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   

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

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Climate change,ecosystems and smallholder agriculture in Central America: an introduction to the special issue     

Pablo Imbach  Megan Beardsley  Claudia Bouroncle  Claudia Medellin  Peter Läderach  Hugo Hidalgo  Eric Alfaro  Jacob Van Etten  Robert Allan  Debbie Hemming  Roger Stone  Lee Hannah  Camila I. Donatti 《Climatic change》2017,140(1):1-4

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Modelling of the acid-base properties of two thermophilic bacteria at different growth times     

Hannah T.M. Heinrich  Phil J. Bremer  Christopher J. Daughney 《Geochimica et cosmochimica acta》2008,72(17):4185-4200

Acid-base titrations and electrophoretic mobility measurements were conducted on the thermophilic bacteria Anoxybacillus flavithermus and Geobacillus stearothermophilus at two different growth times corresponding to exponential and stationary/death phase. The data showed significant differences between the two investigated growth times for both bacterial species. In stationary/death phase samples, cells were disrupted and their buffering capacity was lower than that of exponential phase cells. For G. stearothermophilus the electrophoretic mobility profiles changed dramatically. Chemical equilibrium models were developed to simultaneously describe the data from the titrations and the electrophoretic mobility measurements. A simple approach was developed to determine confidence intervals for the overall variance between the model and the experimental data, in order to identify statistically significant changes in model fit and thereby select the simplest model that was able to adequately describe each data set. Exponential phase cells of the investigated thermophiles had a higher total site concentration than the average found for mesophilic bacteria (based on a previously published generalised model for the acid-base behaviour of mesophiles), whereas the opposite was true for cells in stationary/death phase. The results of this study indicate that growth phase is an important parameter that can affect ion binding by bacteria, that growth phase should be considered when developing or employing chemical models for bacteria-bearing systems.  相似文献   

Tectonic configuration of the Apuseni–Banat—Timok–Srednogorie belt, Balkans-South Carpathians, constrained by high precision Re–Os molybdenite ages     

Aaron Zimmerman  Holly J. Stein  Judith L. Hannah  Dejan Koželj  Kamen Bogdanov  Tudor Berza 《Mineralium Deposita》2008,43(1):1-21

The Apuseni–Banat–Timok–Srednogorie magmatic–metallogenic belt (ABTS belt), forms a substantial metallogenic province in the Balkan-South Carpathian system in southeastern Europe. The belt hosts porphyry, skarn, and epithermal deposits mined since pre-Roman times. Generally, the deposits, prospects, and occurrences within the belt are linked to magmatic centers of calc-alkaline affinity. Fifty-one rhenium-osmium (Re–Os) ages and Re concentration data for molybdenites define systematic geochronologic trends and constrain the geochemical-metallogenic evolution of the belt in space and time. From these data and additional existing geologic-geochemical data, a general tectonic history for the belt is proposed. Mineralization ages in Apuseni-Banat, Timok, and Panagyurishte (the central district of the larger E–W Srednogorie Zone) range from 72–83, 81–88, and 87–92 Ma, respectively, and clearly document increasing age from the northwestern districts to the southeastern districts. Further, Re–Os ages suggest rapidly migrating pulses of Late Cretaceous magmatic–hydrothermal activity with construction of deposits in ~1 m.y., districts in ~10 m.y., and the entire 1,500 km belt in ~20 m.y. Ages in both Timok and Panagyurishte show systematic younging, while deposit ages in Banat and Apuseni are less systematic reflecting a restricted evolution of the tectonic system. Systematic differences are also observed for molybdenite Re concentrations on the belt scale. Re concentrations generally range from hundreds to thousands of parts per million, typical of subduction-related Cu–Au–Mo–(PGE) porphyry systems associated with the generation of juvenile crust. The geochronologic and geochemical trends are compatible with proposed steepening of subducting oceanic slab and relaxation of upper continental plate compression. Resulting influx of sub-continental mantle lithosphere (SCML) and asthenosphere provide a fertile metal source and heat, while the subducting slab contributes connate and mineral dehydration fluids, which facilitate partial melting and metal leaching of SCML and asthenosphere. Cu–Au–Mo–(PGE) porphyry deposits may develop where melts are trapped at shallow crustal levels, often with associated volcanism and epithermal-style deposits (South Banat, Timok, and Panagyurishte). Mo–Fe–Pb–Zn skarn deposits may develop where felsic melts are trapped adjacent to Mesozoic limestones at moderate crustal levels (North Banat and Apuseni). Systematic spatial variations in deposit style, commodity enrichment, Re–Os ages, and Re concentrations support specific tectonic processes that led to ore formation. In a post-collisional setting, subduction of Vardar oceanic crust may have stalled, causing slab steepening and rollback. The slab rollback relaxes compression, facilitating and enhancing orogenic collapse of previously thickened Balkan-South Carpathian crust. The progression of coupled rollback-orogenic collapse is evidenced by the width of Late Cretaceous extensional basins and northward younging of Re–Os ages, from Panagyurishte (~60 km; 92–87 Ma) to Timok (~20 km; 88–81 Ma) to Apuseni-Banat (~5 km; 83–72 Ma). Generation of a well-endowed mineral belt, such as the ABTS, requires a temporally and spatially restricted window of magmatic–hydrothermal activity. This window is quickly opened as upper plate compression relaxes, thereby inducing melt generation and ingress of melt to higher crustal levels. The window is just as quickly closed as upper plate compression is reinstated. The transient tectonic state responsible for economic mineralization in the ABTS belt may be a paleo-analogue to transient intervals in the present subduction tectonics of SE Asia where much mineral wealth has been created in the last few million years.  相似文献