Patterns Of Shape Change Research Articles

New species of Bryophaenocladius Thienemann, 1934 (Diptera: Chironomidae) from Argentina

Three new species of Bryophaenocladius Thienemann are described and figured as male imagines: B. urbanus sp. n. from Central Argentina, and B. virgotruncatus sp. n. and B. nasus sp. n. from Argentinean Patagonia. A geometric morphometric analysis was performed to evaluate the taxonomic value of the shape of the anal point in species delimitation. The analysis involved 96 species. As a result, the Bryophaenocladius species showed significant anal point patterns of shape change, recovering three main shape types: rounded, equilateral triangle-shaped, and isosceles triangle-shaped. An identification key of the Bryophaenocladius species from the Neotropical region is provided.

Метод исследования формоизменения шатунных вкладышей коленчатого вала автомобильного двигателя в эксплуатации (на примере КамАЗ-740)

The relevance of the topic of the article is due to the unresolved problem of failures of automobile engines, in particular, modern mass-produced engines of the KAMAZ-740.10, 7403 families, due to cranking of the connecting rod bearings, and the need for deeper studies of the processes and phenomena that lead to them, and the development of solutions that exclude them in operation. The purpose of the study is to ensure the reliability of automobile engines by reducing the risk of crankshaft connecting rod bearings turning in operation by developing a method for studying their shape change and applying it when substantiating and implementing various design, technological and operational solutions. A prototype is described and a developed method and device for determining the clearance in a connecting rod bearing, suitable for studying the formation of connecting rod bearings under engine test bench conditions. The prototype was a differential-type pneumatic device used in active control devices for honing cylinder liners. With the use of the described device, a method for studying the formation of connecting rod bearings under the conditions of bench tests of KAMAZ-740.10 diesel engines was developed and tested. The use of new methods, devices and techniques makes it possible to investigate the patterns of shape changes of connecting rod bearings in relation to lubrication conditions, temperature and load conditions of the engine, and other factors. The presented experimental results show that the gap in the connecting rod bearing is not stable, is caused not only by wear, but also by the resulting deflection of the liner, and significantly depends on the temperature regime of the engine - with an increase in oil temperature, the gap decreases due to an increase in deflection. The authors explain the formation of deflection and shape change of the liners by the loss of its stability from the action of loads and internal stresses under conditions of instability of the oil supply. The results of experimental studies presented in the article have a scientific novelty, since a previously undescribed and not fixed decrease in the gap due to the deflection of the liners, which is formed immediately from the start of operation after the engine is assembled, is established, and its value is variable and determined by the temperature regime. Practical significance – the developed method makes it possible to study the formation patterns of crankshaft connecting rod bearings to test the effectiveness of design, technological and operational solutions to prevent their turning during the operation of an automobile engine. The main directions of promising research is the substantiation of practical solutions to ensure the stability of the shape of the liners during long-term operation of the engine.

Volume and shape changes of mandibular condyles in growing patients treated with fixed Class II appliances using CBCT

Objective: Evaluate the changes in the mandibular condyle volume and shape in growing Class II malocclusion patients, following the use of fixed functional Class II appliances (Forsus and Advacsync II). CBCT images were used to help understand which appliance might cause more changes. Methods: Twenty growing adolescent patients were randomly allocated to Two groups (Forsus and Advancesync II). A total of fourty CBCT images were taken pre- and posttreatment. The pre- and posttreatment CBCT images were segmented using a newly developed and validated semiautomatic condylar segmentation technique. and the quantitative assessment of the mean distance differences of the condyle surfaces was de using Iterative Closest Point technique. Results: A statistically significant increase in condylar volume was observed in both groups (Forsus and Advancesync II) and no significant differences in the magnitude of condylar volumes between both groups were found. There were no statistically significant changes in the mean distance differences of the condyles shape in both groups.Both groups (Forsus and Advancesync II) expressed different patterns of shape changes with no clear pattern associated with the treatment groups.

Interfacial metric mechanics: stitching patterns of shape change in active sheets.

A flat sheet programmed with a planar pattern of spontaneous shape change will morph into a curved surface. Such metric mechanics is seen in growing biological sheets, and may be engineered in actuating soft matter sheets such as phase-changing liquid crystal elastomers (LCEs), swelling gels and inflating baromorphs. Here, we show how to combine multiple patterns in a sheet by stitching regions of different shape changes together piecewise along interfaces. This approach allows simple patterns to be used as building blocks, and enables the design of multi-material or active/passive sheets. We give a general condition for an interface to be geometrically compatible, and explore its consequences for LCE/LCE, gel/gel and active/passive interfaces. In contraction/elongation systems such as LCEs, we find an infinite set of compatible interfaces between any pair of patterns along which the metric is discontinuous, and a finite number across which the metric is continuous. As an example, we find all possible interfaces between pairs of LCE logarithmic spiral patterns. By contrast, in isotropic systems such as swelling gels, only a finite number of continuous interfaces are available, greatly limiting the potential of stitching. In both continuous and discontinuous cases, we find the stitched interfaces generically carry singular Gaussian curvature, leading to intrinsically curved folds in the actuated surface. We give a general expression for the distribution of this curvature, and a more specialized form for interfaces in LCE patterns. The interfaces thus also have rich geometric and mechanical properties in their own right.

State-of-the-Art Techniques for Diagnosis of Medical Parasites and Arthropods.

Conventional methods such as microscopy have been used to diagnose parasitic diseases and medical conditions related to arthropods for many years. Some techniques are considered gold standard methods. However, their limited sensitivity, specificity, and accuracy, and the need for costly reagents and high-skilled technicians are critical problems. New tools are therefore continually being developed to reduce pitfalls. Recently, three state-of-the-art techniques have emerged: DNA barcoding, geometric morphometrics, and artificial intelligence. Here, data related to the three approaches are reviewed. DNA barcoding involves an analysis of a barcode sequence. It was used to diagnose medical parasites and arthropods with 95.0% accuracy. However, this technique still requires costly reagents and equipment. Geometric morphometric analysis is the statistical analysis of the patterns of shape change of an anatomical structure. Its accuracy is approximately 94.0–100.0%, and unlike DNA barcoding, costly reagents and equipment are not required. Artificial intelligence technology involves the analysis of pictures using well-trained algorithms. It showed 98.8–99.0% precision. All three approaches use computer programs instead of human interpretation. They also have the potential to be high-throughput technologies since many samples can be analyzed at once. However, the limitation of using these techniques in real settings is species coverage.

A human craniofacial life-course: Cross-sectional morphological covariations during postnatal growth, adolescence, and aging.

Covariations between anatomical structures are fundamental to craniofacial ontogeny, maturation, and aging and yet are rarely studied in such a cognate fashion. Here, we offer a comprehensive investigation of the human craniofacial complex using freely available software and MRI datasets representing 575 individuals from 0 to 79 years old. We employ both standard craniometrics methods as well as Procrustes-based analyses to capture and document cross-sectional trends. Findings suggest that anatomical structures behave primarily as modules, and manifest integrated patterns of shape change as they compete for space, particularly with relative expansions of the brain during early postnatal life and of the face during puberty. Sexual dimorphism was detected in infancy and intensified during adolescence with gender differences in the magnitude and pattern of morphological covariation as well as of aging. These findings partly support the spatial-packing hypothesis and reveal important insights into phenotypic adjustments to deep-rooted, and presumably genetically defined, trajectories of morphological size and shape change that characterize the normal human craniofacial life-course.

Ontogenetic shape trajectory of Trichomycterus areolatus varies in response to water velocity environment.

Body and head shape among fishes both vary between environments influenced by water velocity and across ontogeny. Although the shape changes associated with variation in average water velocity and ontogeny are well documented, few studies have tested for the interaction between these two variables (i.e., does ontogenetic shape variation differ between velocity environments). We use geometric morphometrics to characterize shape differences in Trichomycterus areolatus, a freshwater catfish found in high and low-velocity environments in Chile. We identify a significant interaction between velocity environment and body size (i.e., ontogeny). Ontogenetic patterns of shape change are consistent with other studies, but velocity environment differentially affects the ontogenetic trajectory of shape development in T. areolatus. Shape change over ontogeny appears more constrained in high-velocity environments compared to low-velocity environments.

Shape programming lines of concentrated Gaussian curvature

Liquid crystal elastomers (LCEs) can undergo large reversible contractions along their nematic director upon heating or illumination. A spatially patterned director within a flat LCE sheet, thus, encodes a pattern of contraction on heating, which can morph the sheet into a curved shell, akin to how a pattern of growth sculpts a developing organism. Here, we consider theoretically, numerically, and experimentally patterns constructed from regions of radial and circular director, which, in isolation, would form cones and anticones. The resultant surfaces contain curved ridges with sharp V-shaped cross sections, associated with the boundaries between regions in the patterns. Such ridges may be created in positively and negatively curved variants and, since they bear Gauss curvature (quantified here via the Gauss–Bonnet theorem), they cannot be flattened without energetically prohibitive stretch. Our experiments and numerics highlight that, although such ridges cannot be flattened isometrically, they can deform isometrically by trading the (singular) curvature of the V angle against the (finite) curvature of the ridge line. Furthermore, in finite thickness sheets, the sharp ridges are inevitably non-isometrically blunted to relieve bend, resulting in a modest smearing out of the encoded singular Gauss curvature. We close by discussing the use of such features as actuating linear features, such as probes, tongues, and grippers. We speculate on similarities between these patterns of shape change and those found during the morphogenesis of several biological systems.

Carpal Shape Variation Between Pan and Gorilla Mirrors That of Other Mammals With Similar Body Size Differences

Chimpanzees, bonobos (Pan), and gorillas (Gorilla) are the only extant knuckle-walking primates. Two hypotheses have been proposed to explain the evolution of knuckle-walking in Pan and Gorilla. The knuckle-walking hypothesis holds that the last common ancestor of Pan, Gorilla, and Homo knuckle-walked. The alternative hypothesis holds that Pan and Gorilla evolved knuckle-walking independently. One unresolved issue is that, despite sharing knuckle-walking as a common locomotor mode, Pan and Gorilla exhibit different carpal morphologies. This morphological variation has been used to support the theory that Pan and Gorilla evolved knuckle-walking independently. To date, however, little work has focused on the effect of body mass on this functional complex. Here, we compare shape changes in the carpals of Pan and Gorilla to those of other quadrupedal mammals with similar body size differences. If morphological trends in the carpus of Pan and Gorilla mirror those of other mammals with similar body mass variation, then carpal variation in African apes may be attributed to differences in body mass, rather than the independent evolution of knuckle-walking. More specifically, we hypothesize that the carpals of high body mass taxa will be relatively proximo-distally shorter and medio-laterally/antero-posteriorly wider than those of low body mass taxa. The capitate, hamate, and triquetrum of high and low body mass taxa from the mammalian families Hominidae, Cercopithecidae, Bovidae, Canidae, and Myrmecophagidae were surface scanned. A weighted spherical harmonic (SPHARM) analysis was used to quantify the shape of each carpal. During the SPHARM analysis, surface models were mapped onto the surface of a sphere, and then decomposed into a weighted sum of spherical harmonic functions. Shape variation of each carpal (within each mammalian family) was summarized using a principal component analysis (PCA) of coefficients from spherical harmonic functions. The log-centroid size of each surface model was added to each PCA to determine the effect of size on shape variation. Shape changes were visualized by comparing surface models of the average specimen from species with the highest and lowest body mass within each family. Species separate by body mass in all PC plots, and comparison of average specimen surface models indicates that across all mammalian families included in the analysis, the capitate, hamate, and triquetrum exhibit similar shape changes between high and low body mass taxa (i.e., the carpals of high body mass taxa are proximo-distally shorter and medio-laterally wider than those of low body mass taxa). These distinctions are likely caused by the need to accommodate the higher forelimb loading associated with an increase in body mass. Furthermore, because these patterns of shape change are seen in the carpals of multiple mammalian families, morphological variation in the carpals of chimpanzees and gorillas is more likely due to differences in body size than the independent evolution of knuckle-walking.

Embryonic origins of the flattened skull table and snout in Crocodylia

Major groups of vertebrates, such as mammals, birds, and crocodylians, are recognizably distinct due to unique anatomical, physiological, and behavioral characteristics. The origins and ecological consequences of these features have been the focus of intense research, including more recently the developmental mechanisms facilitating their evolution. The dorsoventrally flattened snout and skull table typify extant Crocodylia perhaps more than any other anatomical feature. The origins and ecological consequences of the crocodylian skull have been the focus of extensive study. While it is generally recognized as an adaptation for feeding at the water's surface, the developmental origins of craniofacial flattening have yet to be explored. To understand how the skull table and platyrostral snout develop, we quantified the embryonic development and post-hatching growth (ontogeny) of the crocodylian skull in lateral view using geometric morphometrics. Our dataset (n=103) includes all but one extant genus and all of the major ecomorph groups, including the rare and extremely slender-snouted Gavialis and Tomistoma. Our ontogenetic morphospace captures similar variation in snout length as have been previously found for the ontogeny of dorsal snout shape, including the presence of a conserved embryonic skull shape for all but the two most extremely slender-snouted forms. Comparisons of ontogenetic trajectories revealed that by the end of embryonic development the adult condition of a dorsally flat skull table is achieved in all species and that ecomorphs did not differ in their pattern of skull roof ontogeny. The ontogenetic flattening of the snout did show post-hatching differences among ecomorphs, likely related to differences in the length and depth of the snout, but not during embryonic development. These anatomical changes correlate with recently described molecular and cellular processes that pattern the temporal and facial form, allowing the identification of developmental mechanisms which potentially facilitated the origin of these apomorphic features. These findings demonstrate that the iconic flattened skull table and platyrostral face of Crocodylia are the result of a conserved pattern of shape changes during embryonic development. Considering that these features appear by the Early Jurassic among extinct stem crocodylians, it is likely that these aspects of cranial development have been conserved for over 200 million years.

The effects of phylogeny, body size, and locomotor behavior on the three-dimensional shape of the pelvis in extant carnivorans.

The mammalian pelvis is thought to exhibit adaptations to the functional demands of locomotor behaviors. Previous work in primates has identified form-function relationships between pelvic shape and locomotor behavior; few studies have documented such relationships in carnivorans, instead focusing on long bones. Most work on the functional morphology of the carnivoran pelvis, in particular, has used univariate measures, with only a few previous studies incorporating a three-dimensional (3D) analysis. Here we test the hypothesis that carnivoran taxa that are characterized by different locomotor modes also differ in 3D shape of the os coxae. Using 3D geometric morphometrics and phylogenetic comparative methods, we evaluate the phylogenetic, functional, and size-related effects on 3D pelvis shape in a sample of 33 species of carnivorans. Using surface models derived from laser scans, we collected a suite of landmarks (N = 24) and curve semilandmarks (N = 147). Principal component analysis on Procrustes coordinates demonstrates patterns of shape change in the ischiopubis and ilium likely related to allometry. Phylogenetic generalized least squares analysis on principal component scores demonstrates that phylogeny and body size have greater effects on pelvic shape than locomotor function. Our results corroborate recent research finding little evidence of locomotor specialization in the pelvis of carnivorans. More research on pelvic morphological integration and evolvability is necessary to understand the factors driving pelvic evolution in carnivorans.

Carriage of Supernumerary Sex Chromosomes Decreases the Volume and Alters the Shape of Limbic Structures.

Sex chromosome aneuploidy (SCA) increases risk for several psychiatric disorders associated with the limbic system, including mood and autism spectrum disorders. Thus, SCA offers a genetics-first model for understanding the biological basis of psychopathology. Additionally, the sex-biased prevalence of many psychiatric disorders could potentially reflect sex chromosome dosage effects on brain development. To clarify how limbic anatomy varies across sex and sex chromosome complement, we characterized amygdala and hippocampus structure in a uniquely large sample of patients carrying supernumerary sex chromosomes (n = 132) and typically developing controls (n = 166). After adjustment for sex-differences in brain size, karyotypically normal males (XY) and females (XX) did not differ in volume or shape of either structure. In contrast, all SCAs were associated with lowered amygdala volume relative to gonadally-matched controls. This effect was robust to three different methods for total brain volume adjustment, including an allometric analysis that derived normative scaling rules for these structures in a separate, typically developing population (n = 79). Hippocampal volume was insensitive to SCA after adjustment for total brain volume. However, surface-based analysis revealed that SCA, regardless of specific karyotype, was consistently associated with a spatially specific pattern of shape change in both amygdala and hippocampus. In particular, SCA was accompanied by contraction around the basomedial nucleus of the amygdala and an area crossing the hippocampal tail. These results demonstrate the power of SCA as a model to understand how copy number variation can precipitate changes in brain systems relevant to psychiatric disease.

Trajectory analysis among African hominoids can provide insights into genetic and epigenetic influences during ontogeny.

Prior examination of the ontogeny of Hominoid talo-crural joint morphology using Singular Warp analysis suggested both a genetic and epigenetic signal during development. This question is examined using trajectory analysis and its implications for the Hominin fossil record explored. Trajectory analysis was used to examine talo-crural joint shape at different molar eruption stages during development among a cohort of 221 specimens of Homo sapiens, Gorilla gorilla, Pan troglodytes, and Pan paniscus. Trajectory length, angle, and shape were compared among species. Trajectories that showed a consistent pattern of shape change were predicted to show a genetic signal, while change in that pattern an epigenetic signal. The trajectories of all four hominoid tali were consistent during M1-M2 development, but there was a change in Pan paniscus alone at M2-M3. The tibial trajectories were again consistent in M1-M2 development, however, only Pan paniscus persisted in this trajectory at M2-M3 while the other three changed. Trajectory analysis demonstrated an epigenetic signal in Pan paniscus in the talus and among the other three hominoids in the tibia. Behavioral (epigenetic) changes may impact hominoid ankle shape in extant species. These changes may reflect differences in locomotor repertoire altering shape, as has been suggested in the Hominin fossil record. Further examination of closely related hominoid species may provide insights into potential behavioral influences in the rapid change and diversity of Hominin talo-crural shape in the Plio-pleistocene.

Effects of the Y-chromosome and the dominant hemimelia mutation on the morphology of the mouse mandible.

The aims of this study were to test whether the Y-chromosome and the autosomal dominant hemimelia (Dh) mutation can affect mandible morphology in mice. I analyzed mandible size and shape using landmark-based geometric morphometrics in 16 DH-Chr Y@ -+/+ (@ represents one of the inbred strain names) strains and observed significant differences in mandible size. The largest mandible was identified in strain DH-Chr YC3H and the smallest in strain DH-Chr YKK . Canonical variate and discriminant function analyses suggested that the mandible shapes of strains DH-Chr YC3H and DH-Chr YKK differed from those of the other strains. Because seven of the DH-Chr Y@ -+/+ strains were maintained with dominant hemimelia, I also analyzed the potential influence of dominant hemimelia on mandible morphology because dominant hemimelia is known to cause various skeletal malformations. There were no significant differences in mandible size in seven sets of DH-Chr Y@ -+/+ and DH-Chr Y@ -Dh/+ strains. However, canonical variate analysis mapped strains DH-Chr YCAS -Dh/+ and DH-Chr YCBA -Dh/+ mapped distantly from the rest. Additionally, I observed similar patterns of shape change between DH-Chr YCAS -+/+ and DH-Chr YCAS -Dh/+, and between DH-Chr YCBA -+/+ and DH-Chr YCBA -Dh/+. These data indicate that the Y-chromosome affects the size and shape of the mouse mandible. Dominant hemimelia affects mandible shape but not size, and its effects emerge depending on the kinds of Y-chromosomes.

Mandibular ramus shape variation and ontogeny in Homo sapiens and Homo neanderthalensis

As the interface between the mandible and cranium, the mandibular ramus is functionally significant and its morphology has been suggested to be informative for taxonomic and phylogenetic analyses. In primates, and particularly in great apes and humans, ramus morphology is highly variable, especially in the shape of the coronoid process and the relationship of the ramus to the alveolar margin. Here we compare ramus shape variation through ontogeny in Homo neanderthalensis to that of modern and fossil Homo sapiens using geometric morphometric analyses of two-dimensional semilandmarks and univariate measurements of ramus angulation and relative coronoid and condyle height. Results suggest that ramus, especially coronoid, morphology varies within and among subadult and adult modern human populations, with the Alaskan Inuit being particularly distinct. We also identify significant differences in overall anterosuperior ramus and coronoid shapes between H. sapiens and H. neanderthalensis, both in adults and throughout ontogeny. These shape differences are subtle, however, and we therefore suggest caution when using ramus morphology to diagnose group membership for individual specimens of these taxa. Furthermore, we argue that these morphologies are unlikely to be representative of differences in masticatory biomechanics and/or paramasticatory behaviors between Neanderthals and modern humans, as has been suggested by previous authors. Assessments of ontogenetic patterns of shape change reveal that the typical Neanderthal ramus morphology is established early in ontogeny, and there is little evidence for divergent postnatal ontogenetic allometric trajectories between Neanderthals and modern humans as a whole. This analysis informs our understanding of intraspecific patterns of mandibular shape variation and ontogeny in H. sapiens and can shed further light on overall developmental and life history differences between H. sapiens and H. neanderthalensis.

Hygroscopically actuated wood elements for weather responsive and self-forming building parts – Facilitating upscaling and complex shape changes

For the performance of wood as a building material, its dimensional changes in response to alterations of relative humidity are commonly perceived as an adverse effect. Recently, this material inherent property has been proposed to be utilized in a smart way. Employing the bilayer principle, controlled and reversible shape changes in response to changes of relative humidity were demonstrated. Wood naturally inherits a unique combination of material properties specifically suitable for large-scale shape-changing parts. While being environmentally responsive, it offers high mechanical stiffness throughout shape-change, ease of machining and working, and sustainable availability in large sizes and quantities. In this study, we demonstrate design principles for achieving a range of shape changing patterns such as uni- and bi-directional surface curvature of wood and wood-hybrid bilayers with both negative (hyperboloid curvature) and positive Gaussian curvature (spherical curvature). In parallel, we have developed suitable joints to join multiple elements to facilitate upscaling in length and width while maintaining shape-change. The ability to design and control the type and magnitude of curvature for specific sizes, shapes, and aspect ratios open the opportunity for a new class of large-scale weather responsive elements and self-forming building components.

Femoral ontogeny in humans and great apes and its implications for their last common ancestor

Inferring the morphology of the last common ancestor of humans, chimpanzees and gorillas is a matter of ongoing debate. Recent findings and reassessment of fossil hominins leads to the hypothesis that the last common ancestor was not extant African ape-like. However, an African great-ape-like ancestor with knuckle walking features still remains plausible and the most parsimonious scenario. Here we address this question via an evolutionary developmental approach, comparing taxon-specific patterns of shape change of the femoral diaphysis from birth to adulthood in great apes, humans, and macaques. While chimpanzees and gorillas exhibit similar locomotor behaviors, our data provide evidence for distinct ontogenetic trajectories, indicating independent evolutionary histories of femoral ontogeny. Our data further indicate that anthropoid primates share a basic pattern of femoral diaphyseal ontogeny that reflects shared developmental constraints. Humans escaped from these constraints via differential elongation of femur.

Robust defect detection method for a non-periodic TFT-LCD pad area

In this work, we propose an effective inline inspection method for non-repeating patterns on TFT-LCDs which can be quickly applied to current manufacturing processes and easily automated. Given that the TFT-LCD active area is composed of regularly spaced repeating patterns (pixels) inline inspections are possible using relatively simple methods. However, the pad area, which transfers digital signals to the TFT active pattern, is composed of patterns with complex shapes in the form of either shape changing patterns or repeating patterns with varying periods. This makes it very difficult to examine complex patterns in the pad area, because repeating patterns have to be divided into areas with similar repeating frequencies and the inspection parameters have to be set differently, and can cause a bottleneck preventing inspection yield improvements. In this paper, an inspection method using a discrete Fourier transform (DFT) filter and a local threshold binarization method is proposed. We show that the proposed method works on an image having both impedance matching and fan-out areas at a varying frequency with a single parameter set. This setting of parameters also can be done in an automated way.

Feeding variations and shape changes of a temperate reef clingfish during its early ontogeny

The majority of rocky reef fishes have complex life cycles, involving transition from a pelagic to a benthic environment. This means that as they grow, their morphology, behaviour and feeding habits must change. Therefore, shape changes occurring during early development of these fishes will be related to diet changes. The clingfish Sicyases sanguineus was selected for this study, because it displays a noticeable variation in shape from pelagic larvae to juvenile stage, and it is expected that diet composition will change as well. The pattern of shape changes was studied using geometric morphometrics. A set of 9 landmarks were digitized in 159 larval and juvenile fish and the same specimens were used for gut content analysis. Allometric growth was most prominent early in the ontogeny, from 4 to 12 mm. Morphology changed from a thin and hydrodynamic shape to a more robust and deeper body prior to settlement. The diet of the clingfish during larval stages showed preferences for a variety of copepod stages. As individual grows the ingested prey volume increases, but not the number and width of prey. A partial least square analysis showed low covariance between shape changes and diet composition changes in prey number and volume, suggesting that the two processes were temporally decoupled. The biggest shape changes, a lengthening of the visceral cavity and a flattening of the head, occurred up to 12 mm standard length, while the largest feeding differentiation, shifting from copepods to microalgae, occurred after 16 mm. Results suggest that shape changes precede trophic changes in this clingfish species during the transition from a pelagic to a benthic habitat.

Patterns of divergence in fish species separated by the Isthmus of Panama

BackgroundThe Pleistocene closure of Isthmus of Panama, separating the basins of the Eastern Pacific and the Caribbean Sea, created a unique natural experiment that reveals how marine faunas respond to environmental change. To explore how fishes have been affected by this tectonic event, I compare transisthmian patterns in phylogeny and morphology for geminate lineages in two families, Eleotridae (sleepers) and Apogonidae (cardinalfishes).ResultsTime-calibrated phylogenies for these families show different diversification patterns. In Eleotridae, several independent shallow instances of transisthmian divergences occur, with one or a few species on either side of the Isthmus. Among Apogonidae, a single clade of Eastern Pacific species is nested within a broad Caribbean radiation that also includes a species known from the Mediterranean. Divergence time estimates for taxa isolated by closure of the Isthmus are broadly congruent. Hypotheses dated with deeper, fossil-based legacy calibrations put the divergences in the Miocene at 7.4–15.1 Ma, while those estimated with a shallow biogeographic calibration of final Isthmus closure range from 5.1 to 9.9 Ma, in the late Miocene/early Pliocene. Eleotridae are more euryhaline than Apogonidae, but do not exhibit shallower transisthmian divergences. In both families, descendent lineages on either side of the Isthmus of Panama exhibit significant shape differences, although that distinction disappears for Apogonidae when I apply a correction for phylogenetic relationships. To evaluate the tempo and mode of continuous character evolution, I fit several single and multiple rate evolutionary models to morphometric data reconstructed on the Apogonidae phylogeny. I find that the most highly favored model, as estimated on both legacy and isthmus calibrated hypotheses, is a multiple rate Ornstein-Uhlbeck model, with a mosaic of rate shifts postulated for shape changes among fishes in the Caribbean and Eastern Pacific.ConclusionsAlthough many transisthmian taxa have been compared and their phylogenies calibrated to estimate the dates associated with population sundering, few studies correlate these timing estimates with morphological change. I show that in transisthmian fish lineages, morphometric distinctions are detectable across the Isthmus, and that rates and patterns of shape change have also shifted, with variable manifestations across the body and between the Caribbean and Eastern Pacific.