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854 results for “Disparity”
Data from: Multifaceted disparity approach reveals dinosaur herbivory flourished before the end-Cretaceous mass extinction
Understanding temporal patterns in biodiversity is an enduring question in paleontology. Compared to studies of taxonomic diversity, long-term perspectives on ecological diversity are rare, particularly in terrestrial systems. Yet ecological diversity is critical for the maintenance of biodiversity, particularly during times of major perturbations. Here, we explore the ecological diversity of Cretaceous herbivorous dinosaurs leading up to the K-Pg extinction, using dental and jaw morphological disparity as a proxy. We test the hypothesis that a decline in ecological diversity could have facilitated their rapid extinction 66 mya. We apply three disparity metrics that together capture different aspects of morphospace occupation, and show how this approach is key to understanding patterns of morphological evolution. We find no evidence of declining disparity in herbivorous dinosaurs as a whole – suggesting that dinosaur ecological diversity remained high during the last 10 million years of their existence. Clades show different disparity trends through the Cretaceous, but none except sauropods exhibits a long-term decline. Herbivorous dinosaurs show two disparity peaks characterised by different processes; in the Early Cretaceous by expansion in morphospace and in the Campanian by morphospace packing. These trends were only revealed by using a combination of disparity metrics, demonstrating how this approach can offer novel insights into macroevolutionary processes underlying patterns of disparity and ecological diversity.
Data from: 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 datasets into a set of mosaic suites of evolutionarily linked characters. I introduce a comparative framework that identifies heterogeneity in evolutionary patterns across large datasets 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.
Data from: Relationships of diversity, disparity and their evolutionary rates in squirrels (Sciuridae)
Several theories predict that rapidly diversifying clades will also rapidly diverge phenotypically; yet, there are also reasons for suspecting that diversification and divergence might not be correlated. In the widely distributed squirrel clade (Sciuridae), we test for correlations between per-lineage speciation rates, species richness, disparity and a time-invariant measure of disparity that allows for comparing rates when evolutionary modes differ, as they do in squirrels. We find that species richness and speciation rates are not correlated with clade age or with each other. Disparity appears to be positively correlated with clade age because young, rapidly diversifying Nearctic grassland clades are strongly pulled to a single stable optimum but older, slowly diversifying Paleotropical forest clades contain lineages that diverge along multiple ecological and morphological lines. That contrast is likely due to both the environments they inhabit and their phylogenetic community structure. Our results argue against a shared explanation for diversity and disparity in favor of geographically mediated modes of speciation and ecologically mediated modes of phenotypic evolution.
Data from: Can newts cope with the heat? Disparate thermoregulatory strategies of two sympatric species in water
Many ectotherms effectively reduce their exposure to low or high environmental temperatures using behavioral thermoregulation. In terrestrial ectotherms, thermoregulatory strategies range from accurate thermoregulation to thermoconformity according to the costs and limits of thermoregulation, while in aquatic taxa the quantification of behavioral thermoregulation have received limited attention. We examined thermoregulation in two sympatric newt species, Ichthyosaura alpestris and Lissotriton vulgaris, exposed to elevated water temperatures under semi-natural conditions. According to a recent theory, we predicted that species for which elevated water temperatures pose a lower thermal quality habitat, would thermoregulate more effectively than species in thermally benign conditions. In the laboratory thermal gradient, L. vulgaris maintained higher body temperatures than I. alpestris. Semi-natural thermal conditions provided better thermal quality of habitat for L. vulgaris than for I. alpestris. Thermoregulatory indices indicated that I. alpestris actively thermoregulated its body temperature, whereas L. vulgaris remained passive to the thermal heterogeneity of aquatic environment. In the face of elevated water temperatures, sympatric newt species employed disparate thermoregulatory strategies according to the species-specific quality of the thermal habitat. Both strategies reduced newt exposure to suboptimal water temperatures with the same accuracy but with or without the costs of thermoregulation. The quantification of behavioral thermoregulation proves to be an important conceptual and methodological tool for thermal ecology studies not only in terrestrial but also in aquatic ectotherms.
Data from: Morphological and biomechanical disparity of crocodile-line archosaurs following the end-Triassic extinction
Mesozoic crurotarsans exhibited diverse morphologies and feeding modes, representing considerable ecological diversity, yet macroevolutionary patterns remain unexplored. Here we employ a unique combination of morphological and biomechanical disparity metrics to quantify the ecological diversity and trophic radiations of Mesozoic crurotarsans, using the mandible as a morpho-functional proxy. We recover three major trends. First, the diverse assemblage of Late Triassic crurotarsans was morphologically and biomechanically disparate, implying high levels of ecological variation; but, following the end-Triassic extinction, disparity declined. Second, the Jurassic radiation of marine thalattosuchians resulted in very low morphological disparity but moderate variation in jaw biomechanics, highlighting a hydrodynamic constraint on mandibular form. Third, during the Cretaceous terrestrial radiations of neosuchians and notosuchians, mandibular morphological variation increased considerably. By the Late Cretaceous, crocodylomorphs evolved a range of morphologies equaling Late Triassic crurotarsans. In contrast, biomechanical disparity in the Cretaceous did not increase, essentially decoupling from morphology. This enigmatic result could be attributed to biomechanical evolution in other anatomical regions (e.g. cranium, dentition or postcranium), possibly releasing the mandible from selective pressures. Overall, our analyses reveal a complex relationship between morphological and biomechanical disparity in Mesozoic crurotarsans that culminated in specialized feeding ecologies and associated lifestyles.
Data from: "NGS based generation of expressed sequence tags for Lymantria dispar and Lymantria monacha, two closely related lepidopteran species with different responses to parasitism by Glyptapanteles liparidis" in Genomic Resources Notes accepted 1 December 2013 to 31 January 2014
Introduction: The gypsy moth, Lymantria dispar, and the nun moth, Lymantria monacha, are closely related species (Lepidoptera, Lymantriidae), co-seasonal and economically important forest pests on broadleaf and coniferous trees. In Central Europe, gypsy moth larvae are frequently parasitized by the gregarious, endoparasitic wasp Glyptapanteles liparidis (Hymenoptera, Braconidae). At oviposition, the female wasp injects between 10 and up to 100 eggs into the hemocoel of a single host larva, together with venom and calyx fluid containing polydnavirus (PDV) particles that subsequently play a critical role in suppressing the host immune response so that successful development of the parasitoid can proceed (Schopf 2007). These viruses, which are integrated in the genomic DNA of the wasp and undergo replication only in the female's ovary, rapidly enter host hemocytes, fat body, and nervous system following parasitization, and viral genes are expressed. In L. dispar larvae parasitized by G. liparidis, the host's hemocytes alter their behavior, fail to spread properly (thereby inhibiting the encapsulation response) and partly undergo programmed cell death (apoptosis), resulting in a dramatic drop in the host's total hemocyte number (Schafellner and Schläger 2009).
Data from: Individual objective and subjective fixation disparity in near vision
Binocular vision refers to the integration of images in the two eyes for improved visual performance and depth perception. One aspect of binocular vision is the fixation disparity, which is a suboptimal condition in individuals with respect to binocular eye movement control and subsequent neural processing. The objective fixation disparity refers to the vergence angle between the visual axes, which is measured with eye trackers. Subjective fixation disparity is tested with two monocular nonius lines which indicate the physical nonius separation required for perceived alignment. Subjective and objective fixation disparity represent the different physiological mechanisms of motor and sensory fusion, but the precise relation between these two is still unclear. This study measures both types of fixation disparity at viewing distances of 40, 30, and 24 cm while observers fixated a central stationary fusion target. 20 young adult subjects with normal binocular vision were tested repeatedly to investigate individual differences. For heterophoria and subjective fixation disparity, this study replicated that the binocular system does not properly adjust to near targets: outward (exo) deviations typically increase as the viewing distance is shortened. This exo proximity effect—however—was not found for objective fixation disparity, which–on the average–was zero. But individuals can have reliable outward (exo) or inward (eso) vergence errors. Cases with eso objective fixation disparity tend to have less exo states of subjective fixation disparity and heterophoria. In summary, the two types of fixation disparity seem to respond in a different way when the viewing distance is shortened. Motor and sensory fusion–as reflected by objective and subjective fixation disparity–exhibit complex interactions that may differ between individuals (eso versus exo) and vary with viewing distance (far versus near vision).
Data from: Time for a rethink: time sub-sampling methods in disparity-through-time analyses
Disparity-through-time analyses can be used to determine how morphological diversity changes in response to mass extinctions, and to investigate the drivers of morphological change. These analyses are routinely applied to palaeobiological datasets, yet although there is much discussion about how to best calculate disparity, there has been little consideration of how taxa should be sub-sampled through time. Standard practice is to group taxa into discrete time bins, often based on stratigraphic periods. However, this can introduce biases when bins are of unequal size, and implicitly assumes a punctuated model of evolution. In addition, many time bins may have few or no taxa, meaning that disparity cannot be calculated for the bin and making it harder to complete downstream analyses. Here we describe a different method to complement the disparity-through-time tool-kit: time-slicing. This method uses a time-calibrated phylogenetic tree to sample disparity-through-time at any fixed point in time rather than binning taxa. It uses all available data (tips, nodes and branches) to increase the power of the analyses, specifies the implied model of evolution (punctuated or gradual), and is implemented in R. We test the time-slicing method on four example datasets and compare its performance in common disparity-through-time analyses. We find that the way you time sub-sample your taxa can change your interpretations of the results of disparity-through-time analyses. We advise using multiple methods for time sub-sampling taxa, rather than just time binning, to gain a better understanding disparity-through-time.
FIGURE 1 in First report of Aethaloptera dispar Brauer 1875 (Trichoptera: Hydropsychidae) from IleIfe, southwestern Nigeria, West Africa
FIGURE 1. Map of Africa showing the location of IleIfe in southwestern Nigeria.
FIGURES 32–33. H. planus Thon, 1899 in Larval morphology of Hydryphantes clypeatus Thor, 1899, H. dispar Schaub, 1888 and H. planus Thon, 1899 (Acari, Hydrachnidia: Hydryphantidae)
FIGURES 32–33. H. planus Thon, 1899, larva: 32, dorsal view; 33, ventral view. Scale bar: 50 µm.
FIGURE 1 in Spilogona dispar (Fallén, 1823) and its Palaearctic relatives (Diptera: Muscidae)
FIGURE 1. Spilogona dispar (Fallén), male. (Austria, Tyrol, Obergurgl.)
Data from: The legacy of Eastern Mediterranean mountain uplifts – rapid disparity of phylogenetic niche conservatism and divergence in mountain vipers
<p><b>Aim</b> The orogeny of the eastern Mediterranean region has substantially affected ecological speciation patterns, particularly of mountain-dwelling species. Mountain vipers of the genus <i>Montivipera</i> are among the paramount examples of Mediterranean neo-endemism, with restricted ranges in the mountains of Anatolia, the Levant, Caucasus, Alborz, and Zagros. Here we explore the phylogenetic and ecological diversification of <i>Montivipera</i> to reconstruct its ecological niche evolution and biogeographic history.</p> <p><b>Location</b> Eastern Mediterranean mountain ecosystems</p> <p><b>Methods</b> Using 177 sequences of three mitochondrial genes, a dated molecular phylogeny of mountain vipers was reconstructed. Based on 320 occurrence points within the entire range of the genus and six climatic variables, ecological niches were modelled and used to infer ancestral niche occupancy. In addition, the biogeographic history and ancestral states of the species were reconstructed across climate gradients.</p> <p><b>Results</b> Dated phylogenetic reconstruction revealed that the ancestor of mountain vipers split into two major clades at around 12.18 Mya followed by multiple vicariance events due to rapid orogeny. <i>Montivipera</i> colonised coastal regions from a mountain-dwelling ancestor. We detected a highly complex ecological niche evolution of mountain vipers to temperature seasonality measured by means of a strong phylogenetic signal.</p> <p><b>Conclusion </b>Raising mountain belts in the Eastern Mediterranean region and subsequent remarkable changes in temperature seasonality have led to the formation of important centres of diversification and endemism in this biodiversity hotspot. High rates of niche conservatism, low genetic diversity, and segregation of ranges into the endemic distribution negatively influenced the adaptive capacity of mountain vipers. We suggest that these species should be considered as evolutionary significant units and priority species for conservation in Mediterranean mountain ecosystems.</p>
Same place, different stories: Disparate evolutionary trends of Mygalomorphae from the peripampasic orogenic arc
<p><b>Aim:</b> Comparative phylogeography seeks to unravel similarities in the population structure and evolutionary processes undergone by co-distributed taxa under the assumption that they will have experienced the same geoclimatic events. However, small differences in functional traits, particularly those related to dispersal abilities, may translate into incongruent evolutionary histories. Here, we used a sequence target multi-locus approach to infer and compare the phylogeographical patterns of three sympatric mygalomorph spiders in the Argentinean peripampasic orogenic arc.</p> <p><b>Location:</b> The mountainous systems of central and northern Argentina.</p> <p><b>Taxon:</b> Mygalomorphae spiders (Araneae)</p> <p><b>Methods:</b> We inferred the phylogeny of three species of mygalomorph spiders based on <i>16</i>S+L1+nad1 and ITS sequences from o<span>ne hundred and thirty-four </span>individuals by using a Bayesian and Maximum likelihood approaches and we also estimated divergence dates. Also, nuclear networks were inferred. Based on our molecular phylogeny, we reconstructed <span>ancestral areas using the the Bayesian Binary MCMC method</span>.</p> <p><b>Results:</b> A deep genetic divergence and highly structured populations was obtained in the pycnothelid <i>Acanthogonatus centralis</i>, whereas the theraphosids <i>Plesiopelma longisternale </i>and <i>Grammostola vachoni </i>showed shallow divergences and poorly structured populations. Additionally, we uncovered potentially overlooked species diversity within <i>G</i>. <i>vachoni</i>, which warrants conducting a full taxonomic revision of <i>Grammostola</i>.</p> <p><b>Main conclusions:</b> We propose that differences in dispersion rates and time of colonization between the theraphosids and the pycnothelid led to divergent lineage history despite common environmental conditions. Our results further corroborate the key role played of the Plio-Pleistocene geoclimatic events in shaping the present-day diversity of mygalomorph spiders along the peripampasic orogenic arc.</p>
Disparate movement behaviour and feeding ecology in sympatric ecotypes of Atlantic cod
<p>Co-existence of ecotypes, genetically divergent population units, is a widespread phenomenon, potentially affecting ecosystem functioning and local food web stability. In coastal Skagerrak, Atlantic cod (<i>Gadus morhua</i>) occur as two such co-existing ecotypes. We applied a combination of acoustic telemetry, genotyping and stable isotope analysis to 72 individuals to investigate movement ecology and food niche of putative local "Fjord" and putative oceanic "North Sea" ecotypes – thus named based on previous molecular studies. Genotyping and individual origin assignment suggested 41 individuals were Fjord and 31 were North Sea ecotypes. Both ecotypes were found throughout the fjord. Seven percent of Fjord ecotype individuals left the study system during the study while 42 % of North Sea individuals left, potentially homing to natal spawning grounds. Home range sizes were similar for the two ecotypes but highly variable among individuals. Fjord ecotype cod had significantly higher δ<sup>13</sup>C and δ<sup>15</sup>N stable isotope values than North Sea ecotype cod, suggesting they exploited different food niches. The results suggest coexisting ecotypes may possess innate differences in feeding- and movement ecologies and may thus fill different functional roles in marine ecosystems. This highlights the importance of conserving interconnected populations to ensure stable ecosystem functioning and food web structures.</p>
Data from: A dataset of stereoscopic images and ground-truth disparity mimicking human fixations in peripersonal space
[No abstract entered]
FIGURE 2 in Aphanius kruppi, a new killifish from Oman with comments on the A. dispar species group (Cyprinodontiformes: Aphaniidae)
FIGURE 2. Aphanius kruppi, ZFMK-ICH 103668, holotype, 46 mm SL; Oman: spring in Al Mudayrib.
FIGURE 5 in Aphanius kruppi, a new killifish from Oman with comments on the A. dispar species group (Cyprinodontiformes: Aphaniidae)
FIGURE 5. Aphanius kruppi, FSJF DNA-2577, female, 27 mm SL; male, 24 mm SL; Oman: Wadi Bani Khalid.
FIGURE 8. Aphanius stoliczkanus, FSJF 3533 in Aphanius kruppi, a new killifish from Oman with comments on the A. dispar species group (Cyprinodontiformes: Aphaniidae)
FIGURE 8. Aphanius stoliczkanus, FSJF 3533, female, 40 mm SL, male, 44 mm SL; Oman: Wadi Fanja.
Attenuated sex-related DNA methylation differences in cancer highlight the magnitude bias mediating existing disparities
<p>This is supplementary data for the manuscript, "Attenuated sex-related DNA methylation differences in cancer highlight the magnitude bias mediating existing disparities"</p>
Dataset related to the article: Exploring the recent upsurge in productivity disparities among European regions
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