75 resultados para BIOGEOGRAPHICAL ANCESTRY


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The Tara Oceans Expedition (2009-2013) sampled the world oceans on board a 36 m long schooner, collecting environmental data and organisms from viruses to planktonic metazoans for later analyses using modern sequencing and state-of-the-art imaging technologies. Tara Oceans Data are particularly suited to study the genetic, morphological and functional diversity of plankton. The present data set provides environmental context to all samples from the Tara Oceans Expedition (2009-2013), about mesoscale features related to the sampling date, time and location. Includes calculated averages of mesaurements made concurrently at the sampling location and depth, and calculated averages from climatologies (AMODIS, VGPM) and satellite products.

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This data set describes the distribution of a total of 90 plant species growing on field margins of an agricultural landscape in the Haean-myun catchment in South Korea. We conducted our survey between July and August 2011 in 100 sampling plots, covering the whole catchment. In each plot we measured three environmental variables: slope, width of the field margin, and management type (i.e. "managed" for field margins that had signs of management activities from the ongoing season such as cutting or spraying herbicides and "unmanaged" for field margins that had been left untouched in the season). For the botanical survey each plot was sampled using three subplots of one square meter per subplot; subplots were 4 m apart from each other. In each subplot, we estimated three different vegetation characteristics: vegetation cover (i.e. the percentage of ground covered by vegetation), species richness (i.e. the number of observed species) and species abundance (i.e. the number of observed individuals / species). We calculated the percentage of the non-farmed habitats by creating buffer zones of 100, 200, 300, 400 and 500 m radii around each plot using data provided by (Seo et al. 2014). Non-farmed habitats included field margins, fallows, forest, riparian areas, pasture and grassland.

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We have analysed alkenones in 149 surface sediments from the eastern South Atlantic in order to establish a sediment-based calibration of the U37K' paleotemperature index. Our study covers the major tropical to subpolar production systems and sea-surface temperatures (SST's) between 0° and 27°C. In order to define the most suitable calibration for this region, the U37K' values were correlated to seasonal, annual, and production-weighted annual mean atlas temperatures and compared to previously published culture and core-top calibrations. The best linear correlation between U37K' and SST was obtained using annual mean SST from 0 to 10 m water depth (U37K' = 0.033 T + 0.069, r**2 = 0.981). Data scattering increased significantly using temperatures of waters deeper than 20 m, suggesting that U37K' reflects mixed-layer SST and that alkenone production at thermocline depths was not high enough to significantly bias the mixed-layer signal. Regressions based on both production-weighted and on actual annual mean atlas SST were virtually identical, indicating that regional variations in the seasonality of primary production have no discernible effect on the U37K' vs. SST relationship. Comparison with published core-top calibrations from other oceanic regions revealed a high degree of accordance. We, therefore, established a global core-top calibration using U37K' data from 370 sites between 60°S and 60°N in the Atlantic, Indian, and Pacific Oceans and annual mean atlas SST (0-29°C) from 0 m water depth. The resulting relationship (U37K' = 0.033 T + 0.044, r**2 = 958) is identical within error limits to the widely used E. huxleyi calibrations of and attesting their general applicability. The observation that core-top calibrations extending over various biogeographical coccolithophorid zones are strongly linear and in better accordance than culture calibrations suggests that U37K' is less species-dependent than is indicated by culture experiments. The results also suggest that variations in growth rate of algae and nutrient availability do not significantly affect the sedimentary record of U37K' in open ocean environments.

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The 78 bryozoan species collected by the German R/V "Polarstern" during the LAMPOS cruise in April 2002, encompassing the Scotia Arc archipelagos between Tierra del Fuego and the Antarctic Peninsula, were studied to discern the biogeographical patterns of the Magellan region of South America, the Scotia Arc archipelagos and the Antarctic. The resulting dendrogram shows three clusters: an isolated one with the three easternmost archipelagos and the other two linking some of the northern and southern Scotia Arc archipelagos with Tierra del Fuego. A more comprehensive analysis using all the species previously recorded from the Scotia Arc archipelagos and adjacent areas (214 spp.) produced a clearer zoogeographical pattern without isolated clusters of localities. The Antarctic Peninsula plus the Scotia Arc archipelagos form a large cluster distinct from the Magellan-Falkland Subantarctic area. A third analysis making use of 78 genera present in the study area plus Australia and New Zealand reinforces this pattern, showing two clusters: one uniting South America and the Australian-New Zealand realm and the other linking the Scotia Arc archipelagos with the Antarctic Peninsula. These results indicate that the Scotia Arc archipelagos represent merely a very narrow bridge connecting two different bryozoan faunas with only a few bryozoan species in common between the study areas.

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Calcareous microfossils are widely used by paleoceanographers to investigate past sea-surface hydrology. Among these microfossils, planktonic foraminifera are probably the most extensively used tool (e.g. [1] for a review), as they are easy to extract from the sediment and can also be used for coupled geochemical (e.g; d18O, d13C, Mg/Ca) and paleo-ecological investigations. Planktonic foraminifera are marine protists, which build a calcareous shell made of several chambers which reflect in their chemistry the properties of the ambient water-masses. Planktonic foraminifera are known to thrive in various habitats, distributed not only along a latitudinal gradient, but also along different water-depth intervals within surface waters (0-1000 m). Regarding their biogeographical distribution, planktonic foraminifera assemblages therefore mirror different water-masses properties, such as temperature, salinity and nutrient content of the surface water in which they live. The investigation of the specific composition of a fossil assemblage (relative abundances) is therefore a way to empirically obtain (paleo)information on past variations of sea-surface hydrological parameters. This paper focuses on the planktonic foraminifera record from the Arctic domain. This polar region records peculiar sea-surface conditions, with the influence of nearly perennial sea-ice cover development. This has strong impact on living foraminifera populations and on the preservation of their shells in the underlying sediments.

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A set of 40 Uranium-series datings obtained on the reef-forming scleractinian cold-water corals Lophelia pertusa and Madrepora oculata revealed that during the past 400 kyr their occurrence in the Gulf of Cádiz (GoC) was almost exclusively restricted to glacial periods. This result strengthens the outcomes of former studies that coral growth in the temperate NE Atlantic encompassing the French, Iberian and Moroccan margins dominated during glacial periods, whereas in the higher latitudes (Irish and Norwegian margins) extended coral growth prevailed during interglacial periods. Thus it appears that the biogeographical limits for sustained cold-water coral growth along the NE Atlantic margin are strongly related to climate change. By focussing on the last glacial-interglacial cycle, this study shows that palaeo-productivity was increased during the last glacial. This was likely driven by the fertilisation effect of an increased input of aeolian dust and locally intensified upwelling. After the Younger Dryas cold event, the input of aeolian dust and productivity significantly decreased concurrent with an increase in water temperatures in the GoC. This primarily resulted in reduced food availability and caused a widespread demise of the formerly thriving coral ecosystems. Moreover, these climate induced changes most likely caused a latitudinal shift of areas withoptimum coral growth conditions towards the northern NE Atlantic where more suitable environmental conditions established with the onset of the Holocene.

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The present data set is a registry of samples from the Tara Oceans Expedition (2009-2013) that were selected for publication in a special issue of the SCIENCE journal (see related references below). The registry provides details about the sampling location and methodology of each sample. Uniform resource locators (URLs) offer direct links to additional contextual environmental data and to the corresponding sequence runs used for analysis in the related literature publications in the SCIENCE journal.

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The South America southern coast exhibits many outcrops with abundant shell beds, from the Pleistocene through the Recent. How much biological information is preserved within these shell beds? Or, what is the actual probability a living community has to leave a fossil record corresponding to these shell deposits? Although ecological and biogeographical aspects might had been pointed, considering these temporal scales, up to the moment there is no taphonomically-oriented studies available. Quantitative comparisons between living (LAs), death (DAs) and fossil assemblages (FAs) are important not only in strictly taphonomic studies, but have grown a leading tool for conservation paleobiology analysis. Comparing LAs, DAs and FAs from estuaries and lagoons in the Rio Grande do Sul Coastal Plain makes possible to quantitatively understand the nature and quantity of biological information preserved in fossil associations in Holocene lagoon facies. As already noted by several authors, spatial scale parts the analysis, but we detected that the FAs refl ects live ones, rather than dead ones, as previously not realized. The results herein obtained illustrates that species present in DA are not as good preserved in recent (Holocene) fossil record as originally thought. Strictly lagoon species are most prone to leave fossil record. The authors consider that the fi delity pattern here observed for estuarine mollusks to be driven by (i) high temporal and spatial variability in the LAs, (ii) spatial mixing in the DA and (iii) differential preservation of shells, due to long residence times in the taphonomically active zone.