scholarly journals Demographic determinants of biometric heritability

2018 ◽  
Author(s):  
Julia A. Barthold ◽  
Floriane Plard ◽  
Jean-Michel Gaillard ◽  
Tim Coulson ◽  
Shripad Tuljapurkar
Keyword(s):  
Parental Effects ◽  
Phenotypic Variance ◽  
Confounding Factors ◽  
Response To Selection ◽  
Viability Selection ◽  
Integral Projection ◽  
Quantitative Characters ◽  
Demographic Processes ◽  
Additive Genetic Effects ◽  
Fertility Selection

AbstractThe response of quantitative characters to selection depends on their transmission from parents to offspring. A common estimate of this transmission is the biometric heritability defined as the slope of the regression of offspring phenotype on same-aged mid-parent phenotype (i.e. the ratio of the phenotypic parent-offspring covariance over the parental phenotypic variance). This slope is often interpreted as the percentage of phenotypic variation due to additive genetic effects after accounting for confounding factors such as environment, litter or parental effects. However, researchers seldom account for the possible influence of selection on this estimate. Here we study the effect on biometric heritability of fertility and viability selection, as well as phenotype ontogeny (growth) and inheritance from parents to offspring. We present exact formulas for the elasticities of biometric heritability in age-phenotype-structured integral projection models (IPMs), and illustrate these for two iteroparous long-lived species. We find that both viability and fertility selection can strongly affect heritability, mediated by growth and inheritance. Generally, demographic processes that result in parents reproducing at large phenotypes, regardless of their own birth phenotype, decrease heritability. Analysed at equilibrium, our models imply that a heritable character can show no response to selection, if parental phenotypes affect offspring phenotypes and if phenotypes develop with age. Our results further highlight the importance of accounting for demographic processes when estimating heritability.

Breeding for creeping root in lucerne (Medicago sativa L.). I. The inital response to selection

1962 ◽  
Vol 13 (5) ◽  
pp. 813 ◽  
Author(s):  
H Daday
Keyword(s):  
Correlation Coefficients ◽  
Phenotypic Variance ◽  
Response To Selection ◽  
Gene Effects ◽  
Plant Vigour ◽  
Additive Gene ◽  
F2 Generation ◽  
Additive Genetic Effects ◽  
Short Days ◽  
F1 Generation

A lucerne-breeding programme was initiated in Canberra to combine the creeping-rooted habit of the variety Rambler with the summer and winter vigour of the varieties Hunter River, Hairy Peruvian, and African. The incidence of creeping-rooted plants in the "F1" generation was only 5%, which indicated marked non-additive gene effects concerned with the expression of the character. An "F2" generation, formed by interbreeding creeping plants from the "F1", showed only 6% of creeping individuals. Selection and recombination of the available creepers resulted in an average of 41% creeping-rooted plants in the "F3" families, with a range between families from 0 to 81%. In the "F2" generation approximately 50% of the phenotypic variance for creeping root was found to be additive genetic, and the response to selection was high. However, the persistence of non-additive genetic effects was indicated by a statistical analysis of the '"F3" generation. The genotypic correlation coefficients between creeping and summer forage scores, and creeping and winter forage scores, were –0.09 and 0.59 respectively, and that between summer and winter forage scores was 0.48. Thus an association between creeping rootedness and plant vigour is possible. For Rambler, both the incidence and degree of creep were found to be intensified by short days and low temperature, but this effect was not so apparent in the breeding material used in this study.

scholarly journals Partitioning variation in measurements of beef carcass traits using ultrasound1

2020 ◽  
Vol 4 (3) ◽  
Author(s):  
Bradie M Schmidt ◽  
Michael G Gonda ◽  
Michael D MacNeil
Keyword(s):  
Animal Models ◽  
Carcass Traits ◽  
Genetic Correlations ◽  
Subcutaneous Fat ◽  
Genetic Effects ◽  
Residual Variance ◽  
Phenotypic Variance ◽  
Contemporary Group ◽  
Genetic Evaluations ◽  
Additive Genetic Effects

Abstract Ultrasound technology provides cattle breeders with a quick, noninvasive, and inexpensive way to measure carcass data on live animals. Ultrasound data are used as indicator traits in cattle genetic evaluations for economically relevant carcass traits. Ultrasound cattle genetic evaluations assume homogeneous additive genetic and residual variance. Thus, the objective was to partition phenotypic variance in ultrasound carcass measurements into components for additive genetic effects, technicians, contemporary groups within technicians, and residual and to examine the homogeneity of these variances among image interpretation laboratories. Records of longissimus muscle area (LMA), percentage of intramuscular fat (IMF), and subcutaneous fat depth (SFD), measured using ultrasound, were provided by the American Angus Association (n = 65,967), American Hereford Association (n = 43,182), and American Simmental Association (n = 48,298). The data also included contemporary group, technician, imaging lab, and a three-generation pedigree for each animal. Variance components for ultrasound carcass measurements were first estimated with univariate animal models for each breed and imaging laboratory using derivative-free restricted maximum likelihood. Then, treating data from each imaging laboratory as separate traits, genetic correlations between laboratories for LMA, percentage of IMF, and subcutaneous fat were estimated with trivariate animal models. The technician explained 12–27%, 5–23%, and 4–26% of the variance for IMF, SFD, and LMA, respectively, across all three breeds. Variance due to technician was often greater than variance due to additive genetic effects but almost always less than that explained by the contemporary group. Within breeds, estimates of additive genetic variance for LMA, SFD, and IMF differed (range divided by mean) among laboratories by 4.5%, 21.5%, and 39.4 % (Angus); 31.6%, 15.0%, and 49.1% (Hereford); and 19.9%, 46.6%, and 55.3% (Simmental), respectively. Likewise, estimates of residual variance for LMA, SFD, and IMF differed among laboratories by 43.4%, 22.9%, and 43.3% (Angus); 24.9%, 15.2%, and 79.2% (Hereford); and 26.4%, 32.5%, and 46.2% (Simmental), respectively. Genetic correlations between labs across breeds ranged from 0.79 to 0.95 for IMF, 0.26 to 0.94 for SFD, and 0.78 to 0.98 for LMA. The impact of the observed heterogeneity of variance between labs on genetic evaluation requires further study.

scholarly journals Correlations and Heritability of the Characters Determining the Seed Yield of the Panicle Inflorescence Forms of Alfalfa (Medicago x varia T. Martyn)

2016 ◽  
Vol 74 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Zbigniew Bodzon
Keyword(s):  
Seed Yield ◽  
Correlation Coefficients ◽  
Yield Potential ◽  
Phenotypic Correlation ◽  
Phenotypic Variance ◽  
Selection For ◽  
Additive Genetic Effects ◽  
Pod Number ◽  
Number Of Seeds ◽  
Number Of Branches

Abstract Phenotypic correlation coefficients and heritability of the characters determining seed yield of panicle inflorescence forms of alfalfa was examined. Seed yield per plant, which was positively correlated with 10 generative and morphological traits, depended upon the number of pods per panicle and the number of seeds per pod. Variability of these characters determined about 60% of the variability of seed yield. Multiple linear regression and phenotypic correlations show that simultaneous selection for increased pod number per panicle and increased seed number per pod and number of branches per panicle resulted in enhanced seed yield potential. The share of the additive genetic effects in the phenotypic variance for number of pods per panicle was low and about 23%, while for number of seeds per pod and seeds per panicle amounted to about 75-77% and 56-57% respectively.

scholarly journals Genomic dissection of maternal, additive and non-additive genetic effects for growth and carcass traits in Nile tilapia

2019 ◽  
Author(s):  
Rajesh Joshi ◽  
John Woolliams ◽  
Theodorus Meuwissen ◽  
Hans Magnus Gjøen
Keyword(s):  
Inbreeding Depression ◽  
Nile Tilapia ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Genomic Data ◽  
Genetic Effects ◽  
Phenotypic Variance ◽  
Breeding Schemes ◽  
Additive Genetic Effects ◽  
The Impact

AbstractBackgroundThe availability of both pedigree and genomic sources of information for animal breeding and genetics has created new challenges in understanding how best they may be utilized and how they may be interpreted. This study computed the variance components obtained using genomic information and compared these to the variances obtained using pedigree in a population generated to estimate non-additive genetic variance. Further, the impact of assumptions concerning Hardy-Weinberg Equilibrium (HWE) on the component estimates was examined. The magnitude of inbreeding depression for important commercial traits in Nile tilapia was estimated for the first time, here using genomic data.ResultsThe non-additive genetic variance in a Nile tilapia population was estimated from fullsib families and, where present, was found to be almost entirely additive by additive epistatic variance, although in pedigree studies this source is commonly assumed to arise from dominance. For body depth (BD) and body weight at harvest (BWH), the estimates of the additive by additive epistatic ratio (P<0.05) were found to be 0.15 and 0.17 in the current breeding population using genomic data. In addition, we found maternal variance (P<0.05) for BD, BWH, body length (BL) and fillet weight (FW), explaining approximately 10% of the observed phenotypic variance, which are comparable to the pedigree-based estimates. This study also disclosed detrimental effects of inbreeding in commercial traits of tilapia, which were estimated to cause 1.1%, 0.9%, 0.4% and 0.3% decrease in the trait value with 1% increase in the individual homozygosity for FW, BWH, BD and BL, respectively. The inbreeding depression and lack of dominance variance was consistent with an infinitesimal dominance modelConclusionsAn eventual utilisation of non-additive genetic effects in breeding schemes is not evident or straightforward from our findings, but inbreeding depression suggests for cross-breeding, although commercially this conclusion will depend on cost structures. However, the creation of maternal lines in Tilapia breeding schemes may be a possibility if this variation is found to be heritable.

scholarly journals Effects of X-rays on response to selection for a quantitative character of Drosophila melanogaster

1967 ◽  
Vol 9 (2) ◽  
pp. 221-231 ◽  
Author(s):  
L. P. Jones
Keyword(s):  
Quantitative Character ◽  
Phenotypic Variance ◽  
X Rays ◽  
Response To Selection ◽  
High Frequencies ◽  
Bristle Number ◽  
Two Generations ◽  
The Mean ◽  
Selection For ◽  
Chromosome Ii

1. Lines with ten pairs of parents and selected at an intensity of 20% were exposed to 1000 r. of X-rays for 0, 2, 10 or 30 generations.Lines which received some irradiation generally gave greater response than the unirradiated controls. The phenotypic variance in the irradiated lines was much higher than in the controls. There was little difference in behaviour between lines receiving ten generations of irradiation and those irradiated every generation. Lines receiving only two generations of irradiation had lower variances than the other irradiated lines, but in one of three replicates the response was greater than the corresponding continuously irradiated line.3. Lethal frequencies were much higher in irradiated than unirradiated lines. Particular chromosome II and III lethals were at high frequencies in most of the irradiated lines but in only two out of five controls.4. On relaxation, the mean of the irradiated lines generally declined considerably, but in the unirradiated lines there was only a very small regression.5. It appears that most of the extra response and increased variance in the irradiated lines were caused by a few genes with large effect on bristle number.

Genetic and maternal effects on juvenile survival and fitness-related traits in three populations of Atlantic salmon

2015 ◽  
Vol 72 (5) ◽  
pp. 751-758 ◽  
Author(s):  
Aimee Lee S. Houde ◽  
Craig A. Black ◽  
Chris C. Wilson ◽  
Trevor E. Pitcher ◽  
Bryan D. Neff
Keyword(s):  
Atlantic Salmon ◽  
Maternal Effects ◽  
Environmental Effects ◽  
Genetic Architecture ◽  
Life Stage ◽  
Random Mating ◽  
Genetic Effects ◽  
Phenotypic Variance ◽  
Offspring Performance ◽  
Additive Genetic Effects

Although studies addressing natural selection have primarily focused on additive genetic effects because of their direct relationship with responses to selection, nonadditive genetic and maternal effects can also significantly influence phenotypes. We partitioned the phenotypic variance of survival and fitness-related traits in juvenile Atlantic salmon (Salmo salar) from three allopatric populations (LaHave, Sebago, and Saint-Jean) into additive genetic, nonadditive genetic, and maternal environmental effects using a full-factorial breeding design. We also modelled the potential increase in offspring performance if nonrandom mating (e.g., mate choice) is considered instead of random mating. The three populations exhibited significant differences in trait values as well as the genetic architecture of the traits. Nevertheless, nonadditive genetic and maternal environmental effects tended to be larger than the additive genetic effects. There was also a shift from maternal environmental to genetic effects during development in two of the populations. That is, maternal environmental effects were larger at early (egg and alevin) life stages, whereas nonadditive effects were larger at the later (fry) life stage. The amount of additive genetic effects was small, suggesting the traits will respond slowly to selection. We discuss how different maternal environmental effects across years may influence the genetic architecture of offspring traits.

scholarly journals The evolution of parental effects when selection acts on fecundity versus viability

2019 ◽  
Author(s):  
Bram Kuijper ◽  
Rufus A. Johnstone
Keyword(s):  
Local Environment ◽  
Structured Populations ◽  
Parental Effects ◽  
Viability Selection ◽  
Fecundity Selection ◽  
Two Generations ◽  
Local Patch ◽  
Parental Phenotype ◽  
Viscous Population

AbstractMost predictions on the evolution of adaptive parental effects and phenotypic memory exclusively focus on the role of the abiotic environment. How parental effects are affected by population demography and life history is less well understood. To overcome this, we use an analytical model to assess whether selection acting on fecundity versus viability affects the evolution of parental effects in a viscous population experiencing a spatiotemporally varying environment. We find that parental effects commonly evolve in regimes of viability selection, but are less likely to evolve in regimes of fecundity selection. In regimes of viability selection, an individual’s phenotype becomes correlated with its local environment during its lifetime, as those individuals with a locally adapted phenotype are more likely to survive until parenthood. Hence, a parental phenotype rapidly becomes an informative cue about its local environment, favoring the evolution of parental effects. By contrast, in regimes of fecundity selection, locally maladapted and adapted parents survive at equal rates, so that the parental phenotype, by itself, is not informative about the local environment. Correlations between phenotype and environment still arise, but only when more fecund, locally adapted individuals leave more successfully established offspring to the local patch. Hence, correlations take at least two generations to develop, making them more sensitive to distortion by environmental change or competition with immigrant offspring. Hence, we conclude that viability selection is most conducive to the evolution of adaptive parental effects in spatially structured populations.

scholarly journals Evolution of epigenetic transmission when selection acts on fecundity versus viability

2021 ◽  
Vol 376 (1826) ◽  
Author(s):  
Bram Kuijper ◽  
Rufus A. Johnstone
Keyword(s):  
Environmental Change ◽  
Genetic Factors ◽  
Local Environment ◽  
Parental Effects ◽  
Viability Selection ◽  
Survival Selection ◽  
Fecundity Selection ◽  
Local Patch ◽  
Parental Phenotype

Existing theory on the evolution of parental effects and the inheritance of non-genetic factors has mostly focused on the role of environmental change. By contrast, how differences in population demography and life history affect parental effects is poorly understood. To fill this gap, we develop an analytical model to explore how parental effects evolve when selection acts on fecundity versus viability in spatio-temporally fluctuating environments. We find that regimes of viability selection, but not fecundity selection, are most likely to favour parental effects. In the case of viability selection, locally adapted phenotypes have a higher survival than maladapted phenotypes and hence become enriched in the local environment. Hence, simply by being alive, a parental phenotype becomes correlated to its environment (and hence informative to offspring) during its lifetime, favouring the evolution of parental effects. By contrast, in regimes of fecundity selection, correlations between phenotype and environment develop more slowly: this is because locally adapted and maladapted parents survive at equal rates (no survival selection), so that parental phenotypes, by themselves, are uninformative about the local environment. However, because locally adapted parents are more fecund, they contribute more offspring to the local patch than maladapted parents. In case these offspring are also likely to inherit the adapted parents’ phenotypes (requiring pre-existing inheritance), locally adapted offspring become enriched in the local environment, resulting in a correlation between phenotype and environment, but only in the offspring’s generation. Because of this slower build-up of a correlation between phenotype and environment essential to parental effects, fecundity selection is more sensitive to any distortions owing to environmental change than viability selection. Hence, we conclude that viability selection is most conducive to the evolution of parental effects. This article is part of the theme issue ‘How does epigenetics influence the course of evolution?’

Genetic Factors Account for Half of the Phenotypic Variance in Liability to Sleep-Related Bruxism in Young Adults: A Nationwide Finnish Twin Cohort Study

2012 ◽  
Vol 15 (6) ◽  
pp. 714-719 ◽  
Author(s):  
Katariina Rintakoski ◽  
Christer Hublin ◽  
Frank Lobbezoo ◽  
Richard J. Rose ◽  
Jaakko Kaprio
Keyword(s):  
Cohort Study ◽  
Gender Difference ◽  
Genetic Factors ◽  
Genetic Model ◽  
Large Population ◽  
Population Based ◽  
Genetic Effects ◽  
Phenotypic Variance ◽  
Birth Cohorts ◽  
Additive Genetic Effects

Objectives: The aim of the present study was to examine the role of genetic and environmental factors in the phenotypic variance of bruxism in a large population-based cohort of young adult twins in Finland.Methods: The material of the present study derives from the FinnTwin16 cohort study consisting of five birth cohorts of twin pairs born in 1975–1979 who completed a questionnaire (at mean age 24, range 23–27 years) with data on frequency of sleep-related bruxism in 2000–2002. We used quantitative genetic modeling, based on the genetic similarity of monozygotic and dizygotic twins, to estimate the most probable genetic model for bruxism, based on decomposition of phenotypic variance into components: additive genetic effects (A), dominant genetic effects (D), and non-shared environmental effects (E).Results: On average, 8.7% experienced bruxism weekly, 23.4% rarely, and 67.9% never, with no significant gender difference (p = .052). The best fitting genetic model for bruxism was the AE-model. Additive genetic effects accounted for 52% (95% CI 0.41–0.62) of the total phenotypic variance. Sex-limitation model revealed no gender differences.Conclusions: Genetic factors account for a substantial proportion of the phenotypic variation of the liability to sleep-related bruxism, with no gender difference in its genetic architecture.

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