allometric relationship between size and shape. Although sexual dimorphism was observed in the whole sample, significant differences were only found in tropical populations. Our proposal is that, apart from potential sexual selection, avoiding heat loss might be the limiting factor for sexual dimorphism in cold-adapted populations.

From slenderness to robustness: Understanding long bone shape in sigmodontine rodents.

The morphological evolution of the appendicular skeleton may reflect the selective pressures specific to different environments, phylogenetic inheritance, or allometry. Covariation in bone shapes enhances morphological integration in response to ecological specializations. In contrast to previous multivariate studies using classical linear morphometry, we use a geometric morphometric approach to explore the morphological diversity of long bones and examine relationships between ecological categories and morphological characters in a species-rich and ecomorphologically diverse group of rodents. We examined the humerus, ulna, femur, and tibiofibula of 19 sigmodontine species with different locomotor types (ambulatory, quadrupedal-saltatorial, natatorial, semifossorial and scansorial) to investigate the influence of locomotor type and phylogeny on limb bone shape and morphological integration of the appendicular skeleton. This study represents the most detailed examination of the morphological diversity of long bones in sigmodontines, employing geometric morphometrics within an ecomorphological framework. Our results indicate that functional demands and evolutionary history jointly influence the shape of forelimb and hindlimb bones. The main variation in bone shape is associated with a slenderness-robustness gradient observed across all ecological categories. Quadrupedal-saltatorial species, with their need for agility, possess slender and elongated limbs, while natatorial and semifossorial species exhibit shorter and more robust bone shapes, suited for their respective environments. This gradient also influences bone covariation within limbs, demonstrating interconnectedness between elements. We found functional covariation between the ulna-tibiofibula and humerus-tibiofibula, likely important for propulsion, and anatomical covariation between the humerus-ulna and femur-tibiofibula, potentially reflecting overall limb structure. This study demonstrates that the versatile morphology of long bones in sigmodontines plays a critical role in their remarkable ecological and phylogenetic diversification.

Small- to medium-sized mammals show greater morphological disparity in cervical than lumbar vertebrae across different terrestrial modes of locomotion.

During mammalian terrestrial locomotion, body flexibility facilitated by the vertebral column is expected to be correlated with observed modes of locomotion, known as gait (e.g., sprawl, trot, hop, bound, gallop). In small- to medium-sized mammals (average weight up to 5 kg), the relationship between locomotive mode and vertebral morphology is largely unexplored. Here we studied the vertebral column from 46 small- to medium-sized mammals. Nine vertebrae across cervical, thoracic, and lumbar regions were chosen to represent the whole vertebral column. Vertebra shape was analysed using three-dimensional geometric morphometrics with the phylogenetic comparative method. We also applied the multi-block method, which can consider all vertebrae as a single structure for analysis. We calculated morphological disparity, phylogenetic signal, and evaluated the effects of allometry and gait on vertebral shape. We also investigated the pattern of integration in the column. We found the cervical vertebrae show the highest degree of morphological disparity, and the first thoracic vertebra shows the highest phylogenetic signal. A significant effect of gait type on vertebrae shape was found, with the lumbar vertebrae having the strongest correlation; but this effect was not significant after taking phylogeny into account. On the other hand, allometry has a significant effect on all vertebrae regardless of the contribution from phylogeny. The regions showed differing degrees of integration, with cervical vertebrae most strongly correlated. With these results, we have revealed novel information that cannot be captured from study of a single vertebra alone: although the lumbar vertebrae are the most correlated with gait, the cervical vertebrae are more morphologically diverse and drive the diversity among species when considering whole column shape.

Revisions of the clavipes and pruni species groups of the genus Merodon Meigen, 1803 (Diptera, Syrphidae).

This study focuses on the avidus-nigritarsis lineage within the genus Merodon, exploring morphological, genetic, and distributional aspects of two related assemblies within this lineage: the clavipes and pruni species groups. An integrative taxonomic approach was followed to ensure comprehensive species identification and validation, using adult morphology, wing geometric morphometrics, and genetic analysis of the mtDNA COI gene. In the clavipes group, seven species were identified, including three new species: M.aenigmaticus Vujic, Radenkovic & Likov, sp. nov., M.latens Vujic, Radenkovic & Likov, sp. nov., and M.rufofemoris Vujic, Radenkovic & Likov, sp. nov. In the pruni group, our revision revealed a new species, M.aequalis Vujic, Radenkovic & Likov, sp. nov., and the revalidation of Merodonobscurus Gil Collado, 1929, stat. rev. Merodonpallidus Macquart, 1842 is redescribed. Diagnoses, identification keys to species, and distribution maps are provided, and neotypes for Syrphusclavipes Fabricius, 1781 and Merodonquadrinotatus (Sack, 1931) are designated. Additionally, the following new synonyms are proposed: M.clavipesalbus syn. nov., M.clavipesater syn. nov., M.clavipesniger syn. nov., and M.splendens syn. nov. are junior synonyms of M.clavipes; and M.veloxarmeniacus syn. nov. and M.veloxanathema syn. nov. are junior synonyms of M.velox.