Localized versus regional adaptation in limpet shell morphology across the Iberian Peninsula          下载免费PDF全文

Hunter N. Hines  Hannah Morriss  Karen Saunders  Rachel L. Williams  Sarah L. Young  Richard Stafford 《Marine Ecology》2017,38(6)

The climate‐envelope approach to predicting climate‐induced species range shift is limited. There are many possible reasons for this, but one novel explanation is that species adapt to changes in temperature at the expense of adaptation to other stressors. Here we test this hypothesis using the limpet Patella depressa (Mollusca, Patellidae), over a large geographical area covering most of the Atlantic coast of the Iberian Peninsula, known to consist of a genetically inter‐connected population. We examine limpet shell morphology on four shores in each of three regions, from Northern Spain to Southern Portugal. Within each region, shell morphology (measured as maximum shell profile to length ratio) varied between shore types differing in their insolation, wave action, microhabitat availability and biological factors. However, this ratio, which is known to be an adaptive response to heat stress, was found to be consistently higher in more southern latitudes despite differences between shore types being found in all regions. This implies that localized adaptation to shore type (most likely through phenotypic plasticity) is compromised by factors that change over latitudinal or regional scales, or which could occur in response to climate change. Although such climate‐induced changes may initially be localized, compromised adaptation (through phenotypic or genetic plasticity) may result in altered community interactions and potentially large shifts in community structure.  相似文献   

Impacts of a bivalve mass mortality event on an estuarine food web and bivalve grazing pressure     

Hannah F. E. Jones  Conrad A. Pilditch  David P. Hamilton  Karin R. Bryan 《新西兰海洋与淡水研究杂志》2013,47(3):370-392

Declines in bivalve populations have been quite common worldwide, often associated with coastal development, pollution and climate change. In addition to the impacts of these chronic stressors, occasional mass mortality events may have severe consequences on ecosystem services and biodiversity. In this study, we examined the impact of a mass mortality event of the clam (Austrovenus stutchburyi) on an estuarine food web and the grazing pressure exerted by the bivalve population. In February 2009, c. 60% of the clam population died in Whangateau Harbour, New Zealand. Population clearance rate calculations suggest that the clam population do not exert significant top-down control on phytoplankton biomass in the estuary, and thus the impact of the mortality event on bivalve grazing pressure was less severe than the reduction in abundance would suggest. A trophic model shows that phytoplankton play a limited role in the estuary food web, which is instead dominated by microphytobenthos and clams. This study highlights the importance of microphytobenthos in shallow estuaries, and the application of the trophic model is a useful tool that can identify key components of the ecosystem and could help inform monitoring programmes.  相似文献   

Correction of tree ring stable carbon isotope chronologies for changes in the carbon dioxide content of the atmosphere   总被引：2，自引：0，他引：2  

Danny McCarroll  Mary H. Gagen  Iain Robertson  Sietse Los  Risto Jalkanen  John S. Waterhouse 《Geochimica et cosmochimica acta》2009,73(6):1539-114

Tree-ring stable carbon isotope ratios (δ¹³C) often display a decline over the industrial period (post-AD1850) that is only partly explained by changes in the isotopic ratio of carbon dioxide (CO₂) and may represent a response to increased atmospheric concentrations of CO₂ (ca). If this is not addressed, reconstructions using long tree-ring stable isotope chronologies calibrated using the modern period, for which meteorological records are available, may be compromised. We propose a correction procedure that attempts to calculate the δ¹³C values that would have been obtained under pre-industrial conditions. The correction procedure uses nonlinear (loess) regression but the magnitude of the adjustment made is restricted by two logical constraints based on the physiological response of trees: first, that a unit increase in ca cannot result in more than the same unit increase in the internal concentration of CO₂ (ci), and second, that increases in water-use efficiency as a result of an increase in ca are limited to maintaining a constant ci/ca ratio. The first constraint allows retention of a falling trend in δ¹³C, which exceeds that which could logically be attributed to a passive response to rising ca. The second constraint ensures that any increase in δ¹³C, reflecting a change in water-use efficiency beyond maintenance of a constant ci/ca, is not removed. The procedure is tested using ‘pseudoproxies’, to demonstrate the effect of the correction on time-series with different shapes, and data from three sites in Finland and Norway. Two of the time-series retain a significant trend after correction, and in all three cases the correction improves the correlation with local meteorological measurements.  相似文献   

Subgrain-scale decoupling of Re and Os and assessment of laser ablation ICP-MS spot dating in molybdenite     

Holly Stein  Anders Scherstén  Judith Hannah 《Geochimica et cosmochimica acta》2003,67(19):3673-3686

Reproducibility of Re-Os molybdenite ages depends on sample size and homogeneity, suggesting that Re and Os are decoupled within individual molybdenite crystals and do not remain spatially linked over time. In order to investigate the Re-Os systematics of molybdenite at the subgrain (micron) scale, we report LA-ICP-MS Re-Os ages for an Archean molybdenite crystal from Aittojärvi, Finland, analyzed in situ in a white aplite matrix. A related Aittojärvi molybdenite (A996D), in the form of a very fine-grained mineral separate, is used as one of our in-house NTIMS standards, and thus its age of 2760 ± 9 Ma is well established. Measurements of (¹⁸⁷Re + ¹⁸⁷Os)/¹⁸⁵Re on micron scale spots along 200 μm traverses across the crystal yield a wide range of ages demonstrating that, in this case, microsampling of molybdenite does not produce geologically meaningful ages. Experimentation with mineral separations and sample size over a 7-yr period predicted that this would be the outcome. We suggest that ¹⁸⁷Os is more likely to be the mobile species, based on its charge and ionic radius, and that ¹⁸⁷Os becomes decoupled from parent ¹⁸⁷Re with time on the micron and larger scale. Incompatible charge and ionic radius for Os ions formed during reduction of molybdenite-forming fluids may explain the widely observed absence of common (initial) Os in molybdenite. Geologically accurate ages for molybdenite can only be obtained for fully homogenized crystals (or crystal aggregates) so that any post-crystallization ¹⁸⁷Re-¹⁸⁷Os decoupling is overcome.A growing number of geologically accurate ID-NTIMS ¹⁸⁷Re-¹⁸⁷Os ages for homogenized molybdenite suggest that postcrystallization mobility of radiogenic ¹⁸⁷Os must be limited to within the molybdenite mineral phase. We suggest that radiogenic ¹⁸⁷Os may be stored in micron scale dislocations, kink bands, and delamination cracks produced by deformation, and that the unusual structure and deformation response of molybdenite results in an increased chemical stability in this mineral. Migration of ¹⁸⁷Os into adjacent silicate phases is highly unlikely, but other contacting sulfides may take in Os. In an example from a Proterozoic skarn deposit at Pitkäranta (western Russia), we demonstrate minor loss of radiogenic ¹⁸⁷Os from molybdenite and a corresponding gain in adjacent chalcopyrite such that the molybdenite age is not perceptibly disturbed, whereas the resulting chalcopyrite ages are impossibly old. Therefore, it is unadvisable to perform Re-Os analytical work on any sulfide in contact or intimate association with molybdenite. In addition to large errors in the age, if the isochron method is employed, initial ¹⁸⁷Os/¹⁸⁸Os ratios could be erroneously high, leading to seriously errant genetic interpretations.  相似文献   

Improvement of inertial surveys through post-mission network adjustment and self-calibration     

John Hannah  Ivan I. Mueller 《Journal of Geodesy》1981,55(4):329-339

Present day inertial surveys are limited to single traverse runs in which the number of unknown system parameters to be determined are few, depending on the number of control points available along the traverse. Further, conventional inertial surveys are generally restricted to the determination of coordinates with no possibility for a rigorous post-mission adjustment of the observations. The consequence is the continued presence of systematic trends in the residuals, even after the use of error models such as those proposed by Ball, Gregerson or Kouba. Future work aiming at higher accuracies obviously requires more comprehensive models and rigorous adjustment procedures. These can be accomplished by the development of such error models and by the use of “area surveys”, instead of the single traverses, together with rigorous adjustment procedures suitable for the network of criss-crossing lines inertially surveyed. In such a network the cross-over points serve as constraints for the geodetic parameters (latitude, longitude, height, gravity anomaly, deflection components) and allow the addition of hardware and software related error parameters. Thus an opportunity is provided to effectively self-calibrate the system—a concept successfully used, for example, in photogrammetry or in satellite tracking. The number and the strength of such parameters depend on the number of control and cross-over points. The adjustment, of course, also provides the necessary statistical information on the adjusted parameters, such as their precision and the correlation between them. The presentation will describe current work at OSU in this area. Presented at the Second International Symposium on Inertial Technology for Surveying and Geodesy, Banff, Canada, June 1–5, 1981.  相似文献   

A double spike for osmium analysis of highly radiogenic samples   总被引：1，自引：0，他引：1  

Richard Markey  Judith L. Hannah  John W. Morgan  Holly J. Stein 《Chemical Geology》2003,200(3-4):395-406

Geologic samples containing highly radiogenic Os (molybdenites and low-level, highly radiogenic (LLHR) samples) have no internal means by which to correct for mass fractionation during isotopic measurement by mass spectrometry. We describe a double spike for use with highly radiogenic samples, created by combining isotopically enriched ¹⁸⁸Os and ¹⁹⁰Os. Spiking molybdenite and other highly radiogenic minerals with this tracer allows for a fractionation correction, as well as a more reliable determination of common Os relative to analysis using single spikes.

The precise isotopic composition of the double spike is determined by a calibration against natural Os, in which two separate measurements are necessary: one each for the pure double spike and the spike–standard mixture. An estimate of the true composition of the spike is obtained by least squares approximation, and the errors are obtained by Monte Carlo methods. Sample analyses are then much more straightforward than the calibration because isotopic compositions of all components are known a priori.

Results obtained with a mixed Re-double Os spike demonstrate an improved reproducibility over individual ¹⁸⁵Re and ¹⁹⁰Os spikes. For an Archean in-house molybdenite standard we now observe a reproducibility of 0.08%. The ability to make a fractionation correction is essential for Os measurements made by ion counting. With the double Os spike, young samples and those with low Re contents (i.e., LLHR) can now be accurately analyzed. The ¹⁸⁸Os–¹⁹⁰Os double spike also allows a determination of the common Os contents of highly radiogenic samples. Common Os is poorly determined for ancient samples with high concentrations of ¹⁸⁷Os, which fortunately are not sensitive to estimates of common Os. Common Os can be reasonably well determined for younger samples and those with low Re contents. We report a common Os concentration of 0.4±0.1 ppb for an 11 Ma molybdenite. Consideration of common Os content is important for age determination of young samples and LLHR samples, and is not possible by other published means of Os analysis.  相似文献   

Oxygen isotope compositions of selected laramide-tertiary granitoid stocks in the Colorado Mineral Belt and their bearing on the origin of climax-type granite-molybdenum systems     

Judith L. Hannah  Holly J. Stein 《Contributions to Mineralogy and Petrology》1986,93(3):347-358

Quartz phenocrysts from 31 granitoid stocks in the Colorado Mineral Belt yield ¹⁸O values less than 10.4, with most values between 9.3 and 10.4. An average magmatic value of about 8.5 is suggested. The stocks resemble A-type granites; these data support magma genesis by partial melting of previously depleted, fluorine-enriched, lower crustal granulites, followed by extreme differentiation and volatile evolution in the upper crust.Subsolidus interaction of isotopically light water with stocks has reduced most feldspar and whole rock ¹⁸O values. Unaltered samples from Climax-type molybdenumbearing granites, however, show no greater isotopic disturbance than samples from unmineralized stocks. Although meteoric water certainly played a role in post-mineralization alteration, particularly in feldspars, it is not required during high-temperature mineralization processes. We suggest that slightly low ¹⁸O values in some vein and replacement minerals associated with molybdenum mineralization may have resulted from equilibration with isotopically light magmatic water and/or heavy isotope depletion of the ore fluid by precipitation of earlier phases.Accumulation of sufficient quantities of isotopically light magmatic water to produce measured depletions of ¹⁸O requires extreme chemical stratification in a large magma reservoir. Upward migration of a highly fractionated, volatile-rich magma into a small apical Climax-type diapir, including large scale transport of silica, alkalis, molybdenum, and other vapor soluble elements, may occur with depression of the solidus temperature and reduction of magma viscosity by fluorine. Climax-type granites may provide examples of ¹⁸O depletion in magmatic systems without meteoric water influx.  相似文献   

Attribution of extreme weather events in Africa: a preliminary exploration of the science and policy implications     

Friederike E. L. Otto  Emily Boyd  Richard G. Jones  Rosalind J. Cornforth  Rachel James  Hannah R. Parker  Myles R. Allen 《Climatic change》2015,131(4):531-543

  相似文献   

Extraterrestrial amino acids and L‐enantiomeric excesses in the CM2 carbonaceous chondrites Aguas Zarcas and Murchison     

Daniel P. Glavin  Jamie E. Elsila  Hannah L. McLain  Jos C. Aponte  Eric T. Parker  Jason P. Dworkin  Dolores H. Hill  Harold C. Connolly  Dante S. Lauretta 《Meteoritics & planetary science》2021,56(1):148-173

The abundances, distributions, enantiomeric ratios, and carbon isotopic compositions of amino acids in two fragments of the Aguas Zarcas CM2 type carbonaceous chondrite fall and a fragment of the CM2 Murchison meteorite were determined via liquid chromatography time‐of‐flight mass spectrometry and gas chromatography isotope ratio mass spectrometry. A suite of two‐ to six‐carbon aliphatic primary amino acids was identified in the Aguas Zarcas and Murchison meteorites with abundances ranging from ~0.1 to 158 nmol/g. The high relative abundances of α‐amino acids found in these meteorites are consistent with a Strecker‐cyanohydrin synthesis on these meteorite parent bodies. Amino acid enantiomeric and carbon isotopic measurements in both fragments of the Aguas Zarcas meteorites indicate that both samples experienced some terrestrial protein amino acid contamination after their fall to Earth. In contrast, similar measurements of alanine in Murchison revealed that this common protein amino acid was both racemic (D ≈ L) and heavily enriched in ¹³C, indicating no measurable terrestrial alanine contamination of this meteorite. Carbon isotope measurements of two rare non‐proteinogenic amino acids in the Aguas Zarcas and Murchison meteorites, α‐aminoisobutyric acid and D‐ and L‐isovaline, also fall well outside the typical terrestrial range, confirming they are extraterrestrial in origin. The detections of non‐terrestrial L‐isovaline excesses of ~10–15% in both the Aguas Zarcas and Murchison meteorites, and non‐terrestrial L‐glutamic acid excesses in Murchison of ~16–40% are consistent with preferential enrichment of circularly polarized light generated L‐amino acid excesses of conglomerate enantiopure crystals during parent body aqueous alteration and provide evidence of an early solar system formation bias toward L‐amino acids prior to the origin of life.  相似文献   

An approach to hydrograph classification     

David M. Hannah  Barnaby P. G. Smith  Angela M. Gurnell  Glenn R. McGregor 《水文研究》2000,14(2):317-338

The stream hydrograph is an integration of spatial and temporal variations in water input, storage and transfer processes within a catchment. For glacier basins in particular, inferences concerning catchment‐scale processes have been developed from the varying form and magnitude of the diurnal hydrograph in the proglacial river. To date, however, such classifications of proglacial diurnal hydrographs have developed in a relatively subjective manner. This paper develops an objective approach to the classification of diurnal discharge hydrograph ‘shape’ and ‘magnitude’ using a combination of principal components analysis and cluster analysis applied to proglacial discharge time‐series and to diurnal bulk flow indices. The procedure is applied to discharge time‐series from two different glacier basins and four separate ablation seasons representing a gradient of increasing hydrological perturbation as a result of (i) variable water inputs generated by rainstorm activity and (ii) variable location and response of hydrological stores through a systematic decrease in catchment glacierized area. The potential of the technique for application in non‐glacial hydrological contexts is discussed. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献