Negentropy and population mean fitness in genetical systems

1975 ◽  
Vol 62 (2) ◽  
pp. 61-67
Author(s):  
V. Arunachalam
Keyword(s):  
Population Mean ◽  
Mean Fitness

scholarly journals The relationship between robustness and evolution

2018 ◽  
Author(s):  
Pengyao Jiang ◽  
Martin Kreitman ◽  
John Reinitz
Keyword(s):  
Genetic Model ◽  
Initial Conditions ◽  
Genetic Locus ◽  
Genetic Mutation ◽  
Population Mean ◽  
Fitness Value ◽  
The Face ◽  
Evolutionary Trajectories ◽  
Mean Fitness ◽  
Developmental Noise

AbstractDevelopmental robustness (canalization) is a common attribute of traits in multi-cellular organisms. High robustness ensures the reproducibility of phenotypes in the face of environmental and developmental noise, but it also dampens the expression of genetic mutation, the fuel for adaptive evolution. A reduction in robustness may therefore be adaptive under certain evolutionary scenarios. To better understand how robustness influences phenotypic evolution, and to decipher conditions under which canalization itself evolves, a genetic model was constructed in which phenotype is explicitly represented as a collection of traits, calculated from genotype, and the degree of robustness can be explicitly controlled. The genes were sub jected to mutation, altering phenotype and fitness. We then simulated the dynamics of a population evolving under two classes of initial conditions, one in which the population is at a fitness optimum and one in which it is far away. The model is formulated with two robustness parameters in the genotype to phenotype map, controlling robustness over a tight (γ) or a broad (α) range of values. Within the robustness range determined by γ, high robustness results in a equilibrium population fitness closer to the optimal fitness value than low robustness. High robustness should be favored, therefore, under a constant optimal environment. This situation reverses when populations are challenged to evolve to a new phenotype optimum. In this situation, low robustness populations adapt faster than high robustness populations and reach higher equilibrium mean fitness. A larger set of phenotypes are accessable by mutation when robustness is low, in part explaining why low robustness is favored under this condition. A larger range of robustness could be sampled by varying α, revealing a complex relationship between robustness and both the initial rate of phenotypic adaptation as well as the final equilibrium population mean fitness. Intermediate values of α produced a bifurcation in evolutionary trajectories, with some populations remaining at low population mean fitness, and others escaping to achieve high population mean fitness. We then allowed robustness itself to be encoded by a mutable genetic locus that could co-evolve along with the phenotype under selection. Low robustness genotypes are initially favored when adapting to a new optimal phenotype. A high robustness genotype then replaces it, well before maximum fitness is achieved, and moreover appears to prevent further invasion into the population of a low-robustness genotype. This phenomenon was dependent on having tight linkage (and sufficiently low mutation rate) between the robustness locus and the loci encoding phenotype.

scholarly journals Non-Vertical Cultural Transmission, Assortment, and the Evolution of Cooperation

2020 ◽  
Author(s):  
Dor Cohen ◽  
Ohad Lewin-Epstein ◽  
Marcus W. Feldman ◽  
Yoav Ram
Keyword(s):  
Social Interactions ◽  
Cultural Evolution ◽  
Cultural Transmission ◽  
Horizontal Transmission ◽  
Structured Populations ◽  
Stochastic Simulations ◽  
Evolution Of Cooperation ◽  
Population Mean ◽  
Mean Fitness ◽  
Lower Population

AbstractCultural evolution of cooperation under vertical and non-vertical cultural transmission is studied, and conditions are found for fixation and coexistence of cooperation and defection. The evolution of cooperation is facilitated by its horizontal transmission and by an association between social interactions and horizontal transmission. The effect of oblique transmission depends on the horizontal transmission bias. Stable polymorphism of cooperation and defection can occur, and when it does, reduced association between social interactions and horizontal transmission evolves, which leads to a decreased frequency of cooperation and lower population mean fitness. The deterministic conditions are compared to outcomes of stochastic simulations of structured populations. Parallels are drawn with Hamilton’s rule incorporating assortment and effective relatedness.

Coevolutionary Dynamics of Costly Bonding Ritual and Altruism

2016 ◽  
Author(s):  
Karl Frost
Keyword(s):  
Movement Behavior ◽  
Altruistic Behavior ◽  
Genetic Evolution ◽  
Costs And Benefits ◽  
Honest Signal ◽  
Behavioral Sciences ◽  
Animal Kingdom ◽  
Population Mean ◽  
Or Groups ◽  
Mean Fitness

AbstractWhile altruistic behavior and bonding in altruistic pairs or groups of cooperators is observed throughout the animal kingdom, the genetic evolution of such is on an ongoing source of debate, curiosity, and conflict in the behavioral sciences. Many such bonded groups and pairs are observed to take part in costly ritualized movement behavior that is hypothesized to trigger or maintain altruistic sentiments amongst the participants. Such costly ritualized practices could have evolved if they engaged pre-existing behavioral instincts that manifest as altruism in the new context of ritual bonding. While this seems at first to be a ‘Green Beard’ hypothesis (‘marker (ie., ‘green beard’) as honest signal of altruistic intent', an hypothesis well-known to be problematic), it is distinct in two important ways. First, the ritual as marker is costly, and second the ritual engages a pre-existing behavioral potential caused by genes which, importantly, have some other benefit. This paper models the genetic coevolutionary dynamics both analytically and through simulation. It finds that such coevolution can lead to fixation of altruism in a population or to cycling of altruism in the population, depending on the balance of costs and benefits. Where cycling occurs, even though altruism is consistently present in the population, population mean fitness declines with the introduction of these bonding rituals.

scholarly journals Generation of Variation and Mean Fitness Increase: Necessity is the Mother of Genetic Invention

2017 ◽  
Author(s):  
Yoav Ram ◽  
Lee Altenberg ◽  
Uri Liberman ◽  
Marcus W. Feldman
Keyword(s):  
General Model ◽  
Genetic Modifiers ◽  
Reduction Principle ◽  
Population Mean ◽  
Mean Fitness ◽  
Induced Mutagenesis ◽  
And Migration ◽  
As Stress ◽  
The Individual ◽  
Average Fitness

AbstractGeneration of variation may be detrimental in well-adapted populations evolving under constant selection. In a constant environment, genetic modifiers that reduce the rate at which variation is generated by processes such as mutation and migration, succeed. However, departures from thisreduction principlehave been demonstrated. Here we analyze a general model of evolution under constant selection where the rate at which variation is generated depends on the individual. We find that if a modifier allele increases the rate at which individuals of below-average fitness generate variation, then it will increase in frequency and increase the population mean fitness. This principle applies to phenomena such as stress-induced mutagenesis and condition-dependent dispersal, and exemplifies“Necessity is the mother of genetic invention.”

scholarly journals Non-vertical cultural transmission, assortment and the evolution of cooperation

2021 ◽  
Vol 288 (1951) ◽  
pp. 20203162
Author(s):  
Dor Cohen ◽  
Ohad Lewin-Epstein ◽  
Marcus W. Feldman ◽  
Yoav Ram
Keyword(s):  
Social Interactions ◽  
Cultural Evolution ◽  
Cultural Transmission ◽  
Horizontal Transmission ◽  
Structured Populations ◽  
Stochastic Simulations ◽  
Evolution Of Cooperation ◽  
Population Mean ◽  
Mean Fitness ◽  
Lower Population

Cultural evolution of cooperation under vertical and non-vertical cultural transmission is studied, and conditions are found for fixation and coexistence of cooperation and defection. The evolution of cooperation is facilitated by its horizontal transmission and by an association between social interactions and horizontal transmission. The effect of oblique transmission depends on the horizontal transmission bias. Stable polymorphism of cooperation and defection can occur, and when it does, reduced association between social interactions and horizontal transmission evolves, which leads to a decreased frequency of cooperation and lower population mean fitness. The deterministic conditions are compared to outcomes of stochastic simulations of structured populations. Parallels are drawn with Hamilton’s rule incorporating relatedness and assortment.

Social Selection and the Evolution of Maladaptation

2021 ◽  
Author(s):  
Joel W. McGlothlin ◽  
David N. Fisher
Keyword(s):  
Natural Selection ◽  
Genetic Model ◽  
Inclusive Fitness ◽  
Empirical Work ◽  
General Rule ◽  
Social Selection ◽  
Population Mean ◽  
Individual Level ◽  
Quantitative Genetic ◽  
Mean Fitness

AbstractEvolution by natural selection is often viewed as a process that inevitably leads to adaptation, or an increase in population fitness over time. However, maladaptation, an evolved decrease in fitness, may also occur in response to natural selection under some conditions. Social effects on fitness (or social selection) have been identified as a potential cause of maladaptation, but we lack a general rule identifying when social selection should lead to a decrease in population mean fitness. Here we use a quantitative genetic model to develop such a rule. We show that maladaptation is most likely to occur when social selection is strong relative to the nonsocial component of selection and acts in an opposing direction. In this scenario, evolutionary increases in traits that impose fitness costs on others may outweigh evolved gains in fitness for the individual, leading to a net decrease in population mean fitness. Further, we find maladaptation may also sometimes occur when phenotypes of interacting individuals negatively covary. We outline the biological situations where maladaptation in response to social selection can be expected, provide both quantitative genetic and phenotypic versions of our derived result, and suggest what empirical work would be needed to test it. We also consider the effect of social selection on inclusive fitness and support previous work showing that inclusive fitness cannot suffer an evolutionary decrease. Taken together, our results show that social selection may decrease population mean fitness when it opposes individual-level selection, even as inclusive fitness increases.

scholarly journals SELECTION FOR RECOMBINATION IN PARTIALLY SELF-FERTILIZING POPULATIONS

Genetics ◽  
1979 ◽  
Vol 93 (1) ◽  
pp. 237-244
Author(s):  
D Charlesworth ◽  
B Charlesworth ◽  
C Strobeck
Keyword(s):  
Recombination Fraction ◽  
Population Mean ◽  
Computer Calculations ◽  
Mean Fitness ◽  
Selection For

ABSTRACT This paper confirms HOLDEN'S (1979) suggestion that certain types of fitness interactions between a pair of loci in partially self-fertilizing populations may promote selection for increased recombination between them. Our results are based on both algebraic and computer calculations of the fate of alleles at a third locus, which control the level of recombination between the selected pair. We also show that the behavior of the population mean fitness as a function of recombination fraction is not necessarily an indicator of the direction of selection on recombination in partially selfiig populations.

Reversion Toward the Mean Independently of Regression Toward the Mean

Methodology ◽  
2009 ◽  
Vol 5 (1) ◽  
pp. 3-6 ◽  
Author(s):  
Merton S. Krause
Keyword(s):  
Random Error ◽  
Evaluation Studies ◽  
Internal Validity ◽  
Intervention Evaluation ◽  
Population Mean ◽  
Experimental Intervention ◽  
Sample Data ◽  
The Mean ◽  
Regression Toward The Mean

There is another important artifactual contributor to the apparent improvement of persons subjected to an experimental intervention which may be mistaken for regression toward the mean. This is the phenomenon of random error and extreme selection, which does not at all involve the population regression of posttest on pretest scores but involves a quite different and independent reversion of subjects’ scores toward the population mean. These two independent threats to the internal validity of intervention evaluation studies, however, can be detected and differentiated on the sample data of such studies.

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