An Experimental Study of Interaction between Genetic Drift and Natural Selection

Dobzhansky, Theodosius; Pavlovsky, Olga

doi:10.2307/2405795

Cited by 60 publications

(31 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Evidence in accord with present findings was reported by Dobzhansky and Pavlovsky (1957), Spassky (1962), andSimmons (1966) in D.pseuiloobscura and by Spiess (1966) in D.persimilis. They have shown that in variable genetic backgrounds adaptive values ofthird chromosome gene arrangements (AR and PP in pseuiloobscura and WT, MD, and KL in persimilis) appeared to be different.…”

Section: Discussionsupporting

confidence: 93%

“…Wright and Dobzhansky 1946;Pavlosky and Dobzhansky 1966;Tobari and Kojima 1967;and many others). Evidence also exists to indicate that adaptive values of certain third chromosome gene arrangements in Drosophila pseudoobscura and D. persimilis appear to be conditioned by their genetic background (Dobzhansky and Pavlovsky 1957;Dobzhansky and Spassky 1962;Simmons 1966;Spiess 1966). …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Relative Fitness of a Third Chromosome Inversion in Drosophila Melanogaster

Nassar¹

1968

Aust. Jnl. Of Bio. Sci.

View full text Add to dashboard Cite

SummaryExperiments with D. melanogaster were conducted to obtain information on the relative fitness of the structural heterozygote of a third chromosome inversion, In (3R)P, in five different genetic backgrounds.The results have shown that in all instances the inversion heterozygote was superior in fitness to both homozygotes and that the adaptive value of the chromosomal arrangement was conditioned by the genetic background.Estimates of 8 and t, the reduction in fitness of the standard and inversion homozygotes relative to the inversion heterozygote, were O· 25, 0'27, O· 33, O· 02, and 0·25,0·86,0·63,0·16, respectively, for each of the A, B, C, and D experimental populations, and § equalled 0·071 for the HL population.

show abstract

Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Relative Fitness of a Third Chromosome Inversion in Drosophila Melanogaster

Nassar¹

1968

Aust. Jnl. Of Bio. Sci.

View full text Add to dashboard Cite

show abstract

“…For years, such work mostly used fruitflies (Dobzhansky and Pavlosky 1957;Rose 1984;Moya et al 1995) but recent work has expanded to include viruses (Bull et al 1993;Elena et al 1998;Wichman et al 1999; Burch and Chao 2000), bacteria (Chao and Cox 1983;Lenski et al 1991;Travisano et al 1995;Rainey and Travisano 1998;Velicer et al 1998), yeast (Paquin and Adams 1982;Zeyl 2000), and even vertebrates (Reznick et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Rates of DNA Sequence Evolution in Experimental Populations of Escherichia coli During 20,000 Generations

Lenski

Winkworth

Riley

2003

Journal of Molecular Evolution

119

View full text Add to dashboard Cite

Abstract. We examined rates of DNA sequence evolution in 12 populations of Escherichia coli propagated in a glucose minimal medium for 20,000 generations. Previous work saw mutations mediated by mobile elements in these populations, but the extent of other genomic changes was not investigated. Four of the populations evolved defects in DNA repair and became mutators. Some 500 bp was sequenced in each of 36 genes for 50 clones, including 2 ancestral variants, 2 clones from each population at generation 10,000, and 2 from each at generation 20,000. Ten mutations were found in total, all point mutations including mostly synonymous substitutions and nonsynonymous polymorphisms; all 10 were found in mutator populations. We compared the observed sequence evolution to predictions based on different scenarios. The number of synonymous substitutions is lower than predicted from measured mutation rates in E. coli, but the number is higher than rates based on comparing E. coli and Salmonella genomes. Extrapolating to the entire genome, these data predict about 250 synonymous substitutions on average per mutator population, but only about 3 synonymous substitutions per nonmutator population, during 20,000 generations. These data illustrate the challenge of finding sequence variation among bacterial isolates that share such a recent ancestor. However, this limited variation also provides a useful baseline for research aimed at finding the beneficial substitutions in these populations.

show abstract

“…A key conceptual difficulty in measuring the fitness effects of mutations is to distinguish selection from drift (Beatty 1984;Millstein 2008), which is at the heart of several population cage experiments with Drosophila (Dobzhansky and Pavlovsky 1957). To account for the effect of drift, a selection coefficient can be defined from the expected change in allele frequency over one generation (e.g., Rousset 2004), which can be estimated from the mean frequency change in independent competition experiments.…”

mentioning

confidence: 99%

Measuring Selection Coefficients Below 10−3: Method, Questions, and Prospects

et al. 2012

View full text Add to dashboard Cite

Measuring fitness with precision is a key issue in evolutionary biology, particularly in studying mutations of small effects. It is usually thought that sampling error and drift prevent precise measurement of very small fitness effects. We circumvented these limits by using a new combined approach to measuring and analyzing fitness. We estimated the mutational fitness effect (MFE) of three independent mini-Tn10 transposon insertion mutations by conducting competition experiments in large populations of Escherichia coli under controlled laboratory conditions. Using flow cytometry to assess genotype frequencies from very large samples alleviated the problem of sampling error, while the effect of drift was controlled by using large populations and massive replication of fitness measures. Furthermore, with a set of four competition experiments between ancestral and mutant genotypes, we were able to decompose fitness measures into four estimated parameters that account for fitness effects of our fluorescent marker (a), the mutation (b), epistasis between the mutation and the marker (g), and departure from transitivity (t). Our method allowed us to estimate mean selection coefficients to a precision of 2 · 10 24 . We also found small, but significant, epistatic interactions between the allelic effects of mutations and markers and confirmed that fitness effects were transitive in most cases. Unexpectedly, we also detected variation in measures of s that were significantly bigger than expected due to drift alone, indicating the existence of cryptic variation, even in fully controlled experiments. Overall our results indicate that selection coefficients are best understood as being distributed, representing a limit on the precision with which selection can be measured, even under controlled laboratory conditions. M UTATIONS of small effect can play an important role in evolution, but they are difficult to measure experimentally because the precision with which fitness effects can be measured is relatively low. For this reason, it remains unclear to what extent mutations with small beneficial effects contribute to fitness improvements (Orr 2005). It is also unclear how much deleterious mutations of small effect contribute to the genetic load and inbreeding depression (Charlesworth and Charlesworth 1998;Bataillon and Kirkpatrick 2000). More generally, the existence and influence of mutations of small effect is at the heart of the neutralistselectionist controversy (e.g., Nei 2005). This debate can be addressed experimentally only if the precision of fitness measurements is lower than the inverse of effective population size, which seems beyond reach for large populations (Kreitman 1996). Finally, a low precision in fitness measures limits the ability to determine whether the fitness effect of a mutation varies across different environmental or genetic contexts and adds to other sources of stochasticity ) to make it difficult to reliably predict evolutionary trajectories.Precisely measuring fitness poses technical,...

show abstract

An Experimental Study of Interaction between Genetic Drift and Natural Selection

Cited by 60 publications

References 6 publications

Relative Fitness of a Third Chromosome Inversion in Drosophila Melanogaster

Relative Fitness of a Third Chromosome Inversion in Drosophila Melanogaster

Rates of DNA Sequence Evolution in Experimental Populations of Escherichia coli During 20,000 Generations

Measuring Selection Coefficients Below 10−3: Method, Questions, and Prospects

Contact Info

Product

Resources

About