Patterns Of Morphological Evolution Research Articles

A new abelisaurid dinosaur from the end Cretaceous of Patagonia and evolutionary rates among the Ceratosauria.

Gondwanan dinosaur faunae during the 20 Myr preceding the Cretaceous-Palaeogene (K/Pg) extinction included several lineages that were absent or poorly represented in Laurasian landmasses. Among these, the South American fossil record contains diverse abelisaurids, arguably the most successful groups of carnivorous dinosaurs from Gondwana in the Cretaceous, reaching their highest diversity towards the end of this period. Here we describe Koleken inakayali gen. et sp. n., a new abelisaurid from the La Colonia Formation (Maastrichtian, Upper Cretaceous) of Patagonia. Koleken inakayali is known from several skull bones, an almost complete dorsal series, complete sacrum, several caudal vertebrae, pelvic girdle and almost complete hind limbs. The new abelisaurid shows a unique set of features in the skull and several anatomical differences from Carnotaurus sastrei (the only other abelisaurid known from the La Colonia Formation). Koleken inakayali is retrieved as a brachyrostran abelisaurid, clustered with other South American abelisaurids from the latest Cretaceous (Campanian-Maastrichtian), such as Aucasaurus, Niebla and Carnotaurus. Leveraging our phylogeny estimates, we explore rates of morphological evolution across ceratosaurian lineages, finding them to be particularly high for elaphrosaurine noasaurids and around the base of Abelisauridae, before the Early Cretaceous radiation of the latter clade. The Noasauridae and their sister clade show contrasting patterns of morphological evolution, with noasaurids undergoing an early phase of accelerated evolution of the axial and hind limb skeleton in the Jurassic, and the abelisaurids exhibiting sustained high rates of cranial evolution during the Early Cretaceous. These results provide much needed context for the evolutionary dynamics of ceratosaurian theropods, contributing to broader understanding of macroevolutionary patterns across dinosaurs.

What Are the Causes of Super Activity of Solar Active Regions?

Flare productivity varies among solar active regions (ARs). This study analyzed 20 ARs of contrasting sunspot areas and flare productivities to understand the super flare productivity of certain ARs. We used the flare index (FI) as an indicator of flare activity. We examined the pattern of morphological evolution of magnetic features. Further, we derived a set of magnetic feature parameters to quantitatively characterize ARs. Our study found that the correlation coefficient is the highest (r = 0.78) between FI and the length of the strong gradient polarity inversion line (SgPIL), while the coefficient is the lowest (r = 0.14) between FI and the total unsigned magnetic flux. For the selected ARs, this study also found that the super flare productive ARs have SgPILs (R value) longer (greater) than 50 Mm (4.5). These results suggest that flare productivity is mainly controlled by the size of the subregion that comprises close interaction of opposite magnetic polarities and is weakly correlated with the size of the whole ARs. Further, even though magnetic flux emergence is important, this study shows that it alone is insufficient to increase flare productivity. New emergence can drive either the interaction of like or opposite magnetic polarities of nonconjugate pairs (i.e., polarities not from the same bipole). In the former case, the magnetic configuration remains simple, and flare productivity would be low. In the latter case, the convergence of opposite magnetic fluxes of nonconjugate pairs results in a magnetic configuration with long SgPIL and an increase in flare productivity.

Rphenoscate: An R package for semantics‐aware evolutionary analyses of anatomical traits

Abstract Organismal anatomy is a hierarchical system of anatomical entities often imposing dependencies among multiple morphological characters. Ontologies provide a formal and computable framework for incorporating prior biological knowledge about anatomical dependencies in models of trait evolution. They also offer new opportunities for working with semantic representations of morphological data. In this work, we present a new R package—rphenoscate—that enables incorporating ontological knowledge in evolutionary analyses and exploring semantic patterns of morphological data. In conjunction with rphenoscape, it allows for assembling synthetic phylogenetic character matrices from semantic phenotypes of morphological data. We showcase the package functionality with data sets from bees and fishes. We demonstrate that ontologies can be employed to automatically set up evolutionary models accounting for trait dependencies in stochastic character mapping. We also demonstrate how ontology annotations can be explored to interrogate patterns of morphological evolution. Finally, we demonstrate that synthetic character matrices assembled from semantic phenotypes retain most of the phylogenetic information from their original data sets. Ontologies will become important tools for integrating anatomical knowledge into phylogenetic methods and making morphological data FAIR compliant—a critical step of the ongoing ‘phenomics’ revolution. Our new package offers key advancements towards this goal.

Conical and sabertoothed cats as an exception to craniofacial evolutionary allometry

Among evolutionary trends shaping phenotypic diversity over macroevolutionary scales, CREA (CRaniofacial Evolutionary Allometry) describes a tendency, among closely related species, for the smaller-sized of the group to have proportionally shorter rostra and larger braincases. Here, we used a phylogenetically broad cranial dataset, 3D geometric morphometrics, and phylogenetic comparative methods to assess the validity and strength of CREA in extinct and living felids. To test for the influence of biomechanical constraints, we quantified the impact of relative canine height on cranial shape evolution. Our results provided support to CREA at the family level. Yet, whereas felines support the rule, big cats, like Pantherinae and Machairodontinae, conform weakly if not at all with CREA predictions. Our findings suggest that Machairodontinae constitute one of the first well-supported exceptions to this biological rule currently known, probably in response to the biomechanical demands and developmental changes linked with their peculiar rostral adaptations. Our results suggest that the acquisition of extreme features concerning biomechanics, evo-devo constraints, and/or ecology is likely to be associated with peculiar patterns of morphological evolution, determining potential exceptions to common biological rules, for instance, by inducing variations in common patterns of evolutionary integration due to heterochronic changes under ratchet-like evolution.

Beaks Promote Rapid Morphological Diversification Along Distinct Evolutionary Trajectories in Labrid Fishes (Eupercaria: Labridae).

The upper and lower jaws of some wrasses (Eupercaria: Labridae) possess teeth that have been coalesced into a strong durable beak that they use to graze on hard coral skeletons, hard-shelled prey, and algae, allowing many of these species to function as important ecosystem engineers in their respective marine habitats. While the ecological impact of the beak is well-understood, questions remain about its evolutionary history and the effects of this innovation on the downstream patterns of morphological evolution. Here we analyze 3D cranial shape data in a phylogenetic comparative framework and use paleoclimate modeling to reconstruct the evolution of the labrid beak across 205 species. We find that wrasses evolved beaks three times independently, once within odacines, and twice within parrotfishes in the Pacific and Atlantic Oceans. We find an increase in the rate of shape evolution in the Scarus+Chlorurus+Hipposcarus (SCH) clade of parrotfishes likely driven by the evolution of the intramandibular joint. Paleoclimate modeling shows that the SCH clade of parrotfishes rapidly morphologically diversified during the middle Miocene. We hypothesize that possession of a beak in the SCH clade coupled with favorable environmental conditions allowed these species to rapidly morphologically diversify.

Modeling of solid-air multi-dendrite growth evolution driven by coupled thermal-solute using non-isothermal quantitative phase field method

The safety hazard posed by residual or infiltrated air condensing into external oxygen-rich solid-air (SA) particles in the liquid hydrogen container deserves attention. In this study, the patterns of morphological evolution, oxygen solute distribution, and growth rate of SA single- and multi-dendrite under various thermal environments are investigated using a non-isothermal quantitative phase field model for the first time. The lattice anisotropy problem of six-fold symmetric dendrites is effectively avoided. The results show that the Type II boundary condition is more suitable for the simulation of dendrite growth, which can avoid the influence of boundary conditions on dendrite growth. In addition, the suitability of the isotropic difference method for simulating the growth of SA multi-dendrites with six-fold symmetry is verified in this paper. The maximum values of solid fraction and oxygen solute concentration within the simulated domain are 0.62 and 0.435, respectively, for an initial subcooling degree of 4 K. The temperature distribution is significantly altered by the application of boundary heat flux and affects the growth pattern of SA dendrites. Compared to the scenario with no boundary heat flux, unilateral heat input and heat extraction decreased the solid fraction of SA dendrites by 31% and increased it by 43%, respectively, while the maximum concentration of oxygen solute was reduced to 144.8% and 97.3%, respectively. When boundary heat flux was applied to all quadrilateral boundaries, the solid fraction under heat extraction and heat input conditions is reduced by 82% and enhanced by 138%, respectively, compared to the scenario with no boundary heat flux. Additionally, the maximum concentration of oxygen solute is found to be 197.6% and 69.5% of that without boundary heat flux, respectively. This study improves the understanding of the evolution of solid-air dendrite growth and can provide theoretical guidance for the safe use of liquid hydrogen systems.

Morphological disparity and evolutionary rates of cranial and postcranial characters in sloths (Mammalia, Pilosa, Folivora)

AbstractSloth morphological evolution has been widely studied qualitatively, with comparative anatomy and morpho‐functional approaches, or through quantitative assessments of morphological variation using morphometrics. Only recently, however, have folivoran morphological disparity and evolutionary rates begun to be evaluated using discrete character data. Nonetheless, patterns of morphological evolution in separate character partitions have not been investigated, neither the relative influence of, on the one hand, phylogeny, and on the other, dietary and locomotory adaptations of sloths. Here we evaluate those patterns using a phylomorphospace approach, quantifying morphological disparity and evolutionary rates, and investigating possible drivers of morphological evolution for cranial and postcranial characters in Folivora. The evolution of the morphology in those partitions is associated with distinct patterns of disparity among clades and ecological groups, even though the two partitions do not differ substantially in overall evolutionary tempo. Historical processes shaped the morphological evolution of sloths more consistently than ecological ones, although changes in postcranial characters also seem to be associated with locomotory adaptations, in which morphological convergences were much more common. We also discuss important methodological trade‐offs in investigations of partitioned datasets mostly composed of fossil taxa.

Comparative anatomy of the passerine carpometacarpus helps illuminate the early fossil record of crown Passeriformes.

The hyper-diverse clade Passeriformes (crown group passerines) comprises over half of extant bird diversity, yet disproportionately few studies have targeted passerine comparative anatomy on a broad phylogenetic scale. This general lack of research attention hinders efforts to interpret the passerine fossil record and obscures patterns of morphological evolution across one of the most diverse clades of extant vertebrates. Numerous potentially important crown passeriform fossils have proven challenging to place phylogenetically, due in part to a paucity of phylogenetically informative characters from across the passerine skeleton. Here, we present a detailed analysis of the morphology of extant passerine carpometacarpi, which are relatively abundant components of the passerine fossil record. We sampled >70% of extant family-level passerine clades (132 extant species) as well as several fossils from the Oligocene of Europe and scored them for 54 phylogenetically informative carpometacarpus characters optimised on a recently published phylogenomic scaffold. We document a considerable amount of previously undescribed morphological variation among passerine carpometacarpi, and, despite high levels of homoplasy, our results support the presence of representatives of both crown Passeri and crown Tyranni in Europe during the Oligocene.

Distinct patterns of the natural evolution of soft tissue sarcomas on pre-treatment MRIs captured with delta-radiomics correlate with gene expression profiles.

Radiomics of soft tissue sarcomas (STS) is assumed to correlate with histologic and molecular tumor features, but radiogenomics analyses are lacking. Our aim was to identify if distinct patterns of natural evolution of STS obtained from consecutive pre-treatment MRIs are associated with differential gene expression (DGE) profiling in a pathway analysis. All patients with newly diagnosed STS treated in a curative intent in our sarcoma reference center between 2008 and 2019 and with two available pre-treatment contrast-enhanced MRIs were included in this retrospective study. Radiomics features (RFs) were extracted from fat-sat contrast-enhanced T1-weighted imaging. Log ratio and relative change in RFs were calculated and used to determine grouping of samples based on a consensus hierarchical clustering. DGE and oncogenesis pathway analysis were performed in the delta-radiomics groups identified in order to detect associations between delta-radiomics patterns and transcriptomics features of STS. Secondarily, the prognostic value of the delta-radiomics groups was investigated. Sixty-three patients were included (median age: 63 years, interquartile range: 52.5-70). The consensus clustering identified 3 reliable delta-radiomics patient groups (A, B, and C). On imaging, group B patients were characterized by increase in tumor heterogeneity, necrotic signal, infiltrative margins, peritumoral edema, and peritumoral enhancement before the treatment start (p value range: 0.0019-0.0244), and, molecularly, by downregulation of natural killer cell-mediated cytotoxicity genes and upregulation of Hedgehog and Hippo signaling pathways. Group A patients were characterized by morphological stability of pre-treatment MRI traits and no local relapse (log-rank p = 0.0277). This study highlights radiomics and transcriptomics convergence in STS. Proliferation and immune response inhibition were hyper-activated in the STS that were the most evolving on consecutive imaging. • Three consensual and stable delta-radiomics clusters were identified and captured the natural patterns of morphological evolution of STS on pre-treatment MRIs. • These 3 patterns were explainable and correlated with different well-known semantic radiological features with an ascending gradient of pejorative characteristics from the A group to C group to B group. • Gene expression profiling stressed distinct patterns of up/downregulated oncogenetic pathways in STS from B group in keeping with its most aggressive radiological evolution.

Insularity and Aridity as Drivers of Mandibular Disparity in Thylamys elegans (Waterhouse, 1839) from Populations of the Atacama Desert, Chile.

Simple SummaryThe following article studied the environment influence between island and mainland in an endemic marsupial from Chile the mouse-opossum Thylamys elegans (Waterhouse, 1839). Its important to understand that the isolated habitat could affect the pattern of morphological evolution in organism due to millions of years of being separated from the mainland. In this re-search we used two methodologies to study those effects in the mandible of this marsupial, first a biomechanical methodology which was used to correlate it with the diet, and a second called ge-ometric morphometrics which combine the geometry and biology to identify the principal changes in the morphology. Our results showed that Island populations have more disparity in the mor-phology in comparison to the mailand differences that could be related to the arid environment and other characteristic of the island. Concluding that one of the possible reason of the evolutionary history of this Chilean mouse-opossum was processes of natural selection by a process of coloniza-tion of island after vicariance denominated founder effect.Island ecosystems differ in several elements from mainland ecosystems and may induce variations related to natural selection and patterns of adaptation in most aspects of the biology of an organism. Thylamys elegans (Waterhouse, 1839) is a marsupial endemic to Chile, distributed from Loa River to Concepción. Historically, three subspecies have been described: Thylamys elegans elegans, Thylamys elegans coquimbensis and Thylamys elegans soricinus. For this research, two morphometric approaches and a biomechanical model were used to compare the mandible shapes and biomechanics between two Chilean mouse opossum populations belonging to different subspecies: one from the coastal desert of Chile (T. e. coquimbensis) and the other from the central inland region (T. e. elegans). Additionally, mandibles of insular populations found in the Reserva Nacional Pinguino de Humboldt (RNPH)), from which the subspecies association is unknown, were also included. The results showed that insular populations have differences in mandibular shapes, sizes and biomechanical characteristics compared to continental populations, which may be related to environmental variables like aridity and vegetation cover, prey type, insularity effects and/or the founder effect on micromammals, apart from vicariance hypotheses and other selective pressures.

Early Origins of Divergent Patterns of Morphological Evolution on the Mammal and Reptile Stem-Lineages.

The origin of amniotes 320 million years ago signaled independence from water in vertebrates and was closely followed by divergences within the mammal and reptile stem lineages (Synapsida and Reptilia). Early members of both groups had highly similar morphologies, being superficially “lizard-like” forms with many plesiomorphies. However, the extent to which they might have exhibited divergent patterns of evolutionary change, with the potential to explain the large biological differences between their living members, is unresolved. We use a new, comprehensive phylogenetic dataset to quantify variation in rates and constraints of morphological evolution among Carboniferous–early Permian amniotes. We find evidence for an early burst of evolutionary rates, resulting in the early origins of morphologically distinctive subgroups that mostly persisted through the Cisuralian. Rates declined substantially through time, especially in reptiles. Early reptile evolution was also more constrained compared with early synapsids, exploring a more limited character state space. Postcranial innovation in particular was important in early synapsids, potentially related to their early origins of large body size. In contrast, early reptiles predominantly varied the temporal region, suggesting disparity in skull and jaw kinematics, and foreshadowing the variability of cranial biomechanics seen in reptiles today. Our results demonstrate that synapsids and reptiles underwent an early divergence of macroevolutionary patterns. This laid the foundation for subsequent evolutionary events and may be critical in understanding the substantial differences between mammals and reptiles today. Potential explanations include an early divergence of developmental processes or of ecological factors, warranting cross-disciplinary investigation. [Amniote; body size; constraint; phylogeny; rate.]

Unique traditional villages on the Loess\xa0Plateau of China: historic evolution and challenges to sustainable development of silo-caves

Silo-cave is a unique human habitation form on the Loess Plateau in northern China, which consists of an excavated 6–7 m deep pit as the courtyard and cave dwellings in the surrounding four walls. This architecture has had a history of more than 7000 years, and yet such “living fossils for the history of dwellings” are now facing great crises and challenges during rapid social and economic development. In this paper, remote sensing and GIS techniques are used to comprehensively and systematically investigate the spatial distributions and morphological characteristics of silo-caves at both the macro and micro scales. The research shows that silo-cave villages are mainly distributed in economically underdeveloped areas, such as West Henan (Yuxi), South Shanxi (Jinnan), Central Shaanxi (Guanzhong), and East Gansu (Longdong). The morphological evolution patterns of typical silo-cave villages are identified, including: (1) retaining the periphery and rebuilding the inner parts of the villages, (2) retaining the inner parts and expanding the periphery of the villages, and (3) rebuilding the inner parts and expanding the periphery of the villages. These patterns are demonstrated to be influenced by many factors, including landforms, traffic conditions, economic development, population growth, and administrative division adjustment. Sustainable development of these traditional silo-cave villages relies on administrative policy and planning, people’s awareness of cultural heritage protection, culture inheritance, industrial transformation, and public services.

Formation of Macro- and Microrefugia Explains Morphological Divergence of the Eurasian Jay Garrulus glandarius in the Japanese Archipelago

The Eurasian Jay Garrulus glandarius is a highly polytypic bird species composed of 34–36 subspecies. The contribution of formation of glacial refugia to the evolutionary process that generated its tremendous diversity has not been studied. We investigated the contribution of microrefugia to the subspeciation process of the Eurasian Jay in the Japanese archipelago. By assessing genetic diversity and reconstructing a mitochondrial phylogenetic tree, we asked whether divergence of a subspecies on a peripheral island (Sado Island) from the subspecies on the mainland of the Japanese archipelago (Honshu and Kyushu, hereafter mainland) occurred via formation of a microrefugium outside the mainland macrorefugia. We also assessed morphological differences between the Sado Island and mainland jay populations. We tested whether the observed morphological differences can be explained by adaptation of the Sado Island population to a species-poor microrefugium. Genetic analyses inferred that the Sado Island population survived in a refugium outside the mainland macrorefugia from around the late Middle to Late Pleistocene. The morphology of the Sado Island jay population was characterized by greater trait variance, larger body size, and a disproportionately large bill when compared with the mainland population. These results are consistent with the expected patterns of morphological evolution in microrefugia with reduced species diversity. We suggest the importance of ecological release in a microrefugium on Sado Island for the evolution of geographical variation of the Eurasian Jay in the Japanese archipelago. This is the first study to assess the significance of microrefugia for the diversification of the Eurasian Jay.

A phylogeny of Antirrhinum reveals parallel evolution of alpine morphology.

Parallel evolution of similar morphologies in closely related lineages provides insight into the repeatability and predictability of evolution. In the genus Antirrhinum (snapdragons), as in other plants, a suite of morphological characters are associated with adaptation to alpine environments. We tested for parallel trait evolution in Antirrhinum by investigating phylogenetic relationships using restriction-site associated DNA (RAD) sequencing. We then associated phenotypic information to our phylogeny to reconstruct the patterns of morphological evolution and related this to evidence for hybridisation between emergent lineages. Phylogenetic analyses showed that the alpine character syndrome is present in multiple groups, suggesting that Antirrhinum has repeatedly colonised alpine habitats. Dispersal to novel environments happened in the presence of intraspecific and interspecific gene flow. We found support for a model of parallel evolution in Antirrhinum. Hybridisation in natural populations, and a complex genetic architecture underlying the alpine morphology syndrome, support an important role of natural selection in maintaining species divergence in the face of gene flow.

Patterns of skeletal integration in birds reveal that adaptation of element shapes enables coordinated evolution between anatomical modules.

Birds show tremendous ecological disparity in spite of strong biomechanical constraints imposed by flight. Modular skeletal evolution is generally accepted to have facilitated this, with distinct body regions showing semi-independent evolutionary trajectories. However, this hypothesis has received little scrutiny. We analyse evolutionary modularity and ecomorphology using three-dimensional data from across the entire skeleton in a phylogenetically broad sample of extant birds. We find strongly modular evolution of skeletal element sizes within body regions (head, trunk, forelimb and hindlimb). However, element shapes show substantially less modularity, have stronger relationships to ecology, and provide evidence that ecological adaptation involves coordinated evolution of elements across different body regions. This complicates the straightforward paradigm in which modular evolution facilitated the ecological diversification of birds. Our findings suggest the potential for undetected patterns of morphological evolution in even well-studied groups, and advance the understanding of the interface between evolutionary integration and ecomorphology.

Phylogeny and evolutionary history of the amniote egg.

We review morphological features of the amniote egg and embryos in a comparative phylogenetic framework, including all major clades of extant vertebrates. We discuss 40 characters that are relevant for an analysis of the evolutionary history of the vertebrate egg. Special attention is given to the morphology of the cellular yolk sac, the eggshell, and extraembryonic membranes. Many features that are typically assigned to amniotes, such as a large yolk sac, delayed egg deposition, and terrestrial reproduction have evolved independently and convergently in numerous clades of vertebrates. We use phylogenetic character mapping and ancestral character state reconstruction as tools to recognize sequence, order, and patterns of morphological evolution and deduce a hypothesis of the evolutionary history of the amniote egg. Besides amnion and chorioallantois, amniotes ancestrally possess copulatory organs (secondarily reduced in most birds), internal fertilization, and delayed deposition of eggs that contain an embryo in the primitive streak or early somite stage. Except for the amnion, chorioallantois, and amniote type of eggshell, these features evolved convergently in almost all major clades of aquatic vertebrates possibly in response to selective factors such as egg predation, hostile environmental conditions for egg development, or to adjust hatching of young to favorable season. A functionally important feature of the amnion membrane is its myogenic contractility that moves the (early) embryo and prevents adhering of the growing embryo to extraembryonic materials. This function of the amnion membrane and the liquid-filled amnion cavity may have evolved under the requirements of delayed deposition of eggs that contain developing embryos. The chorioallantois is a temporary embryonic exchange organ that supports embryonic development. A possible evolutionary scenario is that the amniote egg presents an exaptation that paved the evolutionary pathway for reproduction on land. As shown by numerous examples from anamniotes, reproduction on land has occurred multiple times among vertebrates-the amniote egg presenting one "solution" that enabled the conquest of land for reproduction.

Evolution in Sinocyclocheilus cavefish is marked by rate shifts, reversals, and origin of novel traits

BackgroundNatural model systems are indispensable for exploring adaptations in response to environmental pressures. Sinocyclocheilus of China, the most diverse cavefish clade in the world (75 species), provide unique opportunities to understand recurrent evolution of stereotypic traits (such as eye loss and sensory expansion) in the context of a deep and diverse phylogenetic group. However, they remain poorly understood in terms of their morphological evolution. Therefore, we explore key patterns of morphological evolution, habitat utilization and geographic distribution in these fishes.ResultsWe constructed phylogenies and categorized 49 species based on eye-related condition (Blind, Micro-eyed, and Normal-eyed), habitat types (Troglobitic—cave-restricted; Troglophilic—cave-associated; Surface—outside caves) and existence of horns. Geometric-morphometric analyses show Normal-eyed morphs with fusiform shapes segregating from Blind/Micro-eyed deeper bodied morphs along the first principal-component axis; second axis accounts for shape complexity related to horns. The body shapes showed a significant association with eye-related condition and horn, but not habitat types. Ancestral reconstructions suggest at least three independent origins of Blind morphs, each with different levels of modification in relation to their ancestral Normal-eyed morphs; Sinocyclocheilus are also pre-adapted for cave dwelling. Our geophylogeny shows an east-to-west diversification spanning Pliocene and Pleistocene, with early-diversifying Troglobitic species dominating subterranean habitats of karstic plains whereas predominantly Surface forms inhabit hills to the west. Evolutionary rates analyses suggest that lineages leading to Blind morphs were characterized by significant rate shifts, such as a slowdown in body size evolution and a 5–20 fold increase in rate of eye regression, possibly explained by limited resource availability. Body size and eye size have undergone reversals, but not horns, a trait entailing considerable time to form.ConclusionsSinocyclocheilus occupied cave habitats in response to drying associated with aridification of China during late Miocene and the Pliocene. The prominent cave-adaptations (eye-regression, horn-evolution) occur in clades associated with the extensive subterranean cave system in Guangxi and Guizhou provinces. Integration of morphology, phylogeny, rate analyses, molecular-dating and distribution show not only several remarkable patterns of evolution, but also interesting exceptions to these patterns signifying the diversification of Sinocyclocheilus as an invaluable model system to explore evolutionary novelty.

Morphological conservatism of the family Naticidae (Gastropoda) through time: potential causes and consequences

AbstractTaxonomic status of several members of the family Naticidae is extremely vague because of its simple shell morphology. Conventional taxonomic classification schemes suggest that most of the morphological characters tend to be homoplastic and exhibit convergence. Such morphological convergence complicates naticid taxonomy and makes it difficult to understand the evolutionary history of this group; several unrelated taxa are often misidentified as naticids, thereby exaggerating the actual diversity of this group. Here, we employ a standard landmark-based approach to understand the pattern of morphological evolution of this family. Ordination methods such as principal components analysis and canonical variate analysis were used to create morphospaces, and disparity was quantified using variance and range. Our results reveal that when naticids are compared with their sister taxon, Ampullinidae, the two families show significant differences in their average shapes, despite their superficial resemblances. Among naticids, although the mean shapes of the individual subfamilies are different, overall, the family Naticidae has displayed extreme morphological conservatism from the Jurassic to the Holocene. Interestingly, this conservatism has been unaffected by taxonomic changes—neither the extinction of the subfamily Gyrodinae nor the appearance of the subfamily Sininae affected this morphological conservatism. Naticids have always shown strong ecological preference toward an infaunal mode of life and strict behavioral selectivity in handling and preying upon infaunal organisms, and this ecological and behavioral conservatism could have enabled them to diversify without undergoing a change in their basic Bauplan.

Macroevolutionary patterns of body plan canalization in euarthropods

AbstractReconstructing patterns of macroevolution has become a central endeavor in paleobiology, because it offers insight into evolutionary models shaping the history of life. As the most diverse and abundant animals since the Cambrian period, arthropods provide copious data to elucidate the emergence of body plans in metazoan lineages. However, information provided by fossils on the tempo and mode of this phenomenon has lacked a recent synthesis. Here, I investigate macroevolutionary patterns of morphological evolution in Euarthropoda using a combined extinct and extant dataset optimized for multivariate analyses. Overall ordination patterns between the main morphogroups are consistent with another, independently coded, extant-only dataset providing molecular and morphological rates of evolution. Based on a “deep split” phylogenetic framework, total-group Mandibulata and Arachnomorpha emerge as directional morphoanatomical lineages, with basal fossil morphogroups showing heterogeneously spread-out occupations of the morphospace. In addition to a more homogeneous morphological variation, new morphogroups arose by successive reductions of translation distances; this pattern was interrupted only by terrestrialization events and the origin of pancrustaceans. A displaced optimum type of model is proposed to explain the fast assembly of canalized body plans during the Cambrian, with basal fossil morphogroups fitting intermediate fitness peaks in a moving adaptive landscape. Given time constraints imposed by the paleontological evidence, and owing to the interplay between canalization and modularity, as well as a decoupling between molecular and morphological rates, the rise of euarthropods would support the view that the swiftness of the Cambrian explosion was mostly associated with the buildup of genetic regulatory networks.

Morphological evolution in the ant reproductive caste

AbstractThe evolution of eusociality has led to considerable changes in the general hymenopteran body plan. In particular, the evolution of reproductive division of labour caused the worker caste to be largely freed from the demands involved in reproduction. As a consequence, workers were able to evolve highly specialized morphologies for foraging and colony maintenance, whereas the reproductive caste became specialized for reproduction. Despite these important changes, little is known about the general patterns of morphological evolution within the ant reproductive caste. Our goals here were to characterize morphological variation in the ant reproductive caste and to test whether different sexes display variation in their evolutionary rates. We obtained measurements of 897 specimens from a total of 678 ant species. The shapes of the size distributions were similar between sexes, with queens being larger than males in all traits except for eye length. Contrary to the expectation based on Rensch’s rule, although queens were larger, the degree of dimorphism increased with body size. Finally, there was strong evidence for an accelerated tempo of morphological evolution in queens in relation to males. These results represent the first comprehensive treatment of morphological variation in the ant reproductive caste and provide important new insights into their evolution.