scholarly journals Controlling for the species-area effect supports constrained long-term Mesozoic terrestrial vertebrate diversification

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
Roger A. Close ◽  
Roger B.J. Benson ◽  
Paul Upchurch ◽  
Richard J. Butler
Keyword(s):  
Area Effect ◽  
Terrestrial Vertebrate ◽  
Species Area

WEED SPECIES ASSOCIATION IN ARABLE FIELDS: OLD APPROACH, NEW APPLICATION

2018 ◽  
Vol 55 (3) ◽  
pp. 359-370
Author(s):  
G. CONCENÇO ◽  
A. ANDRES ◽  
F. SCHREIBER ◽  
I. S. MOISINHO ◽  
M. C. CORADINI ◽  
...  
Keyword(s):  
Winter Season ◽  
Point Of View ◽  
Plant Association ◽  
Weed Species ◽  
Chi Square ◽  
Species Association ◽  
Arable Fields ◽  
Species Area ◽  
Chi Square Test

SUMMARYWe aimed to assess the potential of the characterization of association among weed species as a tool to understand weed occurrence for further supporting long-term management programs. After a sequence of summer crops, which included irrigated rice and sorghum, the experimental area was submitted to subsoiling, limestone was applied, and ryegrass was planted in the winter season. Six months later, an ACCase-inhibitor herbicide was used to select only non-grassweed species. Field survey was carried out on 100 quadrats with 0.5-m width that were randomly sampled. Plant species were organized in 2 × 2 contingency tables. The results of the calculated chi-squares were compared to the respective tables, and results were presented as a paired chi-square matrix. The species–area curve was also obtained. The relative occurrence of species was determined by its frequency and presented as a wordcloud. The network analysis was obtained by using the Fruchterman–Reingold layout. The hypothesis of plant association aiming survival in arable fields was validated. The methodology of plant association based on the chi-square test was applicable to arable fields, where weed species (usually competitor plant types) occur in clusters. From a practical point of view, preference should be given to herbicides that are efficient on most species within a given cluster.

scholarly journals The fragmentation of Pangaea and Mesozoic terrestrial vertebrate biodiversity

2016 ◽  
Vol 12 (9) ◽  
pp. 20160528 ◽  
Author(s):  
Matthew J. Vavrek
Keyword(s):  
Large Scale ◽  
Climatic Factors ◽  
Sea Levels ◽  
Terrestrial Vertebrate ◽  
Species Area ◽  
Species Area Relationship ◽  
Terrestrial Biodiversity

During the Mesozoic (242–66 million years ago), terrestrial regions underwent a massive shift in their size, position and connectivity. At the beginning of the era, the land masses were joined into a single supercontinent called Pangaea. However, by the end of the Mesozoic, terrestrial regions had become highly fragmented, both owing to the drifting apart of the continental plates and the extremely high sea levels that flooded and divided many regions. How terrestrial biodiversity was affected by this fragmentation and large-scale flooding of the Earth's landmasses is uncertain. Based on a model using the species–area relationship (SAR), terrestrial vertebrate biodiversity would be expected to nearly double through the Mesozoic owing to continental fragmentation, despite a decrease of 24% in total terrestrial area. Previous studies of Mesozoic vertebrates have generally found increases in terrestrial diversity towards the end of the era, although these increases are often attributed to intrinsic or climatic factors. Instead, continental fragmentation over this time may largely explain any observed increase in terrestrial biodiversity. This study demonstrates the importance that non-intrinsic effects can have on the taxonomic success of a group, and the importance of geography to understanding past biodiversity.

scholarly journals Middle Eocene rodents from Peruvian Amazonia reveal the pattern and timing of caviomorph origins and biogeography

2011 ◽  
Vol 279 (1732) ◽  
pp. 1319-1326 ◽  
Author(s):  
Pierre-Olivier Antoine ◽  
Laurent Marivaux ◽  
Darin A. Croft ◽  
Guillaume Billet ◽  
Morgan Ganerød ◽  
...  
Keyword(s):  
South America ◽  
Middle Eocene ◽  
South American ◽  
African Origin ◽  
Small Rodents ◽  
Terrestrial Vertebrate ◽  
Global Cooling ◽  
Initial Radiation ◽  
Caviomorph Rodents

The long-term isolation of South America during most of the Cenozoic produced a highly peculiar terrestrial vertebrate biota, with a wide array of mammal groups, among which caviomorph rodents and platyrrhine primates are Mid-Cenozoic immigrants. In the absence of indisputable pre-Oligocene South American rodents or primates, the mode, timing and biogeography of these extraordinary dispersals remained debated. Here, we describe South America's oldest known rodents, based on a new diverse caviomorph assemblage from the late Middle Eocene (approx. 41 Ma) of Peru, including five small rodents with three stem caviomorphs. Instead of being tied to the Eocene/Oligocene global cooling and drying episode (approx. 34 Ma), as previously considered, the arrival of caviomorphs and their initial radiation in South America probably occurred under much warmer and wetter conditions, around the Mid-Eocene Climatic Optimum. Our phylogenetic results reaffirm the African origin of South American rodents and support a trans-Atlantic dispersal of these mammals during Middle Eocene times. This discovery further extends the gap (approx. 15 Myr) between first appearances of rodents and primates in South America.

An escape-to-radiate model for explaining the high plant diversity and endemism in campos rupestres†

2020 ◽  
Author(s):  
Alessandro Rapini ◽  
Cássia Bitencourt ◽  
Federico Luebert ◽  
Domingos Cardoso
Keyword(s):  
Plant Diversity ◽  
Campos Rupestres ◽  
Glacial Cycle ◽  
Espinhaço Range ◽  
Climatic Oscillations ◽  
Species Area ◽  
Pump Mechanism ◽  
Edaphic Variables ◽  
Suitable Area

Abstract With extraordinary levels of plant diversity and endemism, the Brazilian campos rupestres across the Espinhaço Range have a species/area ratio 40 times higher than the lowland Amazon. Although diversification drivers in campos rupestres remain a matter of debate, the Pleistocene refugium hypothesis (PRH) is often adopted as the most plausible explanation for their high diversity. The PRH has two main postulates: highland interglacial refugia and a species pump mechanism catalysed by climatic changes. We critically assessed studies on campos rupestres diversification at different evolutionary levels and conclude that most of them are affected by sampling biases, unrealistic assumptions or inaccurate results that do not support the PRH. By modelling the palaeo-range of campos rupestres based on the distribution of 1123 species of vascular plants endemic to the Espinhaço Range and using climate and edaphic variables, we projected a virtually constant suitable area for campos rupestres across the last glacial cycle. We challenge the great importance placed on Pleistocene climatic oscillations in campos rupestres plant diversification and offer an alternative explanation named escape-to-radiate model, which emphasizes niche shifts. Under this biogeographic model of diversification, the long-term fragmentation of campos rupestres combined with recurrent extinctions after genetic drift and sporadic events of adaptive radiation may provide an explanation for the current diversity and endemism in the Espinhaço Range. We conclude that long-term diversification dynamics in campos rupestres are mainly driven by selection, while most endemic diversity is ephemeral, extremely fragile and mainly driven by drift.

Therapy and prevention for mental health: What if mental diseases are mostly not brain disorders?

2019 ◽  
Vol 42 ◽  
Author(s):  
John P. A. Ioannidis
Keyword(s):  
Mental Health ◽  
Mental Disease ◽  
Brain Disorders ◽  
Social Stressors ◽  
Labor Education ◽  
Mental Diseases ◽  
Long Term Follow Up ◽  
Political Decisions

AbstractNeurobiology-based interventions for mental diseases and searches for useful biomarkers of treatment response have largely failed. Clinical trials should assess interventions related to environmental and social stressors, with long-term follow-up; social rather than biological endpoints; personalized outcomes; and suitable cluster, adaptive, and n-of-1 designs. Labor, education, financial, and other social/political decisions should be evaluated for their impacts on mental disease.

Sign in / Sign up

Export Citation Format

Share Document