Genetic Variation Promotes Long‐Term Coexistence of Brassica nigra and Its Competitors

The effect of environment on adaptation and divergence was examined in two sets of populations of Escherichia coli selected for 1000 generations in either maltose- or glucose-limited media. Twelve replicate populations selected in maltose-limited medium improved in fitness in the selected environment, by an average of 22.5%. Statistically significant among-population genetic variation for fitness was observed during the course of the propagation, but this variation was small relative to the fitness improvement. Mean fitness in a novel nutrient environment, glucose-limited medium, improved to the same extent as in the selected environment, with no statistically significant among-population genetic variation. In contrast, 12 replicate populations previously selected for 1000 generations in glucose-limited medium showed no improvement, as a group, in fitness in maltose-limited medium and substantial genetic variation. This asymmetric pattern of correlated responses suggests that small changes in the environment can have profound effects on adaptation and divergence.

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The crucial role of genome-wide genetic variation in conservation

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2104642118 ◽

2021 ◽

Vol 118 (48) ◽

pp. e2104642118

Author(s):

Marty Kardos ◽

Ellie E. Armstrong ◽

Sarah W. Fitzpatrick ◽

Samantha Hauser ◽

Philip W. Hedrick ◽

...

Keyword(s):

Genetic Variation ◽

Environmental Changes ◽

Population Viability ◽

Adaptive Potential ◽

Biodiversity Crisis ◽

Genome Wide ◽

Simulation Based ◽

Functional Genetic Variation

The unprecedented rate of extinction calls for efficient use of genetics to help conserve biodiversity. Several recent genomic and simulation-based studies have argued that the field of conservation biology has placed too much focus on conserving genome-wide genetic variation, and that the field should instead focus on managing the subset of functional genetic variation that is thought to affect fitness. Here, we critically evaluate the feasibility and likely benefits of this approach in conservation. We find that population genetics theory and empirical results show that conserving genome-wide genetic variation is generally the best approach to prevent inbreeding depression and loss of adaptive potential from driving populations toward extinction. Focusing conservation efforts on presumably functional genetic variation will only be feasible occasionally, often misleading, and counterproductive when prioritized over genome-wide genetic variation. Given the increasing rate of habitat loss and other environmental changes, failure to recognize the detrimental effects of lost genome-wide genetic variation on long-term population viability will only worsen the biodiversity crisis.

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Artificial selection and maintenance of genetic variance in the global dairy cow population

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2005.1668 ◽

2005 ◽

Vol 360 (1459) ◽

pp. 1479-1488 ◽

Cited By ~ 50

Author(s):

S Brotherstone ◽

M Goddard

Keyword(s):

Genetic Variation ◽

Genetic Improvement ◽

Breeding Value ◽

Payment Systems ◽

Frozen Semen ◽

Best Linear Unbiased ◽

The Uk ◽

Selection Algorithms ◽

Global Population

Genetic improvement of dairy cows, which has increased the milk yield of cows in the UK by 1200 kg per lactation in 12 years, is an excellent example of the application of quantitative genetics to agriculture. The most important traits of dairy cattle are expressed only in females, but the main opportunity for selection is in males. Despite this, genetic improvement was achieved by the invention of a new statistical methodology, called ‘best linear unbiased prediction’ to estimate the breeding value of bulls. Intense selection of the best bulls, combined with the worldwide use of these bulls through artificial insemination and frozen semen, has created a global population and caused concern that the genetic variation available in the future will be reduced. Maintenance of genetic variation and long-term genetic gains would be aided by rational payment systems, use of crossbreeding where profitable, inclusion of all economically important traits in the breeding objective, recognition of genotype by environment interactions and the use of selection algorithms that balance estimated breeding value against the average relationship among the selected animals. Fortunately, all of these things are happening to some degree.

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Prevalence and Adaptive Impact of Introgression

Annual Review of Genetics ◽

10.1146/annurev-genet-021821-020805 ◽

2021 ◽

Vol 55 (1) ◽

Author(s):

Nathaniel B. Edelman ◽

James Mallet

Keyword(s):

Genetic Variation ◽

Adaptive Evolution ◽

Genetic Variants ◽

Genomic Data ◽

Annual Review ◽

Publication Date ◽

Adaptive Introgression ◽

Changing Environments ◽

Potential Benefits

Alleles that introgressed between species can influence the evolutionary and ecological fate of species exposed to novel environments. Hybrid offspring of different species are often unfit, and yet it has long been argued that introgression can be a potent force in evolution, especially in plants. Over the last two decades, genomic data have increasingly provided evidence that introgression is a critically important source of genetic variation and that this additional variation can be useful in adaptive evolution of both animals and plants. Here, we review factors that influence the probability that foreign genetic variants provide long-term benefits (so-called adaptive introgression) and discuss their potential benefits. We find that introgression plays an important role in adaptive evolution, particularly when a species is far from its fitness optimum, such as when they expand their range or are subject to changing environments. Expected final online publication date for the Annual Review of Genetics, Volume 55 is November 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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Evidence for long‐term prevalence of cucumber vein yellowing virus in Sudan and genetic variation of the virus in Sudan and the Mediterranean Basin

Plant Pathology ◽

10.1111/ppa.13055 ◽

2019 ◽

Vol 68 (7) ◽

pp. 1268-1275 ◽

Cited By ~ 3

Author(s):

C. Desbiez ◽

P. Caciagli ◽

C. Wipf‐Scheibel ◽

P. Millot ◽

L. Ruiz ◽

...

Keyword(s):

Genetic Variation ◽

Mediterranean Basin ◽

The Mediterranean ◽

The Mediterranean Basin ◽

Yellowing Virus

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The evolution and fate of diversity under hard and soft selection

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2020.1111 ◽

2020 ◽

Vol 287 (1934) ◽

pp. 20201111

Author(s):

Patrick Chen ◽

Rees Kassen

Keyword(s):

Genetic Variation ◽

Population Regulation ◽

Mixed Population ◽

General Mechanism ◽

Ecological Diversity ◽

Evolutionary Time ◽

Soft Selection ◽

Negative Frequency Dependent Selection ◽

Standing Question

How genetic variation arises and persists over evolutionary time despite the depleting effects of natural selection remains a long-standing question. Here, we investigate the impacts of two extreme forms of population regulation—at the level of the total, mixed population (hard selection) and at the level of local, spatially distinct patches (soft selection)—on the emergence and fate of diversity under strong divergent selection. We find that while the form of population regulation has little effect on rates of diversification, it can modulate the long-term fate of genetic variation, diversity being more readily maintained under soft selection compared to hard selection. The mechanism responsible for coexistence is negative frequency-dependent selection which, while present initially under both forms of population regulation, persists over the long-term only under soft selection. Importantly, coexistence is robust to continued evolution of niche specialist types under soft selection but not hard selection. These results suggest that soft selection could be a general mechanism for the maintenance of ecological diversity over evolutionary time scales.

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High genetic variation in leopards indicates large and long-term stable effective population size

Molecular Ecology ◽

10.1046/j.1365-294x.2000.01067.x ◽

2000 ◽

Vol 9 (11) ◽

pp. 1773-1782 ◽

Cited By ~ 45

Author(s):

G. Spong ◽

M. Johansson ◽

M. Björklund

Keyword(s):

Genetic Variation ◽

Population Size ◽

Effective Population Size ◽

Effective Population

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The breed structure and genetic analysis of the pedigree cattle breeds in Australia. III. The Hereford

Australian Journal of Agricultural Research ◽

10.1071/ar9630093 ◽

1963 ◽

Vol 14 (1) ◽

pp. 93 ◽

Cited By ~ 4

Author(s):

GP Davey ◽

JSF Barker

Keyword(s):

Genetic Variation ◽

Genetic Analysis ◽

Sampling Methods ◽

Rapid Expansion ◽

Genetic Contribution ◽

Genetic History ◽

Effective Generation ◽

History Of ◽

The One

(i) The structure and genetic history of the pedigree Hereford breed in Australia are analysed by pedigree sampling methods. (ii) The pattern of the breed structure is generally similar to that found in other breeds, but it is extremely dynamic owing to the present rapid expansion of the breed. Changes are taking place in the herd composition of the major breeders' groups and there are many new herds yet to find their level in the structure. (iii) Considerable emphasis has been placed on the use of imported animals in the development of the breed. Of all herds registering in Volume 24 of the herd book, 31.6% used imported sires, and the percentage of genes in the breed in 1949 derived from animals imported since 1880 was 97.7, and from animals imported since 1930, 53.9%. (iv) The most important herd in 1949 made a genetic contribution to the breed of 33.1%, while the contributions of the four next most important herds were 17.4, 10.1, 7.4, and 6.1%. In the four-generation pedigrees from which these figures were derived, the contribution of imported animals was 56.1%. (v) The animal with the highest relationship to the breed was Free Town Director (Imp.), with direct relationships of 5.6 and 9.2% to the 1941 and 1949 samples respectively. Of the 16 sires and one dam whose direct relationships are 3.0% or more in any of the three sample years, 12 sires were imported. (vi) The total inbreeding in 1949 (base year 1880) was 2.6%. This comprised 0.2% current inbreeding, 1.6% long-term inbreeding, and 0.8% strain inbreeding. There was no evidence of subdivision of the breed into separate strains. (vii) The effective generation length has decreased since 1930 to about 5.5 years in the 1949–50 sample. Nearly 50% of the animals in this sample were sired by bulls 4 years old or younger, while about 33% were from dams 4 years old or younger. (viii) Bulls from major breeders' herds are used widely throughout the breed, while about 90% of sires and 45% of dams were bred in herds other than the one in which they were used. Therefore, it is unlikely that there is much genetic variation between herds.

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