scholarly journals The effect of offspring number on the adaptation speed of a polygenic trait

2017 ◽  
Author(s):  
Markus Pfenninger
Keyword(s):  
Phenotypic Change ◽  
Phenotypic Variance ◽  
Genetic Trait ◽  
Hedging Strategy ◽  
Diploid Population ◽  
Offspring Number ◽  
Unpredictable Environments ◽  
Soft Selection ◽  
Polygenic Trait ◽  
Density Dependent Selection

There is increasing evidence that rapid phenotypic adaptation of quantitative traits is not uncommon in nature. However, the circumstances under which rapid adaptation of polygenic traits occurs are not yet understood. Building on previous concepts of soft selection, i.e. frequency and density dependent selection, I developed and tested the hypothesis that adaptation speed of a polygenic trait depends on the number of offspring per breeding pair in a randomly mating diploid population. Using individual based modelling on a range of offspring per parent (2-200) in populations of various size (100-10000 individuals), I could show that the by far largest proportion of variance (42%) was explained by the offspring number, regardless of genetic trait architecture (10-50 loci, different locus contribution distributions). In addition, it was possible to identify the majority of the responsible loci and account for even more of the observed phenotypic change with a moderate population size. The simulation results suggest that offspring numbers may a crucial factor for the adaptation speed of quantitative loci. Moreover, as large offspring numbers translates to a large phenotypic variance in the offspring of each parental pair, this genetic bet hedging strategy increases the chance to contribute to the next generation in unpredictable environments.

scholarly journals Transmission of a genetic trait through total conjugation in a hypotrich ciliateParaurostyla weissei. Genetic basis of the multi-left-marginal mutant

1985 ◽  
Vol 46 (3) ◽  
pp. 263-271 ◽  
Author(s):  
Maria Jerka-Dziadosz ◽  
Bozena Dubielecka
Keyword(s):  
Genetic Basis ◽  
Single Gene ◽  
Phenotypic Change ◽  
Wild Type ◽  
Genetic Trait ◽  
Mendelian Segregation ◽  
Cell Cycles ◽  
Slow Growth Rate ◽  
Sexual Process ◽  
Aberrant Phenotype

SUMMARYThe genetic basis of slow growth rate and aberrations in the ciliary pattern was studied in the multi-left-marginal variant ofParaurostyla weissei. The 3:1 segregation in F2 sibling crosses and 1:1 segregation in test crosses indicate that the aberrant phenotype is controlled by a recessive allele at a single gene locus termedmlm. The phenotypic change from wild type tomlmtakes place about 5–8 cell cycles after conjugation. The study established that total conjugation inP. weisseiis a true sexual process in which meiosis, fertilization and Mendelian segregation occur.

scholarly journals Heritability of body size in a natural population of the Great Tit (Parus major) and its relation to age and environmental conditions during growth

1988 ◽  
Vol 51 (2) ◽  
pp. 149-162 ◽  
Author(s):  
A. J. Van Noordwijk ◽  
J. H. Van Balen ◽  
W. Scharloo
Keyword(s):  
Genetic Variation ◽  
Body Size ◽  
Environmental Conditions ◽  
Heritability Estimate ◽  
Phenotypic Change ◽  
Phenotypic Variance ◽  
Adult Size ◽  
Environmental Variance ◽  
Long Term Study ◽  
Heritability Estimates

SummaryWe have analysed data on weight and tarsus length collected during a long-term study of natural populations of Great Tits to evaluate the relative importance of genetic variation in body size. Some of our data were collected over a 25-year period, and therefore include a relatively large sample of naturally occurring environmental conditions. An overall heritability estimate calculated from the uncorrected mean weights of breeding birds amounts to 0·5. This estimate is unlikely to be influenced by resemblance in environmental conditions between relatives. Heritability estimates based on the size of fledglings vary between zero and the value for adults, depending on the environmental conditions during growth. If the feeding conditions for the nestlings are poor, no resemblance between parents and offspring is observed. Selection against small nestlings acts strongly on the environmental variance. This is concluded from the higher heritability estimates in the same cohorts after survival for at least three months after fledging, compared to measurements on nestlings. Such selection acting differentially on the genetic and environmental components of the phenotypic variance has important consequences for our ability to make predictions of phenotypic change from measured natural selection. Nevertheless, the amount of genetic variation would allow rapid response should selection on adult size occur.

scholarly journals Mutation rates in seeds and seed-banking influence substitution rates across the angiosperm phylogeny

2017 ◽  
Author(s):  
Marcel Dann ◽  
Sidonie Bellot ◽  
Sylwia Schepella ◽  
Hanno Schaefer ◽  
Aurélien Tellier
Keyword(s):  
Seed Storage ◽  
Branch Length ◽  
Population Diversity ◽  
Bet Hedging ◽  
Novel Mutations ◽  
Hedging Strategy ◽  
Substitution Rates ◽  
Unpredictable Environments ◽  
Nuclear Its ◽  
Selection Generation

Summary1)BackgroundSeed-banking (the ability to persist in the soil over many generations) is usually considered as a dormant stage where genotypes are “stored” as a bet-hedging strategy in response to unpredictable environments. However, seed dormancy may instead have consequences for the integrity of the DNA and generate novel mutations.2)MethodsWe address this paradox by building phylogenies based on the plastomes and nuclear ITS of species belonging to ten angiosperm clades. In each clade, the substitution rate (branch-length) of a seed-banking species is compared with that of a closely-related non-seed-banking species.3)ResultsSeed-banking species show as high or higher substitution rates than non-seedbanking species, and therefore mutations occur in dormant seeds at a rate at least as high as in above-ground plants. Moreover, seed born mutations have the same probability to reach fixation as those from above ground. Our results are robust to differences in selection, generation time, and polymorphism.4)ConclusionsMutations occurring in seeds, and thus seed-banking, affect the population diversity of plant species, and are observable at the macro-evolutionary scale. Our study has consequences for seed storage projects, since the stored seeds are likely to accumulate mutations at a higher rate than previously thought.

On the offspring number distribution in a genetic population

1966 ◽  
Vol 3 (1) ◽  
pp. 129-141 ◽  
Author(s):  
M. W. Feldman
Keyword(s):  
Overlapping Generations ◽  
Random Mating ◽  
Diploid Population ◽  
Genetic Population ◽  
Offspring Number ◽  
Number Distribution

We consider a dioecious diploid population of N individuals, N1 males and N2 = N – N1 females. The alleles will be represented by a and A, and the population reproduces according to the Wright scheme, that is, by random mating with non-overlapping generations.

On the offspring number distribution in a genetic population

1966 ◽  
Vol 3 (01) ◽  
pp. 129-141 ◽  
Author(s):  
M. W. Feldman
Keyword(s):  
Overlapping Generations ◽  
Random Mating ◽  
Diploid Population ◽  
Genetic Population ◽  
Offspring Number ◽  
Number Distribution

We consider a dioecious diploid population ofNindividuals,N1males andN2=N–N1females. The alleles will be represented byaandA, and the population reproduces according to the Wright scheme, that is, by random mating with non-overlapping generations.

scholarly journals Phenotypic heterogeneity implements a game theoretic mixed strategy in a clonal microbial population

2014 ◽  
Author(s):  
David Healey ◽  
Jeff Gore
Keyword(s):  
Experimental Evidence ◽  
Evolutionary Game ◽  
Phenotypic Heterogeneity ◽  
Microbial Populations ◽  
Bet Hedging ◽  
Hedging Strategy ◽  
Unpredictable Environments ◽  
Game Theoretic ◽  
Pure Strategies ◽  
Genetic Mutants

Genetically identical cells in microbial populations often exhibit a remarkable degree of phenotypic heterogeneity even in homogenous environments. While such heterogeneity is often thought to be a bet-hedging strategy against unpredictable environments, evolutionary game theory also predicts phenotypic heterogeneity as a stable response to evolutionary "hawk-dove" games, in which rare strategies are favored over common ones. Here we provide experimental evidence for this game theoretic explanation in the context of the well-studied yeast GAL network. In an environment containing the two sugars glucose and galactose, the yeast GAL network displays stochastic bimodal activation. We show that genetic mutants playing the "pure" strategies of GAL-ON or GAL-OFF can each invade the opposite strategy when rare, indicating a hawk-dove game between the two. Consistent with the Nash equilibrium of an evolutionary game, the stable mix of pure strategists does not necessarily maximize the growth of the overall population. We also find that the wild type GAL network can invade populations of both pure strategists while remaining uninvasible by either. Taken together, our results provide experimental evidence that evolutionary hawk-dove games between identical cells can explain the phenotypic heterogeneity found in clonal microbial populations.

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