scholarly journals NATURAL SELECTION AND AGE-STRUCTURED POPULATIONS

Genetics ◽  
1975 ◽  
Vol 79 (3) ◽  
pp. 535-544
Author(s):  
Lloyd Demetrius
Keyword(s):  
Natural Selection ◽  
Random Mating ◽  
Reproductive Potential ◽  
Demographic Variables ◽  
Rate Of Change ◽  
Structured Populations ◽  
Age Classes ◽  
Malthusian Parameter ◽  
The Difference ◽  
Age Structured

ABSTRACT This paper studies the properties of a new class of demographic parameters for age-structured populations and analyzes the effect of natural selection on these parameters. Two new demographic variables are introduced: the entropy of a population and the reproductive potential. The entropy of a population measures the variability of the contribution of the different age classes to the stationary population. The reproductive potential measures the mean of the contribution of the different age classes to the Malthusian parameter. The Malthusian parameter is precisely the difference between the entropy and the reproductive potential. The effect of these demographic variables on changes in gene frequency is discussed. The concept of entropy of a genotype is introduced and it is shown that in a random mating population in Hardy-Weinberg equilibrium and under slow selection, the rate of change of entropy is equal to the genetic variance in entropy minus the covariance in entropy and reproductive potential. This result is an information theoretic analog of Fisher's fundamental theorem of natural selection.

scholarly journals Towards a replicator dynamics model of age structured populations

2021 ◽  
Vol 82 (5) ◽  
Author(s):  
K. Argasinski ◽  
M. Broom
Keyword(s):  
Sex Ratio ◽  
Age Structure ◽  
Replicator Dynamics ◽  
Structured Populations ◽  
Reproductive Value ◽  
Leslie Matrix ◽  
Age Classes ◽  
Structured Population Model ◽  
Age Class ◽  
Age Structured

AbstractWe present a new modelling framework combining replicator dynamics, the standard model of frequency dependent selection, with an age-structured population model. The new framework allows for the modelling of populations consisting of competing strategies carried by individuals who change across their life cycle. Firstly the discretization of the McKendrick von Foerster model is derived. We show that the Euler–Lotka equation is satisfied when the new model reaches a steady state (i.e. stable frequencies between the age classes). This discretization consists of unit age classes where the timescale is chosen so that only a fraction of individuals play a single game round. This implies a linear dynamics and individuals not killed during the round are moved to the next age class; linearity means that the system is equivalent to a large Bernadelli–Lewis–Leslie matrix. Then we use the methodology of multipopulation games to derive two, mutually equivalent systems of equations. The first contains equations describing the evolution of the strategy frequencies in the whole population, completed by subsystems of equations describing the evolution of the age structure for each strategy. The second contains equations describing the changes of the general population’s age structure, completed with subsystems of equations describing the selection of the strategies within each age class. We then present the obtained system of replicator dynamics in the form of the mixed ODE-PDE system which is independent of the chosen timescale, and much simpler. The obtained results are illustrated by the example of the sex ratio model which shows that when different mortalities of the sexes are assumed, the sex ratio of 0.5 is obtained but that Fisher’s mechanism, driven by the reproductive value of the different sexes, is not in equilibrium.

scholarly journals When does selection favor learning from the old? Social Learning in age-structured populations

2020 ◽  
Author(s):  
Dominik_Deffner ◽  
Richard McElreath
Keyword(s):  
Social Learning ◽  
Adaptive Behavior ◽  
Age Structure ◽  
Cultural Transmission ◽  
Empirical Work ◽  
Structured Populations ◽  
Older Age ◽  
Age Classes ◽  
Demographic Processes ◽  
Age Structured

Culture and demography jointly facilitate flexible human adaptation, yet it still remains unclear how social learning operates in populations with age structure. Specifically, how do demographic processes affect the adaptive value of culture, cultural adaptation and population growth and when does selection favor copying the behavior of older vs. younger individuals? Here, we develop and analyze a mathematical model of the evolution of social learning in a population with different age classes. We find that adding age structure alone does not resolve Rogers' paradox, i.e. the finding that social learning can evolve without increasing population fitness. Cultural transmission in combination with demographic filtering, however, can lead to much higher adaptation levels. This is because by increasing proportions of adaptive behavior in older age classes, demographic filtering constitutes an additional adaptive force that social learners can benefit from. Moreover, older age classes tend to have higher proportions of adaptive behavior when the environment is relatively stable and adaptive behavior is hard to acquire but confers large survival advantages. Through individual-based simulations comparing temporal and spatial variability in the environment, we find a ``copy older over younger models''-strategy only evolves readily when social learning is erroneous. The opposite ``copy the younger''-strategy is adaptive when the environment fluctuates frequently but still maintains large proportions of social learners. Our results demonstrate that age structure can substantially alter cultural dynamics and should be addressed in further theoretical and empirical work.

A System-of-Equations Approach to Modeling Age-Structured Fish Populations: The Case of Alaskan Red King Crab, Paralithodes camtschaticus

1991 ◽  
Vol 48 (9) ◽  
pp. 1613-1622 ◽  
Author(s):  
Joshua A. Greenberg ◽  
Scott C. Matulich ◽  
Ron C. Mittelhammer
Keyword(s):  
Measurement Errors ◽  
Estimation Method ◽  
Structured Populations ◽  
Trawl Survey ◽  
System Of Equations ◽  
Paralithodes Camtschaticus ◽  
Age Classes ◽  
King Crab ◽  
Multiple Observations ◽  
Age Structured

This paper presents a simultaneous system-of-equations approach to modeling age-structured populations using trawl survey age/size frequency data. The analysis builds upon a Ricker spawner–recruit structure and provides a cohort-based estimation method that retains the underlying dynamic properties of a delay-difference model. The framework shares a common spawner–recruit function across age-class equations. This exploits the commonality among cohort members and serves as an instrumental variable, lessening the effect of measurement errors in estimation. The dynamic features of the underlying age-structured population are retained through age-specific net survivability and growth parameters that link age-classes. The technique uses multiple observations on a cohort to further mitigate the effect of measurement error and improve overall estimation efficiency. A seemingly unrelated regression estimation method is required to address contemporaneous correlation of errors across age-classes. This framework is applied to trawl survey data for adult male Alaskan king crab, Paralithodes camtschaticus.

Investigating the Personality Variable (LOC) & Impression Management Relationship: Exploring the Role of Demographic Variables & Sectoral Difference of Managers

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Poornima Madan ◽  
Shalini Srivastava
Keyword(s):  
Locus Of Control ◽  
Impression Management ◽  
Demographic Variables ◽  
Personality Variable ◽  
Public Sector Organizations ◽  
Private And Public ◽  
The Difference ◽  
The Relationship ◽  
Test Correlation

The purpose of the study is to investigate the relationship between locus of control and impression management. The study also examines the variation in locus of control dimensions namely, internality, externality (others) and externality (chance). It further investigates the difference on perception of demographic variables (gender and marital status) and sectoral difference on impression management. The study was administered on 125 Managers who were representatives of different private and public sector organizations in Delhi/NCR. Variables in the study were assessed using validated instruments. Descriptive Statistics, t-test, Correlation and Regression were used for data analysis. Organizations will be better prepared to dig into the arena of one of the personality variable, i.e. locus of control and its relationship with impression management. The current research is imperative in providing insights into role of personality variable (locus of control) and impression management, which will be one of the pioneer researches available till date. Moreover, the research will highlight the significance of locus of control dimensions and impression management.

scholarly journals Frequency responses of age-structured populations: Pacific salmon as an example

2010 ◽  
Vol 78 (4) ◽  
pp. 239-249 ◽  
Author(s):  
Lee Worden ◽  
Louis W. Botsford ◽  
Alan Hastings ◽  
Matthew D. Holland
Keyword(s):  
Pacific Salmon ◽  
Structured Populations ◽  
Frequency Responses ◽  
Age Structured
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