Showing papers on "Selection (genetic algorithm) published in 1989"

Modeling and variable selection in epidemiologic analysis.

Abstract: This paper provides an overview of problems in multivariate modeling of epidemiologic data, and examines some proposed solutions. Special attention is given to the task of model selection, which involves selection of the model form, selection of the variables to enter the model, and selection of the form of these variables in the model. Several conclusions are drawn, among them: a) model and variable forms should be selected based on regression diagnostic procedures, in addition to goodness-of-fit tests; b) variable-selection algorithms in current packaged programs, such as conventional stepwise regression, can easily lead to invalid estimates and tests of effect; and c) variable selection is better approached by direct estimation of the degree of confounding produced by each variable than by significance-testing algorithms. As a general rule, before using a model to estimate effects, one should evaluate the assumptions implied by the model against both the data and prior information.

The GENITOR Algorithm and Selection Pressure: Why Rank-Based Allocation of Reproductive Trials is Best

Abstract: This paper reports work done over the past three years using rank-based allocation of reproductive trials. New evidence and arguments are presented which suggest that allocating reproductive trials according to rank is superior to tness proportionate reproduction. Ranking can not only be used to slow search speed, but also to increase search speed when appropriate. Furthermore, the use of ranking provides a degree of control over selective pressure that is not possible with tness proportionate reproduction. The use of rank-based allocation of reproductive trials is discussed in the context of 1) Holland's schema theorem, 2) DeJong's standard test suite, and 3) a set of neural net optimization problems that are larger than the problems in the standard test suite. The GENITOR algorithm is also discussed; this algorithm is speciically designed to allocate reproductive trials according to rank.

The evolution of maternal characters

Abstract: We develop quantitative-genetic models for the evolution of multiple traits under maternal inheritance, in which traits are transmitted through non-Mendelian as well as Mendelian mechanisms, and maternal selection, in which the fitness of offspring depends on their mother's phenotype as well as their own. Maternal inheritance results in time lags in the evolutionary response to selection. These cause a population to evolve for an indefinite number of generations after selection ceases and make the rate and direction of evolution change even when the strength of selection and parameters of inheritance remain constant. The rate and direction of evolution depend on the inheritance of traits that are not under selection, unlike under classical Mendelian inheritance. The models confirm earlier findings that the response to selection can be larger or smaller than what is possible with simple Mendelian inheritance, and even in a direction opposite to what selection favors. Maternal selection, in which a mother's phenotype influences her offspring's fitness, is frequency-dependent and can cause a population to evolve maladaptively away from a fitness peak, regardless of whether traits are transmitted by Mendelian or maternal inheritance. Maternal selection differs from other forms of selection in that its force depends not only on the fitness function but also on the phenotypic resemblance of parents and offspring.

Anatomy of the Selection Problem

Abstract: This article considers anew the problem of estimating a regression E(y|x) when realizations of (y, x) are sampled randomly but y is observed selectively The central issue is the failure of the sampling process to identify E(y|x) The problem faced by the researcher is to find correct prior restrictions which, when combined with the data, identify the regression Two kinds of restrictions are examined here One, which has not been studied before, is a bound on the support of y Such a bound implies a simple, useful bound on E(y|x) The other, which has received much attention, is a separability restriction derived from a latent variable model

Visualizing multivariate selection.

Abstract: Recent developments in quantitative-genetic theory have shown that natural selection can be viewed as the multivariate relationship between fitness and phenotype. This relationship can be described by a multidimensional surface depicting fitness as a function of phenotypic traits. We examine the connection between this surface and the coefficients of phenotypic selection that can be estimated by multiple regression and show how the interpretation of multivariate selection can be facilitated through the use of the method of canonical analysis. The results from this analysis can be used to visualize the surface implied by a set of selection coefficients. Such a visualization provides a compact summary of selection coefficients, can aid in the comparison of selection surfaces, and can help generate testable hypotheses as to the adaptive significance of the traits under study. Further, we discuss traditional definitions of directional, stabilizing, and disruptive selection and conclude that selection may be more usefully classified into two general modes, directional and nonlinear selection, with stabilizing and disruptive selection as special cases of nonlinear selection.

Marker assisted selection using best linear unbiased prediction

Abstract: Best linear unbiased prediction (BLUP) is applied to a mixed linear model with additive effects for alleles at a market quantitative trait locus (MQTL) and additive effects for alleles at the remaining quantitative trait loci (QTL). A recursive algorithm is developed to obtain the covariance matrix of the effects of MQTL alleles. A simple method is presented to obtain its inverse. This approach allows simultaneous evaluation of fixed effects, effects of MQTL alleles, and effects of alleles at the remaining QTLs, using known relationships and phenotypic and marker information. The approach is sufficiently general to accommodate individuals with partial or no marker information. Extension of the approach to BLUP with multiple markers is discussed.

Parallel genetic algorithms, population genetics and combinatorial optimization

Abstract: In this paper we introduce our asynchronous parallel genetic algorithm ASPARAGOS. The two major extensions compared to genetic algorithms are the following. First, individuals live on a 2-D grid and selection is done locally in the neighborhood. Second, each individual does local hill climbing. The rationale for these extensions is discussed within the framework of population genetics. We have applied ASPARAGOS to an important combinatorial optimization problem, the quadratic assignment problem. ASPARAGOS found a new optimum for the largest published problem. It is able to solve much larger problems. The algorithm uses a polysexual voting recombination operator.

A quantitative genetic model for growth, shape, reaction norms, and other infinite-dimensional characters

Abstract: Infinite-dimensional characters are those in which the phenotype of an individual is described by a function, rather than by a finite set of measurements. Examples include growth trajectories, morphological shapes, and norms of reaction. Methods are presented here that allow individual phenotypes, population means, and patterns of variance and covariance to be quantified for infinite-dimensional characters. A quantitative-genetic model is developed, and the recursion equation for the evolution of the population mean phenotype of an infinite-dimensional character is derived. The infinite-dimensional method offers three advantages over conventional finite-dimensional methods when applied to this kind of trait: (1) it describes the trait at all points rather than at a finite number of landmarks, (2) it eliminates errors in predicting the evolutionary response to selection made by conventional methods because they neglect the effects of selection on some parts of the trait, and (3) it estimates parameters of interest more efficiently.

Temporal variation in selection on a floral character.

Abstract: Variation temporelle de la direction et de l'importance de la selection phenotypique sur des caracteres de la corolle etudie sur 3 annees chez Calathea ovandensis en relation avec la presence d'insectes pollinisateurs

Sexual selection by the handicap mechanism.

Abstract: The handicap mechanism of sexual selection by female choice has been strongly criticized because it does not cause sexual selection to reinforce viability selection and it cannot account for the origin of mating preferences. However, several models indicate that the handicap mechanism can have important effects when operating in conjunction with Fisher's mechanism in polygynous populations. These models have been criticized because they require that fitness remains heritable indefinitely. I develop a simple haploid model of the handicap mechanism based on nonheritable variation in paternal investment, thus eliminating the problem of heritable fitness. This model produces the same evolutonary dynamics as both simple and quantitative genetic models of the handicap mechanism based on heritable fitness. If the parameters are such that Fisherian runaway selection does not occur in the null model (i.e., the polymorphic equilibria, which lie along the "Fisher line," are stable), then the handicap mechanism turns the Fisher line into an evolutionary trajectory upon which all other trajectories converge. This occurs because Fisher's mechanism generates no net selection on female preference when the population is on the Fisher line, so that any additional source of selection (direct or indirect) on female choice causes the population to evolve deterministically along the Fisher line. This change in the evolutionary dynamics has the important consequence of eliminating the potential for rapid population divergence for mating systems via genetic drift along the Fisher line.

The evolution of resistance to herbivory in ipomoea purpurea. i. attempts to detect selection.

Abstract: In this study, we looked for evidence of directional or stabilizing/disruptive selection on plant size and on the level of damage (resistance) caused by four types of herbivores in the annual morning glory Ipomoea purpurea. Selection was estimated by standard phenotypic regression analysis and by regression on breeding values. The phenotypic regression analysis revealed directional selection for all five characters (i.e., plant size and resistance to four types of herbivores) and indicated that plant size and resistance to corn-earworm damage were subject to stabilizing selection. By contrast, the analysis using breeding values revealed directional selection only for plant size and resistance to corn earworms, while none of the characters examined indicated stabilizing or disruptive selection. These results suggest that intermediate levels of damage in I. purpurea are, in general, not maintained by stabilizing selection. Rather, they may reflect either 1) a transient state that exists while directional selection pushes the population toward complete resistance (or, in one case, total absence of resistance) or 2) the evolution of susceptibility to damage by genetic drift.

Density-dependent habitat selection: Testing the theory with fitness data

Abstract: According to density-dependent habitat selection theory, reproductive success should decline with increased density. Fitness should be similar between habitats if habitat selection follows an ideal free distribution; fitness should be dissimilar between habitats if habitat selection is modified by territorial behavior. I tested these assumptions by examining a variety of fitness estimates obtained from white-footed mice living in nest boxes in forest, forest edge and fencerow habitats in southwestern Ontario. As expected, mean litter size declined with increased population density. Litter sizes, adult longevity and the proportion of adult animals in breeding condition were not significantly different among the three habitats. The success at recruiting at least one offspring to the adult population and the number of recruits per litter were much greater in the forest than in either of the other two habitats. Fitness was thus unequal among habitats and the results confirm both assumptions of density-dependent habitat selection theory for territorial white-footed mice.

Self-organization, Emergence and the Architecture of Complexity

Abstract: It is argued that the problems of emergence and the architecture of complexity can be solved by analysing the self-organizing evolution of complex systems. A generalized, distributed variation- selection model is proposed, in which internal and external aspects of selection and variation are contrasted. "Relational closure" is introduced as an internal selection criterion. A possible application of the theory in the form of a pattern directed computer system for supporting complex problem-solving is sketched.

The Role of Optimizing Selection in Natural Populations

Abstract: Deux hypotheses sur le role de la «selection optimale» sont testees: 1) c'est un processus significatif qui affecte la repartition de certains caracteres phenotypiques; 2) la variete des processus qui menent a une pression de selection optimale et les problemes inherents a l'etude de ces processus limitent notre comprehension de ce que nous observons lorsque la selection agit apparemment de facon optimale

On sampling procedures in population and community ecology

Abstract: In this paper we emphasize that sampling decisions in population and community ecology are context dependent. Thus, the selection of an appropriate sampling procedure should follow directly from considerations of the objectives of an investigation. We recognize eight sampling alternatives, which arise as a result of three basic dichotomies: parameter estimation versus pattern detection, univariate versus multivariate, and a discrete versus continuous sampling universe. These eight alternative sampling procedures are discussed as they relate to decisions regarding the required empirical sample size, the selection or arrangement of sampling units, and plot size and shape. Our results indicate that the decision-making process in sampling must be viewed as a flexible exercise, dictated not by generalized recommendations but by specific objectives: there is no panacea in ecological sampling. We also point to a number of unresolved sampling problems in ecology.

Selection type theories

Abstract: Selection type theories solve adaptation problems. Natural selection, clonal selection for antibody production, and selective theories of higher brain function are examples. An abstract characterization of typical selection processes is generated by analyzing and extending previous work on the nature of natural selection. Once constructed, this abstraction provides a useful tool for analyzing the nature of other selection theories and may be of use in new instances of theory construction. This suggests the potential fruitfulness of research to find other theory types and construct their abstractions.

Selection of the appropriate parameter to measure neural regeneration.

Abstract: A rat sciatic nerve model of regeneration was assessed by multiple techniques to determine the relationship between parameters of neural regeneration in common use today. The results demonstrated significant correlation and internal consistency between electrophysiological and morphological parameters (i.e., conduction velocity and fiber diameter) but not necessarily a correlation between these physiological parameters and overall nerve function as assessed by a modified walking track technique. Guidelines for parameter selection are suggested based upon the specific question being investigated (e.g., sensory and/or motor function versus axoplasmic flow and/or neurotropism) rather than the nonspecific "neural regeneration."

Optimum Selection of Discrete Tolerances

Abstract: Tolerancing involves considerations from all phases of the life cycle of a product including design, manufacturing, assembly, and inspection. Along with minimum cost and maximum functionality and interchangeability, the practice of tolerancing urges a designer to choose an appropriate manufacturing (or inspection) process as well. This situation is formalized as a discrete optimization problem. For an optimum selection of tolerances from a given discrete model involving various manufacturing processes, minimization of manufacturing cost is achieved under the constraint of tolerance stack-up. A random variable and its standard deviation are associated with a dimension and its tolerance. This probabilistic approach enables a trade-off between performance and tolerance (cost). But it also suggests probabilistic optimization. With the aid of a notion called the reliability index [8], tolerance selection is formulated as an integer programming problem. A branch and bound algorithm for ensuring optimum selection is developed by exploiting the special structure of the constraints. To make the enumeration tree small, monotonic relations among the reliability index, cost, and tolerance are examined. The algorithm is tested with examples.

Diet selection on depletable resources

Abstract: We tested a number of patch use and diet choice strategies using natural populations of kangaroo rats, Dipodomys merriami. Patch use strategies included leaving patches: 1) at a fixed quitting harvest rate, 2) after a fixed search time, and 3) after a fixed amount of harvest. The diet choice strategies included: 1) expanding specialist, 2) micropatch partitioning, and 3) resource-specific encounter rates. The predictions of these strategies were couched in terms of forager use of patches containing two resource types and subject to resource depletion. The giving up densitites of kangaroo rats in manipulated resource patches provided the measure of utilization. With respect to patch use, the kangaroo rats use a fixed quitting harvest rate strategy. With respect to diet choice, they incorporate elements of all three diet strategies. This latter result is reasonable given: 1) the biology of kangaroo rats, 2) the characteristics of the resource patches, and 3) that the diet choice strategies are not mutually exclusive.

Selection and use of engineering materials

Abstract: INCLUDE: Preface Introduction Motivation for selection Cost basis for selection Establishment of service requirements and failure analysis Specifications and quality control Static strength Toughness Stiffness Fatigue Creep and temperature resistance Selection for corrosion resistance Selection of materials for resistance to wear The relationship between materials selection and materials processing The formalization of selection procedures Materials for airframes Materials for engines and power generation Materials for automobile structures Materials for bearings Investigative case studies Index.

Aligning managers with strategies: Management development versus selection

Abstract: Several articles have recently been published stressing the importance of matching managerial talent with organizational strategy. These have generally relied on selection to ‘fit’ the manager to the strategy. This paper proposes the use of management development as an alternate means of achieving manager—strategy alignment. Management development is defined, its role in strategy implementation is discussed, and its benefits and costs are identified. These are contrasted with the costs, benefits and strategic role of selection. It is suggested that choice of alignment method (i.e. management development versus selection) is contingent upon particular strategic, structural, and cultural factors. These contingency relationships are presented as a series of research propositions.

Strategic evaluation and selection of R&D projects

Abstract: The most important families of R&D project evaluation and selection methodologies and associated techniques are briefly reviewed. For each family, generally one or two methods were chosen to be analysed from the point of view of the integration with the strategy. But, first some definitions and some aspects of the new strategic role of the evaluation and selection of R&D projects, which were in mind during the interviews, are presented. Finally, some empirical results of the use of these methodologies in France and Japan are presented. The strong and weak points of the most prevalent methods are described as they are considered by the users.