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Competition Models (competition + models)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

SNP Haplotypes in the Angiotensin I-Converting Enzyme (ACE) Gene: Analysis of Nigerian Family Data Using Gamete Competition Models

ANNALS OF HUMAN GENETICS, Issue 2 2005
C. A. McKenzie
Summary Gamete competition models were used to explore the relationships between 13 ACE gene polymorphisms and plasma ACE concentration in a set of Nigerian families. Several markers in the 5, and 3, regions of the gene were significantly associated with ACE concentration (P < 10 -4). Multi-locus genotypes comprising different combinations of markers from the 5, UTR and the 3, region of the gene were also analysed; in addition to G2350A, in the 3, region, two markers from the 5, UTR (A-5466C and A-240T) were found to be associated with ACE concentration. These results are consistent with reports that have suggested the presence of at least two ACE-linked QTLs, and demonstrate the utility of gamete competition models in the exploratory investigation of the relationship between a quantitative trait and multiple variants in a small genomic region. [source]

Mutualism as a constraint on invasion success for legumes and rhizobia

DIVERSITY AND DISTRIBUTIONS, Issue 3 2001
Matthew A. Parker
Abstract Because hereditary symbiont transmission is normally absent in the mutualism of legume plants and root-nodule bacteria (rhizobia), dispersing plants may often arrive at new habitats where mutualist partners are too rare to provide full benefits. Factors governing invasion success were explored by analysing a system of two coupled pairwise competition models: a legume invader competing with a resident non-mutualistic plant, and a rhizobial population competing with a resident population of nonsymbiotic bacteria. The non-linear dependence of benefits on partner abundance in this mutualism creates the possibility of two alternative population size equilibria, so that a threshold density can exist for invasion. If legumes and rhizobia exceed a critical population size, both species achieve rapid population growth, while if initial densities of both species are below their respective thresholds, they remain rare and are thus vulnerable to extinction in the presence of competitors. Overall, the results indicate that legumes may often fail at colonization attempts within habitats where mutualist partners are scarce. Data on legume prevalence in island floras and rates of geographical spread by legume weeds are consistent with this inference. Predictive insights about invasiveness may emerge from comparative research on key traits identified by the model, especially the shape of the function determining the number of nodules formed at low rhizobial density. [source]

Managing arable weeds for biodiversity

PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 6 2007
Jonathan Storkey
Abstract As a result of the recent intensification of crop production, the abundance and diversity of UK arable weeds adapted to cultivated land have declined, with an associated reduction in farmland birds. A number of questions need to be addressed when considering how these declines can be reversed. Firstly, can the delivery of crop production and biodiversity be reconciled by spatially separating cropping from designated wildlife areas? A number of subsidised environmental schemes in the UK take this approach and are focused on establishing vegetation cover on uncropped land. However, because of the lack of regular disturbance in these habitats, they are dominated by perennials and they therefore have limited potential for promoting the recovery of annual weed populations. A number of farmland bird species also rely on the provision of resources in field centres, and it is therefore likely that the recovery of their populations will rely on weed management options targeted at the cropped areas of the field. This raises two further questions. Firstly, is it possible to identify beneficial weed species that are relatively poor competitors with the crop and also have biodiversity value? Secondly, are the tools available to manage these species at acceptable levels while controlling pernicious weeds? A number of approaches are being employed to answer these questions, including predicting yield loss from weed competition models and exploiting herbicide selectivity. The further development of these tools is crucial if farmer opposition to managing weeds in crops is to be overcome. Copyright © 2007 Society of Chemical Industry [source]

Endogenous Markups and Fiscal Policy

THE MANCHESTER SCHOOL, Issue 2004
Luís F. Costa
This paper analyses a simple imperfectly competitive general equilibrium model where the entry mechanism generates an endogenous markup. In this second-best world fiscal policy is more effective than in Walrasian or in fixed-markup monopolistic competition models, as it produces efficiency gains through entry. [source]