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126 results for “morphological disparity”
Data from: Morphological disparity and evolutionary patterns of Cambrian hyoliths
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Data from: Phylogenetic sampling affects evolutionary patterns of morphological disparity
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Data from: Morphological disparity and evolutionary rates of cranial and postcranial characters in sloths (Mammalia, Pilosa, Folivora)
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Data from: Mosaic evolution underlies feliform morphological disparity
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Categorical versus geometric morphometric approaches to characterising the evolution of morphological disparity in Osteostraci (Vertebrata, stem-Gnathostomata)
Morphological variation (disparity) is almost invariably characterised by two non-mutually exclusive approaches: (i) quantitatively, through geometric morphometrics, and (ii) in terms of discrete, 'cladistic', or categorical characters. Uncertainty over the comparability of these approaches diminishes the potential to obtain nomothetic insights into the evolution of morphological disparity and the few benchmarking studies conducted so far show contrasting results. Here, we apply both approaches to characterising morphology in the stem-gnathostome clade Osteostraci in order to assess congruence between these alternative methods as well as to explore the evolutionary patterns of the group in terms of temporal disparity and the influence of phylogenetic relationships and habitat on morphospace occupation. Our results suggest that both approaches yield similar results in morphospace occupation and clustering, but also some differences indicating that these metrics may capture different aspects of morphology. Phylomorphospaces reveal convergence towards a generalised 'horseshoe'-shaped cranial morphology and two strong trends involving major groups of osteostracans (benneviaspidids and thyestiids), which probably reflect adaptations to different lifestyles. Temporal patterns of disparity obtained from categorical and morphometric approaches appear congruent, however disparity maxima are recorded at very different times in the evolutionary history of the group when increasing the number of taxa and characters in the categorical dataset. The results of our analyses indicate that categorical and continuous datasets may characterize different patterns of morphological disparity and that discrepancies could reflect preservational limitations of morphometric data and differences in the potential of each data type for characterizing more or less inclusive aspects of overall phenotype.
Analyzing disparity and rates of morphological evolution with model-based phylogenetic comparative methods
<p>Understanding variation in rates of evolution and morphological disparity is a goal of macroevolutionary research. In a phylogenetic comparative methods framework, we present three explicit models for linking the rate of evolution of a trait to the state of another evolving trait. This allows testing hypotheses about causal influences on rates of phenotypic evolution with phylogenetic comparative data. We develop a statistical framework for fitting the models with generalized least-squares regression, and use this to discuss issues and limitations in the study of rates of evolution more generally. We show that the power to detect effects on rates of evolution is low in that even strong causal effects are unlikely to explain more than a few percent of observed variance in disparity. We illustrate the models and issues by testing if rates of beak-shape evolution in birds are influenced by brain size, as may be predicted from a Baldwin effect in which presumptively more behaviorally flexible large-brained species generate more novel selection on themselves leading to higher rates of evolution. From an analysis of morphometric data for 645 species we find evidence that both macro- and microevolution of the beak are faster in birds with larger brains, but with the caveat that there are no consistent effects of relative brain size.</p>
Supplementary files for: Why should we compare morphological and molecular disparity?
<p><span>1. </span><span>Indices of morphological disparity seek to summarise the highly multivariate morphological variation across groups of species within clades, time bins or other groups. Morphological variation can be quantified using geometric morphometric, outline or surface-based methods. These are most effective when morphological differences are relatively modest and there are numerous ubiquitous landmarks and phase-aligned features of shape variation. The most disparate samples, such as those across classes and phyla, typically necessitate the use of discrete characters. Unfortunately, such characters are often compiled subjectively in a manner reflecting the level of morphological and taxonomic focus and the intensity of taxon sampling. </span></p> <p><span>2. </span><span>Sampling intensity is often highly variable within a single data set, especially in repurposed and amalgamated cladistic matrices. Here we propose indices of molecular disparity analogous to those of morphological disparity. Molecular sequence data can be obtained in a more objective, automated and scaleable manner than morphological data. </span></p> <p><span>3. </span><span>Comparisons of the morphological and molecular disparity of subclades in sixteen large data sets suggest that molecular disparity is less susceptible to sampling biases than morphological disparity. Moreover, distance matrices inferred from individual genes tend to correlate strongly with each other and with distances from all concatenated genes. By contrast, morphological and molecular disparity are typically not significantly correlated across subclades, such that comparisons for groups can help to give a fuller picture of their evolution. Within mammals, Afrotheria have conspicuously high morphological disparity but modest molecular disparity, suggesting unusually high morphological plasticity. Even more strikingly, the molecular disparity of rodents is over five times that for Artiodactyla, despite having only half of their morphological disparity. These contrasts suggest the differential operation of geometric, biomechanical, ontogenetic and environmental constraints on form. </span></p> <p><span>4. </span><span>Given the increasing abundance of total evidence data sets in the literature and the widespread and sometimes uncritical repurposing of discrete morphological characters, we propose the comparison of morphological and molecular disparity as a useful tool to understand subclade evolution more fully. </span></p>
Supplementary files for: Why should we compare morphological and molecular disparity?
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Data from: Morphological disparity in the evolution of the ophthalmosaurid forefin: new clues from the Upper Jurassic of Argentina
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Data from: Morphological disparity of mammalian limb bones throughout the Cenozoic: the role of biotic and abiotic factors
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Analyzing disparity and rates of morphological evolution with model-based phylogenetic comparative methods
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Categorical versus geometric morphometric approaches to characterising the evolution of morphological disparity in Osteostraci (Vertebrata, stem-Gnathostomata)
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Data for: Colonization dynamics explain the decoupling of species richness and morphological disparity in syngnatharian fishes across oceans
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Nested whole-genome duplications coincide with diversification and high morphological disparity in Brassicaceae
<p>Angiosperms have become the dominant terrestrial plant group by diversifying for ~145 million years into a broad range of environments. During the course of evolution, numerous morphological innovations arose, often preceded by whole genome duplications (WGD). The mustard family (Brassicaceae), a successful angiosperm clade with ~4000 species, has been diversifying into many evolutionary lineages for more than 30 million years. Here we develop a species inventory, analyze morphological variation, and present a maternal, plastome-based genus-level phylogeny. We show that increased morphological disparity, despite an apparent absence of clade-specific morphological innovations, is found in tribes with WGDs or diversification rate shifts. Both are important processes in Brassicaceae, resulting in an overall high net diversification rate. Character states show frequent and independent gain and loss, and form varying combinations. Therefore, Brassicaceae pave the way to concepts of phylogenetic genome-wide association studies to analyze the evolution of morphological form and function.</p>
Supplementary data from: Decoupling of morphological disparity and taxonomic diversity during the end-Permian mass extinction
<p>An increasing number of unexpectedly diverse benthic communities are being reported from microbially-precipitated carbonate facies in shallow-marine platform settings after the end-Permian mass extinction. Ostracoda, which was one of the most diverse and abundant metazoan groups during this interval, recorded their greatest diversity and abundance associated with these facies. Previous studies, however, focused mainly on their taxonomic diversity and, therefore, left room for discussion of paleoecological significance. Here, we apply a morphometric method (semi-landmarks) to investigate morphological variance through time to better understand the ecological consequences of the end-Permian mass extinction, and to examine the hypothesis that microbial mats played a key role in ostracod survival. Our results show that taxonomic diversity and morphological disparity were decoupled during the end-Permian extinction, and that morphological disparity declined rapidly at the onset of the end-Permian extinction, even though the high diversity of ostracods initially survived in some places. The decoupled changes in taxonomic diversity and morphological disparity suggest that the latter is a more robust proxy for understanding the ecological impact of the extinction event, and the low morphological disparity of ostracod faunas is a consequence of sustained environmental stress or a delayed post-Permian radiation. Furthermore, the similar morphological disparity of ostracods between microbialite and non-microbialite facies indicates that microbial mats most likely represent a taphonomic window rather than a biological refuge during the end-Permian extinction interval.</p>
Data from: A new Pliosaurus species (Sauropterygia, Plesiosauria) from the Upper Jurassic of Patagonia: new insights on the Tithonian morphological disparity of mandibular symphyseal morphology
Abstract.—Most species of the genus Pliosaurus come from the Northern Hemisphere, however a growing number of new specimens are now available from the Southern Hemisphere. Here a new species of Pliosaurus is described, the second for the genus from the Southern Hemisphere, collected from the upper Tithonian (Jurassic) levels of the Vaca Muerta Formation, Neuquén Province. Pliosaurus almanzai n. sp. is characterized by two autapomophies: angular participating in the mandibular symphysis and occipital condyle without a notochordal pit or several, irregularly-arranged grooves. Additionally P. almanzai can be differentiated from other Pliosaurus species by the following characters: trihedral teeth; nine or more symphyseal alveoli; 15-17 post symphyseal alveoli; and parasphenoid without ventral keel. Pliosaurus almanzai n. sp. shows that Pliosaurus species with nine or more 9 symphyseal alveoli persisted until the late Tithonian, contrary to previous assumptions that only species with six symphyseal alveoli were present.
Data from: Static dental disparity and morphological turnover in sharks across the end-Cretaceous mass extinction
The Cretaceous–Palaeogene (K–Pg) mass extinction profoundly altered vertebrate ecosystems and prompted the radiation of many extant clades [1, 2]. Sharks (Selachimorpha) were one of the few larger-bodied marine predators that survived the K–Pg event and are represented by an almost-continuous dental fossil record. However, the precise dynamics of their transition through this interval remain uncertain [3]. Here, we apply 2D geometric morphometrics to reconstruct global and regional dental morphospace variation among Lamniformes (Mackerel sharks) and Carcharhiniformes (Ground sharks). These clades are prevalent predators in today's oceans, and were geographically widespread during the late Cretaceous–early Palaeogene. Our results reveal a decoupling of morphological disparity and taxonomic richness. Indeed, shark disparity was nearly static across the K–Pg extinction, in contrast to abrupt declines among other higher-trophic-level marine predators [4, 5]. Nevertheless, specific patterns indicate that an asymmetric extinction occurred among lamniforms possessing low-crowned/triangular teeth and that a subsequent proliferation of carcharhiniforms with similar tooth morphologies took place during the early Paleocene. This compositional shift in post-Mesozoic shark lineages hints at a profound and persistent K–Pg signature evident in the heterogeneity of modern shark communities. Moreover, such wholesale lineage turnover coincided with the loss of many cephalopod [6] and pelagic amniote [5] groups, as well as the explosive radiation of middle trophic-level teleost fishes [1]. We hypothesize that a combination of prey availability and post-extinction trophic cascades favored extant shark antecedents and laid the foundation for their extensive diversification later in the Cenozoic [7, 8, 9, 10].
Data from: Decoupling of taxonomic diversity and morphological disparity during decline of the Cambrian trilobite family Pterocephaliidae
Though discordance between taxonomic diversity and morphological disparity is common, little is known about the underlying dynamics that drive this decoupling. Early in the history of the Cambrian trilobite family Pterocephaliidae, there was an increase in taxonomic diversity and morphological diversity. As taxonomic diversity declined in the later history of the clade, range of variation stayed high, and disparity continued to increase. However, per-branch rates of morphological evolution estimated from a recent phylogeny decreased with time. Neither within-trait nor within-species variation increased or decreased, suggesting that the declining rates of morphological evolution were more likely related to ecological opportunity or niche partitioning rather than increasing intrinsic constraints. This is further supported by evidence for increased biofacies associations throughout the time period. Thus the high disparity seen at low taxonomic diversity late in the history of this clade was due to extinction—either random or targeting mean forms—rather than increased rates of morphological evolution. This pattern also provides a scenario that could account for instances of low taxonomic diversity but high morphological disparity in modern groups.
FIGURE 3 in Morphological disparity despite genetic similarity; new species of Lobosorchis Miller & Cribb, 2005 (Digenea: Cryptogonimidae) from the Great Barrier Reef and the Maldives
FIGURE 3. Phylogram of relationships between species of Lobosorchis Miller & Cribb, 2005 and the other cryptogonimid taxa included based on Bayesian inference analysis of the combined ITS (includes partial ITS1 and complete 5.8S and ITS2) and LSU rDNA dataset. Posterior probabilities are shown above the nodes and bootstrap support values shown below. Phylogram is midpoint rooted.
FIGURE 4 in Morphological disparity despite genetic similarity; new species of Lobosorchis Miller & Cribb, 2005 (Digenea: Cryptogonimidae) from the Great Barrier Reef and the Maldives
FIGURE 4. Phylogram of relationships between species of Lobosorchis Miller & Cribb, 2005 (including the two putative species A and B from metacercariae obtained from the flesh of species of Blenniidae, Pomacentridae and Tetraodontidae off Lizard Island, Great Barrier Reef) and the other cryptogonimid taxa included based on minimum evolution analysis of the ITS2 rDNA dataset. Bootstrap values are indicated at the nodes. Phylogram is midpoint rooted.
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Allen Brain Atlas
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Annotated Behaviour and Observability Dataset (ABODe)
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