scholarly journals Late Cenozoic onset of the latitudinal diversity gradient of North American mammals

2016 ◽  
Vol 113 (26) ◽  
pp. 7189-7194 ◽  
Author(s):  
Jonathan D. Marcot ◽  
David L. Fox ◽  
Spencer R. Niebuhr
Keyword(s):  
North America ◽  
North American ◽  
Global Climate ◽  
Temporal And Spatial Variation ◽  
Latitudinal Diversity Gradient ◽  
Terrestrial Mammals ◽  
Diversity Gradient ◽  
Temporal And Spatial ◽  
Living Organisms

The decline of species richness from equator to pole, or latitudinal diversity gradient (LDG), is nearly universal among clades of living organisms, yet whether it was such a pervasive pattern in the geologic past remains uncertain. Here, we calculate the strength of the LDG for terrestrial mammals in North America over the past 65 My, using 27,903 fossil occurrences of Cenozoic terrestrial mammals from western North America downloaded from the Paleobiology Database. Accounting for temporal and spatial variation in sampling, the LDG was substantially weaker than it is today for most of the Cenozoic and the robust modern LDG of North American mammals evolved only over the last 4 My. The strength of the LDG correlates negatively with global temperature, suggesting a role of global climate patterns in the establishment and maintenance of the LDG for North American mammals.

The systematics of Ranunculus gmelinii and R. hyperboreus in North America

1974 ◽  
Vol 52 (7) ◽  
pp. 1713-1722 ◽  
Author(s):  
Peter J. Scott
Keyword(s):  
Phenotypic Plasticity ◽  
North America ◽  
Morphological Variation ◽  
North American ◽  
Growth Conditions ◽  
Controlled Growth ◽  
The North ◽  
Representative Material

A consideration of the taxonomy of Ranunculus gmelinii DC. and R. hyperboreus Rottb. is presented. The role of phenotypic plasticity is indicated as a factor contributing to the range of morphological variation in these species and to the confusion found in their taxonomy. The present work, by a reexamination of representative material collected throughout the North American range of the species, and the use of controlled growth conditions, has suggested new limits for the species. This has resulted in modifications of the descriptions of the species and (or) the reduction of taxa to synonymy.Ranunculus hyperboreus Rottb. var. turquetilianus Polunin has been made a synonym of R. gmelinii DC.; R. natans C.A. Mey. var. intertextus (Greene) L. Benson has been made a synonym of R. hyperboreus Rottb.

scholarly journals Comparison of temporal and spatial variation of periphytic algal community in two urban lakes in Umuarama-PR (Brazil)

2020 ◽  
Vol 42 ◽  
pp. e94
Author(s):  
Rodrigo Felipe Bedim Godoy ◽  
Elias Trevisan ◽  
Enzo Luigi Crisiogiovanni ◽  
Matheus Haddad Nudi ◽  
Carlos Eduardo Porto ◽  
...  
Keyword(s):  
Water Resources ◽  
Water Sample ◽  
Spatial Variation ◽  
Algal Community ◽  
Ammoniacal Nitrogen ◽  
Dry Period ◽  
Temporal And Spatial Variation ◽  
Sampling Points ◽  
Temporal And Spatial ◽  
Living Organisms

Water resources are very important for all living organisms, and as being of vital importance need to be preserved. Thus, many water bodies are monitored as an essential strategy for identification of possible alterations over space and time. The analyses were performed in two different hydrological conditions, and water sample and rocks were collected in two different points at each lake. The results showed higher values of Ammoniacal Nitrogen in Aratimbó Lake, mainly during dry period (Ammoniacal Nitrogen = 4.2 mgL-1) at P1. However, P2 at Tucuruvi Lake presented higher concentration of Orthophosphate (2.24 mgL-1). Total Periphyton density also demonstrated variation among the different hydrological scenarios and lakes. The Highest density was of 385.30 10³ ind.cm-2at Aratimbó Lake and 180.43 10³ ind.cm-2at Tucuruvi Lake in rainy condition. Comparing the predominance of species, In Aratimbó Lake, Chlorophyceae class was predominant at P1, while Cyanophyceae class was predominant at P2. In dry period, Bacillarophyceae class was seen as the predominant class for both of lakes and for all sampling points. Differently from Aratimbó Lake, in Tucuruvi Lake Bacillarophyceae class was predominant in both of hydrological scenarios.

scholarly journals The latitudinal diversity gradient of tetrapods across the Permo-Triassic mass extinction and recovery interval

2020 ◽  
Vol 287 (1929) ◽  
pp. 20201125 ◽  
Author(s):  
Bethany J. Allen ◽  
Paul B. Wignall ◽  
Daniel J. Hill ◽  
Erin E. Saupe ◽  
Alexander M. Dunhill
Keyword(s):  
Mass Extinction ◽  
Large Scale ◽  
Middle Triassic ◽  
Global Climate ◽  
Time Interval ◽  
Late Permian ◽  
Biodiversity Patterns ◽  
Latitudinal Diversity Gradient ◽  
Earth History ◽  
Diversity Gradient

The decline in species richness from the equator to the poles is referred to as the latitudinal diversity gradient (LDG). Higher equatorial diversity has been recognized for over 200 years, but the consistency of this pattern in deep time remains uncertain. Examination of spatial biodiversity patterns in the past across different global climate regimes and continental configurations can reveal how LDGs have varied over Earth history and potentially differentiate between suggested causal mechanisms. The Late Permian–Middle Triassic represents an ideal time interval for study, because it is characterized by large-scale volcanic episodes, extreme greenhouse temperatures and the most severe mass extinction event in Earth history. We examined terrestrial and marine tetrapod spatial biodiversity patterns using a database of global tetrapod occurrences. Terrestrial tetrapods exhibit a bimodal richness distribution throughout the Late Permian–Middle Triassic, with peaks in the northern low latitudes and southern mid-latitudes around 20–40° N and 60° S, respectively. Marine reptile fossils are known almost exclusively from the Northern Hemisphere in the Early and Middle Triassic, with highest diversity around 20° N. Reconstructed terrestrial LDGs contrast strongly with the generally unimodal gradients of today, potentially reflecting high global temperatures and prevailing Pangaean super-monsoonal climate system during the Permo-Triassic.

scholarly journals The Islamic State Threat to European and North American Security

2018 ◽  
Vol 1 (2) ◽  
pp. 25
Author(s):  
Anthony Celso
Keyword(s):  
North America ◽  
Homeland Security ◽  
North American ◽  
Islamic State ◽  
The West

This essay examines Islamic State (IS) terror activity in Europe and North America. It does so in four parts. First, it analyses the pioneering role of Abu Muhammad al-Adnani who from 2012-2016 served as IS’ chief propagandist and terror orchestrator. Second, it looks at IS’ terror campaign to weaken Western homeland security. Third, it discusses the Islamic State attacks in Europe and North America. Finally, it assesses future IS’s terrorism in the West.

scholarly journals Projections of North American Snow from NA-CORDEX and their Uncertainties, with a Focus on Model Resolution

2021 ◽  
Author(s):  
Rachel McCrary ◽  
Linda Mearns ◽  
Mimi Hughes ◽  
Sébastien Biner ◽  
Melissa Bukovsky
Keyword(s):  
North America ◽  
North American ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
High Elevation ◽  
Climate Impacts ◽  
Global Climate Models ◽  
High Latitudes ◽  
Model Resolution

Abstract Snow is important for many physical, social, and economic sectors in North America. In a warming climate, the characteristics of snow will likely change in fundamental ways, therefore compelling societal need for future projections of snow. However many stakeholders require climate change information at finer resolutions that global climate models (GCMs) can provide. The North American Coordinated Regional Downscaling Experiment (NA-CORDEX) provides an ensemble of regional climate model (RCMs) simulations at two resolutions (~0.5º and ~0.25º) designed to help serve the climate impacts and adaptation communities. This is the first study to examine the differences in end-of-21st-century projections of snow from the NA-CORDEX RCMs and their driving GCMs. We find the broad patterns of change are similar across RCMs and GCMs: snow cover retreats, snow mass decreases everywhere except at high latitudes, and the duration of the snow covered season decreases. Regionally, the spatial details, magnitude, percent, and uncertainty of future changes varies between the GCM and RCM ensemble, but are similar between the two resolutions of the RCM ensembles. Increases in winter snow amounts at high latitudes is a robust response across all ensembles. Percent snow losses are found to be more substantial in the GCMs than the RCMs over most of North America, especially in regions with high-elevation topography. Specifically, percent snow losses decrease with increasing elevation as the model resolution becomes finer.

scholarly journals Adaptations of Truth and Reconciliation Commissions in the North American Context: Local Examples of a Global Restorative Justice Intervention

10.18060/1970 ◽  
2012 ◽  
Vol 13 (2) ◽  
pp. 408-419 ◽  
Author(s):  
David K. Androff
Keyword(s):  
North America ◽  
Restorative Justice ◽  
North American ◽  
Racial Violence ◽  
Indigenous Populations ◽  
Truth And Reconciliation ◽  
The North ◽  
Truth And Reconciliation Commissions ◽  
Context Shapes

Truth and Reconciliation Commissions (TRCs) are restorative justice mechanisms for addressing human rights violations and injustice at the macro level. Mainly applied in the Global South, they have only recently been adapted within North America. The Greensboro, NC TRC was launched by grassroots and community-based organizations in 2004 to examine the causes and consequences of a 1979 incident of racial violence. The Canadian TRC was established in 2008 to address the legacy of colonial policies of assimilation and the forced schooling of indigenous populations. Through a comparison of these two cases, this paper will investigate how the North American context shapes the nature of the problems that these TRCs address, how they are organized, their relationship to the legal system, the role of civil society, and their relationship to poverty and reparations. Implications for social work, restorative justice and the potential for additional TRCs in North America are discussed.

The latitudinal diversity gradient in brush-footed butterflies (Nymphalidae): conserved ancestral tropical niche but different continental histories

2020 ◽  
Author(s):  
Nicolas Chazot ◽  
Fabien L. Condamine ◽  
Gytis Dudas ◽  
Carlos Peña ◽  
Pavel Matos-Maraví ◽  
...  
Keyword(s):  
Global Climate ◽  
Spatial Diversity ◽  
Extinction Rate ◽  
Latitudinal Diversity Gradient ◽  
Extinction Rates ◽  
Diversity Gradient ◽  
Speciation Rates ◽  
Global Increase ◽  
Underlying Mechanisms ◽  
Taxonomic Groups

AbstractThe latitudinal diversity gradient (LDG) is arguably one of the most striking patterns in nature. The global increase in species richness toward the tropics across continents and taxonomic groups stimulated the formulation of many hypotheses to explain the underlying mechanisms of this pattern. We evaluated several of these hypotheses to explain spatial diversity patterns in the butterfly family, Nymphalidae, by assessing the contributions of speciation, extinction, and dispersal to the LDG, and also the extent to which these processes differ among regions at the same latitude. We generated a new, time-calibrated phylogeny of Nymphalidae based on 10 gene fragments and containing ca. 2,800 species (∼45% of extant diversity). Neither speciation nor extinction rate variations consistently explain the LDG among regions because temporal diversification dynamics differ greatly across longitude. For example, we found that Neotropical nymphalid diversity results from low extinction rates, not high speciation rates, and that biotic interchanges with other regions were rare. Southeast Asia was also characterized by a low speciation rate but, unlike the Neotropics, was the main source of dispersal events through time. Our results suggest that global climate change throughout the Cenozoic, particularly during the Eocene-Oligocene transition, combined with the conserved ancestral tropical niches, played a major role in generating the modern LDG of butterflies.

scholarly journals Conserved ancestral tropical niche but different continental histories explain the latitudinal diversity gradient in brush-footed butterflies

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Nicolas Chazot ◽  
Fabien L. Condamine ◽  
Gytis Dudas ◽  
Carlos Peña ◽  
Ullasa Kodandaramaiah ◽  
...  
Keyword(s):  
Global Climate ◽  
Spatial Diversity ◽  
Extinction Rate ◽  
Latitudinal Diversity Gradient ◽  
Extinction Rates ◽  
Diversity Gradient ◽  
Speciation Rates ◽  
Global Increase ◽  
Underlying Mechanisms ◽  
Taxonomic Groups

AbstractThe global increase in species richness toward the tropics across continents and taxonomic groups, referred to as the latitudinal diversity gradient, stimulated the formulation of many hypotheses to explain the underlying mechanisms of this pattern. We evaluate several of these hypotheses to explain spatial diversity patterns in a butterfly family, the Nymphalidae, by assessing the contributions of speciation, extinction, and dispersal, and also the extent to which these processes differ among regions at the same latitude. We generate a time-calibrated phylogeny containing 2,866 nymphalid species (~45% of extant diversity). Neither speciation nor extinction rate variations consistently explain the latitudinal diversity gradient among regions because temporal diversification dynamics differ greatly across longitude. The Neotropical diversity results from low extinction rates, not high speciation rates, and biotic interchanges with other regions are rare. Southeast Asia is also characterized by a low speciation rate but, unlike the Neotropics, is the main source of dispersal events through time. Our results suggest that global climate change throughout the Cenozoic, combined with tropical niche conservatism, played a major role in generating the modern latitudinal diversity gradient of nymphalid butterflies.

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