scispace - formally typeset
Search or ask a question
Institution

International Institute for Applied Systems Analysis

NonprofitLaxenburg, Austria
About: International Institute for Applied Systems Analysis is a nonprofit organization based out in Laxenburg, Austria. It is known for research contribution in the topics: Population & Greenhouse gas. The organization has 1369 authors who have published 5075 publications receiving 280467 citations. The organization is also known as: IIASA.


Papers
More filters
Journal ArticleDOI
TL;DR: The approach provides a mechanistic understanding of several phenomena that have been found in previous models and demonstrates how even in a simple model, the evolutionary outcome depends in a complex way on ecological and genetic parameters.
Abstract: Several recent models have shown that frequency‐dependent disruptive selection created by intraspecific competition can lead to the evolution of assortative mating and, thus, to competitive sympatric speciation. However, since most of these results rely on limited numerical analyses, their generality has been debated. Here, we consider one of the standard models (the so‐called Roughgarden model) with a simplified genetics where the selected trait is determined by a single diallelic locus. This model is sufficiently complex to maintain key properties of the general multilocus case but simple enough to allow for comprehensive analytical treatment by means of invasion fitness arguments. Depending on (1) the strength and (2) the shape of stabilizing selection, (3) the strength and (4) the shape of pairwise competition, (5) the shape of the mating function, and (6) whether assortative mating leads to sexual selection, we find five different evolutionary regimes. In one of these regimes, complete repr...

88 citations

Journal ArticleDOI
TL;DR: Analysis of the evolution of a quantitative trait in populations that are spatially extended along an environmental gradient, with gene flow between nearby locations shows that the shape of competition kernels is important for clustering: the sign structure of the Fourier transform of a competition kernel determines whether the kernel promotes clustering.
Abstract: We have analyzed the evolution of a quantitative trait in populations that are spatially extended along an environmental gradient, with gene flow between nearby locations. In the absence of competition, there is stabilizing selection toward a locally best-adapted trait that changes gradually along the gradient. According to traditional ideas, gradual spatial variation in environmental conditions is expected to lead to gradual variation in the evolved trait. A contrasting possibility is that the trait distribution instead breaks up into discrete clusters. Doebeli and Dieckmann (2003) argued that competition acting locally in trait space and geographical space can promote such clustering. We have investigated this possibility using deterministic population dynamics for asexual populations, analyzing our model numerically and through an analytical approximation. We examined how the evolution of clusters is affected by the shape of competition kernels, by the presence of Allee effects, and by the strength of gene flow along the gradient. For certain parameter ranges clustering was a robust outcome, and for other ranges there was no clustering. Our analysis shows that the shape of competition kernels is important for clustering: the sign structure of the Fourier transform of a competition kernel determines whether the kernel promotes clustering. Also, we found that Allee effects promote clustering, whereas gene flow can have a counteracting influence. In line with earlier findings, we could demonstrate that phenotypic clustering was favored by gradients of intermediate slope.

88 citations

Journal ArticleDOI
TL;DR: In this paper, the impact of the positive and negative phases of three climate modes (i) Pacific decadal oscillation (PDO), (ii) El Nino-Southern Oscillation (ENSO) with EL Nino (EN) and La Nina (LN) were assessed.
Abstract: Climate-related disasters in Bolivia are frequent, severe, and manifold and affect large parts of the population, economy, and ecosystems. Potentially amplified through climate change, natural hazards are of growing concern. To better understand these events, homogenized daily observations of temperature (29 stations) and precipitation (68 stations) from 1960 to 2009 were analyzed in this study. The impact of the positive (+) and negative (−) phases of the three climate modes (i) Pacific decadal oscillation (PDO), (ii) El Nino–Southern Oscillation (ENSO) with El Nino (EN) and La Nina (LN) events, and (iii) Antarctic Oscillation (AAO) were assessed. Temperatures were found to be higher during PDO(+), EN, and AAO(+) in the Andes. Total amounts of rainfall, as well as the number of extreme events, were higher during PDO(+), EN, and LN in the lowlands. During austral summer [December–February (DJF)], EN led to drier conditions in the Andes with more variable precipitation. Temperatures increased at a ...

88 citations

Journal ArticleDOI
TL;DR: It is demonstrated that the response of primary production to nitrogen and phosphorus additions is accurately predicted by the stoichiometric framework, with predicted responses supported by a meta-analysis of N–P fertilization experiments.
Abstract: In most terrestrial ecosystems, plant growth is limited by nitrogen and phosphorus. Adding either nutrient to soil usually affects primary production, but their effects can be positive or negative. Here we provide a general stoichiometric framework for interpreting these contrasting effects. First, we identify nitrogen and phosphorus limitations on plants and soil microorganisms using their respective nitrogen to phosphorus critical ratios. Second, we use these ratios to show how soil microorganisms mediate the response of primary production to limiting and non-limiting nutrient addition along a wide gradient of soil nutrient availability. Using a meta-analysis of 51 factorial nitrogen-phosphorus fertilization experiments conducted across multiple ecosystems, we demonstrate that the response of primary production to nitrogen and phosphorus additions is accurately predicted by our stoichiometric framework. The only pattern that could not be predicted by our original framework suggests that nitrogen has not only a structural function in growing organisms, but also a key role in promoting plant and microbial nutrient acquisition. We conclude that this stoichiometric framework offers the most parsimonious way to interpret contrasting and, until now, unresolved responses of primary production to nutrient addition in terrestrial ecosystems.

88 citations


Authors

Showing all 1418 results

NameH-indexPapersCitations
Martin A. Nowak14859194394
Paul J. Crutzen13046180651
Andreas Richter11076948262
David G. Streets10636442154
Drew Shindell10234049481
Wei Liu102292765228
Jean-Francois Lamarque10038555326
Frank Dentener9722058666
James W. Vaupel8943434286
Keywan Riahi8731858030
Larry W. Horowitz8525328706
Robert J. Scholes8425337019
Mark A. Sutton8342330716
Brian Walsh8223329589
Börje Johansson8287130985
Network Information
Related Institutions (5)
Wageningen University and Research Centre
54.8K papers, 2.6M citations

87% related

University of Exeter
50.6K papers, 1.7M citations

85% related

Lancaster University
44.5K papers, 1.6M citations

85% related

ETH Zurich
122.4K papers, 5.1M citations

85% related

University of Maryland, College Park
155.9K papers, 7.2M citations

84% related

Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202360
202263
2021414
2020406
2019383
2018325