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The genetic analysis of female preferences has been seen as a particularly challenging empirical endeavor because of difficulties in generating suitable preference metrics in experiments large enough to adequately characterize variation. In this article, we take an alternative approach, treating female preference as a function-valued trait and exploiting random-coefficient models to characterize the genetic basis of female preference without measuring preference functions in each individual. Applying this approach to Drosophila bunnanda, in which females assess males through a multivariate contact pheromone system, we gain three valuable insights into the genetic basis of female preference functions. First, most genetic variation was attributable to one eigenfunction, suggesting shared genetic control of preferences for nine male pheromones. Second, genetic variance in female preference functions was not associated with genetic variance in the pheromones, implying that genetic variation in female preference did not maintain genetic variation in male traits. Finally, breeding values for female preference functions were skewed away from the direction of selection on the male traits, suggesting directional selection on female preferences. The genetic analysis of female preference functions as function-valued traits offers a robust statistical framework for investigations of female preference, in addition to alleviating some experimental difficulties associated with estimating variation in preference functions.  相似文献   

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In this paper we study the evolution of function-valued traits for cooperation in environments that display varying degrees of population viscosity. Traits measure an individual's intrinsic propensity to cooperate in a standard bilateral Prisoner's dilemma and can be increasing, decreasing or constant functions of the probability to interact with individuals of ones own genotype. We first analyse adaptation to homogenous environments (with constant degree of viscosity). Comparing environments characterized by different degrees of viscosity, we find that the relation between viscosity and the equilibrium type distribution is not monotone. In fact, it is possible that in fluid populations (no viscosity) there is more cooperation in equilibrium than in populations with intermediate degrees of viscosity. In a second step we analyse heterogenous environments (with varying degrees of viscosity). We find that under very weak assumptions on the distribution of the viscosity parameter strictly increasing functions are always selected and under some parameter constellations they are uniquely so.  相似文献   

4.
Pletcher SD  Geyer CJ 《Genetics》1999,153(2):825-835
The extension of classical quantitative genetics to deal with function-valued characters (also called infinite-dimensional characters) such as growth curves, mortality curves, and reaction norms, was begun by Kirkpatrick and co-workers. In this theory, the analogs of variance components for single traits are covariance functions for function-valued traits. In the approach presented here, we employ a variety of parametric models for covariance functions that have a number of desirable properties: the functions (1) are positive definite, (2) can be estimated using procedures like those currently used for single traits, (3) have a small number of parameters, and (4) allow simple hypotheses to be easily tested. The methods are illustrated using data from a large experiment that examined the effects of spontaneous mutations on age-specific mortality rates in Drosophila melanogaster. Our methods are shown to work better than a standard multivariate analysis, which assumes the character value at each age is a distinct character. Advantages over existing methods that model covariance functions as a series of orthogonal polynomials are discussed.  相似文献   

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A major aim in some plant-based studies is the determination of quantitative trait loci (QTL) for multiple traits or across multiple environments. Understanding these QTL by trait or QTL by environment interactions can be of great value to the plant breeder. A whole genome approach for the analysis of QTL is presented for such multivariate applications. The approach is an extension of whole genome average interval mapping in which all intervals on a linkage map are included in the analysis simultaneously. A random effects working model is proposed for the multivariate (trait or environment) QTL effects for each interval, with a variance-covariance matrix linking the variates in a particular interval. The significance of the variance-covariance matrix for the QTL effects is tested and if significant, an outlier detection technique is used to select a putative QTL. This QTL by variate interaction is transferred to the fixed effects. The process is repeated until the variance-covariance matrix for QTL random effects is not significant; at this point all putative QTL have been selected. Unlinked markers can also be included in the analysis. A simulation study was conducted to examine the performance of the approach and demonstrated the multivariate approach results in increased power for detecting QTL in comparison to univariate methods. The approach is illustrated for data arising from experiments involving two doubled haploid populations. The first involves analysis of two wheat traits, α-amylase activity and height, while the second is concerned with a multi-environment trial for extensibility of flour dough. The method provides an approach for multi-trait and multi-environment QTL analysis in the presence of non-genetic sources of variation.  相似文献   

7.
Methods of evaluating and comparing the performance of diagnostic tests are of increasing importance as new tests are developed and marketed. When a test is based on an observed variable that lies on a continuous or graded scale, an assessment of the overall value of the test can be made through the use of a receiver operating characteristic (ROC) curve. The curve is constructed by varying the cutpoint used to determine which values of the observed variable will be considered abnormal and then plotting the resulting sensitivities against the corresponding false positive rates. When two or more empirical curves are constructed based on tests performed on the same individuals, statistical analysis on differences between curves must take into account the correlated nature of the data. This paper presents a nonparametric approach to the analysis of areas under correlated ROC curves, by using the theory on generalized U-statistics to generate an estimated covariance matrix.  相似文献   

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Summary Two lines of Tribolium castaneum were selected in each of three replicates for egg laying between 7 and 11 days after adult emergency and for adult weight at 12 days, using theoretical (IT) and empirical (IP) index selection methods. Index coefficients were given empirically in the IP line and they were adjusted in the successive generations of selection according to the results obtained in the previous ones. Highly repeatable selection responses in all replicates occurred in both lines for the aggregate genotype (egg laying plus adult weight) and for each individual trait. The IP line tended to increase slightly more than the IT line for aggregate genotype and egg laying, while the highest response in adult weight was obtained with the IT method. The two methods gave consistently different responses in each replicate. The expected results were that IT selection should not exceed IP selection for the aggregate genotype and egg laying while theoretically the IT method should have been superior for increase adult weight. Theoretical expectations for adult weight have been fulfilled in practice. The IP method would be preferred in a practical sense because of its simplicity and freedom from need of parameter estimation.  相似文献   

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MOTIVATION: Population allele frequencies are correlated when populations have a shared history or when they exchange genes. Unfortunately, most models for allele frequency and inference about population structure ignore this correlation. Recent analytical results show that among populations, correlations can be very high, which could affect estimates of population genetic structure. In this study, we propose a mixture beta model to characterize the allele frequency distribution among populations. This formulation incorporates the correlation among populations as well as extending the model to data with different clusters of populations. RESULTS: Using simulated data, we show that in general, the mixture model provides a good approximation of the among-population allele frequency distribution and a good estimate of correlation among populations. Results from fitting the mixture model to a dataset of genotypes at 377 autosomal microsatellite loci from human populations indicate high correlation among populations, which may not be appropriate to neglect. Traditional measures of population structure tend to overestimate the amount of genetic differentiation when correlation is neglected. Inference is performed in a Bayesian framework. CONTACT: fur@ohsu.edu.  相似文献   

11.
Evolutionary Ecology - Stenocereus pruinosus and S. stellatus are columnar cacti from central Mexico, distributed in the Valle de Tehuacán and the Mixteca Baja regions. Both species have...  相似文献   

12.
B. Karmakar  K. Yakovenko  E. Kobyliansky   《HOMO》2003,53(3):263-278
Five different endogamous populations who encompass the main social rank in the caste hierarchy of West Bengal were analysed for this report. The present approach is to compare the pattern of sex differences/similarities exhibited by two different sets of dermatoglyphic traits. Cluster and discriminant analysis and Mantel test of matrix correlations were performed. The nature of variation between sexes within population groups and two types of variable sets has a good similarity in all five populations. These results strongly suggest that the two categories of dermatoglyphic variables provide similar possibilities to discriminate between the sexes in populations.  相似文献   

13.
Nine leaf traits (area, fresh weight, dry weight, volume, density, thickness, specific leaf area (SLA), dry matter content (LDMC), leaf nitrogen content (LNC)) from ten plant species at eight sites in southern mediterranean France were investigated in order to assess their variability along a climatic gradient and their ranking congruency power. After examination of trait correlation patterns, we reduced the nine initial leaf traits to four traits, representative of three correlation groups: allometric traits (dry weight), functional traits (SLA and dry matter percentage) and Leaf Thickness. We analysed the variability of these four leaf traits at species and site level. We observed that between species variation (between 64.5 for SLA and 91% for LDMC) is higher than within species variation. Allowing a good congruency of species ranking assessed by spearman rank correlation () and a good reallocation of individuals to species by discriminant analysis. A site level variability (between 0.7% for Dry weight and 6.9% for SLA) was identified and environmental parameters (altitude, temperature, precipitation, nitrogen, pH) were considered as probable control factors. We found significant correlation between SLA, LDMC and the average minimum temperature (respectively r=0.87 and r=-0,9) and no correlation for the other traits or environmental parameters. Furthermore, we conclude that two leaf traits appear to be central in describing species: specific leaf area (SLA), percentage of dry matter (LDMC. While, SLA and LDMC are strongly correlated, LDMC appears to be less variable than SLA. According to our results the Dry Matter Content (or its reversal Leaf Water Content) appears the best leaf trait to be quantified for plant functional screening. Leaf thickness appeared to be rather uncorrelated with other leaf traits and show no environmental contingency; its variability could not have been explained in this study. Further studies should focus on this trait. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

14.
At present there is no standardized method to derive frequencies from bilateral non-metric traits. In this paper the commonly used methods are evaluated in light of statistical considerations and degree of sample preservation. In particular, we explore the question of dependence between sides for the bilateral traits. Several workers have tested for bilateral trait correlation in incorrect ways, confusing tests for differences in side frequencies with tests for independence. An easy method to test for independence, using the chi-squared test, is recommended. This test is used on 16 bilateral traits in a large sample of prehistoric carnia from Central California and significant dependence is found for all 16 of these traits. We suggest the traditional method of deriving frequencies be used. Both sides of the cranium should be considered, dividing the number of times the trait occurs by the number of sides available for observation. This method can be used even in poorly preserved samples. Side to side correlation may be compensated for by modifying the constants subtracted in the mean measure of divergence and in the expression for the approximate variance of the mean measure of divergence when the samples are drawn from identical populations.  相似文献   

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The palaeoecological significance of calcareous dinoflagellate cysts is illustrated by various examples. Genetically fixed and ecologically triggered character traits are distinguished. A summary is given regarding intraspe-cific variability, cyst size and shape, wall thickness, size and shape of the calcitic wall crystals, paratabulation, and archeopyle morphology based on the knowledge, which has been accumulated during the last two decades. Diversity and characteristic cyst associations from different localities are compared. Information on sea level changes, water temperature, oceanographic distribution, and nutrient conditions can be gained from the investigated character traits of calcareous dinoflagellates.   相似文献   

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Simultaneous analysis of correlated traits that change with time is an important issue in genetic analyses. Several methodologies have already been proposed for the genetic analysis of longitudinal data on single traits, in particular random regression and character process models. Although the latter proved, in most cases, to compare favourably to alternative approaches for analysis of single function-valued traits, they do not allow a straightforward extension to the multivariate case. In this paper, another methodology (structured antedependence models) is proposed, and methods are derived for the genetic analysis of two or more correlated function-valued traits. Multivariate analyses are presented of fertility and mortality in Drosophila and of milk, fat and protein yields in dairy cattle. These models offer a substantial flexibility for the correlation structure, even in the case of complex non-stationary patterns, and perform better than multivariate random regression models, with fewer parameters.  相似文献   

19.

Background

It has been argued that multibreed animal models should include a heterogeneous covariance structure. However, the estimation of the (co)variance components is not an easy task, because these parameters can not be factored out from the inverse of the additive genetic covariance matrix. An alternative model, based on the decomposition of the genetic covariance matrix by source of variability, provides a much simpler formulation. In this study, we formalize the equivalence between this alternative model and the one derived from the quantitative genetic theory. Further, we extend the model to include maternal effects and, in order to estimate the (co)variance components, we describe a hierarchical Bayes implementation. Finally, we implement the model to weaning weight data from an Angus × Hereford crossbred experiment.

Methods

Our argument is based on redefining the vectors of breeding values by breed origin such that they do not include individuals with null contributions. Next, we define matrices that retrieve the null-row and the null-column pattern and, by means of appropriate algebraic operations, we demonstrate the equivalence. The extension to include maternal effects and the estimation of the (co)variance components through the hierarchical Bayes analysis are then straightforward. A FORTRAN 90 Gibbs sampler was specifically programmed and executed to estimate the (co)variance components of the Angus × Hereford population.

Results

In general, genetic (co)variance components showed marginal posterior densities with a high degree of symmetry, except for the segregation components. Angus and Hereford breeds contributed with 50.26% and 41.73% of the total direct additive variance, and with 23.59% and 59.65% of the total maternal additive variance. In turn, the contribution of the segregation variance was not significant in either case, which suggests that the allelic frequencies in the two parental breeds were similar.

Conclusion

The multibreed maternal animal model introduced in this study simplifies the problem of estimating (co)variance components in the framework of a hierarchical Bayes analysis. Using this approach, we obtained for the first time estimates of the full set of genetic (co)variance components. It would be interesting to assess the performance of the procedure with field data, especially when interbreed information is limited.  相似文献   

20.
A deterministic, continuous time model for the dynamics of two locus, two allele Mendelian traits in a large randomly mating diploid population is derived. The model allows for frequency and time dependent birth and death rates. It is analyzed under the assumption that the selective forces acting in the population are small. Slow selection approximations to the system's solution are then constructed. Two particular cases are studied. First, when linkage between loci is tight, the population is shown to rapidly approach Hardy-Weinberg proportions, which then may vary on a (slow) time scale determined by differential fitness. In the case of constant birth and death rates, a measure of the population's fitness is shown to increase on the slow time scale after an initial rapid adjustment. The second case considered is for loose linkage; a population near linkage equilibrium is studied. It is shown that the epistatic parameters cancel and that the results agree with the tight linkage case to leading order. The linkage disequlibrium is described in both cases.  相似文献   

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