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2,107 results for “margin;”
Water availability influences thermal safety margins for leaves
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Effects of niche marginality on hotter-drought tree mortality in angiosperms and gymnosperms
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Leaf margins in a deciduous lineage from the Greater Cape Floristic Region track climate in unexpected directions
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Data from: The influence of post-glacial migration and hybridization on the gene pool of marginal Quercus pubescens populations in Central Europe
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Data from: A new Middle Jurassic lagoon margin assemblage of theropod and sauropod dinosaur trackways from the Isle of Skye, Scotland
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Field margins as ecological corridors: Uncovering connectivity in agricultural landscapes using high-resolution tracking data and translocation experiments
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Wildfires increasingly threaten oil and gas wells in the western United States with disproportionate impacts on marginalized populations
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Data from: No‐till establishment improves the climate benefit of bioenergy crops on marginal grasslands
<p>Expanding biofuel production is expected to accelerate the conversion of unmanaged marginal lands to meet biomass feedstock needs. Greenhouse gas production during conversion jeopardizes ensuing climate benefits, but most research to date has focused only on conversion to annual crops and only following tillage. Here we report the global warming impact of converting USDA Conservation Reserve Program (CRP) grasslands to three types of bioenergy crops using no-till (NT) versus conventional tillage (CT). In three CRP fields planted to continuous corn, switchgrass, or restored prairie we established replicated NT and CT plots. For the two years following an initial soybean year in all fields, we found that, on average, NT conversion reduced nitrous oxide (N2O) emissions by 50% and carbon dioxide (CO2) emissions by 20% compared to CT conversion. Differences were higher in year 1 than in year 2 in the continuous corn field, and in the two perennial systems the differences disappeared after year 1. In all fields net CO2 emissions (as measured by eddy covariance) were positive for the first two years following CT establishment, but following NT establishment net CO2 emissions were close to zero or negative, indicating net C sequestration. Overall, NT improved the global warming impact of biofuel crop establishment following CRP conversion by over 20-fold compared to CT (-6.01 Mg CO2e ha-1 yr-1 for NT vs. -0.25 Mg CO2e ha-1 yr-1 for CT, on average). We also found that IPCC estimates of N2O emissions (as measured by static chambers) greatly underestimated actual emissions for converted fields regardless of tillage. Policies should encourage adoption of NT for converting<br> marginal grasslands to perennial bioenergy crops in order to reduce carbon debt and maximize climate benefits.</p>
Data from: Lowest drought sensitivity and decreasing growth synchrony towards the dry distribution margin of European beech
<p class="MsoPlainText"><strong>Aim:</strong> Climate limits the potential distribution ranges of species. Establishment and growth of individuals at range margins is assumed to be more limited by extreme events such as drought or frost events than in the centre of their range. We explore whether the growth of beech is more sensitive to drought towards the dry distribution margin and more sensitive to frost towards the cold distribution margin. Furthermore, we aim to gain insight into the adaptive potential of beech towards both the dry and cold distribution margins.</p> <p class="MsoPlainText"><strong>Location:</strong> European gradient from the dry (Spain) to the cold (Poland, Sweden) distribution margin of beech.</p> <p class="MsoPlainText"><strong>Taxon:</strong> European beech (<em>Fagus sylvatica</em> L.)</p> <p class="MsoPlainText"><strong>Methods:</strong> We applied a range-wide dendroecological study to analyse spatial and temporal trends in climate-growth relationships. We further investigated negative growth anomalies and growth synchrony towards the range margins.</p> <p class="MsoPlainText"><strong>Results:</strong> We found beech to be drought sensitive across its whole range, except at the dry distribution margin. Further, sensitivity to winter temperature was not found in the centre or at the cold distribution margin, but at the southern distribution margin. Growth synchrony was lower at the dry than at the cold distribution margin.</p> <p class="MsoPlainText"><strong>Main conclusions:</strong> Beech seems to be adapted to drought at the dry distribution margin with a high adaptive potential indicated by the lowest growth synchrony along the gradient. At the cold distribution margin, cold events in winter and spring were less important for growth than drought. Still, the importance of spring frost for beech growth appears to increase in recent decades. Considering a projected north-eastward shift of the distribution range, beech is likely facing drought stress in combination with spring frost risk at the cold margin which could lead to a hampered range expansion.</p>
The importance of wetland margin microhabitat mosaics; the case of shorebirds and thermoregulation
<ol> <li><span><span>Wetlands, and the species that rely upon them, are under significant threat worldwide, with wetlands </span>often being completely removed or drastically altered. Successful wetland management requires an understanding of the interactions between wetland species and the microhabitats they use. The use of microhabitats for thermoregulation in wetland species is poorly studied, though anthropogenic influence on wetlands can reduce the diversity of microhabitats and thus the thermoregulatory options for animals. At high ambient temperatures birds may use the water-logged wetland margins to help with thermoregulation, and are often observed roosting in the sitting position within this microhabitat. However, whether sitting on the wet substrate helps in thermoregulation is unknown. </span></li> <li><span>In this study, we tested whether birds selectively use microhabitats across temperatures by conducting field observations of nine species of shorebirds. We use comparative analysis to determine whether birds roost more on wet substrate in the sitting posture, <i>i.e. '</i>wet-sitting', at high ambient temperatures. </span></li> <li><span>We found substrate type across the wetland margins to be important in shorebird thermoregulation, with the time spent sitting being significantly mediated by the substrate on which the bird roosted. Individuals tended to sit on bare, wet ground much more under high ambient temperatures compared with low ambient temperatures. Vegetation on the other hand was used similarly across temperatures, and likely does not provide the same thermoregulatory benefits. </span></li> <li><span>By roosting on wet substrate at high ambient temperatures, birds may increase the potential for heat dissipation across the uninsulated legs, as water-logged wetland margins are known to remain cooler than the ambient temperature or vegetated microhabitats under hot climatic conditions. </span></li> <li><span><i>Synthesis and applications</i>. Wetland creation and management requires an understanding of the functional significance of such microhabitats, not only for foraging and breeding, but also for roosting. We demonstrate that managing wetland margins is likely important in minimising heat stress in birds, with our findings emphasising the importance of maintaining open spaces in habitat mosaics for birds to use for thermoregulation. The ability of wetland species to manage heat stress is becoming exceedingly important as they are threatened by both decreased wetland availability and increasing ambient temperatures under climate change.</span></li> </ol>
Data from: Chloroplast population genetics reveals low levels of genetic variation and conformation to the central–marginal hypothesis in Taxus wallichiana var. mairei, an endangered conifer endemic to China
The central–marginal hypothesis predicts that geographically peripheral populations should exhibit reduced genetic diversity and increased genetic differentiation than central populations due to smaller effective population size and stronger geographical isolation. We evaluated these predictions in the endangered conifer Taxus wallichiana var. mairei. Eight plastid simple sequence repeats (cpSSRs) were used to investigate plastid genetic variation in 22 populations of Taxus wallichiana var. mairei, encompassing nearly its entire distribution range. Low levels of plastid genetic variation and differentiation were detected in the populations, and the findings were attributed to low mutation rates, small population sizes, habitat fragmentation and isolation, and effective pollen or seed dispersal. Hunan and Hubei were identified as major refugia based on the number of private haplotypes and species distribution modeling. Trends in plastid genetic diversity and genetic differentiation from central to peripheral populations supported the predictions of the central–marginal hypothesis. In scenarios wherein the future climate becomes warmer, we predict that some peripheral populations will disappear and southern and southeastern regions will become significantly less habitable. Factors that include the levels of precipitation during the driest month, annual precipitation level, and annual temperature range will be decisive in shaping the future distribution of these populations. This study provides a theoretical basis for the conservation of T. wallichiana var. mairei.
Drought sensitivity of Empetrum nigrum shrub growth at the species' southern lowland distribution range margin
<p>The ongoing warming of the Earth's atmosphere is projected to cause a northward shift of species' distributions, as they track their climatic optimum. In the rapidly warming Arctic, this has already led to an increase of shrubs in tundra ecosystems. While this northern expansion of woody biomass has been studied relatively extensively over the last decade, little research has been devoted to shrub growth responses at the southern margins of Northern Hemisphere shrubs.</p> <p>Here, we studied shoot length growth, its responses to climate over the period 2010-2017, and differences in leaf C and N content of the evergreen dwarf shrub <i>Empetrum nigrum</i>, as well as the vegetation composition and soil parameters at four sites located along a gradient of increasing dune age on the island Spiekeroog, northern Germany. The sites are located in the tri-national UNESCO world heritage site, the Wadden Sea. <i>E. nigrum</i> has a predominantly circum-arctic-boreal distribution and its southern distribution mbargin in European lowlands runs through northern Germany, where it is retreating northwards.</p> <p>We found a negative response to autumn (surface) temperatures and previous summer surface temperatures and/or a positive response to summer precipitation of <i>E. nigrum</i> growth, except at the oldest dune with the strongest <i>E. nigrum</i> dominance. Growth rates and plant species diversity declined with dune age. Our results suggest that <i>E. nigrum</i> growth is drought sensitive at its European southern range margin. We hypothesize that this sensitivity may form the basis for its northward retreat, which is supported by recent observations of <i>E. nigrum</i> dieback in Germany after the extreme drought in 2018 and model projections.</p>
FIGURE. 5 in A novel species Spinonema gracilispiculum sp. n. (Nematoda: Desmodoridae) from the oxygen minimum zone of Eastern Arabian Sea margin
FIGURE. 5 Pictorial key to species of the genus Spinonema Larrazábal-Filho et al., 2019 (A) Spinonema absente LarrazábalFilho et al., 2019, (B) Spinonema spirale Larrazábal-Filho et al., 2019, (C) Spinonema cuticulatum Larrazábal-Filho et al., 2019, (D) Spinonema gracilispiculum sp. n.
FIGURE. 1 in A novel species Spinonema gracilispiculum sp. n. (Nematoda: Desmodoridae) from the oxygen minimum zone of Eastern Arabian Sea margin
FIGURE. 1 Spinonema gracilispiculum sp. n. Holotype male (A) Entire male, (B) Head region, (C) Spicular apparatus, (D) Pharyngeal horn, (E) Lateral alae, (F) Beginning of lateral alae, (G) Ending of lateral alae. (Scale bar 20 µm).
FIGURE. 2 in A novel species Spinonema gracilispiculum sp. n. (Nematoda: Desmodoridae) from the oxygen minimum zone of Eastern Arabian Sea margin
FIGURE. 2 Spinonema gracilispiculum sp. n. Holotype male (A) Pharyngeal region, (B) Caudal region showing spicule. (Scale bar 20 µm).
PLATE 2 in A novel species Spinonema gracilispiculum sp. n. (Nematoda: Desmodoridae) from the oxygen minimum zone of Eastern Arabian Sea margin
PLATE 2. Spinonema gracilispiculum sp. n. (A) Head region showing amphid and cephalic setae, (B) & (C) Pharyngeal thorn, (D) Pharyngeal thorn dorsal view, (E) Cuticular ornamentation, (F) Somatic setae, (G) & (H) Lateral alae, (I) Caudal region of male showing spicule, (J) Vulval region of female. (Scale bar 20 µm).
Apical_margin_of_elytra_Agonum
<p>Apical margin of elytra marked by a red ellipsoid, Agonum specimen</p>
Data from: A global phylogeny of turtles reveals a burst of climate-associated diversification on continental margins
<p>Living turtles are characterized by extraordinarily low species diversity given their age. The clade's extensive fossil record indicates that climate and biogeography may have played important roles in determining their diversity. We investigated this hypothesis by collecting a molecular dataset for 591 individual turtles that together represent 80% of all turtle species, including representatives of all families and 98% of genera, and used it to jointly estimate phylogeny and divergence times. We found that the turtle tree is characterized by relatively constant diversification (speciation minus extinction) punctuated by a single threefold increase. We also found that this shift is temporally and geographically associated with newly emerged continental margins that appeared during the Eocene-Oligocene transition about 30 million years before present. In apparent contrast, the fossil record from this time period contains evidence for a major, but regional, extinction event. These seemingly discordant findings appear to be driven by a common global process: Global cooling and drying at the time of the Eocene Oligocene transition. This climatic shift led to aridification that drove extinctions in important fossil-bearing areas, while simultaneously exposing new continental margin habitat that subsequently allowed for a burst of speciation associated with these newly exploitable ecological opportunities.</p>
Data from: Postglacial recolonisation in a cold climate specialist in Western Europe: patterns of genetic diversity in the adder (Vipera berus) support the central-marginal hypothesis
Understanding the impact of postglacial recolonization on genetic diversity is essential in explaining current patterns of genetic variation. The central–marginal hypothesis (CMH) predicts a reduction in genetic diversity from the core of the distribution to peripheral populations, as well as reduced connectivity between peripheral populations. While the CMH has received considerable empirical support, its broad applicability is still debated and alternative hypotheses predict different spatial patterns of genetic diversity. Using microsatellite markers, we analysed the genetic diversity of the adder (Vipera berus) in western Europe to reconstruct postglacial recolonization. Approximate Bayesian Computation (ABC) analyses suggested a postglacial recolonization from two routes: a western route from the Atlantic Coast up to Belgium and a central route from the Massif Central to the Alps. This cold-adapted species likely used two isolated glacial refugia in southern France, in permafrost-free areas during the last glacial maximum. Adder populations further from putative glacial refugia had lower genetic diversity and reduced connectivity; therefore, our results support the predictions of the CMH. Our study also illustrates the utility of highly variable nuclear markers, such as microsatellites, and ABC to test competing recolonization hypotheses.
Data from: Sex at the margins: parthenogenesis vs. facultative and obligate sex in a Neotropical ant
Geographic parthenogenesis is a distribution pattern, in which parthenogenetic populations tend to live in marginal habitats, at higher latitudes and altitudes and island-like habitats compared with the sexual forms. The facultatively parthenogenetic ant Platythyrea punctata is thought to exhibit this general pattern throughout its wide range in Central America and the Caribbean Islands. Workers of P. punctata from the Caribbean produce diploid female offspring from unfertilized eggs by thelytokous parthenogenesis, and mated females and males are rare. In contrast, workers in one colony from Costa Rica were incapable of thelytoky; instead mated workers produced all female offspring. Because sample sizes were very low in former studies, we here use microsatellite markers and explicit tests of thelytoky to examine the population genetic structure of ancestral and derived populations of P. punctata throughout the Caribbean and Central America. Populations from the Caribbean islands were fully capable of parthenogenesis and population genetic signatures indicate that this is the predominant mode of reproduction, although males are occasionally produced. In contrast, the northernmost population on the mainland (Texas) showed signatures of sexual reproduction and individuals were incapable of reproduction by thelytoky. Contrary to expectations from a geographic parthenogenesis distribution pattern, most parts of the mainland populations were found to be facultatively thelytokous, with population genetic signatures of both sexual and parthenogenetic reproduction.
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.