Arbuscular mycorrhizal (AM) fungi play important functional roles in ecosystems, including the uptake and transfer of nutrients, modification of the physical soil environment and alteration of plant ...interactions with other biota. Several studies have demonstrated the potential for variation in AM fungal diversity to also affect ecosystem functioning, mainly via effects on primary productivity. Diversity in these studies is usually characterized in terms of the number of species, unique evolutionary lineages or complementary mycorrhizal traits, as well as the ability of plants to discriminate among AM fungi in space and time. However, the emergent outcomes of these relationships are usually indirect, and thus context dependent, and difficult to predict with certainty. Here, we advocate a fungal-centric view of AM fungal biodiversity–ecosystem function relationships that focuses on the direct and specific links betweenAMfungal fitness and consequences for their roles in ecosystems, especially highlighting functional diversity in hyphal resource economics. We conclude by arguing that an understanding of AM fungal functional diversity is fundamental to determine whether AM fungi have a role in the exploitation of marginal/novel environments (whether past, present or future) and highlight avenues for future research.
A metamorphic devolatilization model can explain the enrichment, segregation, timing, distribution and character of many goldfields such as those found in Archean greenstone belts, slate‐belts and ...other gold‐only provinces. In this genetic model, hydrated and carbonated greenschist facies rocks, particularly metabasic rocks, are devolatilized primarily across the greenschist–amphibolite facies boundary in an orogenic setting. Devolatilization operates on the scale of individual mineral grains, extracting not just H2O and CO2 but also S and, in turn, Au. Elevated gold in solution is achieved by complexing with reduced S, and by H2CO3 weak acid buffering near the optimal fluid pH for gold solubility (the buffering is more important than being at the point of maximum gold solubility). Low salinity ensures low base metal concentrations in the auriferous metamorphic fluid. Migration of this fluid upwards is via shear zones and/or into hydraulic fracture zones in rocks of low tensile strength. The geometry of the shear zones dictates the kilometre‐scale fluid migration paths and the degree of fluid focusing into small enough volumes to form economic accumulations of gold. Deposition of gold from solution necessitates breakdown of the gold–thiosulphide complex and is especially facilitated by fluid reduction in contact with reduced carbon‐bearing host rocks and/or by sulphidation of wallrocks to generate iron‐bearing sulphide and precipitated gold. As such, black slate, carbon seams, banded iron formation, tholeiitic basalt, magnetite‐bearing diorite and differentiated tholeiitic dolerite sills are some of the important hosts to major goldfields. Gold deposition is accompanied by carbonation, sulphidation and muscovite/biotite alteration where the host rock is of suitable bulk composition. The correlation of major gold deposits with rock type, even when the gold is primarily in veins, argues for rock‐dominated depositional systems, not fluid‐dominated ones. As a consequence, a general role in gold deposition for fluid mixing, temperature decrease and/or fluid pressure decrease and boiling is unlikely, although such effects may be involved locally. Several geological features that are recorded at gold‐only deposits today reflect subsequent modifications superimposed upon the products of this generic metamorphic devolatilization process. Overprinting by higher‐grade metamorphism and deformation, and/or (palaeo)‐weathering may provide many of the most‐obvious features of goldfields including their mineralogy, geochemistry, geometry, small‐scale timing features, geophysical response and even mesoscopic gold distribution.
The thermodynamic properties of 254 end‐members, including 210 mineral end‐members, 18 silicate liquid end‐members and 26 aqueous fluid species are presented in a revised and updated internally ...consistent thermodynamic data set. The PVT properties of the data set phases are now based on a modified Tait equation of state (EOS) for the solids and the Pitzer & Sterner (1995) equation for gaseous components. Thermal expansion and compressibility are linked within the modified Tait EOS (TEOS) by a thermal pressure formulation using an Einstein temperature to model the temperature dependence of both the thermal expansion and bulk modulus in a consistent way. The new EOS has led to improved fitting of the phase equilibrium experiments. Many new end‐members have been added, including several deep mantle phases and, for the first time, sulphur‐bearing minerals. Silicate liquid end‐members are in good agreement with both phase equilibrium experiments and measured heat of melting. The new dataset considerably enhances the capabilities for thermodynamic calculation on rocks, melts and aqueous fluids under crustal to deep mantle conditions. Implementations are already available in thermocalc to take advantage of the new data set and its methodologies, as illustrated by example calculations on sapphirine‐bearing equilibria, sulphur‐bearing equilibria and calculations to 300 kbar and 2000 °C to extend to lower mantle conditions.
Assay of Transposase Accessible Chromatin sequencing (ATAC-seq) is widely used in studying chromatin biology, but a comprehensive review of the analysis tools has not been completed yet. Here, we ...discuss the major steps in ATAC-seq data analysis, including pre-analysis (quality check and alignment), core analysis (peak calling), and advanced analysis (peak differential analysis and annotation, motif enrichment, footprinting, and nucleosome position analysis). We also review the reconstruction of transcriptional regulatory networks with multiomics data and highlight the current challenges of each step. Finally, we describe the potential of single-cell ATAC-seq and highlight the necessity of developing ATAC-seq specific analysis tools to obtain biologically meaningful insights.
To predict the future contributions of the Antarctic ice sheets to sea-level rise, numerical models use reconstructions of past ice-sheet retreat after the Last Glacial Maximum to tune model ...parameters
. Reconstructions of the West Antarctic Ice Sheet have assumed that it retreated progressively throughout the Holocene epoch (the past 11,500 years or so)
. Here we show, however, that over this period the grounding line of the West Antarctic Ice Sheet (which marks the point at which it is no longer in contact with the ground and becomes a floating ice shelf) retreated several hundred kilometres inland of today's grounding line, before isostatic rebound caused it to re-advance to its present position. Our evidence includes, first, radiocarbon dating of sediment cores recovered from beneath the ice streams of the Ross Sea sector, indicating widespread Holocene marine exposure; and second, ice-penetrating radar observations of englacial structure in the Weddell Sea sector, indicating ice-shelf grounding. We explore the implications of these findings with an ice-sheet model. Modelled re-advance of the grounding line in the Holocene requires ice-shelf grounding caused by isostatic rebound. Our findings overturn the assumption of progressive retreat of the grounding line during the Holocene in West Antarctica, and corroborate previous suggestions of ice-sheet re-advance
. Rebound-driven stabilizing processes were apparently able to halt and reverse climate-initiated ice loss. Whether these processes can reverse present-day ice loss
on millennial timescales will depend on bedrock topography and mantle viscosity-parameters that are difficult to measure and to incorporate into ice-sheet models.
The adaptation of insect vectors of human diseases to breed in human habitats (domestication) is one of the most important phenomena in medical entomology. Considerable data are available on the ...vector mosquito Aedes aegypti in this regard and here we integrate the available information including genetics, behaviour, morphology, ecology and biogeography of the mosquito, with human history. We emphasise the tremendous amount of variation possessed by Ae. aegypti for virtually all traits considered. Typological thinking needs to be abandoned to reach a realistic and comprehensive understanding of this important vector of yellow fever, dengue and Chikungunya.
Activity‐composition (a–x) models have been generated for zirconium‐bearing haplogranitic silicate melt and garnet from experimental data on zircon dissolution and natural rock data, respectively. ...Additionally including the recently proposed a–x model for Zr‐bearing rutile Tomkins et al., Journal of Metamorphic Geology25 (2007) 401, calculated phase diagrams that explicitly include ZrO2 in the bulk composition predict the growth and dissolution of zircon at sub‐ and supra‐solidus conditions. This occurs within the context of the evolution of major metamorphic minerals and mineral assemblages in pressure‐temperature‐composition space for a metapelitic rock composition. The stability of zircon is a function of the bulk ZrO2 content. Garnet contains insufficient Zr to affect the stability of zircon whereas rutile does contain sufficient Zr that zircon stability can be curtailed in rocks with significant rutile. Silicate melt contains appreciable Zr and zircon abundance varies inversely with melt abundance. Thermometers based on the Zr‐content of rutile (and potentially garnet) can be graphically portrayed as compositional contours in mineral assemblage fields on the phase diagrams, thereby potentially adding to the utilization of such thermometers. The ability to calculate phase diagrams explicitly including Zr is a major step towards more systematically linking zircon growth – and zircon geochronology – and accessory phase thermometry in a readily adaptable way to the metamorphic evolution of major silicate minerals in a wide range of rocks.
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