scholarly journals Effective population size for culturally evolving traits

2021 ◽  
Author(s):  
Dominik Deffner ◽  
Anne Kandler ◽  
Laurel Fogarty
Keyword(s):  
Population Genetics ◽  
Social Network ◽  
Cultural Diversity ◽  
Population Size ◽  
Effective Population Size ◽  
Network Structure ◽  
Cultural Exchange ◽  
Effective Size ◽  
Effective Population ◽  
Social Network Structure

ABSTRACTPopulation size has long been considered an important driver of cultural diversity and complexity. Results from population genetics, however, demonstrate that in populations with complex demographic structure or mode of inheritance, it is not the census population size, N, but the effective size of a population, Ne, that determines important evolutionary parameters. Here, we examine the concept of effective population size for traits that evolve culturally, through processes of innovation and social learning. We use mathematical and computational modeling approaches to investigate how cultural Ne and levels of diversity depend on (1) the way traits are learned, (2) population connectedness, and (3) social network structure. We show that one-to-many and frequency-dependent transmission can temporally or permanently lower effective population size compared to census numbers. We caution that migration and cultural exchange can have counter-intuitive effects on Ne. Network density in random networks leaves Ne unchanged, scale-free networks tend to decrease and small-world networks tend to increase Ne compared to census numbers. For one-to-many transmission and different network structures, effective size and cultural diversity are closely associated. For connectedness, however, even small amounts of migration and cultural exchange result in high diversity independently of Ne. Our results highlight the importance of carefully defining effective population size for cultural systems and show that inferring Ne requires detailed knowledge about underlying cultural and demographic processes.AUTHOR SUMMARYHuman populations show immense cultural diversity and researchers have regarded population size as an important driver of cultural variation and complexity. Our approach is based on cultural evolutionary theory which applies ideas about evolution to understand how cultural traits change over time. We employ insights from population genetics about the “effective” size of a population (i.e. the size that matters for important evolutionary outcomes) to understand how and when larger populations can be expected to be more culturally diverse. Specifically, we provide a formal derivation for cultural effective population size and use mathematical and computational models to study how effective size and cultural diversity depend on (1) the way culture is transmitted, (2) levels of migration and cultural exchange, as well as (3) social network structure. Our results highlight the importance of effective sizes for cultural evolution and provide heuristics for empirical researchers to decide when census numbers could be used as proxies for the theoretically relevant effective numbers and when they should not.

scholarly journals The population genetics of haplo-diploids and X-linked genes

1984 ◽  
Vol 44 (3) ◽  
pp. 321-341 ◽  
Author(s):  
P. J. Avery
Keyword(s):  
Population Genetics ◽  
Genetic Variability ◽  
Population Size ◽  
Effective Population Size ◽  
Disease Genes ◽  
Effective Population ◽  
Random Drift ◽  
Mutation Pressure ◽  
Electrophoretic Data ◽  
Fitness Parameters

SUMMARYFrom the available electrophoretic data, it is clear that haplodiploid insects have a much lower level of genetic variability than diploid insects, a difference that is only partially explained by the social structure of some haplodiploid species. The data comparing X-linked genes and autosomal genes in the same species is much more sparse and little can be inferred from it. This data is compared with theoretical analyses of X-linked genes and genes in haplodiploids. (The theoretical population genetics of X-linked genes and genes in haplodiploids are identical.) X-linked genes under directional selection will be lost or fixed more quickly than autosomal genes as selection acts more directly on X-linked genes and the effective population size is smaller. However, deleterious disease genes, maintained by mutation pressure, will give higher disease incidences at X-linked loci and hence rare mutants are easier to detect at X-linked loci. Considering the forces which can maintain balanced polymorphisms, there are much stronger restrictions on the fitness parameters at X-linked loci than at autosomal loci if genetic variability is to be maintained, and thus fewer polymorphic loci are to be expected on the X-chromosome and in haplodiploids. However, the mutation-random drift hypothesis also leads to the expectation of lower heterozygosity due to the decrease in effective population size. Thus the theoretical results fit in with the data but it is still subject to argument whether selection or mutation-random drift are maintaining most of the genetic variability at X-linked genes and genes in haplodiploids.

scholarly journals EFFECTIVE SIZE OF AUTO-TETRAPLOID POPULATION UNDER PARTIAL SELFING

2015 ◽  
Vol 24 (1) ◽  
pp. 31
Author(s):  
Muhamad Sabran
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Numerical Study ◽  
Effective Size ◽  
Double Reduction ◽  
Effective Population ◽  
Census Size ◽  
Sister Chromatids ◽  
Tetraploid Population ◽  
Arbitrary Rate

Effective population size is defined as the number of breeding individual in an idealized population that would show the same amount of dispersion of allele frequencies under random genetic drift or the same amount of inbreeding as the population under consideration. Effective population size depends on the census size of the population and the mating system. In autotetraploid population, effective population size also depends on the probability of double reduction, i.e., a meiotic event when two sister chromatids end in the same gamete. In this research, we will study the effect of the probability of double reduction on the effective size of autotetraploid population reproduced by partial selfing. The formula for the effective population size was derived by equating the variance of the change in gene frequency in idealized population and its value in the autotetraploid population with arbitrary rate of partial selfing and double reduction. The resulted formula, and numerical study based on the formula, indicated that the effective size decreases by the increase of probability of double reduction and the rate of selfing. When there is complete selfing, however, the effective size is not affected by the probability of double reduction.

scholarly journals Effective size of nonrandom mating populations.

Genetics ◽  
1992 ◽  
Vol 130 (4) ◽  
pp. 909-916 ◽  
Author(s):  
A Caballero ◽  
W G Hill
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Family Size ◽  
Genetic Drift ◽  
Effective Size ◽  
Effective Population ◽  
Gene Frequencies ◽  
Nonrandom Mating ◽  
Sib Mating ◽  
Census Number

Abstract Nonrandom mating whereby parents are related is expected to cause a reduction in effective population size because their gene frequencies are correlated and this will increase the genetic drift. The published equation for the variance effective size, Ne, which includes the possibility of nonrandom mating, does not take into account such a correlation, however. Further, previous equations to predict effective sizes in populations with partial sib mating are shown to be different, but also incorrect. In this paper, a corrected form of these equations is derived and checked by stochastic simulation. For the case of stable census number, N, and equal progeny distributions for each sex, the equation is [formula: see text], where Sk2 is the variance of family size and alpha is the departure from Hardy-Weinberg proportions. For a Poisson distribution of family size (Sk2 = 2), it reduces to Ne = N/(1 + alpha), as when inbreeding is due to selfing. When nonrandom mating occurs because there is a specified system of partial inbreeding every generation, alpha can be substituted by Wright's FIS statistic, to give the effective size as a function of the proportion of inbred mates.

scholarly journals On the effective size of populations with separate sexes, with particular reference to sex-linked genes.

Genetics ◽  
1995 ◽  
Vol 139 (2) ◽  
pp. 1007-1011 ◽  
Author(s):  
A Caballero
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Effective Size ◽  
Effective Population ◽  
Poisson Distributions

Abstract Inconsistencies between equations for the effective population size of populations with separate sexes obtained by two different approaches are explained. One approach, which is the most common in the literature, is based on the assumption that the sex of the progeny cannot be identified. The second approach incorporates identification of the sexes of both parents and offspring. The approaches lead to identical expressions for effective size under some situations, such as Poisson distributions of offspring numbers. In general, however, the first approach gives incorrect answers, which become particularly severe for sex-linked genes, because then only numbers of daughters of males are relevant. Predictions of the effective size for sex-linked genes are illustrated for different systems of mating.

scholarly journals The comparative population genetics of Neisseria meningitidis and Neisseria gonorrhoeae

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7216 ◽  
Author(s):  
Lucile Vigué ◽  
Adam Eyre-Walker
Keyword(s):  
Population Genetics ◽  
Gene Transfer ◽  
Neisseria Meningitidis ◽  
Population Size ◽  
Effective Population Size ◽  
Adaptive Evolution ◽  
Lateral Gene Transfer ◽  
Pathogenic Bacteria ◽  
Core Genome ◽  
Effective Population

Neisseria meningitidis and N. gonorrhoeae are closely related pathogenic bacteria. To compare their population genetics, we compiled a dataset of 1,145 genes found across 20 N. meningitidis and 15 N. gonorrhoeae genomes. We find that N. meningitidis is seven-times more diverse than N. gonorrhoeae in their combined core genome. Both species have acquired the majority of their diversity by recombination with divergent strains, however, we find that N. meningitidis has acquired more of its diversity by recombination than N. gonorrhoeae. We find that linkage disequilibrium (LD) declines rapidly across the genomes of both species. Several observations suggest that N. meningitidis has a higher effective population size than N. gonorrhoeae; it is more diverse, the ratio of non-synonymous to synonymous polymorphism is lower, and LD declines more rapidly to a lower asymptote in N. meningitidis. The two species share a modest amount of variation, half of which seems to have been acquired by lateral gene transfer and half from their common ancestor. We investigate whether diversity varies across the genome of each species and find that it does. Much of this variation is due to different levels of lateral gene transfer. However, we also find some evidence that the effective population size varies across the genome. We test for adaptive evolution in the core genome using a McDonald–Kreitman test and by considering the diversity around non-synonymous sites that are fixed for different alleles in the two species. We find some evidence for adaptive evolution using both approaches.

Effective Population Size and the Effects of Demography on Cultural Diversity and Technological Complexity

2016 ◽  
Vol 81 (4) ◽  
pp. 605-622 ◽  
Author(s):  
L. S. Premo
Keyword(s):  
Cultural Diversity ◽  
Population Size ◽  
Effective Population Size ◽  
Cultural Transmission ◽  
Effective Population ◽  
Technological Complexity ◽  
Central Tenet ◽  
Empirical Tests ◽  
Census Population Size ◽  
The Relationship

A central tenet of the so-called demographic hypothesis is that larger populations ought to be associated with more diverse and complex toolkits. Recent empirical tests of this expectation have yielded mixed results, leading some to question to what extent changes in population size might explain interesting changes in the prehistoric archaeological record. Here, I employ computer simulation as a heuristic tool to address whether these mixed results reflect deficiencies in the formal models borrowed from population genetics or problems with the generalizations archaeologists have derived from them. I show that two previously published and highly influential models highlight two different effects of demography. My results illustrate how natural selection and cultural selection weaken the relationship between census population size, cultural diversity, and mean skill level, suggesting that one should not expect population size to predict the diversity or complexity of a cultural trait under all conditions. The concept of effective population size is central to understanding why the effects of population size can vary among traits that are passed by different mechanisms of cultural transmission within the same population. In light of these findings, I suggest ways to strengthen (rather than abandon) empirical tests of the demographic hypothesis.

scholarly journals Effective population size when fertility is inherited

1966 ◽  
Vol 8 (2) ◽  
pp. 257-260 ◽  
Author(s):  
Masatoshi Nei ◽  
Motoi Murata
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Effective Size ◽  
Effective Population

A formula for effective population size when fertility is inherited is worked out. It is shown that the effective size decreases as the heritability of fertility or progeny number increases.

scholarly journals GENETIC DRIFT AND ESTIMATION OF EFFECTIVE POPULATION SIZE

Genetics ◽  
1981 ◽  
Vol 98 (3) ◽  
pp. 625-640
Author(s):  
Masatoshi Nei ◽  
Fumio Tajima
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Random Mating ◽  
Effective Size ◽  
Isolated Population ◽  
Effective Population ◽  
Dacus Oleae ◽  
Census Size ◽  
Mating Population ◽  
Frequency Changes

ABSTRACT The statistical properties of the standardized variance of gene frequency changes (a quantity equivalent to Wright's inbreeding coefficient) in a random mating population are studied, and new formulae for estimating the effective population size are developed. The accuracy of the formulae depends on the ratio of sample size to effective size, the number of generations involved (t), and the number of loci or alleles used. It is shown that the standardized variance approximately follows the Χ2 distribution unless t is very large, and the confidence interval of the estimate of effective size can be obtained by using this property. Application of the formulae to data from an isolated population of Dacus oleae has shown that the effective size of this population is about one tenth of the minimum census size, though there was a possibility that the procedure of sampling genes was improper.

scholarly journals Genetic diversity and structure of two endangered mole salamander species of the Trans-Mexican Volcanic Belt

Herpetozoa ◽  
2019 ◽  
Vol 32 ◽  
pp. 237-248 ◽  
Author(s):  
Octavio Monroy-Vilchis ◽  
Rosa-Laura Heredia-Bobadilla ◽  
Martha M. Zarco-González ◽  
Víctor Ávila-Akerberg ◽  
Armando Sunny
Keyword(s):  
Genetic Diversity ◽  
Population Genetics ◽  
Population Size ◽  
Effective Population Size ◽  
Volcanic Belt ◽  
Population Declines ◽  
Effective Population ◽  
Mexican Volcanic Belt ◽  
Genetic Diversity And Structure ◽  
Trans Mexican Volcanic Belt

The most important factor leading to amphibian population declines and extinctions is habitat degradation and destruction. To help prevent further extinctions, studies are needed to make appropriate conservation decisions in small and fragmented populations. The goal of this study was to provide data from the population genetics of two micro-endemic mole salamanders from the Trans-Mexican Volcanic Belt. Nine microsatellite markers were used to study the population genetics of 152 individuals from two Ambystoma species. We sampled 38 individuals in two localities for A. altamirani and A. rivualre. We found medium to high levels of genetic diversity expressed as heterozygosity in the populations. However, all the populations presented few alleles per locus and genotypes. We found strong genetic structure between populations for each species. Effective population size was small but similar to that of the studies from other mole salamanders with restricted distributions or with recently fragmented habitats. Despite the medium to high levels of genetic diversity expressed as heterozygosity, we found few alleles, evidence of a genetic bottleneck and that the effective population size is small in all populations. Therefore, this study is important to propose better management plans and conservation efforts for these species.

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