Showing papers on "Selection (genetic algorithm) published in 1972"
TL;DR: The mathematics given here applies not only to genetical selection but to selection in general, intended mainly for use in deriving general relations and constructing theories, and to clarify understanding of selection phenomena, rather than for numerical calculation.
Abstract: This paper gives some extensions of the selection mathematics based on the covariance function published in Price (1970). Application of the mathematics to ‘group selection’ is briefly illustrated. More about applications will be shown in a later paper concerning ‘ Selection in populations with overlapping generations’, which will be submitted to this journal. To facilitate reference in that paper, the equations in this paper are labelled with the letter ‘A. The mathematics given here applies not only to genetical selection but to selection in general. It is intended mainly for use in deriving general relations and constructing theories, and to clarify understanding of selection phenomena, rather than for numerical calculation.
827 citations
Book•
01 Jun 1972
414 citations
TL;DR: A general step-by-step solution technique is presented for the evaluation of the dynamic response of structural systems with physical and geometrical nonlinearities and in the analysis of linear systems introduces a predictable amount of error for a specified time step.
Abstract: A general step-by-step solution technique is presented for the evaluation of the dynamic response of structural systems with physical and geometrical nonlinearities. The algorithm is stable for all time increments and in the analysis of linear systems introduces a predictable amount of error for a specified time step. Guidelines are given for the selection of the time step size for different types of dynamic loadings. The method can be applied to the static and dynamic analysis of both discrete structural systems and continuous solids idealized as an assemblage of finite elements. Results of several nonlinear analyses are presented and compared with results obtained by other methods and from experiments.
358 citations
TL;DR: It is hypothesized that maximal tolerable niche overlap should vary inversely with the level of competition, and a test is suggested.
Abstract: The concepts of r and K selection and b and d selection are discussed and compared. The former pair of concepts will play a central role in the development of new theories in population biology which relax the assumptions that communities (and portions thereof) are either fully saturated or completely unsaturated. It is hypothesized that maximal tolerable niche overlap should vary inversely with the level of competition, and a test is suggested.
317 citations
197 citations
01 Jan 1972
176 citations
169 citations
TL;DR: It is demonstrated that although zygotic selection operates in the system, the component of major importance for the dynamics is sexual selection, and it is this component that is responsible for the stability of the polymorphism.
Abstract: The total dynamics of a fourth chromosome polymorphism in Drosophila melanogaster is studied in an experimental population in which it is possible to measure various selection components simultaneously in each generation. It is demonstrated that although zygotic selection operates in the system, the component of major importance for the dynamics is sexual selection, and it is this component that is responsible for the stability of the polymorphism. Fecundity selection is of very minor importance. Both zygotic and sexual selection components behave in a frequency-dependent way. The results are discussed in relation to genetic load and the detection of selection in natural and experimental populations.
167 citations
TL;DR: Although the variance-covariance structure of the responses depends on the heritability, it is found that for most relevant combinations of parameters these linear estimators ale almost as efficient as a maximum likelihood (ML) estimator, and can be recommended for practical use.
Abstract: Methods of estimating realised heritability from selection experiments are compared. For designs in which divergent selection is practiced, formulae are given for the sampling variance of some simple linear estimators of realised heritability, such as the regression of cumulative response on cumulative selection differential. Although the variance-covariance structure of the responses depends on the heritability, it is found that for most relevant combinations of parameters these linear estimators ale almost as efficient as a maximum likelihood (ML) estimator, and can be recommended for practical use. Standard methods of calculating the variance of these estimators are shown to be very biased, downwards for the regression of cumulative response on cumulative selection differential. Methods of estimatinlg the variance from experimen-tal data, which are almost unbiased, are described.
154 citations
TL;DR: In this article, the effect of optimizing selection, mutation and drift on a metric character determined by a large number of loci with equal effects without dominance was investigated theoretically and conditions for a stable equilibrium under selection and mutation, in the absence of drift, have been obtained, and hence the amount of genetic variability which can be maintained by mutation has been determined.
Abstract: The effect of optimizing selection, mutation and drift on a metric character determined by a large number of loci with equal effects without dominance was investigated theoretically. Conditions for a stable equilibrium under selection and mutation, in the absence of drift, have been obtained, and hence the amount of genetic variability which can be maintained by mutation has been determined. An approximate expression for the average amount of genetic variability to be expected in the presence of drift in a population of finite size has also been obtained and evaluated.
123 citations
TL;DR: It is suggested that some widely held concepts of biological control should be discarded to enable the rigorous application of genetic strategies for pest control.
Abstract: Selection and maintenance of insect stocks for biological control programmes depend on the objective and the scope of propagation. Propagation for inoculative releases with the objective of colonization must ensure that the source colony contains a sufficient amount of genetic diversity. The implications of the origin and the size of the source colony are discussed. During propagation genetic decay can result from, among other processes, the founder effect, inbreeding or the selection of laboratory «ecotypes». Standardized strains of insect parasites and predators are recommended for mass production programmes for inundative releases. In addition to laboratory-construted strains for genetic controls, hybrid strains showing superior fitness, new pathotypes, and strains carrying genetic markers, may be useful for biological control. Some inferences are drawn from population genetic theory and applied to insectary rearing programmes. It is suggested that some widely held concepts of biological control should be discarded to enable the rigorous application of genetic strategies for pest control.
TL;DR: Disruptive selection has been shown to be capable of increasing phenotypic and genetic variance, of producing and maintaining polymorphisms, of causing divergence of sub-populations between which substantial gene exchange occurs, and of splitting a population into two which are genetically isolated from one another.
Abstract: A population is exposed to disruptive selection if more than one phenotype has optimal fitness and intermediate phenotypes have lower fitnesses. Maintenance of the two or more optima may depend upon their relative fitnesses being frequency dependent. Such selection may be expected in two contrasting types of situation. First the two or more optimal phenotypes may depend on one another as do the two sexes in a bisexual species. Secondly the optima may be set by heterogeneity of the environment. Then we may think in terms of a mosaic of ecological niches or a clinal situation, and may expect that gene flow will tend to promote convergence of the sub-populations while disruptive selection tends to promote their divergence. Disruptive selection may therefore be relevant both to the evolution and maintenance of polymorphisms and to the divergence of parts of populations one from another, under the influence of variation of ecological conditions within the range of gametic and/or zygotic dispersal. Disruptive selection has been shown to be capable of increasing phenotypic and genetic variance, of producing and maintaining polymorphisms, of causing divergence of sub-populations between which substantial gene exchange occurs, and of splitting a population into two which are genetically isolated from one another. These results are reviewed and their relevance to natural populations discussed.
TL;DR: The overall goal of these studies has been to determine the factors conducive to optimal adjustment and to develop services that will support and foster these circumstances.
Abstract: ary handicaps of a psychologic and social nature.2 Because it is assumed that many of these secondary handicaps are preventable, the overall goal of these studies has been to determine the factors conducive to optimal adjustment and to develop services that will support and foster these circumstances. In the first stage of the RCHS, the families of a random sample of 209 chronically ill children were interviewed. One striking finding was the frequency with which families needed, but were not receiving, many forms of assistance. These needs included
TL;DR: Fluctuations in demographic structure of a population with overlapping generations can induce gene frequency changes in polymorphic systems, even if there are no specific relations between genotypic differences and environmental agents which cause demographic changes.
Abstract: Fluctuations in demographic structure of a population with overlapping generations can induce gene frequency changes in polymorphic systems, even if there are no specific relations between genotypic differences and environmental agents which cause demographic changes. The possible relevance of this finding to gene frequency changes in natural populations is discussed.
TL;DR: In this paper, a number of criteria for selecting the best subset of predictor variables in a linear regression model has been reviewed and a cooperative effort to resolve the problem is recommended; however, the properties of these criteria are generally not understood and the relative merits of contending criteria are not clear.
Abstract: The problem of selecting the best subset of predictor variables in a linear regression model has led to the development of a number of criteria for choosing between contending subsets. Unfortunately, the properties of these criteria are generally not understood and the relative merits of contending criteria are not clear. In this note, a number of criteria are reviewed and a cooperative effort to resolve the problem is recommended.
TL;DR: A simple method is presented for approximating the behavior of a multiple genetic system under the action of selection and linkage and it is found that the results are close to those obtained from a computer simulation of the same problem by Franklin and Lewontin (1970).
Abstract: A simple method is presented for approximating the behavior of a multiple genetic system under the action of selection and linkage. The effects of genetic drift and mutation are left out. It is found that the results are close to those obtained from a computer simulation of the same problem by Franklin and Lewontin (1970). It is possible to describe the system in terms of a correlation length on the chromosome which measures the degree to which the different parts are bound by linkage. There is also a brief discussion about the higher order correlation coefficients as a measure of the interaction effects.
TL;DR: The results (ref. 10 and in preparation) with wild blackbirds and artificial prey suggest that selection may be stabilizing or apostatic according to the density of the prey.
Abstract: When predators concentrate on rare varieties of a prey species, as previous work has suggested1–4, there is a tendency towards the elimination of variability. This type of selection is stabilizing5. When predators choose the most common varieties, the selection is apostatic6 and may result in the maintenance of variability6–9. My results (ref. 10 and in preparation) with wild blackbirds (Turdus merula L.) and artificial prey suggest that selection may be stabilizing or apostatic according to the density of the prey.
TL;DR: The overall response is similar in both lines because selection intensity is greater in the high than in the low line, and there is no evidence of a plateaued response to selection in either selected line.