The central tenet of ecomorphology links ecological and morphological variation through the process of selection. Traditionally used to rationalise morphological differences between taxa, an ...ecomorphological approach is increasingly being utilised to study morphological differences expressed through ontogeny. Elasmobranchii (sharks, rays and skates) is one clade in which such ontogenetic shifts in body form have been reported. Such studies are limited to a relatively small proportion of total elasmobranch ecological and morphological diversity, and questions remain regarding the extent to which ecological selection are driving observed morphometric trends. In this study, we report ontogenetic growth trajectories obtained via traditional linear morphometrics from a large data set of the brown smoothhound shark (Mustelus henlei). We consider various morphological structures including the caudal, dorsal and pectoral fins, as well as several girth measurements. We use an ecomorphological approach to infer the broad ecological characteristics of this population and refine understanding of the selective forces underlying the evolution of specific morphological structures. We suggest that observed scaling trends in M. henlei are inconsistent with migratory behaviour, but do not contradict a putative trophic niche shift. We also highlight the role of predation pressure and sex‐based ecological differences in driving observed trends in morphometry, a factor which has previously been neglected when considering the evolution of body form in sharks.
Ontogenetic shifts in body form have been reported in a number of shark species and are primarily thought to result from differences in trophic ecology or habitat usage between life stages. However, existing studies are taxonomically and ecologically restricted, meaning ontogenetic scaling trends across Elasmobranchii (sharks and rays) are poorly understood. We report ontogenetic morphometric trajectories in the brown smoothhound shark (Mustelus henlei), using existing theory to predict basic ecological characteristics of the population in question. We also highlight potential roles of sexual dimorphism and predation pressure in driving ontogenetic changes in body form.”
The riffle bugs of the Rhagovelia angustipes complex have presented problems in taxonomy due to high intra-specific variability. Here we identified variation in the complex with morphometric ...techniques. We analyzed variation of the characters and performed a phylogenetic analysis of a combined matrix of linear measurements, geometric configurations, and discrete characters. We found that characters such as head length, metanotum length, femur width, and the evaluated shape of four characters (head, abdomen, fore tibia, hind femur) were important for the delimitation of species. In particular, we identified the metanotum length as a character that had not been previously considered in the taxonomy of the complex. The phylogenetic reconstruction allowed us to recover some relationships established for the taxonomy of the complex for the salina group, except for the species R. colombiana that was closer to R. calceola and R. calopa. This may be due to a similar natural history, since they share areas of distribution, while the R. bisignata and R. hambletoni groups could not be recovered, showing their low morphological support. In general, the geometric morphometric characters showed high levels of homology, with the head and the anterior tibia being the ones that had the best performance in the tree. Finally, the use of morphometric tools proved to be a powerful input for the taxonomic resolution of species complexes that have problems in their delimitation.
•Linear and geometric morphometrics identify characters for species discrimination.•Variance in shape characters solves species inconsistencies in the Rhagovelia angustipes complex.•Phylogenetic reconstruction of characters suggests new relationships in the taxonomy of the complex.
The taxonomy of the South American river dolphins of the genus Inia has been a focus of intense debate. While traditionally it is thought to be composed of a single species with three geographically ...structured subspecies (Inia geoffrensis geoffrensis, I. g. humboldtiana, and I. g. boliviensis), recent molecular studies have highlighted substantial differentiation, suggesting the existence of two species (I. geoffrensis and I. araguaiaensis). Despite this evidence, the recognition of the specific status of these taxa has been hindered by inconsistent morphological diagnoses. Here, we aim to provide evidence for the morphological differentiation (or lack thereof) between subspecies and putative species. We employ geometrics and traditional morphometrics to measure skull variation to support efforts of integrative taxonomy. Our results show that morphometric diversity within the group is inconsistent with a single taxon. Morphometric evidence supports the traditional differentiation of three distinct morphotypes within the analyzed sample. These morphotypes largely correspond to described subspecies I. g. geoffrensis, I. g. humboldtiana—the latter differing from the former by size—and I. g. boliviensis, which differs from the remaining groups by shape. Furthermore, morphometric data show no differences between I. g. geoffrensis and a newly proposed species, I. araguaiaensis. Given the conservation importance of this genus and the different threats they are subject to, we strongly suggest an urgent integrative taxonomic treatment of the group to better protect these singular cetaceans. A taxonomia dos golfinhos de água doce da América do Sul pertencentes ao gênero Inia têm sido foco de intenso debate. Enquanto tradicionalmente considera-se a existência de uma única espécie e três subespécies (Inia geoffrensis geoffrensis, I. g. humboldtiana, and I. g. boliviensis), estudos moleculares recentes evidenciam diferenciação substancial, sugerindo a existência de mais de uma espécie (I. geoffrensis and I. araguaiaensis). Apesar desta evidência, o reconhecimento do status específico desses táxons tem sido limitado pela presença de diagnoses morfológicas inconsistentes. Nosso objetivo no presente trabalho é proporcionar evidências para a diferenciação morfológica (ou a sua ausência) entre as subespécies e as possíveis espécies. Utilizamos morfometria geométrica e tradicional para medir a variação do cranio de forma a sustentar esforços de taxonomia integrativa. Nossos resultados mostram que a diversidade morfométrica dentro do grupo é inconsistente com um único táxon. A evidência morfométrica aponta a diferenciação tradicional de três morfotipos distintos dentro da amostra analisada. Esses morfotipos correspondem em grande parte às subespecies I. g. geoffrensis, I. g. humboldtiana, que diverge da primeira através do seu tamanho, e I. g. boliviensis, que diverge das demais através de sua forma. Ademais, dados morfométricos não mostram diferenças entre Inia g. geoffrensis e a espécie recém proposta, I. araguaiaensis. Dada a importância para conservação desse gênero e as diferentes ameaças às quais estão sujeitos, nós sugerimos enfaticamente um tratamento de taxonomia integrativa para o grupo, de forma a melhor proteger esses cetáceos singulares.
Previous studies investigated the relationship between facial asymmetry, perceived attractiveness and peoples' traits. The diversity of results might be due to methodological issues and poor ...standardization between asymmetry scoring methods. We evaluate two traditional scoring methods, the Horizontal Angular Asymmetry (HAA) and the Horizontal Fluctuating Asymmetry (HFA), and propose a geometric morphometrics-based Holistic Facial Asymmetry Score (HFAS). In Study 1, 1000 photographs with different types of asymmetry were simulated and then correlated with the estimated facial asymmetry scores. Results indicate that HFA was highly affected by extrinsic factors, while HAA and HFAS were less affected and rather capture intrinsic asymmetry. In Study 2, HFAS and HAA were compared for 160 facial images (45% Female, M = 27.6 years) by estimating their correlations with ratings of attractiveness and targets' traits provided by 81 adults (51% Female, M = 27.7 years). Results suggest that attractiveness was only related with extrinsic factors. HAA was related with higher fairness, femininity, modesty, and sincerity, but less greediness and masculinity. HFAS was related with low femininity, high masculinity, and greediness, as well as low negativity, higher fairness, and sincerity. We discuss the benefits of HFAS as a scoring method for the assessment of facial asymmetry.
•Existing asymmetry scores have limitations, e.g. correlation with head pose.•Our new holistic score distinguishes between pose and various types of asymmetry.•Attractiveness ratings correlate with pose but not with asymmetry.•Perceived personality and femininity/masculinity correlate with asymmetry.
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•We use incongruences among data sets to uncover evolutionary histories.•Messor “structor” encompasses five species, two of which are new to science.•No single data set was sufficient ...to disentangle the final species limits.•Integrating independent data sets is key to solving complex taxonomic problems.
Seed harvesting ants are ecosystem engineers that shape vegetation, nutrient cycles, and microclimate. Progress in ecological research is, however, slowed down by poor species delimitation. For example, it has not been resolved to date, how many species the European harvester ant Messor “structor” (Latreille, 1798) represents. Since its first description, splitting into additional taxa was often proposed but not accepted later on due to inconsistent support from morphology and ecology. Here, we took an iterative integrative-taxonomy approach – comparing multiple, independent data sets of the same sample – and used traditional morphometrics, Wolbachia symbionts, mitochondrial DNA, amplified fragment length polymorphism, and ecological niche modelling. Using the complementarity of the data sets applied, we resolved multiple, strong disagreements over the number of species, ranging from four to ten, and the allocation of individuals to species. We consider most plausible a five-species hypothesis and conclude the taxonomic odyssey by redescribing Messor structor, M. ibericus Santschi, 1925, and M. muticus (Nylander, 1849) stat.rev., and by describing two new species, M. ponticus sp.n. and M. mcarthuri sp.n. The evolutionary explanations invoked in resolving the various data conflicts include pronounced morphological crypsis, incomplete lineage-sorting or ongoing cospeciation of endosymbionts, and peripatric speciation – these ants’ significance to evolutionary biology parallels that to ecology. The successful solution of this particular problem illustrates the usefulness of the integrative approach to other systematic problems of comparable complexity and the importance of understanding evolution to drawing correct conclusions on species’ attributes, including their ecology and biogeography.
In conventional morphometrics, researchers often collect and analyze data using large numbers of morphometric features to study the shape variation among biological organisms. Feature selection is a ...fundamental tool in machine learning which is used to remove irrelevant and redundant features. Recursive feature elimination (RFE) is a popular feature selection technique that reduces data dimensionality and helps in selecting the subset of attributes based on predictor importance ranking. In this study, we perform RFE on the craniodental measurements of the Rattus rattus data to select the best feature subset for both males and females. We also performed a comparative study based on three machine learning algorithms such as Naïve Bayes, Random Forest, and Artificial Neural Network by using all features and the RFE-selected features to classify the R. rattus sample based on the age groups. Artificial Neural Network has shown to provide the best accuracy among these three predictive classification models.
This work aimed to study sexual dimorphism in the first rib of modern humans, with a special focus on whether differences in shape are due to divergent allometric growth in males and females. Also, ...we compare the accuracy of sex classification using different approaches based on two methodologies, traditional morphometry based on linear measurements and geometric morphometric analysis based on 2D landmark coordinates. The sample studied here comprised 121 right and left first ribs from 65 female and male adult recent Euro‐American Homo sapiens individuals. For traditional morphometrics, 12 metric variables were collected from each rib using a digital caliper, and for geometric morphometrics, six landmarks and 31 semilandmarks were captured from photographs using digital software. Both geometric morphometric and metric data were analyzed to calculate the index of sexual dimorphism, variation related to lateral asymmetry, variation in size and shape, and allometric trends between males and females. Finally, a linear discriminant analysis (LDA) was performed comparing both methodologies to test the best approach for sex classification. Results indicated that there are significant sex differences in the size and shape of the first ribs of recent Euro‐American Homo sapiens. Regression analysis revealed different allometric patterns for males and females, and this could partially explain shape differences between sexes. Additionally, traditional morphometrics showed that all characteristics analyzed are significantly dimorphic, with the midshaft minimum craniocaudal diameter, the sternal end minimum diameter, and the neck minimum craniocaudal diameter displaying the most dimorphic scores. Similarly, geometric morphometrics results indicated that males have more curved and interno‐exteriorly wider first ribs. Finally, analysis of sex classification using LDA yielded slightly better accuracy for traditional morphometry (83.8%) than the geometric morphometrics approach (81.3%) based on form Procrustes coordinates. This study demonstrates the usefulness of applying two different morphometric approaches to obtain more comprehensive results.
Our study revealed different allometric patterns for males and females, and this could partially explain shape differences between sexes. Also, traditional morphometrics and geometric morphometrics analyses showed that the first rib of Homo sapiens is sexually significantly dimorphic. Finally, analysis of sex classification yielded slightly better accuracy for traditional morphometry than the geometric morphometrics approach based on form Procrustes coordinates.
To compare the application of traditional morphometric methods (TMMs) and geometric morphometric methods (GMMs) in the study of intraspecific leaf morphological characters of
Quercus dentata
, ...fifteen linear measurement indices and thirteen landmarks of leaves were used to study leaf morphology of three provenances (H1, H2, and H3). In TMMs, principal component analysis (PCA) showed that leaf size–related indices played an important role in population classification. Partial least square (PLS) analysis showed that the main morphological characters affecting leaf size were the average depth of the lobes and the length–width ratios. However, the important indices to distinguish the provenances were circularity, leaf width, and length–width ratio. The results of discriminant analysis (DA) showed that 74.0% of H1, 68.0% of H2, and 74.0% of H3 were correctly classified. Cluster analysis showed that the Mahalanobis distances between H1 and H2, H1 and H3, and H2 and H3 were 4.3761, 11.4629, and 10.2067, respectively. In GMMs, PCA based on symmetrical components showed that the difference in leaf morphology was mainly due to the changing trend of the leaf apex and base, petiole length, and degree of leaf cracking. PLS analysis showed that there was a significant covariation between the leaf symmetrical components and size: as the leaf enlarged, the widest part gradually moved up, and the shape changed from nearly oval to lanceolate. DA results showed that 86.0% and 78.0% of H1 and H2, 70.0% and 80.0% of H1 and H3, and 82.0% and 76.0% of H2 and H3 were correctly classified. Canonical variate analysis results showed that the Mahalanobis distances between H1 and H2, H1 and H3, and H2 and H3 were 1.7238, 1.5380, and 1.6329, respectively. Both GMMs and TMMs showed significant differences in morphology among the three
Q. dentata
provenances, but GMMs had higher classification accuracy and could provide more information about leaf shape, whereas TMMs could provide more information about leaf size. Based on our results, GMMs are promising in the study of leaf morphological variation within
Q. dentata
provenances.
The alpha taxonomy of scaphopods is based mainly on the shell morphology, as it is for most molluscs. In the last three decades, the employment of morphometric variables of the shell in combination ...with statistics has considerably increased to aid species discrimination, but this has not been used above species level. In this study, a traditional morphometric approach was used to distinguish congeners, genera and families within the orders Dentallida and Gadilida. We studied 28 species of scaphopods from Brazil, belonging to 12 genera and five families. Twelve morphometric variables were measured, and a correlation test was done to select a set of variables without correlation as input data to perform a discriminant analysis. In the analysis of congeners, the discrimination power was high in both orders. Among the genera studied, the robustness of the analysis was drastically reduced in Dentaliida, while Gadilida maintained a high percentage of correct classifications. At the family level, both orders presented high percentages of correct classification, but the imbalance of cases for each taxon masks an inconsistent result. Based on our results, the morphometric approach was a useful tool to discriminate congeneric species of both orders and to discriminate the genera of Gadilida.
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