scholarly journals The genetic structure of natural populations of Drosophila melanogaster. XXIV. Effects of hybrid dysgenesis on the components of genetic variance of variability.

Genetics ◽  
1991 ◽  
Vol 127 (3) ◽  
pp. 545-552
Author(s):  
D S Suh ◽  
T Mukai
Keyword(s):  
Drosophila Melanogaster ◽  
Population Genetic ◽  
Genetic Parameters ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Natural Populations ◽  
Deleterious Mutations ◽  
Degree Of Dominance ◽  
Population Genetic Parameters ◽  
P Type

Abstract Eight hundred second chromosomes were extracted from the Ishigakijima population, one of the southernmost populations of Drosophila melanogaster in Japan. Half of them were extracted in Native cytoplasm (P-type), and half in Foreign cytoplasm (M-type). Various population-genetic parameters, including the frequency of lethal-carrying second chromosomes (Q = 0.235 for the Native; 0.218 for the Foreign), the allelism rate of lethal second chromosome (Ic = 0.0217 for the Native; 0.0134 for the Foreign), the homozygous detrimental and lethal loads (D = 0.179 for the Native; 0.270 for the Foreign; L = 0.262 for the Native; 0.240 for the Foreign), the average degree of dominance of mildly deleterious mutations (ĥE = 0.244 for the Native; 0.208 for the Foreign), and the components of genetic variance for viability [additive (sigma A2) and dominance (sigma D2)](ŝigma A2 = 0.0187 for the Native; 0.0172 for the Foreign; ŝigma D2 = 0.0005 for the Native; 0.0009 for the Foreign) were estimated. The data indicate that D was significantly larger and hE was significantly smaller in the Foreign cytoplasm. However, the estimates of additive and dominance variances were not significantly different between the two cytoplasms. The additive genetic variance for viability in the Ishigakijima population was greater than expected on the basis of mutation-selection balance confirming previous studies on papers of D. melanogaster in warm climates.

scholarly journals The Limits to Estimating Population-Genetic Parameters with Temporal Data

2020 ◽  
Vol 12 (4) ◽  
pp. 443-455
Author(s):  
Michael Lynch ◽  
Wei-Chin Ho
Keyword(s):  
Population Genetic ◽  
Genetic Parameters ◽  
Natural Populations ◽  
Estimation Methods ◽  
Frequency Change ◽  
Sampling Variance ◽  
Effective Population ◽  
Closed Population ◽  
Temporal Variance ◽  
Population Genetic Parameters

Abstract The ability to obtain genome-wide sequences of very large numbers of individuals from natural populations raises questions about optimal sampling designs and the limits to extracting information on key population-genetic parameters from temporal-survey data. Methods are introduced for evaluating whether observed temporal fluctuations in allele frequencies are consistent with the hypothesis of random genetic drift, and expressions for the expected sampling variances for the relevant statistics are given in terms of sample sizes and numbers. Estimation methods and aspects of statistical reliability are also presented for the mean and temporal variance of selection coefficients. For nucleotide sites that pass the test of neutrality, the current effective population size can be estimated by a method of moments, and expressions for its sampling variance provide insight into the degree to which such methodology can yield meaningful results under alternative sampling schemes. Finally, some caveats are raised regarding the use of the temporal covariance of allele-frequency change to infer selection. Taken together, these results provide a statistical view of the limits to population-genetic inference in even the simplest case of a closed population.

scholarly journals The Genetic Structure of Natural Populations of Drosophila melanogaster. XX. Comparison of Genotype-Environment Interaction in Viability Between a Northern and a Southern Population

Genetics ◽  
1987 ◽  
Vol 117 (2) ◽  
pp. 245-254
Author(s):  
Toshiyuki Takano ◽  
Shinichi Kusakabe ◽  
Terumi Mukai
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Natural Populations ◽  
Environment Interaction ◽  
Southern Population ◽  
Genotypic Variance ◽  
Diversifying Selection ◽  
Genotype Environment Interaction ◽  
Interaction Variance

ABSTRACT In order to examine the operation of diversifying selection as the maintenance mechanism of excessive additive genetic variance for viability in southern populations in comparison with northern populations of Drosophila melanogaster, two sets of experiments were conducted using second chromosomes extracted from the Ogasawara population (a southern population in Japan) and from the Aomori population (a northern population in Japan). Chromosomal homozygote and heterozygote viabilities were estimated in eight kinds of artificially produced breeding environments. The main findings in the present investigation are as follows: (1) Significant genotype-environment interaction was observed using chromosomes extracted from the Ogasawara population. Indeed, the estimate of the genotype-environment interaction variance for heterozygotes was significantly larger than that of the genotypic variance. On the other hand, when chromosomes sampled from the Aomori population were examined, that interaction variance was significant only for homozygotes and its value was no more than one quarter of that for the chromosomes from the Ogasawara population. (2) The average genetic correlation between any two viabilities of the same lines estimated in the eight kinds of breeding environments for the chromosomes sampled from the Ogasawara population was smaller than that for the chromosomes from the Aomori population both in homozygotes and in heterozygotes, especially in the latter. (3) The stability of heterozygotes over homozygotes against fluctuations of environmental conditions was seen in the chromosomes from the Ogasawara population, but not from the Aomori population. (4) From the excessive genotype-environment interaction variance compared with the genotypic variance in heterozygotes, it was suggested for the chromosomes from the Ogasawara population that the reversal of viability order between homozygotes took place in some environments at the locus level. On the basis of these findings, it is strongly suggested that diversifying selection is operating in a southern population of D. melanogaster on some of the viability polygenes which are probably located outside the structural loci, and the excessive additive genetic variance of viability in southern populations is maintained by this type of selection.

THE GENETIC STRUCTURE OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER. XIV. EFFECTS OF THE INCOMPLETE DOMINANCE OF THE IN(2LR)SM1 (Cy) CHROMOSOME ON THE ESTIMATES OF VARIOUS GENETIC PARAMETERS

Genetics ◽  
1980 ◽  
Vol 94 (1) ◽  
pp. 169-184
Author(s):  
Terumi Mukai
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Structure ◽  
Mutation Rate ◽  
Homologous Chromosome ◽  
Genetic Parameters ◽  
Natural Populations ◽  
Incomplete Dominance ◽  
Degree Of Dominance

ABSTRACT Recent reports (MUKAI et al. 1974; KATZand CARDELLINO1978; COCKER-HAM and MUEAI 1978) have indicated that the Cy chromosome is not always dominant over its homologous chromosome with respect to viability. Thus,the genetic parameters previously estimated using viabilities determined by the Cy method are biased. In the present paper, the biases of the estimates for the polygenic mutation rate, the degree of dominance and the homozygous load are examined. The results indicate that the biases for the mutation rate and the degree ofdominance are small and that the estimate of the homozygous load relative to the average viability of the population is not biased.

THE GENETIC STRUCTURE OF NATURAL POPULATIONS OF DROSOPHILA MELANOGASTER. XIX. GENOTYPE-ENVIRONMENT INTERACTION IN VIABILITY

Genetics ◽  
1985 ◽  
Vol 111 (1) ◽  
pp. 43-55
Author(s):  
Hidenori Tachida ◽  
Terumi Mukai
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Variance ◽  
Culture Media ◽  
Additive Genetic Variance ◽  
Natural Populations ◽  
Environment Interaction ◽  
Diversifying Selection ◽  
Genotype Environment Interaction ◽  
Significant Difference ◽  
Experimental Findings

ABSTRACT To investigate whether or not an excess of additive genetic variance for viability detected in southern natural populations of Drosophila melanogaster was created by diversifying selection, genotype-environment interaction was tested as follows. (1) Two karyotype chromosomes were used: 61 second chromosomes with the standard karyotype and 63 second chromosomes carrying In(2L)t. Their homozygote viabilities were larger than 50% of the average viability of random heterozygotes. (2) The effects of two factors (culture media and yeasts) were examined at three levels (the culture media: tomato, corn and banana; and the yeasts: sake, brewer's and baker's). The results of 16 three by three factorial experiments by the Cy method in the same karyotype groups for relative viabilities of homozygotes and heterozygotes elucidated the following findings: (1) there was no significant difference between the two karyotype groups, (2) the variance components of genotype-environment interaction were highly significant, (3) the variance component of heterozygotes was significantly smaller than that of homozygotes. From the experimental findings and previous results, diversifying selection in natural populations acting on viability polygenes to increase the additive genetic variance was suggested. The relation of the present result to protein polymorphism is also discussed.

scholarly journals The Rate of Mutation and the Homozygous and Heterozygous Mutational Effects for Competitive Viability: A Long-Term Experiment With Drosophila melanogaster

Genetics ◽  
2001 ◽  
Vol 158 (2) ◽  
pp. 681-693 ◽  
Author(s):  
David Chavarrías ◽  
Carlos López-Fanjul ◽  
Aurora García-Dorado
Keyword(s):  
Drosophila Melanogaster ◽  
Minimum Distance ◽  
Deleterious Mutations ◽  
Regression Estimate ◽  
Term Experiment ◽  
Degree Of Dominance ◽  
Long Term Experiment ◽  
Rate Of Decline ◽  
Good Agreement

Abstract The effect of 250 generations of mutation accumulation (MA) on the second chromosome competitive viability of Drosophila melanogaster was analyzed both in homozygous and heterozygous conditions. We used full-sib MA lines, where selection hampers the accumulation of severely deleterious mutations but is ineffective against mildly deleterious ones. A large control population was simultaneously evaluated. Competitive viability scores, unaffected by the expression of mutations in heterozygosis, were obtained relative to a Cy/L2 genotype. The rate of decline in mean ΔM ≈ 0.1% was small. However, that of increase in variance ΔV ≈ 0.08 × 10-3 was similar to the values obtained in previous experiments when severely deleterious mutations were excluded. The corresponding estimates of the mutation rate λ ≥ 0.01 and the average effect of mutations E(s) ≤ 0.08 are in good agreement with Bateman-Mukai and minimum distance estimates for noncompetitive viability obtained from the same MA lines after 105 generations. Thus, competitive and noncompetitive viability show similar mutational properties. The regression estimate of the degree of dominance for mild-to-moderate deleterious mutations was ∼0.3, suggesting that the pertinent value for new unselected mutations should be somewhat smaller.

scholarly journals Sapling and coppice biomass heritabilities and potential gains from Eucalyptus polybractea progeny trials

2021 ◽  
Vol 17 (2) ◽  
Author(s):  
Beren Spencer ◽  
Richard Mazanec ◽  
Mark Gibberd ◽  
Ayalsew Zerihun
Keyword(s):  
Western Australia ◽  
Growth Rates ◽  
Genetic Parameters ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Short Rotation ◽  
Sapling Growth ◽  
Genetic And Phenotypic Correlations ◽  
Breeding Selections ◽  
Cross Site

AbstractEucalyptus polybractea has been planted as a short-rotation coppice crop for bioenergy in Western Australia. Historical breeding selections were based on sapling biomass and despite a long history as a coppice crop, the genetic parameters of coppicing are unknown. Here, we assessed sapling biomass at ages 3 and 6 from three progeny trials across southern Australia. After the second sapling assessment, all trees were harvested. Coppice biomass was assessed 3.5 years later. Mortality following harvest was between 1 and 2%. Additive genetic variance for the 6-sapling estimate at one site was not significant. Sapling heritabilities were between 0.06 and 0.36 at 3 years, and 0.18 and 0.20 at 6 years. The heritability for the coppice biomass was between 0.07 and 0.17. Within-site genetic and phenotypic correlations were strong between all biomass assessments. Cross-site correlations were not different from unity. Selections based on net breeding values revealed positive gains in sapling and coppice biomass. Lower or negative gains were estimated if 3-year sapling selections were applied to the coppice assessments (−7.1% to 3.4%) with useful families culled. Positive gains were obtained if 6-year sapling selections were applied to the coppice assessment (6.4% to 9.3%) but these were lower than those obtained by applying coppice selections to the coppice assessment (8.4% to 14.8%). Removal of poor performing families and families that displayed fast sapling growth rates but under-performed as coppice will benefit potential coppice production. These results indicate that selections should be made using coppice data.

scholarly journals Population genetic characteristics of horse chestnut in Serbia

2013 ◽  
Vol 65 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Mirjana Ocokoljic ◽  
Dragica Vilotic ◽  
Mirjana Sijacic-Nikolic
Keyword(s):  
Population Genetic ◽  
Genetic Parameters ◽  
Individual Variability ◽  
Horse Chestnut ◽  
Statistical Parameters ◽  
Genetic Characteristics ◽  
Different Populations ◽  
Growth Phenotype ◽  
Population Genetic Parameters ◽  
Cultivated Populations

The general population genetic characteristics of cultivated horse chestnut trees excelling in growth, phenotype characteristics, type of inflorescence, productivity and resistance to the leafminer Cameraria ohridella Deschka and Dimic were analyzed in Serbia. The analyzed population genetic parameters point to fundamental differences in the genetic structure among the cultivated populations in Serbia. The study shows the variability in all properties among the populations and inter-individual variability within the populations. The variability and differential characteristics were assessed using statistical parameters, taking into account the satisfactory reflection of the hereditary potential. The assessed differences in the vitality and evolution potential of different populations can determine the methods of horse chestnut gene pool collection, reconstruction and improvement.

scholarly journals Quantitative genetics of response to competitors in Nemophila menziesii: a field experiment.

Genetics ◽  
1995 ◽  
Vol 139 (1) ◽  
pp. 397-406 ◽  
Author(s):  
R G Shaw ◽  
G A Platenkamp ◽  
F H Shaw ◽  
R H Podolsky
Keyword(s):  
Field Experiment ◽  
Genetic Variance ◽  
Plant Density ◽  
Additive Genetic Variance ◽  
Natural Populations ◽  
Plant Size ◽  
Heterogeneous Environments ◽  
Environmental Complexity ◽  
Sources Of Variation ◽  
Nemophila Menziesii

Abstract Recent investigations of evolution in heterogeneous environments have begun to accommodate genetic and environmental complexity typical of natural populations. Theoretical studies demonstrate that evolution of polygenic characters depends heavily on the genetic interdependence of the expression of traits in the different environments in which selection occurs, but information concerning this issue is scarce. We conducted a field experiment to assess the genetic variability of the annual plant Nemophila menziesii in five biotic regimes differing in plant density and composition. Significant, though modest, additive genetic variance in plant size was expressed in particular treatments. Evidence of additive genetic tradeoffs between interspecific and intraspecific competitive performance was found, but this result was not consistent throughout the experiment. Two aspects of experimental design may tend to obscure genetically based tradeoffs across environments in many previously published experiments: (1) inability to isolate additive genetic from other sources of variation and (2) use of novel (e.g., laboratory) environments.

scholarly journals Estimate of genetic parameters and predicted gains with early selection of physic nut families

2012 ◽  
Vol 36 (2) ◽  
pp. 163-170 ◽  
Author(s):  
Bruno Galvêas Laviola ◽  
Alexandre Alonso Alves ◽  
Fábio de Lima Gurgel ◽  
Tatiana Barbosa Rosado ◽  
Rhayanne Dias Costa ◽  
...  
Keyword(s):  
Grain Yield ◽  
Genetic Parameters ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Biodiesel Production ◽  
Early Selection ◽  
Physic Nut ◽  
Genetic Gains ◽  
Canopy Volume ◽  
Selection Of

An initial evaluation of early selection of physic nut genotypes based on phenotypic data is presented. In order to predict the genetic gains with early selection, genetic parameters, e.g. additive genetic variance, were first obtained for grain yield along with other numerous traits. The results demonstrated that additive genetic variance exists not only for grain yield, which is considered to be the most important trait for oil and biodiesel production, but also for numerous other traits. The predicted genetic gains for grain yield, considering the selection of the 30, 20, 10 and 5 best families in the second crop year are respectively, 40.47, 48.43, 61.78 and 70.28%. With the selection of highly yielding physic nut genotypes indirectly genotypes with enhanced volume would be also selected, because yield exhibits moderate to high genetic correlations with height e canopy volume. The results here presented demonstrate the potential of the population gathered in the Brazilian physic nut germplasm bank for genetic breeding purposes and that superior physic nut families can be selected with high accuracy based on the evaluation of its second crop.

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