Demography and Evolution in an Immigrant Ethnic Community: Hungarian Settlement, Louisiana, USA

1983 ◽  
Vol 15 (2) ◽  
pp. 223-236 ◽  
Author(s):  
Tibor Koertvelyessy
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
Genetic Drift ◽  
Demographic Characteristics ◽  
Ethnic Population ◽  
Marriage Patterns ◽  
Evolutionary Forces ◽  
Evolutionary Force ◽  
Demographic Processes ◽  
Over Time

SummaryThis paper describes the fertility, mortality, and marriage patterns of the Hungarian Settlement, Louisiana, USA, immigrant ethnic population and relates these demographic processes to the evolutionary forces of natural selection, genetic drift, and gene flow. The results indicate that the maximum opportunity for natural selection decreased over time, and natural selection could have operated in the case of this population at only a very moderate level. The demographic characteristics of this population suggest that genetic drift may be important as an agent of microdifferentiation. Gene flow, however, appears to be the most important evolutionary force in this population. The process, based on the increasing incorporation of non-Hungarians into the gene pool, is causing the breakdown of this ethnic/genetic isolate.

Population structure and evolutionary progress

Genome ◽  
1989 ◽  
Vol 31 (1) ◽  
pp. 196-202 ◽  
Author(s):  
Montgomery Slatkin
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
Genetic Drift ◽  
Natural Populations ◽  
New Combination ◽  
Balance Theory ◽  
Reasonable Time ◽  
Shifting Balance Theory ◽  
Shifting Balance ◽  
Demographic Processes

Wright's shifting-balance theory is discussed as an example of a process that can cause species to evolve combinations of characters that could not evolve under natural selection alone. A review of the existing theory of peak shifts indicates that the conditions of extreme isolation that are necessary to permit genetic drift to alter the outcome of natural selection in local populations would make gene flow too weak to spread a new combination of genes to other populations in a reasonable time. Instead, it seems likely that major demographic changes must occur in a species for the shifting-balance process to work. A discussion of direct and indirect studies of gene flow in natural populations suggests that the current genetic structure of many species is likely to reflect past demographic events rather than ongoing gene flow. It is possible then that demographic processes could be responsible for spreading new traits in a species, but that would be true whether those new traits evolved only owing to natural selection or owing in addition to genetic drift and other forces.Key words: shifting-balance theory, gene flow.

scholarly journals Evolution of gene regulatory networks by means of selection and random genetic drift

2018 ◽  
Author(s):  
Antonios Kioukis ◽  
Pavlos Pavlidis
Keyword(s):  
Natural Selection ◽  
Positive Selection ◽  
Genetic Drift ◽  
Regulatory Networks ◽  
Fitness Landscape ◽  
Random Genetic Drift ◽  
Maturation Period ◽  
Evolutionary Forces ◽  
Gene Regulatory

The evolution of a population by means of genetic drift and natural selection operating on a gene regulatory network (GRN) of an individual has not been scrutinized in depth. Thus, the relative importance of various evolutionary forces and processes on shaping genetic variability in GRNs is understudied. Furthermore, it is not known if existing tools that identify recent and strong positive selection from genomic sequences, in simple models of evolution, can detect recent positive selection when it operates on GRNs. Here, we propose a simulation framework, called EvoNET, that simulates forward-in-time the evolution of GRNs in a population. Since the population size is finite, random genetic drift is explicitly applied. The fitness of a mutation is not constant, but we evaluate the fitness of each individual by measuring its genetic distance from an optimal genotype. Mutations and recombination may take place from generation to generation, modifying the genotypic composition of the population. Each individual goes through a maturation period, where its GRN reaches equilibrium. At the next step, individuals compete to produce the next generation. As time progresses, the beneficial genotypes push the population higher in the fitness landscape. We examine properties of the GRN evolution such as robustness against the deleterious effect of mutations and the role of genetic drift. We confirm classical results from Andreas Wagner’s work that GRNs show robustness against mutations and we provide new results regarding the interplay between random genetic drift and natural selection.

Applications of Supercomputers in Population Genetics

2015 ◽  
pp. 176-200
Author(s):  
Gerard G. Dumancas
Keyword(s):  
Population Genetics ◽  
Natural Selection ◽  
Genetic Drift ◽  
Critical Role ◽  
Allele Frequency Distribution ◽  
Modern Approach ◽  
Mathematical Discipline ◽  
Modern Evolutionary Synthesis ◽  
Changes Over Time ◽  
Over Time

Population genetics is the study of the frequency and interaction of alleles and genes in population and how this allele frequency distribution changes over time as a result of evolutionary processes such as natural selection, genetic drift, and mutation. This field has become essential in the foundation of modern evolutionary synthesis. Traditionally regarded as a highly mathematical discipline, its modern approach comprises more than the theoretical, lab, and fieldwork. Supercomputers play a critical role in the success of this field and are discussed in this chapter.

scholarly journals The colours of humanity: the evolution of pigmentation in the human lineage

2017 ◽  
Vol 372 (1724) ◽  
pp. 20160349 ◽  
Author(s):  
Nina G. Jablonski ◽  
George Chaplin
Keyword(s):  
Natural Selection ◽  
Genetic Drift ◽  
Homo Sapiens ◽  
Skin Colour ◽  
Population Bottlenecks ◽  
Melanin Pigmentation ◽  
Evolutionary Forces ◽  
History Of ◽  
Skin Coloration ◽  
Perception Function

Humans are a colourful species of primate, with human skin, hair and eye coloration having been influenced by a great variety of evolutionary forces throughout prehistory. Functionally naked skin has been the physical interface between the physical environment and the human body for most of the history of the genus Homo , and hence skin coloration has been under intense natural selection. From an original condition of protective, dark, eumelanin-enriched coloration in early tropical-dwelling Homo and Homo sapiens , loss of melanin pigmentation occurred under natural selection as Homo sapiens dispersed into non-tropical latitudes of Africa and Eurasia. Genes responsible for skin, hair and eye coloration appear to have been affected significantly by population bottlenecks in the course of Homo sapiens dispersals. Because specific skin colour phenotypes can be created by different combinations of skin colour–associated genetic markers, loss of genetic variability due to genetic drift appears to have had negligible effects on the highly redundant genetic ‘palette’ for the skin colour. This does not appear to have been the case for hair and eye coloration, however, and these traits appear to have been more strongly influenced by genetic drift and, possibly, sexual selection. This article is part of the themed issue ‘Animal coloration: production, perception, function and application’.

scholarly journals Models of the population genetics of transposable elements

2005 ◽  
Vol 85 (3) ◽  
pp. 171-181 ◽  
Author(s):  
ARNAUD LE ROUZIC ◽  
GRÉGORY DECELIERE
Keyword(s):  
Population Genetics ◽  
Drosophila Melanogaster ◽  
Natural Selection ◽  
Transposable Elements ◽  
Genetic Drift ◽  
Self Regulation ◽  
Evolutionary Forces ◽  
Classical Models

Although transposable elements (TEs) have been found in all organisms in which they have been looked for, the ways in which they invade genomes and populations are still a matter of debate. By extending the classical models of population genetics, several approaches have been developed to account for the dynamics of TEs, especially in Drosophila melanogaster. While the formalism of these models is based on simplifications, they enable us to understand better how TEs invade genomes, as a result of multiple evolutionary forces including duplication, deletion, self-regulation, natural selection and genetic drift. The aim of this paper is to review the assumptions and the predictions of these different models by highlighting the importance of the specific characteristics of both the TEs and the hosts, and the host/TE relationships. Then, perspectives in this domain will be discussed.

scholarly journals The rate and molecular spectrum of mutation are selectively maintained in yeast

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Haoxuan Liu ◽  
Jianzhi Zhang
Keyword(s):  
Natural Selection ◽  
Genetic Drift ◽  
Fundamental Question ◽  
Molecular Spectrum ◽  
Mutational Bias ◽  
Stabilizing Selection ◽  
Deleterious Mutations ◽  
Random Mutation ◽  
Evolutionary Forces ◽  
Yeast Strains

AbstractWhat determines the rate (μ) and molecular spectrum of mutation is a fundamental question. The prevailing hypothesis asserts that natural selection against deleterious mutations has pushed μ to the minimum achievable in the presence of genetic drift, or the drift barrier. Here we show that, contrasting this hypothesis, μ substantially exceeds the drift barrier in diverse organisms. Random mutation accumulation (MA) in yeast frequently reduces μ, and deleting the newly discovered mutator gene PSP2 nearly halves μ. These results, along with a comparison between the MA and natural yeast strains, demonstrate that μ is maintained above the drift barrier by stabilizing selection. Similar comparisons show that the mutation spectrum such as the universal AT mutational bias is not intrinsic but has been selectively preserved. These findings blur the separation of mutation from selection as distinct evolutionary forces but open the door to alleviating mutagenesis in various organisms by genome editing.

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

Lankesteriana ◽  
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>

scholarly journals Contrasting the effects of natural selection, genetic drift and gene flow on urban evolution in white clover ( Trifolium repens )

2018 ◽  
Vol 285 (1883) ◽  
pp. 20181019 ◽  
Author(s):  
Marc T. J. Johnson ◽  
Cindy M. Prashad ◽  
Mélanie Lavoignat ◽  
Hargurdeep S. Saini
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
Genetic Drift ◽  
White Clover ◽  
Trifolium Repens ◽  
Rural Areas ◽  
Isolation By Distance ◽  
Urban Centre ◽  
Production Of Hydrogen ◽  
Urban Rural

Urbanization is a global phenomenon with profound effects on the ecology and evolution of organisms. We examined the relative roles of natural selection, genetic drift and gene flow in influencing the evolution of white clover ( Trifolium repens ), which thrives in urban and rural areas. Trifolium repens exhibits a Mendelian polymorphism for the production of hydrogen cyanide (HCN), a potent antiherbivore defence. We quantified the relative frequency of HCN in 490 populations sampled along urban–rural transects in 20 cities. We also characterized genetic variation within 120 populations in eight cities using 16 microsatellite loci. HCN frequency increased by 0.6% for every kilometre from an urban centre, and the strength of this relationship did not significantly vary between cities. Populations did not exhibit changes in genetic diversity with increasing urbanization, indicating that genetic drift is unlikely to explain urban–rural clines in HCN frequency. Populations frequently exhibited isolation-by-distance and extensive gene flow along most urban–rural transects, with the exception of a single city that exhibited genetic differentiation between urban and rural populations. Our results show that urbanization repeatedly drives parallel evolution of an ecologically important trait across many cities that vary in size, and this evolution is best explained by urban–rural gradients in natural selection.

Evolution of single characters in the Jurassic ammonite Kosmoceras

Paleobiology ◽  
1981 ◽  
Vol 7 (2) ◽  
pp. 200-215 ◽  
Author(s):  
David M. Raup ◽  
Rex E. Crick
Keyword(s):  
Random Walk ◽  
Natural Selection ◽  
Temporal Variation ◽  
Genetic Drift ◽  
Null Hypothesis ◽  
Morphological Characters ◽  
Biological Interpretation ◽  
Changes Over Time ◽  
Biometrical Study ◽  
Over Time

The classic biometrical study of phyletic evolution in Kosmoceras (Brinkmann 1929) is evaluated using unpublished raw data provided by Professor Brinkmann. Most morphological characters show statistically significant changes over time yet it is difficult to provide an unequivocal biological interpretation for these changes. In a few cases, runs tests indicate that evolution was nonrandom in the sense that fewer reversals in the direction of evolution occurred than would be predicted from a null hypothesis based on a random walk. These cases suggest persistence of natural selection regimes for fairly long periods of time. In other cases, and with other kinds of testing, the random walk model cannot be rejected although failure to reject the hypothesis does not justify its acceptance! Thus, the contribution of random factors (either genetic drift or selection in a randomly changing environment) cannot be assessed with confidence. It is problematical also whether the Kosmoceras series represent significant evolution by phyletic gradualism or just the natural temporal variation that characterizes stasis (sensu Eldredge and Gould 1972).

Evolution of animals and plants

1983 ◽  
Vol 83 ◽  
pp. 433-447
Author(s):  
R. J. Berry
Keyword(s):  
Gene Flow ◽  
Natural Selection ◽  
Ancestral Population ◽  
Species Differentiation ◽  
Clinal Variation ◽  
Evolutionary Forces ◽  
Lepidopteran Species ◽  
Outer Hebrides ◽  
Local Extinctions ◽  
Field Mice

SynopsisFifty years ago James Ritchie declared that “in recent times we are looking in Scotland upon Evolution in its course”. The basis for Ritchie's remark was the large number of distinct taxa which have been described on Scottish islands, mainly on the Outer Hebrides. The most effective ingredient in producing taxonomic distinctiveness is isolation, particularly when the isolated form is founded by a small group of organisms which will almost inevitably differ genetically from its ancestral population. Subsequent adaptation may produce divergence between two related but isolated groups, but the process of differentiation will be fairly slow, since natural selection must depend upon the inherited variation present, never mind consideration of evolutionary ‘cost’, etc.The Inner Hebrides are ecologically very diverse, but the gene-flow between animals and plants living on them and on the mainland of Scotland must be much greater than is the case for Outer Hebridean populations. Notwithstanding, subspecifically distinct races of field mice, voles, shrews, and stoats have been described, and clinal variation shows that adaptive changes have taken place in several bird and lepidopteran species.The Inner Hebrides offer excellent experimental opportunities to measure gene-flow between different islands, and between islands and mainland. It should be possible to estimate some of the evolutionary forces involved in producing species differentiation, as well as in local extinctions.

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