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61.
PER AHLBERG NIKLAS AXHEIMER LOREN E. BABCOCK MATS E. ERIKSSON BIRGER SCHMITZ FREDRIK TERFELT 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2009,42(1):2-16
A core drilling (Andrarum‐3), from the classical locality at Andrarum, Scania, southernmost Sweden, penetrated a 28.90‐m‐thick Cambrian succession. The core comprises dark grey to black, finely laminated mudstones and shales with early concretionary carbonate lenses (stinkstones or orsten) and a few primary carbonate beds. The middle Cambrian (provisional Series 3) part of the core comprises 17.35 m, whereas the Furongian Series (upper Cambrian) part covers the remaining 11.55 m. Nineteen trilobite and two phosphatocopine genera are present in the middle Cambrian, whereas the less diverse Furongian interval yielded four trilobite and three phosphatocopine genera. Other, less frequent, faunal elements include conodonts (s. l.), brachiopods, sponge spicules, bradoriids, and coprolites. Trilobites and phosphatocopines were used to subdivide the core into seven biozones ranging from the Ptychagnostus atavus Zone to the Parabolina spinulosa Zone (P. spinulosa Subzone). Carbon isotopic analyses (δ13Corg) through the core show two important excursions, the negative DrumIan Carbon isotope Excursion (DICE) in the Pt. atavus Zone, and the Steptoean Positive Carbon Isotope Excursion (SPICE) beginning near the first appearance of Glyptagnostus reticulatus and extending upward into the Olenus and Agnostus (Homagnostus) obesus Zone. The DICE displays a peak value, in the samples at hand, of –30.45‰δ13Corg in the lower part of the P. atavus Zone. The δ13Corg values increase through the overlying L. laevigata and A. pisiformis zones and display peak values of c. –28.00‰δ13Corg in the lowermost Furongian Olenus wahlenbergi and O. attenuatus subzones. Thereafter the values decrease significantly through the O. scanicus Subzone. Both isotopic excursions have been documented from several palaeocontinents, but never before from Baltica. Moreover, for the first time these excursions are recorded from organic matter in an alum shale setting. The recorded shift of +1.50–2.00‰δ13Corg is approximately half the magnitude of the SPICE documented from other regions. This discrepancy may be related to temporal variations in the type, origin, or diagenesis of the organic fraction analysed. 相似文献
62.
MARY BETH REW M. ZACHARIAH PEERY STEVEN R. BEISSINGER MARTINE BRUB JEFFREY D. LOZIER EMILY M. RUBIDGE PER J. PALSB
LL 《Molecular ecology resources》2006,6(1):241-244
We developed 31 novel, polymorphic microsatellite loci in the marbled murrelet (Brachyramphus marmoratus), a critically endangered seabird. Variability was tested on 15 individuals from the Santa Cruz, California population, with each locus characterized by two to 12 alleles. Observed levels of heterozygosity ranged from 0.13 to 0.93. These loci provide a valuable means of assessing the population structure and demographic parameters of this species, which may be critical to its conservation across a fragmented habitat. 相似文献
63.
Body size in proboscideans, with notes on elephant metabolism 总被引:4,自引:0,他引:4
PER CHRISTIANSEN 《Zoological Journal of the Linnean Society》2004,140(4):523-549
Mass estimates for a number of fossil proboscideans were computed using regression analyses on appendicular bones to body mass, for seven specimens of modern elephants, for which body masses had been recorded prior to death. The marked differences in physical proportions between extant Loxodonta and Elephas , implying substantial differences in body mass at any given shoulder height, were not present in their long bone parameters. Length and least circumferences proved to be the best parameters for prediction of body mass. Some extinct proboscideans, notably certain Mammuthus and Deinotherium , were much larger than extant elephants. Both the basal and the field metabolic rates of extant elephants are lower than predicted for a hypothetical mammal, in accordance with their body size and subsistence on low-quality foods. The feeding quantities often ascribed to extant wild elephants are exaggerated, and would in fact have sufficed to nourish much larger species. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society , 2004, 140 , 523–549. 相似文献
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MARKUS LINDHOLM FRODE STORDAL S. JANNICKE MOE DAG O. HESSEN PER AASS 《Freshwater Biology》2012,57(12):2591-2601
1. Species responses to global warming are predicted to be manifest as poleward and upward extension of species ranges, whereas cold‐adapted species experience range retractions. We report on recent range retraction of a freshwater crustacean, the Arctic fairy shrimp Branchinecta paludosa (Branchiopoda, Anostraca) from alpine ponds of southern Norway, a southernmost extension of its otherwise arctic range. 2. The species was mapped during two separate surveys, in 1970 and 2011. In 1970, it occurred in numerous ponds from the tree line at 900 m altitude to high alpine sites at 1500 m. Re‐sampling of the same ponds 41 years later revealed extinction of populations from ponds along the lowest 200 m of its altitudinal range. 3. Reconstruction of summer temperatures for the periods 1965–70 and 2005–10 revealed a thermal increase for the period, corresponding to a c. 200‐m upward shift of the local isotherms. More specifically, the number of warm summer days had doubled in the lowest 200 m of the region, which might be particularly detrimental for the species. 4. The extinctions at lower altitudes were not compensated for by corresponding upward colonisations. The range retraction of B. paludosa is possibly associated with oxygen stress and hypoxia, induced by increased water temperatures. 相似文献
68.
Multiphasic Uptake in Plants I. Phosphate and Sulfate 总被引:2,自引:0,他引:2
PER NISSEN 《Physiologia plantarum》1973,28(2):304-316
Uptake of phosphate and sulfate is shown by reanalysis of available data to be mediated by single, multiphasic mechanisms which may be fundamentally similar in a variety of plants and tissues. 相似文献
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PER ALSTRÖM PAMELA C. RASMUSSEN URBAN OLSSON PER SUNDBERG 《Zoological Journal of the Linnean Society》2008,154(2):291-307
We demonstrate the importance of using multiple criteria in species delimitations, whatever the conceptual base for species delimitation. We do this by studying plumage, biometrics, egg coloration, song, mitochondrial DNA and habitat/altitudinal distribution in the Spotted Bush Warbler Bradypterus thoracicus (Blyth) complex, and by conducting playback experiments. Taxa that we suggest are best treated as separate species [B. thoracicus (Blyth), B. davidi (La Touche) and B. kashmirensis (Sushkin)] differ in most or all of these aspects, particularly in song and mitochondrial DNA, while those that we treat as subspecies (suschkini) or synonyms (przevalskii) differ slightly and only in morphology. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154 , 291–307. 相似文献