Selection in natural and experimental populations of Drosophila pseudoobscura

Genome ◽  
1989 ◽  
Vol 31 (1) ◽  
pp. 239-245 ◽  
Author(s):  
Wyatt W. Anderson
Keyword(s):  
Natural Populations ◽  
Selective Advantage ◽  
Drosophila Pseudoobscura ◽  
Heterozygote Advantage ◽  
Male Mating ◽  
Fitness Components ◽  
Balanced Polymorphism ◽  
Experimental Populations ◽  
Shed Light

The inverted gene arrangements of Drosophila pseudoobscura were used by Th. Dobzhansky in pioneering analyses of natural selection. Recent experiments have shed light on the mechanisms of selection contributing to the balanced polymorphism for the gene arrangements. In experimental populations, both major components of fitness, viability and fertility, are frequency dependent, and rare genotypes often have a selective advantage. Viabilities are also density dependent. The frequency dependence and density dependence of the fitness components are not universal. Some karyotypes are strongly influenced by frequency or density, some are slightly influenced, and some do not appear to be influenced at all. The role of heterozygote advantage in the selection on the gene arrangements is not clear. It is probably one important element in the overall selection, but viability and fertility do not always show a heterozygote advantage. Viability and fertility components of selection seem to be about equally important in changing inversion frequencies. Male mating success is an important component of selection in natural populations, and in one population rare male karyotypes have been found to have a pronounced mating advantage.Key words: selection, selection components, Drosophila pseudoobscura, inversions.

scholarly journals Evidence for selection by male mating success in natural populations of Drosophila pseudoobscura.

1979 ◽  
Vol 76 (3) ◽  
pp. 1519-1523 ◽  
Author(s):  
W. W. Anderson ◽  
L. Levine ◽  
O. Olvera ◽  
J. R. Powell ◽  
M. E. de la Rosa ◽  
...  
Keyword(s):  
Mating Success ◽  
Natural Populations ◽  
Drosophila Pseudoobscura ◽  
Male Mating ◽  
Male Mating Success

scholarly journals FITNESS OF ALLOZYME VARIANTS IN DROSOPHILA PSEUDOOBSCURA. I. SELECTION AT THE PGM-1 AND ME-2 LOCI

Genetics ◽  
1975 ◽  
Vol 79 (1) ◽  
pp. 85-95
Author(s):  
Dragoslav Marinković ◽  
Francisco J Ayala
Keyword(s):  
Natural Populations ◽  
Allozyme Variation ◽  
Adult Survival ◽  
Drosophila Pseudoobscura ◽  
Fitness Components ◽  
Female Fecundity ◽  
Rate Of Development ◽  
Egg Hatchability ◽  
Single Genotype ◽  
Allozyme Polymorphisms

ABSTRACT We have studied in Drosophila pseudoobscura the effect of allozyme variation on seven fitness components: female fecundity, egg hatchability, egg-to-adult survival under near-optimal and under competitive conditions, rate of development under near-optimal and under competitive conditions, and mating capacity of males. Three genotypes at each of two loci, Pgm-1 and Me-2, have been studied in various combinations. These two loci are highly polymorphic in natural populations of D. pseudoobscura. Statistically significant differences involving one or more genotypes exist for all components of fitness. No single genotype is best for all fitness components; rather the relative fitnesses of genotypes are reversed when different parameters are considered, or when they are studied in different environmental conditions. Also, the average egg-to-adult survival and rate of development are better when different genotypes are reared together than when they occur in pure culture. Four different modes of selection have been uncovered by our experiments. These forms of selection may account for the persistence of the two allozyme polymorphisms in nature, and for previously observed seasonal fluctuations of the allelic frequencies in natural populations.

scholarly journals Genetic divergence in M. Vetukhiv's experimental populations of Drosophila pseudoobscura 3. Divergence in Body Size

1966 ◽  
Vol 7 (2) ◽  
pp. 255-266 ◽  
Author(s):  
Wyatt W. Anderson
Keyword(s):  
Body Size ◽  
Genetic Divergence ◽  
Genetic Difference ◽  
Natural Populations ◽  
Phenotypic Change ◽  
Drosophila Pseudoobscura ◽  
Experimental Populations ◽  
Lower Temperature ◽  
Two Populations ◽  
Significant Genetic Divergence

1. Six initially identical populations of Drosophila pseudoobscura have been maintained in population cages for 7 years. Two populations have been kept at 16°C, two at 25°C, and two at 27°C.2. One and a half years after the start, there was no significant genetic divergence in body size among the populations. When the populations were about 6 years old, a striking genetic divergence in body size was found. The genetic difference between the populations having the smallest and the largest mean sizes is over half the total phenotypic change in size between the two extreme temperatures at which the populations were kept. The populations kept at the lower temperature have genetically larger flies than the populations kept at the higher temperatures.3. Accompanying the changes in body size were changes in the time of develop ment from egg to adult, the faster developers being the larger flies.4. The F1 hybrids from crossses between Vetukhiv's populations showed non-additivity of the genes for body size, the F1's in most cases being significantly larger than the midparent. There was no change in variability of body size in the F1 or F2 hybrids.5. The temperature-directed selection for body size found in Vetukhiv's experimental populations may well be similar in kind to that which has produced temperature-oriented geographic gradients for body size in natural populations of several species of Drosophila.

scholarly journals Fitness of allozyme variants in Drosophila pseudoobscura: II. Selection at the Est-5, Odh and Mdh-2 loci

1974 ◽  
Vol 24 (2) ◽  
pp. 137-149 ◽  
Author(s):  
Dragoslav Marinković ◽  
Francisco J. Ayala
Keyword(s):  
Allelic Variation ◽  
Balancing Selection ◽  
Natural Populations ◽  
Superior Performance ◽  
Adult Survival ◽  
Drosophila Pseudoobscura ◽  
Male Mating ◽  
Female Fecundity ◽  
Single Genotype ◽  
Fitness Parameters

SUMMARYWe have studied the effects on fitness of allelic variation at three gene loci (Est-5, Odh, and Mdh-2)coding for enzymes in Drosophila pseudoobscura. Genotype has a significant effect on fitness for all six parameters measured (female fecundity, male mating capacity, egg-to-adult survival under near-optimal and under competitive conditions, and rate of development under near-optimal and under competitive conditions). No single genotype is best for all six fitness parameters; rather, genotypes with superior performance during a certain stage of the life-cycle may have low fitness at some other stage, or in different environmental conditions. Heterozygotes are sometimes best when all fitness parameters are considered. There are significant interactions between loci. The various forms of balancing selection uncovered in our experiments may account for the polymorphisms occurring in natural populations of D. pseudoobscura at the three loci studied.

scholarly journals Obstruction of adaptation in diploids by recessive, strongly deleterious alleles

2015 ◽  
Vol 112 (20) ◽  
pp. E2658-E2666 ◽  
Author(s):  
Zoe June Assaf ◽  
Dmitri A. Petrov ◽  
Jamie R. Blundell
Keyword(s):  
Genetic Disorders ◽  
Natural Populations ◽  
Selective Advantage ◽  
Adaptive Mutation ◽  
Heterozygote Advantage ◽  
Deleterious Mutations ◽  
Beneficial Mutation ◽  
Recessive Mutations ◽  
Deleterious Alleles ◽  
Signature Of Selection

Recessive deleterious mutations are common, causing many genetic disorders in humans and producing inbreeding depression in the majority of sexually reproducing diploids. The abundance of recessive deleterious mutations in natural populations suggests they are likely to be present on a chromosome when a new adaptive mutation occurs, yet the dynamics of recessive deleterious hitchhikers and their impact on adaptation remains poorly understood. Here we model how a recessive deleterious mutation impacts the fate of a genetically linked dominant beneficial mutation. The frequency trajectory of the adaptive mutation in this case is dramatically altered and results in what we have termed a “staggered sweep.” It is named for its three-phased trajectory: (i) Initially, the two linked mutations have a selective advantage while rare and will increase in frequency together, then (ii), at higher frequencies, the recessive hitchhiker is exposed to selection and can cause a balanced state via heterozygote advantage (the staggered phase), and (iii) finally, if recombination unlinks the two mutations, then the beneficial mutation can complete the sweep to fixation. Using both analytics and simulations, we show that strongly deleterious recessive mutations can substantially decrease the probability of fixation for nearby beneficial mutations, thus creating zones in the genome where adaptation is suppressed. These mutations can also significantly prolong the number of generations a beneficial mutation takes to sweep to fixation, and cause the genomic signature of selection to resemble that of soft or partial sweeps. We show that recessive deleterious variation could impact adaptation in humans and Drosophila.

scholarly journals Epicuticular Compounds of Protopiophila litigata (Diptera: Piophilidae): Identification and Sexual Selection Across Two Years in the Wild

2019 ◽  
Vol 113 (1) ◽  
pp. 40-49
Author(s):  
Christopher S Angell ◽  
Sharon Curtis ◽  
Anaïs Ryckenbusch ◽  
Howard D Rundle
Keyword(s):  
Sexual Selection ◽  
Mate Choice ◽  
Mating Success ◽  
Natural Populations ◽  
Male Mating ◽  
Cross Sectional ◽  
Or Groups ◽  
In The Wild ◽  
Males And Females

Abstract The epicuticular compounds (ECs) of insects serve both to waterproof the cuticle and, in many taxa, as pheromones that are important for various social interactions, including mate choice within populations. However, ECs have not been individually identified in many species and most studies of their role in mate choice have been performed in a laboratory setting. Here we newly identify and quantify the ECs of the antler fly, Protopiophila litigata Bonduriansky, and use a cross-sectional selection analysis to quantify their association with male mating success in the wild across two years (2013 and 2017). The ECs of antler flies include straight-chain and methylated alkanes, alkenes, and a family of branched wax esters. We find all ECs to be shared between males and females but also demonstrate sexual dimorphism in the abundance of several. Male EC relative abundances were significantly associated with mating success in both years, although the multivariate direction of selection differed significantly between the years. Surprisingly, only two of the 18 compounds (or groups of compounds) we identified were similarly associated with mating success across the sampling years. In 2017, we further partitioned sexual selection into intra- and intersexual components, revealing selection on ECs to be significant via female choice but not male–male competition. Our study is one of few to investigate the potential role of ECs in mating success in the wild and adds to a growing body of evidence demonstrating significant temporal variability in selection in natural populations.

scholarly journals Resolving the conflict between associative overdominance and background selection

2016 ◽  
Author(s):  
Lei Zhao ◽  
Brian Charlesworth
Keyword(s):  
Selective Advantage ◽  
Heterozygote Advantage ◽  
Background Selection ◽  
Effective Population ◽  
Infinite Population ◽  
Recessive Mutations ◽  
Neutral Locus ◽  
Large Populations ◽  
Marker Loci ◽  
Shed Light

In small populations, genetic linkage between a polymorphic neutral locus and loci subject to selection, either against partially recessive mutations or in favor of heterozygotes, may result in an apparent selective advantage to heterozygotes at the neutral locus (associative overdominance), and a retardation of the rate of loss of variability by genetic drift at this locus. In large populations, selection against deleterious mutations has previously been shown to reduce variability at linked neutral loci (background selection). We describe analytical, numerical and simulation studies that shed light on the conditions under which retardation versus acceleration of loss of variability occurs at a neutral locus linked to a locus under selection. We consider a finite, randomly mating population initiated from an infinite population in equilibrium at a locus under selection, with no linkage disequilibrium. With mutation and selection, retardation only occurs when S, the product of twice the effective population size and the selection coefficient, is of order one. With S >> 1, background selection always causes an acceleration of loss of variability. Apparent heterozygote advantage at the neutral locus is, however, always observed when mutations are partially recessive, even if there is an accelerated rate of loss of variability. With heterozygote advantage at the selected locus, there is nearly always a retardation of loss of variability. The results shed light on experiments on the loss of variability at marker loci in laboratory populations, and on the results of computer simulations of the effects of multiple selected loci on neutral variability.

scholarly journals The Existence and Stability of Selectively Balanced Polymorphism at a Sex-Linked Locus

1958 ◽  
Vol 11 (4) ◽  
pp. 598 ◽  
Author(s):  
JH Bennett
Keyword(s):  
Sex Ratio ◽  
Sufficient Conditions ◽  
Selective Advantage ◽  
Necessary And Sufficient Conditions ◽  
Drosophila Pseudoobscura ◽  
Published Data ◽  
Balanced Polymorphism ◽  
Existence And Stability ◽  
Necessary And Sufficient

Necessary and sufficient conditions are given for the existence and stability of a selectively balanced polymorphism at a sex-linked locus. It is shown that selective superiority of the heterozygote is neither necessary nor sufficient and also that the occurrence of heterozygotes with a frequency greater than that of homozygotes does not necessarily indicate that the heterozygote has a selective advantage over both homozygotes. These results are considered in relation to Wallace's published data for populations of Drosophila pseudoobscura in which selection is acting on the sex-linked condition "sex ratio".

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