Showing papers on "Selection (genetic algorithm) published in 1990"

A theory of visual attention.

Abstract: A unified theory of visual recognition and attentional selection is developed by integrating the biased-choice model for single-stimulus recognition (Luce, 1963; Shepard, 1957) with a choice model for selection from multielement displays (Bundesen, Pedersen, & Larsen, 1984) in a race model framework. Mathematically, the theory is tractable, and it specifies the computations necessary for selection. The theory is applied to extant findings from a broad range of experimental paradigms. The findings include effects of object integrality in selective report, number and spatial position of targets in divided-attention paradigms, selection criterion and number of distracters in focused-attention paradigms, delay of selection cue in partial report, and consistent practice in search. On the whole, the quantitative fits are encouraging.

Efficiency of marker-assisted selection in the improvement of quantitative traits.

Abstract: Molecular genetics can be integrated with traditional methods of artificial selection on phenotypes by applying marker-assisted selection (MAS). We derive selection indices that maximize the rate of improvement in quantitative characters under different schemes of MAS combining information on molecular genetic polymorphisms (marker loci) with data on phenotypic variation among individuals (and their relatives). We also analyze statistical limitations on the efficiency of MAS, including the detectability of associations between marker loci and quantitative trait loci, and sampling errors in estimating the weighting coefficients in the selection index. The efficiency of artificial selection can be increased substantially using MAS following hybridization of selected lines. This requires initially scoring genotypes at a few hundred molecular marker loci, as well as phenotypic traits, on a few hundred to a few thousand individuals; the number of marker loci scored can be greatly reduced in later generations. The increase in selection efficiency from the use of marker loci, and the sample sizes necessary to achieve them, depend on the genetic parameters and the selection scheme.

Analysis of the inheritance, selection and evolution of growth trajectories.

Abstract: We present methods for estimating the parameters of inheritance and selection that appear in a quantitative genetic model for the evolution growth trajectories and other "infinite-dimensional" traits that we recently introduced. Two methods for estimating the additive genetic covariance function are developed, a "full" model that fully fits the data and a "reduced" model that generates a smoothed estimate consistent with the sampling errors in the data. By decomposing the covariance function into its eigenvalues and eigenfunctions, it is possible to identify potential evolutionary changes in the population's mean growth trajectory for which there is (and those for which there is not) genetic variation. Algorithms for estimating these quantities, their confidence intervals, and for testing hypotheses about them are developed. These techniques are illustrated by an analysis of early growth in mice. Compatible methods for estimating the selection gradient function acting on growth trajectories in natural or domesticated populations are presented. We show how the estimates for the additive genetic covariance function and the selection gradient function can be used to predict the evolutionary change in a population's mean growth trajectory.

On the relationship between r/K selection and environmental carrying capacity: a new habitat templet for plant life history strategies.

Abstract: We propose a revision of the habitat templet approach for modelling the relationship between r/K selection and selection related to the level of resource impoverishment within vegetation. The latter is represented as a continuum on one axis of the templet by the mean annual environmental carrying capacity of the habitat. This is perpendicular to the second axis representing the traditional r/K selection continuum and defined by the mean annual distance below environmental carrying capacity that the vegetation is maintained at, usually as a consequence of different levels of disturbance (...)

Adaptive Cluster Sampling

Abstract: In many real-world sampling situations, researchers would like to be able to adaptively increase sampling effort in the vicinity of observed values that are high or otherwise interesting. This article describes sampling designs in which, whenever an observed value of a selected unit satisfies a condition of interest, additional units are added to the sample from the neighborhood of that unit. If any of these additional units satisfies the condition, still more units may be added. Sampling designs such as these, in which the selection procedure is allowed to depend on observed values of the variable of interest, are in contrast to conventional designs, in which the entire selection of units to be included in the sample may be determined prior to making any observations. Because the adaptive selection procedure introduces biases into conventional estimators, several estimators are given that are design unbiased for the population mean with the adaptive cluster designs of this article; that is, the ...

Optimization models, quantitative genetics, and mutation.

Abstract: The process of selection on a multivariate set of characters subject to functional constraints is considered from the points of view of both evolutionary optimization theory and quantitative genetics. Special attention is given to life-history characteristics. It is shown that, under suitable conditions (including weak selection), useful approximate formulas for the relations between the functional constraints and the additive genetic variance-covariance matrix can be derived. These can be used to show that the conditions for equilibrium under selection according to the two different approaches are approximately equivalent. Although large negative genetic correlations are to be expected between some pairs of life-history traits in populations at equilibrium under selection, in general some small negative genetic correlations and some positive genetic correlations will also be present. Thus, the observation of a positive genetic correlation between a pair of life-history traits does not necessarily refute the possibility of trade-offs among a multivariate set of traits that contains the pair in question. The relation between the pattern of functional constraints and the genetic correlations is often complex, and little insight into the former can be derived from the latter. The effects of mutations that lower the overall efficiency of resource utilization, thereby creating a positive component to the genetic covariances among life-history traits, are also considered for a specific model. Although such mutations can have a substantial effect on the form of the life history, extreme conditions seem to be needed for them to produce a large effect on the pattern of genetic correlations in a random-mating population. They can, however, cause the appearance of positive correlations following inbreeding, due to the exposure of deleterious recessive or partially recessive mutations. The analysis also suggests that the population means of individual components of a constrained multivariate system may often equilibrate at values that are far from the optima that would be attained if they were selected in isolation from the other members of the system.

Pleiotropic Models of Quantitative Variation

Abstract: It is widely held that each gene typically affects many characters, and that each character is affected by many genes. Moreover, strong stabilizing selection cannot act on an indefinitely large number of independent traits. This makes it likely that heritable variation in any one trait is maintained as a side effect of polymorphisms which have nothing to do with selection on that trait. This paper examines the idea that variation is maintained as the pleiotropic side effect of either deleterious mutation, or balancing selection. If mutation is responsible, it must produce alleles which are only mildly deleterious (s approximately 10(-3)), but nevertheless have significant effects on the trait. Balancing selection can readily maintain high heritabilities; however, selection must be spread over many weakly selected polymorphisms if large responses to artificial selection are to be possible. In both classes of pleiotropic model, extreme phenotypes are less fit, giving the appearance of stabilizing selection on the trait. However, it is shown that this effect is weak (of the same order as the selection on each gene): the strong stabilizing selection which is often observed is likely to be caused by correlations with a limited number of directly selected traits. Possible experiments for distinguishing the alternatives are discussed.

Genetic search - An approach to the nonconvex optimization problem

Abstract: Principles of genetics and natural selection are adapted into a search procedure for function optimization. Such methods are based on a randomized selection from that restricted region of the design space that yields and improvement in the objective function. An implementation of the approach to a class of problems in structural optimization with demonstrated nonconvexities or disjointness is discussed in the paper. The principal drawback of the method is an increase in function evaluations necessary to locate an optimum. Possible strategies to overcome this limitation are presented

Use of molecular markers in breeding for oligogenic disease resistance

Abstract: In several plant species, genetic maps have recently been developed for restriction fragment length polymorphisms (RFLPs). Together with isozymes, they offer alternative solutions to many breeding problems. This review deals with the current and potential uses of molecular markers in breeding for oligogenic resistance traits. In the first part, segregation analyses and analyses of near-isogenic lines are collated with respect to the mapping of resistance genes. Also, various types of populations are compared for the amount of information obtained in segregation analyses. In the second part, theoretical and numerical results are presented dealing with the number of individuals required for marker-facilitated selection of a resistance gene in a backcross program. Both the use of a single marker and a marker bracket are considered and the influence of the following parameters is investigated: (a) recombination frequency between the resistance gene and marker(s), (b) size of backcross families, (c) number of backcross generations, and (d) number of carriers of the resistance gene to be recovered in the final backcross generation. The results provide information with regard to the optimum design of marker-facilitated selection programs and the required expenditures compared to direct selection of the resistance trait. In the third part, applications of molecular markers are discussed with respect to (1) advantages of marker-facilitated selection for resistance genes under a variety of special circumstances, (2) pyramiding of resistance genes, (3) selection against the genetic background of a donor parent, and (4) their use as a starting point for chromosome Walking.

Genetic Algorithms and Evolution Strategies - Similarities and Differences

Abstract: Evolution Strategies (ESs) and Genetic Algorithms (GAs) are compared in a formal as well as in an experimental way. It is shown, that both are identical with respect to their major working scheme, but nevertheless they exhibit significant differences with respect to the details of the selection scheme, the amount of the genetic representation and, especially, the self-adaptation of strategy parameters.

Evolution of diversity at the major histocompatibility complex

Abstract: Recent evidence from both population data and DNA sequence analyses indicates that the unprecedented genetic diversity found at MHC loci is selectively maintained in contemporary natural populations, although the strength and nature of this selection are currently unclear. Due to the critical role played by MHC molecules in immune recognition, it is generally assumed that some form of parasite-driven selection is operating. However, the general failure to implicate MHC in the susceptibility to specific infectious diseases has been troubling, and may indicate that selection is too weak to detect directly. Alternatively, strong selection can be reconciled by a variety of factors including the amplification of minor (disease-based) vigor differences into large fitness differences by intraspecific competition, or non-disease-based selection such as mating preferences and selective abortion.

The geometry of evolution.

Abstract: Some structures are more suitable for self-organization through the Darwin-Wallace mechanism of variation and selection than others. Such evolutionary adaptability (or evolvability) can itself evolve through variation and selection, either by virtue of being associated with reliability and stability or by hitchhiking along with the advantageous traits whose appearance it facilitates. In order for a structure to evolve there must be a reasonable probability that genetic variation carries it from one adaptive peak to another; at the same time the structure should not be overly unstable to phenotypic perturbations, as this is incompatible with occupying a peak. Organizations that are complex in terms of numbers of components and interactions are more likely to meet the peak-climbing condition, but less likely to meet the stability condition. Biological structures that are characterized by a high degree of component redundancy and multiple weak interactions satisfy these conflicting pressures.

The evolution of sexual dimorphism by sexual selection: the separate effects of intrasexual selection and intersexual selection.

Abstract: Libellula luctuosa, a pond dragonfly found in eastern North America, is apparently sexually dimorphic. Previous studies of the mating behavior in this species suggested that both male-male competition and female mate choice are important influences. Males compete for territories, where they attract females and where mating occurs. Female behavior influences both the copulation success and the fertilization success of males. Because of temporal and spatial separation of these episodes of sexual selection, multivariate and nonparametric statistical techniques could be used to investigate the influence of components of sexual selection on various sexually dimorphic traits. Sexual dimorphism in L. luctuosa was first quantified; then the direct effects and the form of selection were estimated. Sexually dimorphic wing size, body size, wing coloration, and body coloration are distributed either continuously or discontinuously between the sexes in L. luctuosa. These traits have apparently diverged between the sexes as a result of directional sexual selection. Body size is further influenced by stabilizing selection. Intrasexual selection (success in gaining access to a territory) and intersexual selection (success in copulation and fertilization) can influence the same or different sexually dimorphic characters. Body size is influenced by directional selection during the intrasexual phase of sexual selection and is also influenced by stabilizing selection during intersexual selection. The size of the brown wing patch is influenced by directional selection, primarily during the intersexual phase of sexual selection. There is directional selection on the white wing patch during both phases. Thus, the different proximate mechanisms of sexual selection may jointly or separately affect the evolution of sexually dimorphic characters. Further empirical and theoretical investigations into the differences in the effects of intrasexual selection and intersexual selection are needed to clarify the circumstances leading to separate consequences of these two mechanisms of sexual selection.

Weak Altruism, Strong Group Selection

Abstract: Throughout its history, the group selection controversy has been dominated by two major themes. The first involves the selection of groups in a metapopulation as a process analogous to the selection of individuals within single groups. The second involves altruistic behaviors that benefit others at the expense of the individual actor. Usually it is assumed that the two themes are fully compatible and that altruistic behaviors are the primary outcome of group selection. In this essay I point out some inconsistencies between the two themes. I also show that, by following the first theme to its natural conclusions, it is reasonable to expect strong group selection to operate in random associations, without any genetic relatedness among group members.

Prediction of rates of inbreeding in selected populations.

Abstract: A method is presented for the prediction of rate of inbreeding for populations with discrete generations. The matrix of Wright's numerator relationships is partitioned into 'contribution' matrices which describe the contribution of the Mendelian sampling of genes of ancestors in a given generation to the relationship between individuals in later generations. These contributions stabilize with time and the value to which they stabilize is shown to be related to the asymptotic rate of inbreeding and therefore also the effective population size, Ne approximately 2N/(mu 2r + sigma 2r), where N is the number of individuals per generation and mu r and sigma 2r are the mean and variance of long-term relationships or long-term contributions. These stabilized values are then predicted using a recursive equation via the concept of selective advantage for populations with hierarchical mating structures undergoing mass selection. Account is taken of the change in genetic parameters as a consequence of selection and also the increasing 'competitiveness' of contemporaries as selection proceeds. Examples are given and predicted rates of inbreeding are compared to those calculated in simulations. For populations of 20 males and 20, 40, 100 or 200 females the rate of inbreeding was found to increase by as much as 75% over the rate of inbreeding in an unselected population depending on mating ratio, selection intensity and heritability of the selected trait. The prediction presented here estimated the rate of inbreeding usually within 5% of that calculated from simulation.

Application of Analytical Hierarchy Process in Operations Management

Abstract: The use of Analytical Hierarchy Process (AHP) is an effective way to deal with qualitative decision areas of operations management. Four published applications of AHP are briefly reviewed in forecasting, supplier selection, facility location, and choice of technology. Furthermore, four more potential applications are suggested in other areas of operations management, including product design, plant layout, maintenance frequency selection, and choice of logistic carrier. In addition, suggestions for other areas of research are discussed.

Phenotypic Selection on Heritable Size Traits: Environmental Variance and Genetic Response

Abstract: PHENOTYPIC SELECTION ON HERITABLE SIZE TRAITS - ENVIRONMENTAL VARIANCE AND GENETIC RESPONSE

Examining hypotheses generated by field measures of sexual selection on male lizards, uta palmeri

Abstract: I examined sexual selection in the iguanid lizard Uta palmeri by measuring phenotypic selection in a cohort of males. Relative fitness was estimated by copulation rate from one breeding season, and I analyzed selection on five morphological traits (snout-vent length, mass, jaw length, head width, and head depth) and on male territory quality. Only territory quality and head depth were identified as direct targets of selection in a linear selection gradient analysis. Head depth was suggested to also be subject to quadratic selection. All traits exhibited significant directional selection differentials, suggesting indirect selection also was present because of the correlation of these traits with direct targets of selection. I used these results to generate hypotheses about the mechanisms of selection. For traits not identified as direct targets of selection (snout-vent length, mass, head width, jaw length), I could accept the null hypothesis of no female preference for the analyzed male traits; if these morphological traits were preferred by females in mate choice, they would have been identified as direct targets of selection. Exploring possible functional relationships within the cohort, I found that all five morphological traits contributed to explaining variation in territorial status. And in staged aggressive interactions between males that were similar in snout-vent length and mass, winning was associated only with greater head depth and not with head width or jaw length. Several possible interpretations of these results are presented. This study suggests that differential mating success arising from variation in territory quality gives rise to indirect selection on morphology. The possible mechanisms giving rise to the proposed direct selection on head depth require further study.

Fluctuating selection and response in a population of freshwater copepods.

Abstract: The timing of springtime production of diapausing eggs by a population of the freshwater copepod, Diaptomus sanguineus, has been shown previously to be consistent with avoidance of seasonally intense fish predation. Natural selection acting on the timing of diapause fluctuates between years depending upon the population density of fish. Here we show that, in the field, the mean timing of diapause shifts between years in response to fluctuations in selection. Diapause is earlier in years following high predator density, and is later in years following low predator density. Although selection intensity in individual years may be large, the mean intensity over the decade of fluctuating selection investigated here is close to zero. Photoperiod sensitivity of the diapausetiming trait is heritable in the laboratory. The combination of fluctuating selection and multi-generation storage of genotypes as diapausing eggs in lake sediments may contribute to the maintenance of the genetic variation that permits the rapid selection response seen in the field.

Parental quality and selection on egg size in the magellanic penguin.

Abstract: We examined the relative contributions of egg size and parental quality to hatching success, fledging success, and chick growth in the Magellanic penguin (Spheniscus magellanicus) be exchanging clutches between nests to reduce the covariation between egg and parental factors. Among control nests, fledging success increased slightly with egg size. However, the effect of egg size independently of parental quality was limited to an influence on chick mass and size for the first 10 days post-hatching. In contrast, attributes of the parents influenced nesting success and chick size at fledging, independently of the egg size actually raised. We suggest that the common occurrence of a positive phenotypic correlation between egg size and fledging success is due to two factors: (1) adults laying large eggs tend to be of higher quality; and (2) to the extent that egg size does influence early survival independently of parental quality, the effect on survival is due to a maternal effect on egg composition rather than an inherent effect of egg size.

Spatial autocorrelation of genotypes under directional selection.

Abstract: The spatial distributions of genetic variation under selection-mutation equilibrium within populations that have limited dispersal are investigated. The results show that directional selection with moderate strength rapidly reduces the amount of genetic structure and spatial autocorrelations far below that predicted for selectively neutral loci. For the latter, homozygotes are spatially clustered into separate areas or patches, each consisting of several hundred homozygotes. When selection is added the patches of the deleterious homozygotes are much smaller, in the range of 25 to 50 individuals. Selection also reduces temporal correlations. Also investigated are the effects of random replacement processes, such as mutation, immigration, and long-distance migration, on spatial and temporal correlations. The detection of natural selection through spatial pattern analysis is discussed, and applied to data from populations of the morning glory, Ipomoea purpurea.

Advances in statistical methods for genetic improvement of livestock

Abstract: Design of experiments and breeding programmes estimation of genetic parameters prediction and estimation of genetic merit prediction and estimation in non-linear models selection and non-random mating statistics and new genetic technology.

Service allocation system

Abstract: A system (2) for allocating service resources to a plurality of individuals who have requested services, the system including a plurality of communication devices (8), each one of which is for assignment to a different one of the individuals; assignment logic for assigning each one of the individuals to a corresponding one of the queues (102), each one of the queues (102) having a different priority associated with it; indication logic for indicating that a service resource is or will become available to serve a next individual; selection logic for selecting the next individual from the queue (102) having the highest priority and having at least one individual assigned to it; and a communicator (22) for communication with the communication device (8) assigned to the next individual so as to notify the next individual that service is available.

The logic of university students' misunderstanding of natural selection

Abstract: Misunderstanding of the idea of evolution (natural selection) was assumed to occur because students were basing their explanations on the following mistaken assumptions: (1) variations in a population have little importance in its change process; (2) when nature changes, it is not at random. From these assumptions, hypotheses were developed and tested by analyzing the responses of 322 university sophomores (education majors) on an evolution problem “How could the bat have evolved wings?”. A classification system that was developed required judgments on whether a population or typological focus was used, whether the change process was open or closed to environmental information and how the selection process functioned. The contention that misunderstanding is logical was supported by acceptance of the following hypotheses: (1) students adopting a population focus also used a closed-change process; (2) students seeing change as more directed used less functional selection processes, with one exception; (3) students using acquired traits did not use a functional idea of selection.

Selection and evolution of virulence in bacteria: an ecumenical excursion and modest suggestion.

Abstract: Why do parasites kill their hosts? During this past decade, research in three different areas; evolutionary ecology, medical microbiology, and population genetics has provided theory and data that address this and related questions of selection and the evolution and maintenance of parasite virulence. A general theory of parasite-host coevolution and the conditions for selection to favour parasite virulence has been put forth. Considerable advances have been made in elucidating the mechanisms of pathogenicity and inheritance of virulence in bacteria. The population genetic structure and the relationship between pathogenic and non-pathogenic forms has been determined for a number of species of bacteria. We critically review these developments and their implications for questions of selection and the evolution and maintenance of virulence in bacteria. We postulate how selection may operate on specific types of bacterial virulence and present a general protocol to experimentally test hypotheses concerning selection and the evolution of virulence in bacteria.

Malthusian Selection of Preferences

Abstract: The authors study natural selection of preferences using a golden-age model with endogenous population In equilibrium, all agents have preferences with maximum biological fitness, given resource constraints, and total population is the maximum the environment can sustain Naturally selected agents follow the golden rule, acting as if they maximize the undiscounted sum of per-capita felicities of current and future generations Selected preferences and, hence, work, saving, consumption, and population density vary predictably with environmental differences Copyright 1990 by American Economic Association