Temporal sampling helps unravel the genetic structure of naturally occurring populations of a phytoparasitic nematode. 2. Separating the relative effects of gene flow and genetic drift

The article describes the additional evolutionary factors, apart from natural selection, which can influence the genetic structure of the populations of the main carriers of the plague microbe – the great gerbil. The influence of genetic drift on random fluctuation of alleles is considered. With the help of a stochastic matrix, on the example of the family group of gerbils consisting of four individuals, the probabilities of the transition of allele frequencies from parents to offspring are calculated. Based on the previously calculated size of the neighborhood in gerbils, it is concluded that any large population of great gerbils can be considered as small in terms of deviation of gene frequencies. In such small groups – parcels – the drift of genes will be of great importance. In addition, the effect of the gene flow on the genetic structure of the gerbil population on the example of the simplest population model “continent-island” is considered. The dynamics of changes in allelic frequencies for 100 generations has been calculated. It is shown that the allele frequency during the 20-30 generations changes at the maximum rate, and then slows as the equilibrium is approached. It is concluded that different populations of gerbils should be considered as separate historically formed structures, with different sequence of influence of external environmental factors on them.

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The genetic structure of populations of orchids and its evolutionary importance: understanding processes from patterns

Lankesteriana ◽

10.15517/lank.v3i2.23024 ◽

2016 ◽

Vol 3 (2) ◽

Author(s):

Raymond L. Tremblay

Keyword(s):

Gene Flow ◽

Natural Selection ◽

Genetic Structure ◽

Population Size ◽

Effective Population Size ◽

Genetic Drift ◽

Mating Systems ◽

Mutation Rates ◽

Effective Population ◽

Genetic Structure Of Populations

<div class="page" title="Page 1"><div class="layoutArea"><div class="column"><p><span>Evolution through either natural selection or genetic drift is dependent on variation at the genetic and mor- phological levels. Processes that influence the genetic structure of populations include mating systems, effective population size, mutation rates and gene flow among populations. </span></p></div></div></div>

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Recent large-scale landscape changes, genetic drift and reintroductions characterize the genetic structure of Norwegian wild reindeer

Conservation Genetics ◽

10.1007/s10592-019-01225-w ◽

2019 ◽

Vol 20 (6) ◽

pp. 1405-1419 ◽

Cited By ~ 1

Author(s):

Kjersti S. Kvie ◽

Jan Heggenes ◽

Bård-Jørgen Bårdsen ◽

Knut H. Røed

Keyword(s):

Genetic Variation ◽

Gene Flow ◽

Genetic Structure ◽

Population Size ◽

Genetic Drift ◽

Genetic Connectivity ◽

Conservation Strategies ◽

Landscape Changes ◽

Anthropogenic Habitat ◽

Wild Reindeer

Abstract Landscape changes, such as habitat loss and fragmentation, subdivide wild populations, reduce their size, and limit gene flow. These changes may further lead to depletion of genetic variation within populations as well as accelerating differentiation among populations. As a migratory species requiring large living areas, wild reindeer (Rangifer tarandus) is highly vulnerable to human activity. The number and continued presence of wild reindeer have been significantly reduced due to accelerating anthropogenic habitat modifications, as well as displacement in benefit of domesticated herds of the species. As a basis for future management strategies we assess genetic structure and levels of genetic variation in Norwegian wild reindeer by analysing 12 microsatellite loci and the mitochondrial control region in 21 management units with varying population sizes. Overall, both markers showed highly varying levels of genetic variation, with reduced variation in the smaller and more isolated populations. The microsatellite data indicated a relationship between population size and genetic variation. This relationship was positive and linear until a threshold for population size was reached at approximately 1500 reindeer. We found high levels of differentiation among most populations, indicating low levels of gene flow, but only a weak correlation between geographic and genetic distances. Our results imply that the genetic structure of Norwegian wild reindeer is mainly driven by recent colonization history, population size, as well as human-induced landscape fragmentation, restricting gene flow and leading to high levels of genetic drift. To sustain viable populations, conservation strategies should focus on genetic connectivity between populations.

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Hierarchical Analysis of Genetic Structure in Native Fire Ant Populations: Results From Three Classes of Molecular Markers

Genetics ◽

10.1093/genetics/147.2.643 ◽

1997 ◽

Vol 147 (2) ◽

pp. 643-655 ◽

Cited By ~ 3

Author(s):

Kenneth G Ross ◽

Michael J B Krieger ◽

D DeWayne Shoemaker ◽

Edward L Vargo ◽

Laurent Keller

Keyword(s):

Gene Flow ◽

Genetic Structure ◽

Solenopsis Invicta ◽

Large Scale ◽

Fire Ant ◽

Nuclear Markers ◽

Social Forms ◽

Native Populations ◽

Nest Level ◽

Nuclear Differentiation

We describe genetic structure at various scales in native populations of the fire ant Solenopsis invicta using two classes of nuclear markers, allozymes and microsatellites, and markers of the mitochondrial genome. Strong structure was found at the nest level in both the monogyne (single queen) and polygyne (multiple queen) social forms using allozymes. Weak but significant microgeographic structure was detected above the nest level in polygyne populations but not in monogyne populations using both classes of nuclear markers. Pronounced mitochondrial DNA (mtDNA) differentiation was evident also at this level in the polygyne form only. These microgeographic patterns are expected because polygyny in ants is associated with restricted local gene flow due mainly to limited vagility of queens. Weak but significant nuclear differentiation was detected between sympatric social forms, and strong mtDNA differentiation also was found at this level. Thus, queens of each form seem unable to establish themselves in nests of the alternate type, and some degree of assortative mating by form may exist as well. Strong differentiation was found between the two study regions usinga all three sets of markers. Phylogeographic analyses of the mtDNA suggest that recent limitations on gene flow rather than longstanding barriers to dispersal are responsible for this large-scale structure.

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Geographic Structure of Mitochondrial and Nuclear Gene Polymorphisms in Australian Green Turtle Populations and Male-Biased Gene Flow

Genetics ◽

10.1093/genetics/147.4.1843 ◽

1997 ◽

Vol 147 (4) ◽

pp. 1843-1854 ◽

Cited By ~ 8

Author(s):

Nancy N FitzSimmons ◽

Craig Moritz ◽

Colin J Limpus ◽

Lisa Pope ◽

Robert Prince

Keyword(s):

Gene Flow ◽

Genetic Structure ◽

Green Turtle ◽

Nuclear Dna ◽

Nuclear Gene ◽

Chelonia Mydas ◽

Single Copy ◽

Microsatellite Data ◽

Ecological Data ◽

Infinite Allele Model

Abstract The genetic structure of green turtle (Chelonia mydas) rookeries located around the Australian coast was assessed by (1) comparing the structure found within and among geographic regions, (2) comparing microsatellite loci vs. restriction fragment length polymorphism analyses of anonymous single copy nuclear DNA (ascnDNA) loci, and (3) comparing the structure found at nuclear DNA markers to that of previously analyzed mitochondrial (mtDNA) control region sequences. Significant genetic structure was observed over all regions at both sets of nuclear markers, though the microsatellite data provided greater resolution in identifying significant genetic differences in pairwise tests between regions. Inferences about population structure and migration rates from the microsatellite data varied depending on whether statistics were based on the stepwise mutation or infinite allele model, with the latter being more congruent with geography. Estimated rates of gene flow were generally higher than expected for nuclear DNA (nDNA) in comparison to mtDNA, and this difference was most pronounced in comparisons between the northern and southern Great Barrier Reef (GBR). The genetic data combined with results from physical tagging studies indicate that the lack of nuclear gene divergence through the GBR is likely due to the migration of sGBR turtles through the courtship area of the nGBR population, rather than male-biased dispersal. This example highlights the value of combining comparative studies of molecular variation with ecological data to infer population processes.

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