Critical migration rate in the evolutionary dynamics of subdivided populations

2021 ◽  
Author(s):  
Yung-Gyung Kang ◽  
Jeong-Man Park
Keyword(s):  
Migration Rate ◽  
Evolutionary Dynamics ◽  
Subdivided Populations

Heterogeneity, Spatial Population Dynamics, and the Migration Rate

1992 ◽  
Vol 24 (6) ◽  
pp. 775-791 ◽  
Author(s):  
A Rogers
Keyword(s):  
Return Migration ◽  
Migration Rate ◽  
Evolutionary Dynamics ◽  
Population Analysis ◽  
Model Fitting ◽  
Initial Model ◽  
Migration Rates ◽  
Net Migration ◽  
Spatial Population ◽  
True Occurrence

The literature on the impacts of heterogeneity and selection in population analysis has been limited largely to the conventional unistate perspective in which only decrements are considered; and their temporal (selectivity) impacts on independent subpopulations examined. In this paper, the focus is on the evolutionary dynamics of (multistate) multiregional populations whose interdependent subpopulations can experience increments as well as decrements. It is shown that in such instances migration rates that are not true occurrence-exposure rates are ambiguous, because they depend on the relative weightings existing during the initial model-fitting period. Net migration rates, lifetime migration rates, and return migration proportions all are imperfect measures of migration propensities, and their use as input measures to an analysis should be avoided whenever possible.

scholarly journals Inbreeding coefficients and coalescence times

1991 ◽  
Vol 58 (2) ◽  
pp. 167-175 ◽  
Author(s):  
Montgomery Slatkin
Keyword(s):  
Migration Rate ◽  
Sequence Data ◽  
Island Model ◽  
Dna Sequence Data ◽  
Local Populations ◽  
Inbreeding Coefficients ◽  
Subdivided Populations ◽  
Stepping Stone Models ◽  
The Relationship ◽  
Coalescence Times

SummaryThis paper describes the relationship between probabilities of identity by descent and the distribution of coalescence times. By using the relationship between coalescence times and identity probabilities, it is possible to extend existing results for inbreeding coefficients in regular systems of mating to find the distribution of coalescence times and the mean coalescence times. It is also possible to express Sewall Wright's FST as the ratio of average coalescence times of different pairs of genes. That simplifies the analysis of models of subdivided populations because the average coalescence time can be found by computing separately the time it takes for two genes to enter a single subpopulation and time it takes for two genes in the same subpopulation to coalesce. The first time depends only on the migration matrix and the second time depends only on the total number of individuals in the population. This approach is used to find FST in the finite island model and in one- and two-dimensional stepping-stone models. It is also used to find the rate of approach of FST to its equilibrium value. These results are discussed in terms of different measures of genetic distance. It is proposed that, for the purposes of describing the amount of gene flow among local populations, the effective migration rate between pairs of local populations, M^, which is the migration rate that would be estimated for those two populations if they were actually in an island model, provides a simple and useful measure of genetic similarity that can be defined for either allozyme or DNA sequence data.

scholarly journals Decay of linkage disequilibrium in a finite island model

1994 ◽  
Vol 64 (2) ◽  
pp. 137-144 ◽  
Author(s):  
Hidenori Tachida
Keyword(s):  
Linkage Disequilibrium ◽  
Migration Rate ◽  
Natural Populations ◽  
Decay Rates ◽  
Island Model ◽  
The Past ◽  
Linkage Disequilibria ◽  
Subdivided Populations ◽  
Time Dependent Behaviour ◽  
Dependent Behaviour

SummaryTime-dependent behaviour of linkage disequilibrium when there was initial linkage disequilibrium is studied in a finite island model assuming neutrality. Explicit expressions for linkage disequilibrium parameters are obtained. From these expressions, the initial and the ultimate decay rates of linkage disequilibrium parameters are found to be increased and decreased, respectively, by finiteness of the population when recombination rate, migration rate and inverse of subpopulation size are of comparable order. Thus, linkage disequilibrium created in the past may persist longerin smaller subdivided populations. Also, differentiation of the gametic parameter of linkage disequilibrium among subpopulations is found to diminish quickly compared tothe linkage disequilibrium in the whole population. Implications of these results for the interpretation of linkage disequilibria in natural populations are discussed.

Coalescence times and F ST values in subdivided populations with symmetric structure

2003 ◽  
Vol 35 (03) ◽  
pp. 665-690
Author(s):  
Hilde M. Wilkinson-Herbots
Keyword(s):  
Migration Rate ◽  
Recent Common Ancestor ◽  
Regularity Conditions ◽  
Simple Relationship ◽  
Total Size ◽  
Graph Theoretic ◽  
Most Recent Common Ancestor ◽  
Subdivided Populations ◽  
Structured Coalescent ◽  
Infinite Alleles Model

The structured coalescent is a continuous-time Markov chain which describes the genealogy of a sample of homologous genes from a subdivided population. Assuming this model, some results are proved relating to the genealogy of a pair of genes and the extent of subpopulation differentiation, which are valid under certain graph-theoretic symmetry and regularity conditions on the structure of the population. We first review and extend earlier results stating conditions under which the mean time since the most recent common ancestor of a pair of genes from any single subpopulation is independent of the migration rate and equal to that of two genes from an unstructured population of the same total size. Assuming the infinite alleles model of neutral mutation with a small mutation rate, we then prove a simple relationship between the migration rate and the value of Wright's coefficient F ST for a pair of neighbouring subpopulations, which does not depend on the precise structure of the population provided that this is sufficiently symmetric.

scholarly journals The role of migration in mutant evolution in fragmented populations

2021 ◽  
Author(s):  
Jesse Kreger ◽  
Donovan Brown ◽  
Natalia Komarova ◽  
Dominik Wodarz ◽  
Justin Pritchard
Keyword(s):  
Migration Rate ◽  
Evolutionary Biology ◽  
Evolutionary Dynamics ◽  
Hematopoietic Stem ◽  
Fragmented Populations ◽  
Colonic Crypts ◽  
Hematopoietic Stem Cell Niches ◽  
The Mean ◽  
Clonal Composition

Mutant evolution in fragmented populations has been studied extensively in evolutionary biology. With an increased focus on evolutionary dynamics in medical research, quantification of mutant load in fragmented populations with varying levels of migration has become especially important. Examples of fragmented populations are hematopoietic stem cell niches in the bone marrow where cells can re-circulate between niches through the blood, or colonic crypts where movement of cells across different crypts is not thought to be common. Here we use a combination of experiments and theory to investigate the role of migration in mutant distribution. In the case of neutral mutants, the experiments confirmed that while the mean number of mutants is not influenced by migration, the probability distribution is, which manifested itself in a change in the skewedness of the distribution of the mutant numbers in the demes. In the case of disadvantageous mutants, we investigated the phenomenon of the increase in the expected number of mutants compared to that of the selection-mutation balance. In a single deme, this increase is observed when the deme size is lower than the critical size, $N_c$. In a fragmented system that consists of connected demes with a probability of migration, the increase in mutant numbers above the selection-mutation balance can be maintained in small ($N<N_c$) demes as long as the migration rate is sufficiently small. The migration rate above which the mutants approach the selection-mutation balance decays exponentially with $N/N_c$. These findings are relevant in the context of the complex and poorly understood processes that may lead to changes in the clonal composition in tissues and tumors.

scholarly journals Genetic diversity of Anadenanthera colubrina Vell. (Brenan) var cebil, a tree species from the South American subtropical forest as revealed by cpSSR markers

2011 ◽  
Vol 60 (1-6) ◽  
pp. 123-132 ◽  
Author(s):  
M. E. Barrandeguy ◽  
M.V. García ◽  
C. F. Argüelles ◽  
G. D. L. Cervigni
Keyword(s):  
Genetic Diversity ◽  
Genetic Structure ◽  
Tree Species ◽  
Evolutionary Dynamics ◽  
Pairwise Comparison ◽  
Fixation Index ◽  
Haplotypic Diversity ◽  
Adult Trees ◽  
Minimum Spanning Network ◽  
Subdivided Populations

Abstract Anadenanthera colubrina var cebil is a tree species native to the Upper Parana Atlantic Forest where human activities have severely impacted causing deep fragmentation. Microsatellites are not available in this species. Therefore, the first objective of this study was to generate chloroplast simple sequence repeats (cpSSR) by cross-species transfer. Understanding the evolutionary dynamics of subdivided populations is an important matter. In this way, a first approach to the characterization of the haplotypic diversity within and between populations as well as the genetic structure of native Argentinean populations were the main goals of this study. Twenty four individuals from two populations of the Misiones province were studied and four cpSSR loci were tested. Two of them exhibited polymorphic patterns leading to the identification of 11 cpDNA haplotypes with high mean genetic diversity (GD=0.73). The minimum spanning network defined three clear groups which can be assigned to at least three subpopulations. AMOVA indicated that the total variance showed the highest percentage of variation (48%) within subpopulations with a fixation index (FST) statistically significant (FST=0.520; p<0.05). Brown’s two loci component analysis indicated that substructure population is present. Jost’s differentiation global index (Dest) was 0.049 while Dest pairwise comparison reflected a certain level of genetic structure. The high diversity level detected in the adult trees of A. colubrina var cebil from the populations under study could be due to recent human influence. In this way, the reduction in population size caused a reduction in the number of trees leading to surviving trees showing the historical diversity of the populations analyzed.

Coalescence times and FST values in subdivided populations with symmetric structure

2003 ◽  
Vol 35 (3) ◽  
pp. 665-690 ◽  
Author(s):  
Hilde M. Wilkinson-Herbots
Keyword(s):  
Migration Rate ◽  
Recent Common Ancestor ◽  
Regularity Conditions ◽  
Simple Relationship ◽  
Total Size ◽  
Graph Theoretic ◽  
Most Recent Common Ancestor ◽  
Subdivided Populations ◽  
Structured Coalescent ◽  
Infinite Alleles Model

The structured coalescent is a continuous-time Markov chain which describes the genealogy of a sample of homologous genes from a subdivided population. Assuming this model, some results are proved relating to the genealogy of a pair of genes and the extent of subpopulation differentiation, which are valid under certain graph-theoretic symmetry and regularity conditions on the structure of the population. We first review and extend earlier results stating conditions under which the mean time since the most recent common ancestor of a pair of genes from any single subpopulation is independent of the migration rate and equal to that of two genes from an unstructured population of the same total size. Assuming the infinite alleles model of neutral mutation with a small mutation rate, we then prove a simple relationship between the migration rate and the value of Wright's coefficient FST for a pair of neighbouring subpopulations, which does not depend on the precise structure of the population provided that this is sufficiently symmetric.

scholarly journals LINKAGE DISEQUILIBRIUM IN SUBDIVIDED POPULATIONS

Genetics ◽  
1973 ◽  
Vol 75 (1) ◽  
pp. 213-219
Author(s):  
Masatoshi Nei ◽  
Wen-Hsiung Li
Keyword(s):  
Linkage Disequilibrium ◽  
Migration Rate ◽  
Random Mating ◽  
Isolated Populations ◽  
Gene Frequencies ◽  
Average Linkage ◽  
Subdivided Population ◽  
Overdominant Selection ◽  
Subdivided Populations ◽  
Recombination Value

ABSTRACT The linkage disequilibrium in a subdivided populaton is shown to be equal to the sum of the average linkage disequilibrium for all subpopulations and the covariance between gene frequencies of the loci concerned. Thus, in a subdivided population the linkage disequilibrium may not be 0 even if the linkage disequilibrium in each subpopulation is 0. If a population is divided into two subpopulations between which migration occurs, the asymptotic rate of approach to linkage equilibrium is equal to either r or 2(m  1 + m  2) - (m  1 + m  2)2, whichever is smaller, where r is the recombination value and m  1 and m  2 are the proportions of immigrants in subpopulations 1 and 2, respectively. Thus, if migration rate is high compared with recombination value, the change of linkage disequilibrium in subdivided populations is similar to that of a single random mating population. On the other hand, if migration rate is low, the approach to lnkage equilibrium may be retarded in subdivided populations. If isolated populations begin to exchange genes by migration, linkage disequilibrium may increase temporarily even for neutral loci. If overdominant selection operates and the equilibrium gene frequencies are different in the two subpopulations, a permanent linkage disequilibrium may be produced without epistasis in each subpopulation.

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