scholarly journals Genetic Differentiation and Estimation of Effective Population Size and Migration Rates in Two Sympatric Ecotypes of the Marine Snail Littorina saxatilis

2005 ◽  
Vol 96 (4) ◽  
pp. 460-464 ◽  
Author(s):  
J. Fernández ◽  
J. Galindo ◽  
B. Fernández ◽  
A. Pérez-Figueroa ◽  
A. Caballero ◽  
...  
Keyword(s):  
Genetic Differentiation ◽  
Population Size ◽  
Effective Population Size ◽  
Littorina Saxatilis ◽  
Effective Population ◽  
Marine Snail ◽  
Migration Rates ◽  
And Migration

Estimating Effective Population Size and Migration Rates From Genetic Samples Over Space and Time

Genetics ◽  
2003 ◽  
Vol 163 (1) ◽  
pp. 429-446 ◽  
Author(s):  
Jinliang Wang ◽  
Michael C Whitlock
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Joint Estimation ◽  
Large Sample Size ◽  
Effective Population ◽  
Likelihood Methods ◽  
Marker Allele ◽  
Migration Rates ◽  
Space And Time ◽  
And Migration

Abstract In the past, moment and likelihood methods have been developed to estimate the effective population size (Ne) on the basis of the observed changes of marker allele frequencies over time, and these have been applied to a large variety of species and populations. Such methods invariably make the critical assumption of a single isolated population receiving no immigrants over the study interval. For most populations in the real world, however, migration is not negligible and can substantially bias estimates of Ne if it is not accounted for. Here we extend previous moment and maximum-likelihood methods to allow the joint estimation of Ne and migration rate (m) using genetic samples over space and time. It is shown that, compared to genetic drift acting alone, migration results in changes in allele frequency that are greater in the short term and smaller in the long term, leading to under- and overestimation of Ne, respectively, if it is ignored. Extensive simulations are run to evaluate the newly developed moment and likelihood methods, which yield generally satisfactory estimates of both Ne and m for populations with widely different effective sizes and migration rates and patterns, given a reasonably large sample size and number of markers.

scholarly journals The effect of sample size on estimates of genetic differentiation and effective population size for Schistosoma mansoni populations

2018 ◽  
Vol 48 (14) ◽  
pp. 1149-1154 ◽  
Author(s):  
Lúcio M. Barbosa ◽  
Bruna C. Barros ◽  
Moreno de Souza Rodrigues ◽  
Luciano K. Silva ◽  
Mitermayer G. Reis ◽  
...  
Keyword(s):  
Genetic Differentiation ◽  
Schistosoma Mansoni ◽  
Sample Size ◽  
Population Size ◽  
Effective Population Size ◽  
Effective Population

Spatial and temporal genetic differentiation and effective population size of brown trout (Salmo trutta, L.) in small Danish rivers

2005 ◽  
Vol 6 (4) ◽  
pp. 615-621 ◽  
Author(s):  
Lasse F. Jensen ◽  
Michael M. Hansen ◽  
Jens Carlsson ◽  
Volker Loeschcke ◽  
Karen-Lise D. Mensberg
Keyword(s):  
Genetic Differentiation ◽  
Population Size ◽  
Effective Population Size ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Effective Population ◽  
Brown Trout Salmo Trutta

scholarly journals Patterns of Inbreeding Depression and Architecture of the Load in Subdivided Populations

Genetics ◽  
2003 ◽  
Vol 165 (4) ◽  
pp. 2193-2212 ◽  
Author(s):  
Sylvain Glémin ◽  
Joëlle Ronfort ◽  
Thomas Bataillon
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Inbreeding Depression ◽  
Local Population ◽  
Population Subdivision ◽  
Deleterious Mutations ◽  
Effective Population ◽  
Subdivided Populations ◽  
And Migration ◽  
Insight Into

AbstractInbreeding depression is a general phenomenon that is due mainly to recessive deleterious mutations, the so-called mutation load. It has been much studied theoretically. However, until very recently, population structure has not been taken into account, even though it can be an important factor in the evolution of populations. Population subdivision modifies the dynamics of deleterious mutations because the outcome of selection depends on processes both within populations (selection and drift) and between populations (migration). Here, we present a general model that permits us to gain insight into patterns of inbreeding depression, heterosis, and the load in subdivided populations. We show that they can be interpreted with reference to single-population theory, using an appropriate local effective population size that integrates the effects of drift, selection, and migration. We term this the “effective population size of selection” (NeS). For the infinite island model, for example, it is equal to NeS=N(1+m∕hs), where N is the local population size, m the migration rate, and h and s the dominance and selection coefficients of deleterious mutation. Our results have implications for the estimation and interpretation of inbreeding depression in subdivided populations, especially regarding conservation issues. We also discuss the possible effects of migration and subdivision on the evolution of mating systems.

scholarly journals Long-term monitoring of a brown trout (Salmo trutta) population reveals kin-associated migration patterns and contributions by resident trout to the anadromous run

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Eloïse Duval ◽  
Øystein Skaala ◽  
María Quintela ◽  
Geir Dahle ◽  
Aurélien Delaval ◽  
...  
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Anthropogenic Pressure ◽  
Parentage Assignment ◽  
Effective Population ◽  
Migration Timing ◽  
Brown Trout Salmo Trutta ◽  
And Migration

Abstract Background In species showing partial migration, as is the case for many salmonid fishes, it is important to assess how anthropogenic pressure experienced by migrating individuals affects the total population. We focused on brown trout (Salmo trutta) from the Guddal River in the Norwegian Hardanger Fjord system, which encompasses both resident and anadromous individuals. Aquaculture has led to increased anthropogenic pressure on brown trout during the marine phase in this region. Fish traps in the Guddal River allow for sampling all ascending anadromous spawners and descending smolts. We analyzed microsatellite DNA markers from all individuals ascending in 2006–2016, along with all emigrating smolts in 2017. We investigated (1) if there was evidence for declines in census numbers and effective population size during that period, (2) if there was association between kinship and migration timing in smolts and anadromous adults, and (3) to what extent resident trout were parents of outmigrating smolts. Results Census counts of anadromous spawners showed no evidence for a decline from 2006 to 2016, but were lower than in 2000–2005. Estimates of effective population size also showed no trends of declines during the study period. Sibship reconstruction of the 2017 smolt run showed significant association between kinship and migration timing, and a similar association was indicated in anadromous spawners. Parentage assignment of 2017 smolts with ascending anadromous trout as candidate parents, and assuming that unknown parents represented resident trout, showed that 70% of smolts had at least one resident parent and 24% had two resident parents. Conclusions The results bear evidence of a population that after an initial decline has stabilized at a lower number of anadromous spawners. The significant association between kinship and migration timing in smolts suggests that specific episodes of elevated mortality in the sea could disproportionally affect some families and reduce overall effective population size. Finally, the results based on parentage assignment demonstrate a strong buffering effect of resident trout in case of elevated marine mortality affecting anadromous trout, but also highlight that increased mortality of anadromous trout, most of which are females, may lower overall production in the system.

scholarly journals Simple life-history traits explain key effective population size ratios across diverse taxa

2013 ◽  
Vol 280 (1768) ◽  
pp. 20131339 ◽  
Author(s):  
Robin S. Waples ◽  
Gordon Luikart ◽  
James R. Faulkner ◽  
David A. Tallmon
Keyword(s):  
Life History ◽  
Population Size ◽  
Effective Population Size ◽  
Life History Traits ◽  
Vital Rates ◽  
Effective Population ◽  
Adult Lifespan ◽  
Census Size ◽  
The Rich ◽  
And Migration

Effective population size ( N e ) controls both the rate of random genetic drift and the effectiveness of selection and migration, but it is difficult to estimate in nature. In particular, for species with overlapping generations, it is easier to estimate the effective number of breeders in one reproductive cycle ( N b ) than N e per generation. We empirically evaluated the relationship between life history and ratios of N e , N b and adult census size ( N ) using a recently developed model ( agene ) and published vital rates for 63 iteroparous animals and plants. N b / N e varied a surprising sixfold across species and, contrary to expectations, N b was larger than N e in over half the species. Up to two-thirds of the variance in N b / N e and up to half the variance in N e / N was explained by just two life-history traits (age at maturity and adult lifespan) that have long interested both ecologists and evolutionary biologists. These results provide novel insights into, and demonstrate a close general linkage between, demographic and evolutionary processes across diverse taxa. For the first time, our results also make it possible to interpret rapidly accumulating estimates of N b in the context of the rich body of evolutionary theory based on N e per generation.

scholarly journals Estimation of Effective Population Size and Migration Rate From One- and Two-Locus Identity Measures

Genetics ◽  
2001 ◽  
Vol 157 (2) ◽  
pp. 911-925
Author(s):  
Renaud Vitalis ◽  
Denis Couvet
Keyword(s):  
Population Size ◽  
Effective Population Size ◽  
Joint Estimation ◽  
Demographic Parameters ◽  
Effective Population ◽  
Mutation Bias ◽  
Infinite Allele Model ◽  
Immigration Rate ◽  
And Migration ◽  
Allele Model

Abstract Standard methods for inferring demographic parameters from genetic data are based mainly on one-locus theory. However, the association of genes at different loci (e.g., two-locus identity disequilibrium) may also contain some information about demographic parameters of populations. In this article, we define one- and two-locus parameters of population structure as functions of one- and two-locus probabilities for the identity in state of genes. Since these parameters are known functions of demographic parameters in an infinite island model, we develop moment-based estimators of effective population size and immigration rate from one- and two-locus parameters. We evaluate this method through simulation. Although variance and bias may be quite large, increasing the number of loci on which the estimates are derived improves the method. We simulate an infinite allele model and a K allele model of mutation. Bias and variance are smaller with increasing numbers of alleles per locus. This is, to our knowledge, the first attempt of a joint estimation of local effective population size and immigration rate.

scholarly journals Influence of gene flow and breeding tactics on gene diversity within populations.

Genetics ◽  
1991 ◽  
Vol 129 (2) ◽  
pp. 573-583 ◽  
Author(s):  
R K Chesser
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Population Size ◽  
Effective Population Size ◽  
Gene Diversity ◽  
Island Model ◽  
Effective Population ◽  
Migration Rates ◽  
Asymptotic Values ◽  
Fixation Indices

Abstract Expressions describing the accumulation of gene correlations within and among lineages and individuals of a population are derived. The model permits different migration rates by males and females and accounts for various breeding tactics within lineages. The resultant equations enable calculation of the probabilistic quantities for the fixation indices, rates of loss of genetic variation, accumulation of inbreeding, and coefficients of relationship for the population at any generation. All fixation indices were found to attain asymptotic values rapidly despite the consistent loss of genetic variation and accumulation of inbreeding within the population. The time required to attain asymptotic values, however, was prolonged when gene flow among lineages was relatively low (less than 20%). The degree of genetic differentiation among breeding groups, inbreeding coefficients, and gene correlations within lineages were found to be primarily functions of breeding tactics within groups rather than gene flow among groups. Thus, the asymptotic value of S. Wright's island model is not appropriate for describing genetic differences among groups within populations. An alternative solution is provided that under limited conditions will reduce to the original island model. The evolution of polygynous breeding tactics appears to be more favorable for promoting intragroup gene correlations than modification of migration rates. Inbreeding and variance effective sizes are derived for populations that are structured by different migration and breeding tactics. Processes that reduce the inbreeding effective population size result in a concomitant increase in variance effective population size.

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