scholarly journals Global patterns of β-diversity along the phylogenetic time-scale: The role of climate and plate tectonics

2017 ◽  
Vol 26 (10) ◽  
pp. 1211-1221 ◽  
Author(s):  
Florent Mazel ◽  
Rafael O. Wüest ◽  
Jean-Philippe Lessard ◽  
Julien Renaud ◽  
Gentile Francesco Ficetola ◽  
...  
Keyword(s):  
Time Scale ◽  
Plate Tectonics ◽  
Β Diversity ◽  
Global Patterns

scholarly journals Arthropod community structure in pastures of an island archipelago (Azores): looking for local–regional species richness patterns at fine-scales

2004 ◽  
Vol 94 (2) ◽  
pp. 111-121 ◽  
Author(s):  
P.A.V. Borges ◽  
V.K. Brown
Keyword(s):  
Species Richness ◽  
Regional Scale ◽  
Local Scale ◽  
Local Species Richness ◽  
Β Diversity ◽  
Arthropod Species ◽  
Α Diversity ◽  
Local Species ◽  
Richness Patterns

AbstractThe arthropod species richness of pastures in three Azorean islands was used to examine the relationship between local and regional species richness over two years. Two groups of arthropods, spiders and sucking insects, representing two functionally different but common groups of pasture invertebrates were investigated. The local–regional species richness relationship was assessed over relatively fine scales: quadrats (= local scale) and within pastures (= regional scale). Mean plot species richness was used as a measure of local species richness (= α diversity) and regional species richness was estimated at the pasture level (= γ diversity) with the ‘first-order-Jackknife’ estimator. Three related issues were addressed: (i) the role of estimated regional species richness and variables operating at the local scale (vegetation structure and diversity) in determining local species richness; (ii) quantification of the relative contributions of α and β diversity to regional diversity using additive partitioning; and (iii) the occurrence of consistent patterns in different years by analysing independently between-year data. Species assemblages of spiders were saturated at the local scale (similar local species richness and increasing β-diversity in richer regions) and were more dependent on vegetational structure than regional species richness. Sucking insect herbivores, by contrast, exhibited a linear relationship between local and regional species richness, consistent with the proportional sampling model. The patterns were consistent between years. These results imply that for spiders local processes are important, with assemblages in a particular patch being constrained by habitat structure. In contrast, for sucking insects, local processes may be insignificant in structuring communities.

An inter-dependence of flood and drought: disentangling amphibian beta diversity in seasonal floodplains

2017 ◽  
Vol 68 (11) ◽  
pp. 2115 ◽  
Author(s):  
Leonardo F. B. Moreira ◽  
Tainá F. Dorado-Rodrigues ◽  
Vanda L. Ferreira ◽  
Christine Strüssmann
Keyword(s):  
Community Structure ◽  
Environmental Factors ◽  
Quantitative Data ◽  
Explanatory Variable ◽  
Biotic Interactions ◽  
Ecological Role ◽  
Β Diversity ◽  
Amphibian Community ◽  
Dry Seasons

Species composition in floodplains is often affected by different structuring factors. Although floods play a key ecological role, habitat selection in the dry periods may blur patterns of biodiversity distribution. Here, we employed a partitioning framework to investigate the contribution of turnover and nestedness to β-diversity patterns in non-arboreal amphibians from southern Pantanal ecoregion. We investigated whether components of β-diversity change by spatial and environmental factors. We sampled grasslands and dense arboreal savannas distributed in 12 sampling sites across rainy and dry seasons, and analysed species dissimilarities using quantitative data. In the savannas, both turnover and nestedness contributed similarly to β diversity. However, we found that β diversity is driven essentially by turnover, in the grasslands. In the rainy season, balanced variation in abundance was more related to altitude and factors that induce spatial patterns, whereas dissimilarities were not related to any explanatory variable during dry season. In the Pantanal ecoregion, amphibian assemblages are influenced by a variety of seasonal constraints on terrestrial movements and biotic interactions. Our findings highlighted the role of guild-specific patterns and indicated that mass effects are important mechanisms creating amphibian community structure in the Pantanal.

scholarly journals Role of entropy in the thermodynamic evolution of the time scale of molecular dynamics near the glass transition

2015 ◽  
Vol 91 (6) ◽  
Author(s):  
K. Grzybowska ◽  
A. Grzybowski ◽  
S. Pawlus ◽  
J. Pionteck ◽  
M. Paluch
Keyword(s):  
Molecular Dynamics ◽  
Glass Transition ◽  
Time Scale

The human brain: Chairman’s introduction

1981 ◽  
Vol 292 (1057) ◽  
pp. 151-153
Keyword(s):  
Human Brain ◽  
Cultural Evolution ◽  
Positive Feedback ◽  
Time Scale ◽  
Biological Evolution ◽  
Internal Models ◽  
Adaptive Behaviour ◽  
Myelin Sheaths ◽  
The Brain

Much has been said at the symposium about the pre-eminent role of the brain in the continuing emergence of man. Tobias has spoken of its explosive enlargement during the last 1 Ma, and how much of its enlargement in individual ontogeny is postnatal. We are born before our brains are fully grown and ‘wired up ’. During our long adolescence we build up internal models of the outside world and of the relations of parts of our bodies to it and to one another. Neurons that are present at birth spread their dendrites and project axons which acquire their myelin sheaths, and establish innumerable contacts with other neurons, over the years. New connections are formed; genetically endowed ones are stamped in or blanked off. People born without arms may grow up to use their toes in skills that are normally manual. Tobias, Darlington and others have stressed the enormous survival value of adaptive behaviour and the ‘positive feedback’ relation between biological and cultural evolution. The latter, the unique product of the unprecedentedly rapid biological evolution of big brains, advances on a time scale unknown to biological evolution.

scholarly journals Has erosion globally increased? Long-term erosion rates as a function of climate derived from the impact crater inventory

2018 ◽  
Author(s):  
Stefan Hergarten ◽  
Thomas Kenkmann
Keyword(s):  
Time Scale ◽  
Impact Crater ◽  
Regional Effect ◽  
Tropical Zone ◽  
Erosion Rates ◽  
Continental Scale ◽  
River Loads ◽  
The Impact

Abstract. Worldwide erosion rates seem to have increased strongly since the beginning of the Quaternary, but there is still discussion about the role of glaciation as a potential driver and even whether the increase is real at all or an artefact due to losses in the long-term sedimentary record. In this study we derive estimates of average erosion rates on the time scale of some tens of million years from the terrestrial impact crater inventory. This approach is completely independent from all other methods to infer erosion rates such as river loads, preserved sediments, cosmogenic nuclides and thermochronometry. Our approach yields average erosion rates as a function of present-day topography and climate. The results confirm that topography accounts for the main part of the huge variation of erosion on Earth, but also identifies a significant systematic dependence on climate in contrast to several previous studies. We found a fivefold increase in erosional efficacy from the cold regimes to the tropical zone and that temperate and arid climates are very similar in this context. Combining our results to a worldwide mean erosion rate we found that erosion rates on the time scale of some tens of million years are at least as high as present-day rates and suggest that glaciation has a rather regional effect with a limited impact at the continental scale.

scholarly journals Reduced fecal short-chain fatty acids levels and the relationship with gut microbiota in IgA nephropathy

2021 ◽  
Author(s):  
Lingxiong Chai ◽  
Qun Luo ◽  
Kedan Cai ◽  
Kaiyue Wang ◽  
Binbin Xu
Keyword(s):  
Gut Microbiota ◽  
Iga Nephropathy ◽  
Butyric Acid ◽  
Intestinal Flora ◽  
Short Chain Fatty Acids ◽  
Caproic Acid ◽  
Isobutyric Acid ◽  
Control Group ◽  
Β Diversity

Abstract Background: IgA nephropathy(IgAN)) is the common pathological type of glomerular diseases. The role of gut microbiota in mediating "gut-IgA nephropathy" has not received sufficient attention in the previous studies. The purpose of this study was to investigate the changes of fecal short-chain fatty acids(SCFAs), a metabolite of the intestinal microbiota, in patients with IgAN and its correlation with intestinal flora and clinical indicators, and to further investigate the role of the gut-renal axis in IgAN.Methods: There were 29 patients with IgAN and 29 normal control subjects recruited from January 2018 to May 2018. The fresh feces were collected. The fecal SCFAs were measured by gas chromatography/mass spectrometry and gut microbiota was analysed by16S rDNA sequences, followed by estimation of α- and β-diversity. Correlation analysis was performed using the spearman’s correlation test between SCFAs and gut microbiota. Results:The levels of acetic acid, propionic acid, butyric acid, isobutyric acid and caproic acid in the IgAN patients were significantly reduced compared with control group(P<0.05). Butyric acid(r=-0.336, P=0.010) and isobutyric acid(r=-0.298, P=0.022) were negatively correlated with urea acid; butyric acid(r=-0.316, P=0.016) was negatively correlated with urea nitrogen; caproic acid(r=-0.415,P=0.025) showed negative correlation with 24-h urine protein level.Exemplified by the results of α-diversity and β-diversity, the intestinal flora of IgAN patients was significantly different from that of the control group. Acetic acid was positively associated with c_Clostridia(r=0.357, P=0.008), o_Clostridiales(r=0.357, P=0.008) and g_Eubacterium_coprostanoligenes_group(r=0.283, P=0.036). Butyric acid was positively associated with g_Alistipes (r=0.278, P=0.040). The relative abundance of those were significantly decreased in IgAN group compared to control group.Conclusion: The levels of fecal SCFAs in the IgAN patients were reduced, and correlated with clinical parameters and gut microbiota, which may be involved in the pathogenesis of IgAN, and this finding may provide a new therapeutic approach.

scholarly journals The Role of Occultations in the Improvement of the Lunar Ephemeris

1972 ◽  
Vol 47 ◽  
pp. 395-401
Author(s):  
L. V. Morrison
Keyword(s):  
Time Scale ◽  
The Moon ◽  
Secular Acceleration ◽  
Lunar Ephemeris ◽  
Occultation Data ◽  
Correction Terms ◽  
Empirical Constants ◽  
Atomic Time

Analyses of occultation timings show that periodic correction terms with semi-amplitude as great as 0.″18 arise from corrections required to the empirical constants of the Brown/Eckert theory. Using the atomic time-scale, some of the occultation data have been used to determine a correction of – 30 ± 16″/cy2 to Spencer Jones' value for the secular acceleration of the Moon. In the light of this correction, and previous determinations, attention is drawn to the possible weakness of Spencer Jones' value, which is not reflected in his quoted error of ± 1″/cy2. Further analyses of 50000 occultations observed since 1943 promise to reveal more accurately-determined corrections.

Cancer Epidemiology and Prevention

2017 ◽  
Keyword(s):  
Cancer Epidemiology ◽  
Preventive Interventions ◽  
Fourth Edition ◽  
Cancer Etiology ◽  
Gene Environment ◽  
Incidence And Mortality ◽  
Global Patterns ◽  
Prevention Of Cancer ◽  
First Time

Since its initial publication in 1982, Cancer Epidemiology and Prevention has served as the premier reference work for both students and professionals working to understand the causes and prevention of cancer in humans. Now revised for the first time in more than a decade, this fourth edition provides an updated and comprehensive summary of the global patterns of cancer incidence and mortality, current understanding of the major causal determinants, and a rationale for preventive interventions. In this edition, special attention has been paid to molecular epidemiologic approaches that address the wider role of genetic predisposition and gene-environment interactions in cancer etiology and pathogenesis.

3. Minerals and the interior of the Earth

2014 ◽  
Author(s):  
David Vaughan
Keyword(s):  
Upper Mantle ◽  
Lower Mantle ◽  
Plate Tectonics ◽  
Inner Core ◽  
Indirect Evidence ◽  
Outer Core ◽  
The Earth ◽  
Granite Formation ◽  
Temperature And Pressure

‘Minerals and the interior of the Earth’ looks at the role of minerals in plate tectonics during the processes of crystallization and melting. The size and range of minerals formed are dependent on the temperature and pressure of the magma during its movement through the crust. The evolution of the continental crust also involves granite formation and processes of metamorphism. Our understanding of the interior of the Earth is based on indirect evidence, mainly the study of earthquake waves. The Earth consists of concentric shells: a solid inner core; liquid outer core; a solid mantle divided into a lower mantle, a transition zone, and an upper mantle; and then the outer rigid lithosphere.

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