Showing papers on "Selection (genetic algorithm) published in 1975"

Best linear unbiased estimation and prediction under a selection model.

Abstract: Mixed linear models are assumed in most animal breeding applications. Convenient methods for computing BLUE of the estimable linear functions of the fixed elements of the model and for computing best linear unbiased predictions of the random elements of the model have been available. Most data available to animal breeders, however, do not meet the usual requirements of random sampling, the problem being that the data arise either from selection experiments or from breeders' herds which are undergoing selection. Consequently, the usual methods are likely to yield biased estimates and predictions. Methods for dealing with such data are presented in this paper.

A theory of group selection

Abstract: In organisms possessing a dispersal phase the processes of mating, competition, feeding, and predation are often carried out within "trait-groups," defined as populations enclosed in areas smaller than the boundaries of the deme. A simple model shows that this can lead to the selection of "altruistic" traits that favor the fitness of the group over that of the individual. The extent of group selection that occurs depends mainly on the variation in the composition of genotypes between trait-groups. The traditional concepts of group and individual selection are seen as two extremes of a continuum, with systems in nature operating over the interval in between.

Expected time bounds for selection

Abstract: A new selection algorithm is presented which is shown to be very efficient on the average, both theoretically and practically. The number of comparisons used to select the ith smallest of n numbers is n + min(i,n-i) + o(n). A lower bound within 9 percent of the above formula is also derived.

Fish predation on bosmina longirostris: body-size selection versus visibility selection'

Abstract: We examine the effects of fish predation on a population of Bosmina longiros- tris (0. F. Muller), a small, limnetic cladoceran, in Gatun Lake, Panama. We test the relative importance of two different modes of predator selection: body-size selection, in which fish choose the largest of otherwise identically appearing individuals, and visibility selection, in which fish choose individuals having the greatest amount of body pigmentation. In B. longiros- tris, this pigmentation is most heavily concentrated in the large, black, compound eye of these otherwise transparent animals. We find that these predators are feeding according to visibility selection and that body-size selection is of negligible importance under these circumstances. We then discuss the general applicability of these findings, and the evolutionary consequences for prey populations under this type of selective pressure.

The contribution of ecological genetics to evolutionary theory: detecting the direct effects of natural selection on particular polymorphic loci.

Abstract: It is possible to define a strategy for experimentally demonstrating that natural selection acts directly on a particular polymorphic locus, rather than on other loci in linkage disequilibrium with it. This strategy has been applied to the alcohol dehydrogenase polymorphism of Drosophila melanogaster and has provided very strong evidence that the polymorphism is directly subject to selection. It is equally applicable to other polymorphisms and offers the hope of resolving the long-standing debate about the causes of enzyme variation.

Group selection in predator-prey communities.

Abstract: Many animals regulate their population density by patterns of behavior that would be easy to explain if the forces of natural selection acted to optimize group properties. But Darwinian selection acts on individuals, not groups, and most simple theories have shown group selection to be too slow ever to oppose individual selection successfully. In this book Michael Gilpin presents a model, based on predator-prey dynamics, wherein nonlinear effects are important, so that small advantages to the selfish individual are nonlinearly amplified into disaster for his group. The result is that group selection can be rapid and powerful. Of course many instances of apparent group selection can be explained by kin selection; in other cases, close examination reveals that seemingly altruistic behavior directly benefits the individual genotype as well as the group. The value of the monograph is that it provides a robust model in which group selection, pure and unadulterated, can be seen to work.

Hard and Soft Selection in a Subdivided Population

Abstract: Hard and soft selection are compared in a population subdivided into random mating subpopulations. The possibility for protected polymorphism is greater with soft than with hard selection. Protected polymorphism is more readily achieved with increasing isolation, an effect that is more pronounced with hard selection. The results are discussed in relation to selection components.

Supplier Selection in an International Environment-An Experimental Study

Abstract: This experiment indicates the important influence of the location of the supplier when the industrial purchaser selects a supplier. The results also indicate, contrary to interview studies, that pr...

Natural Selection for within-Generation Variance in Offspring Number II. Discrete Haploid Models

Abstract: In the classical model of genetic drift in population genetics theory, use is made of a hypothetical "infinite-gametic pool". If, instead, the gametic pool is determined by the random number of offspring per individual, a new form of natural selection acting on the variance in offspring number occurs. A diffusion model of this selection process is derived and some of its properties are explored. It is shown that, independent of the sampling scheme used, the diffusion equation has the drift coefficient M ( p ) = p (1- p ) (µ 1 -µ 2 + σ ee 2 2 - σ e e 1 2 ) and the diffusion coefficient v ( p ) = p (1-σ) [pσ ee 2 2 + (1-σ)σ ee 1 2 ]. It is also pointed out that the Direct Product Branching process model of genetic drift introduces a non-biological interaction between individuals and is thus inappropriate for modeling natural selection.

Selection index when genetic gains of individual traits are of primary concern

Abstract: A new procedure for constructing economic weight free selection index, based on exclusively breeder's intention, is presented In its derivation the aggregate genotype which is absolutely required in the conventional method was ignored In this sense this method is completely new and is applicable to the case in which the relative economic weight of each trait is unknown or difficult to assess because of no available standard for the assessmentThe use of the technique to evaluate the breeder's objective whether it is attainable within a given period of time with a given selection intensity is describedThis selection index has a wide application to practical breeding operations, since it includes several conditions of constraints proposed by other workers The formula for predicting genetic gains in those traits which are not of the breeder's primary objective is also presented

Natural selection for resistance to epidemics

Abstract: A model of selection for resistance to epidemics in haploid and diploid or- ganisms is described. Using results from the mathematical theory of epidemics, I show that such selection is both frequency- and density-dependent, and that it can lead to genetic poly- morphism if certain conditions are met. This form of selection may account for some of the observed genetic variation in natural populations. the change in frequency of the two alleles, we must introduce some aspects of epidemic theory that will predict what fraction of the A1 individuals will con- tract the disease. Suppose that the generations of this haploid species are distinct and that within each generation a small number of Al individuals are

Comments on "An optimized output stage for MOS integrated circuits" [with reply]

Abstract: An interesting approach to improving the performance of MOS off-chip drivers has previously been described (see ibid., vol.10, no.2, p.106 (Apr. 1975)). The selection of the optimization criterion is discussed.

Population size and selection intensity effects on long-term selection response in mice.

Abstract: Long-term response to within full-sib family selection for increased postweaning gain was evaluated in lines having different effective population sizes ( Ne ) and selection intensities ( i ). Line designations were I4(4), I8(2), I16(2), M4(4), M8(2) and M16(2), where I and M indicate selection of the top 50% and 25%, respectively; 4, 8 and 16 represent the number of parental pairs per replicate and number of replicates is given in parentheses. Realized within full-sib family heritabilities ( hR2 ) in the first phase of selection (0-14 generations) were larger in 16-pair lines than in 4- and 8-pair lines. In the second phase of selection (>14 generations), hR2 declined significantly (P<.01) in all lines, and only the I16 and M16 lines had hR2 values significantly (P<.01) greater than zero. Realized genetic correlations involving number born, 12-day litter weight, weaning weight and six-week weight tended to decline in the second phase of selection. The I16, M16 and control (C16) replicates were crossed in all combinations at generation 14. Crosses were then selected within litters for high postweaning gain. The hR2 values in the crossbred lines were all larger than those in the second selection phase for M16-1, M16-2 and I16-1, but not for I16-2. Within each Ne level, total response was significantly (P<.01) less for I lines compared with M lines. Total response increased as Ne increased, within each level of i . Relatively small differences in realized i values among Ne lines could not account for this result. The difference in total response among the Ne lines at a given selection intensity may be due to inbreeding depression and a combination of interactions involving "drift" and selection. By crossing replicates of the M lines with the C16 control, the effects of inbreeding depression were removed. Inbreeding depression and genetic drift, as defined herein, were equally important in accounting for differences among Ne lines in total response.

Group selection, sex, and fossils.

Abstract: The first use of natural selection to explain the differences among the faunas and floras of different geological times (by means of differential extinction) was in 1832, six years before Darwin discovered its applicability to the origin of species. Charles Lyell (1832, chap. 8-11, e.g., p. 176) was still an anti-evolutionist, for good reasons, but like Darwin he had insights that are still being rediscovered. One of these insights was group selection. This term is applied (Wright, 1945, as "intergroup selection") to selection of populations below, at, and above the species level. It is clearly one of the most important processes of human evolution, although it is usually not recognized (e.g., Thompson, 1972). Different human populations have different rates of increase and decrease for diverse and interacting cultural reasons. Culture is necessarily a group character. This group selection has obviously led to important changes in the composition of the human species, and continues to do so today. Man is probably the best species for the study of group selection within a species. We are not exempt from nature but anesthetized.

The possible use of superovulation and embryo transfer in cattle to increase response to selection

Abstract: The possible use of superovulation and embryo transfer in selection programmes in cattle is investigated theoretically, in terms of both rates of response and inbreeding.In a selection programme for growth rate, it should be possible to achieve about twice the response of a conventional performance testing programme, so that 400-day weight, for example, could be increased by 16 rather than 9 kg per year.The improvement of reproductive performance by the use of laparoscopy to measure the natural ovulation rate of animals over several oestrous cycles followed by superovulation of selected animals is investigated. The rate of progress is dependent upon the incidence of twin ovulations in the base population and is unlikely to exceed 0·6% per year unless the initial frequency is 8% or more.

Selection models with fertility differences

Abstract: While in the classical selection models fitness is introduced as viability or as fertility of a single genotype a model is investigated where fertility is a property of a mating type. Under this quite natural hypothesis the fundamental law of population genetics does not hold. Nevertheless for a symmetric model a thorough analysis of the equilibrium states is given. In particular it is proved that there are at most five polymorphisms. Examples can be given where all these polymorphisms occur. The stability problem can be discussed at least for the symmetric equilibria.

Respondent Selection in a Time of Changing Household Composition

Abstract: Changing lifestyles bring shifts in household composition which affect male-female proportions in the Troldahl-Carter method of random selection of respondents within a household. Five field tests ...

Selection on sex-ratio and the evolution of sex-determination

Abstract: Deterministic selection forces operating at a modifier level within a population lead to the establishment of systems of sex-determination which, under a variety of natural conditions, induce sex-ratios close to 1 : 1.

On the selection of mass production systems

Abstract: SUMMARY This paper is concerned with the comparison and selection of systems for the mass production, in particular the assembly, of complex discrete items. A possible procedure is proposed for system selection based upon (a) an examination of the feasibility of using certain basic system types in particular situations, (b) a comparison of feasible alternatives based upon certain quantifiable factors, and finally (c) a study of the non-quantifiable aspects of systems. Basic system types are listed, a detailed procedure is proposed for the quantitative analysis and some relevant non-quantifiable factors are identified.