Patterns In Disparity Research Articles

Fossilization can mislead analyses of phenotypic disparity.

Analyses of morphological disparity can incorporate living and fossil taxa to facilitate the exploration of how phenotypic variation changes through time. However, taphonomic processes introduce non-random patterns of data loss in fossil data and their impact on perceptions of disparity is unclear. To address this, we characterize how measures of disparity change when simulated and empirical data are degraded through random and structured data loss. We demonstrate that both types of data loss can distort the disparity of clades, and that the magnitude and direction of these changes varies between the most commonly employed distance metrics and disparity indices. The inclusion of extant taxa and exceptionally preserved fossils mitigates these distortions and clarifies the full extent of the data lost, most of which would otherwise go uncharacterized. This facilitates the use of ancestral state estimation and evolutionary simulations to further control for the effects of data loss. Where the addition of such reference taxa is not possible, we urge caution in the extrapolation of general patterns in disparity from datasets that characterize subsets of phenotype, which may represent no more than the traits that they sample.

Morphological evolution during the last hurrah of the trilobites: morphometric analysis of the Devonian asteropyginid trilobites

AbstractThe Asteropyginae Delo, 1935 is a group of phacopid trilobites in the family Acastidae Delo, 1935 that has served as the focus for several studies due to their distinctive morphologies and diversity. However, despite an interest in these characteristic morphologies, there have been no studies that have examined this group using morphometric techniques. Our investigation utilized both geometric morphometric and elliptical Fourier methods to quantify the morphology of cephalic sclerites of asteropyginid specimens representing wide taxonomic sampling of the clade. We constructed a phylomorphospace that shows temporal and spatial patterns of phenotypic evolution within the framework of a novel tip-dated phylogenetic tree generated using Bayesian inference. We recovered similar patterns in disparity regardless of the morphometric approach. Both analyses illustrated a marked expansion into morphospace throughout the temporal range of the clade, peaking in disparity in the Emsian and with European taxa exhibiting the highest disparity in glabellar morphospace. Additionally, glabellar shape showed low phylogenetic signal and no major patterns in phylomorphospace. This study highlights the utility of employing different methodologies to quantitatively explore the disparity of fossil taxa. It also illustrates some of the patterns of morphological change occurring during one of the final and major evolutionary radiations within Phacopida.

Trends and socioeconomic disparities in all-cause mortality among adults with diagnosed diabetes by race/ethnicity: a population-based cohort study - USA, 1997–2015

ObjectivesBy race/ethnicity and socioeconomic position (SEP), to estimate and examine changes over time in (1) mortality rate, (2) mortality disparities and (3) excess mortality risk attributed to diagnosed diabetes (DM).DesignPopulation-based...

Mosaic evolution, preadaptation, and the evolution of evolvability in apes.

A major goal in postsynthesis evolutionary biology has been to better understand how complex interactions between traits drive movement along and facilitate the formation of distinct evolutionary pathways. I present analyses of a character matrix sampled across the haplorrhine skeleton that revealed several modules of characters displaying distinct patterns in macroevolutionary disparity. Comparison of these patterns to those in neurological development showed that early ape evolution was characterized by an intense regime of evolutionary and developmental flexibility. Shifting and reduced constraint in apes was met with episodic bursts in phenotypic innovation that built a wide array of functional diversity over a foundation of shared developmental and anatomical structure. Shifts in modularity drove dramatic evolutionary changes across the ape body plan in two distinct ways: (1) an episode of relaxed integration early in hominoid evolution coincided with bursts in evolutionary rate across multiple character suites; (2) the formation of two new trait modules along the branch leading to chimps and humans preceded rapid and dramatic evolutionary shifts in the carpus and pelvis. Changes to the structure of evolutionary mosaicism may correspond to enhanced evolvability that has a "preadaptive" effect by catalyzing later episodes of dramatic morphological remodeling.

Detecting Mosaic Patterns in Macroevolutionary Disparity.

Evolutionary biologists have long sought to understand the full complexity in pattern and process that shapes organismal diversity. Although phylogenetic comparative methods are often used to reconstruct complex evolutionary dynamics, they are typically limited to a single phenotypic trait. Extensions that accommodate multiple traits lack the ability to partition multidimensional data sets into a set of mosaic suites of evolutionarily linked characters. I introduce a comparative framework that identifies heterogeneity in evolutionary patterns across large data sets of continuous traits. Using a model of continuous trait evolution based on the differential accumulation of disparity across lineages in a phylogeny, the approach algorithmically partitions traits into a set of character suites that best explains the data, where each suite displays a distinct pattern in phylogenetic morphological disparity. When applied to empirical data, the approach revealed a mosaic pattern predicted by developmental biology. The evolutionary distinctiveness of individual suites can be investigated in more detail either by fitting conventional comparative models or by directly studying the phylogenetic patterns in disparity recovered during the analysis. This framework can supplement existing comparative approaches by inferring the complex, integrated patterns that shape evolution across the body plan from disparate developmental, morphometric, and environmental sources of phenotypic data.

Identifying geospatial patterns in wealth disparity in child malnutrition across 640 districts in India.

We assessed district-level geospatial trends in precision weighted prevalence and absolute wealth disparity in stunting, underweight, wasting, low birthweight, and anemia among children under five in India. The largest wealth disparities were found for anthropometric failures and substantial variation existed across states. We identified statistically significant (p < 0.001) geospatial patterns in district-wide wealth disparities for all outcomes, which differed from geospatial patterns for the overall prevalence. We characterized each district as either a “Disparity”, “Pitfall”, “Intensity”, or “Prosperity” area based on its overall burden and wealth disparity, as well as discuss the importance of considering both measures for geographically-targeted public health interventions to improve health equity.

Bayesian placement of fossils on phylogenies using quantitative morphometric data.

Jointly developing a comprehensive tree of life from living and fossil taxa has long been a fundamental goal in evolutionary biology. One major challenge has stemmed from difficulties in merging evidence from extant and extinct organisms. While these efforts have resulted in varying stages of synthesis, they have been hindered by their dependence on qualitative descriptions of morphology. Though rarely applied to phylogenetic inference, traditional and geometric morphometric data can improve these issues by generating more rigorous ways to quantify variation in morphological structures. They may also facilitate the rapid and objective aggregation of large morphological datasets. I describe a new Bayesian method that leverages quantitative trait data to reconstruct the positions of fossil taxa on fixed reference trees composed of extant taxa. Unlike most formulations of phylogenetic Brownian motion models, this method expresses branch lengths in units of morphological disparity, suggesting a new framework through which to construct Bayesian node calibration priors for molecular dating and explore comparative patterns in morphological disparity. I am hopeful that the approach described here will help to facilitate a deeper integration of neo- and paleontological data to move morphological phylogenetics further into the genomic era.

Beyond the sniffer: frontal sinuses in Carnivora.

Paranasal sinuses are some of the most poorly understood features of mammalian cranial anatomy. They are highly variable in presence and form among species, but their function is not well understood. The best-supported explanations for the function of sinuses is that they opportunistically fill mechanically unnecessary space, but that in some cases, sinuses in combination with the configuration of the frontal bone may improve skull performance by increasing skull strength and dissipating stresses more evenly. We used CT technology to investigate patterns in frontal sinus size and shape disparity among three families of carnivores: Canidae, Felidae, and Hyaenidae. We provide some of the first quantitative data on sinus morphology for these three families, and employ a novel method to quantify the relationship between three-dimensional sinus shape and skull shape. As expected, frontal sinus size and shape were more strongly correlated with frontal bone size and shape than with the morphology of the skull as a whole. However, sinus morphology was also related to allometric differences among families that are linked to biomechanical function. Our results support the hypothesis that frontal sinuses most often opportunistically fill space that is mechanically unnecessary, and they can facilitate cranial shape changes that reduce stress during feeding. Moreover, we suggest that the ability to form frontal sinuses allows species to modify skull function without compromising the performance of more functionally constrained regions such as the nasal chamber (heat/water conservation, olfaction), and braincase (housing the brain and sensory structures).

State-level variations in racial disparities in life expectancy.

To explore state patterns in the racial life expectancy gap. The 1997-2004 Multiple Cause of Death PUF, 2000 U.S. Census. We calculated life expectancy at birth for black and white men and women. Data were obtained by the NCHS and U.S. Census Bureau. States with small racial differences are due to higher-than-expected life expectancy for blacks or lower-than-expected for whites. States with large disparity are explained by higher-than-average life expectancy among whites or lower-than-average life expectancy among blacks. Heterogeneous state patterns in racial disparity in life expectancy exist. Eliminating disparity in states with large black populations would make the greatest impact nationally.

Temporal patterns in disparity and diversity of the Jurassic ammonoids of southern Germany

A morphometric analysis of the characteristic whorl cross-sections of 1,200 Jurassic ammonoid species from southern Germany enabled us to characterise their morphospace. The successive Jurassic ammonoid faunas of southern Germany show characteristic patterns in morphospace occupation. While Early and Middle Jurassic ammonoids occupy limited areas of the morphospace range, the Late Jurassic ammonoids cover the entire spectrum. The ammonoids are characterised by an overall increase of both taxonomic diversity and morphological disparity in the course of the Jurassic. Strong fluctuations occur until the middle Late Jurassic, followed by a diversity decrease in the early Kimmeridgian and a disparity reduction in the early Tithonian. While diversity and disparity show similar progression during most of the Early Jurassic, they diverge subsequently and show only poor correlation until the end of the Jurassic. Particularly in the Middle Jurassic diversity and sea level changes correlate strongly. Neither temporal patterns in diversity nor disparity support the hypothesis of a mass extinction event in the early Toarcian. Significant changes in diversity and disparity in the early Callovian support a putative migration event of Boreal ammonoids into the Tethyan realm. &lt;br&gt;&lt;br&gt; doi:&lt;a href="http://dx.doi.org/10.1002/mmng.201000016" target="_blank"&gt;10.1002/mmng.201000016&lt;/a&gt;

Temporal patterns in disparity and diversity of the Jurassic ammonoids of southern Germany

Abstract. A morphometric analysis of the characteristic whorl cross-sections of 1,200 Jurassic ammonoid species from southern Germany enabled us to characterise their morphospace. The successive Jurassic ammonoid faunas of southern Germany show characteristic patterns in morphospace occupation. While Early and Middle Jurassic ammonoids occupy limited areas of the morphospace range, the Late Jurassic ammonoids cover the entire spectrum. The ammonoids are characterised by an overall increase of both taxonomic diversity and morphological disparity in the course of the Jurassic. Strong fluctuations occur until the middle Late Jurassic, followed by a diversity decrease in the early Kimmeridgian and a disparity reduction in the early Tithonian. While diversity and disparity show similar progression during most of the Early Jurassic, they diverge subsequently and show only poor correlation until the end of the Jurassic. Particularly in the Middle Jurassic diversity and sea level changes correlate strongly. Neither temporal patterns in diversity nor disparity support the hypothesis of a mass extinction event in the early Toarcian. Significant changes in diversity and disparity in the early Callovian support a putative migration event of Boreal ammonoids into the Tethyan realm. doi: 10.1002/mmng.201000016