scholarly journals Amitosis confers benefits of sex in the absence of sex to Tetrahymena

2019 ◽  
Author(s):  
Hao Zhang ◽  
Joe A. West ◽  
Rebecca A. Zufall ◽  
Ricardo B. R. Azevedo
Keyword(s):  
Genetic Variation ◽  
Copy Number ◽  
Environmental Changes ◽  
Nuclear Division ◽  
Biotic Interactions ◽  
Deleterious Mutations ◽  
Mutation Load ◽  
Low Expectations ◽  
Genetic Mechanisms

Sex appears to be the most successful reproductive strategy in eukaryotes despite its many costs1–3. While a complete explanation for sex’s success remains elusive, several evolutionary benefits of sex have been identified4, 5, such as, the purging of deleterious mutations6, 7, the accumulation of beneficial mutations8, 9, and an advantage in biotic interactions3, 10, 11. It is predicted that, by forgoing these benefits, asexual lineages are evolutionary dead-ends2, 12 due to genetic deterioration and/or an inability to adapt to environmental changes. Consistent with this prediction, many asexual lineages show signs of accelerated accumulation of deleterious mutations compared to their sexual relatives13–18. Despite these low expectations, some asexual eukaryotic lineages appear to be successful, including the ciliate Tetrahymena19. Here, we show that the mechanism of somatic nuclear division in Tetrahymena, termed amitosis, provides benefits similar to sex, allowing for the long-term success of asexual lineages. We found that, when compared to mitosis, amitosis with chromosome copy number control reduces mutation load deterministically, slows the accumulation of deleterious mutations under genetic drift, and accelerates adaptation. These benefits arise because, like sex, amitosis can generate substantial genetic variation in fitness among (asexual) progeny. Our results indicate that the ability of Tetrahymena to persist in the absence of sex may depend on non-sexual genetic mechanisms conferring benefits typically provided by sex, as has been found in other asexual lineages20–23.

scholarly journals The crucial role of genome-wide genetic variation in conservation

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.

scholarly journals The crucial role of genome-wide genetic variation in conservation

2021 ◽  
Author(s):  
Martin Kardos ◽  
Ellie Armstrong ◽  
Sarah W Fitzpatrick ◽  
Samantha Hauser ◽  
Philip 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 the conservation of genome-wide genetic variation, and that this approach should be replaced with another that focuses instead 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 the conserving genome-wide genetic variation is generally the best approach to prevent inbreeding depression and loss of adaptive potential from driving populations towards 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 variation on long-term population viability will only worsen the biodiversity crisis.

scholarly journals Long-Term Environmental Monitoring in an Arctic Lake Polluted by Metals under Climate Change

Environments ◽  
2020 ◽  
Vol 7 (5) ◽  
pp. 34 ◽  
Author(s):  
Elena M. Zubova ◽  
Nikolay A. Kashulin ◽  
Vladimir A. Dauvalter ◽  
Dmitry B. Denisov ◽  
Svetlana A. Valkova ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Biotic Interactions ◽  
Aquatic Organisms ◽  
Polluted Water ◽  
Ecological Niches ◽  
Murmansk Region ◽  
Large Populations ◽  
High Concentrations ◽  
Taxonomic Groups

Lake Kuetsjarvi (in the lower reaches of the Pasvik River, Murmansk Region, Russia) in the border area between Russia and Norway, is one of the most polluted water reservoirs in the European Arctic. The operation of the Pechenganikel Smelter located on its shores has led to the extremely high concentrations of heavy metals observed in the waters and sediments of the lake. Long-term comprehensive studies of the ecosystem of Lake Kuetsjarvi have made it possible to identify the response of its components to the global and regional change in the environment and climate as a whole, resulting in increased water toxicity and eutrophication, reduction in the number of stenobiont species of aquatic organisms against the background of an increase in the number of eurybiontic and invasive species. Modern communities of Lake Kuetsjarvi are the result of a combination of long-term changes in the abiotic environment and biotic interactions. Heavy-metal pollution of Lake Kuetsjarvi, observed since the 1930s, has led to the formation of a community that is resistant to this type of impact and supports large populations of adapted species. Adaptations of communities to the dynamics of the environmental conditions that their members are exposed to include changes in the species composition, quantitative indicators, ratios between individual taxonomic groups, and the population structure. The development of sympatric forms that differ in the ecological niches they occupy, morphology, and life cycle strategies, including the transition to a short-cycle survival strategy, allows whitefish to remain the dominant species and maintain high population numbers. Unlike the organismal level, responses to medium-term environmental changes on the population and community level are less specific and characterized by stronger inertia.

scholarly journals Cryptic genetic variation accelerates evolution by opening access to diverse adaptive peaks

Science ◽  
2019 ◽  
Vol 365 (6451) ◽  
pp. 347-353 ◽  
Author(s):  
Jia Zheng ◽  
Joshua L. Payne ◽  
Andreas Wagner
Keyword(s):  
Genetic Variation ◽  
Fluorescent Proteins ◽  
Adaptive Landscape ◽  
Deleterious Mutations ◽  
Historical Contingency ◽  
Green Fluorescence ◽  
Cryptic Genetic Variation ◽  
Adaptive Mutations ◽  
Cryptic Variation ◽  
Genetic Mechanisms

Cryptic genetic variation can facilitate adaptation in evolving populations. To elucidate the underlying genetic mechanisms, we used directed evolution in Escherichia coli to accumulate variation in populations of yellow fluorescent proteins and then evolved these proteins toward the new phenotype of green fluorescence. Populations with cryptic variation evolved adaptive genotypes with greater diversity and higher fitness than populations without cryptic variation, which converged on similar genotypes. Populations with cryptic variation accumulated neutral or deleterious mutations that break the constraints on the order in which adaptive mutations arise. In doing so, cryptic variation opens paths to adaptive genotypes, creates historical contingency, and reduces the predictability of evolution by allowing different replicate populations to climb different adaptive peaks and explore otherwise-inaccessible regions of an adaptive landscape.

scholarly journals Evidence of long-term purging of mutation load in killer whale genomes

2021 ◽  
Author(s):  
Andrew D. Foote ◽  
M. Thomas P. Gilbert ◽  
Shyam Gopalakrishnan ◽  
Marie Louis ◽  
Michael D. Martin ◽  
...  
Keyword(s):  
North Atlantic ◽  
High Latitude ◽  
Late Holocene ◽  
Killer Whale ◽  
Deleterious Mutations ◽  
Mutation Load ◽  
Synonymous Mutations ◽  
Standing Variation ◽  
Founder Populations

AbstractGenomes of high latitude killer whales harbour signatures of post-glacial founding and expansion. Here, we investigate whether reduced efficacy of selection increased mutation load in founder populations, or whether recessive deleterious mutations exposed to selection in homozygous genotypes were purged. Comparing the accumulation of synonymous and non-synonymous mutations across pairs of globally sampled genomes reveals that the most significant outliers are high latitude North Atlantic genomes, which have accumulated significantly fewer non-synonymous mutations than all other populations. Comparisons with the genome of a 7.5-Kyr-old North Atlantic killer whale, inferred to be closely related to the population directly ancestral to present-day Icelandic and Norwegian populations, calibrates the timing of the action of selection on non-synonymous mutations predominantly to the mid-late Holocene. Non-synonymous mutations purged in modern Norwegian killer whale genomes are found as globally shared standing variation in heterozygote genotypes more often than expected, suggesting overdominance. Taken together, our findings are consistent with purging of recessive non-synonymous mutations exposed to selection in founder-associated homozygous genotypes.

scholarly journals Selection in males purges the standing genetic load on female fitness

2020 ◽  
Author(s):  
Karl Grieshop ◽  
Paul L. Maurizio ◽  
Göran Arnqvist ◽  
David Berger
Keyword(s):  
Genetic Variation ◽  
Callosobruchus Maculatus ◽  
Diallel Cross ◽  
Inbred Strains ◽  
Deleterious Mutations ◽  
Male Fitness ◽  
Mutation Load ◽  
Female Fitness ◽  
Deleterious Alleles ◽  
Males And Females

AbstractTheory predicts that the ability of selection and recombination to purge mutation load is enhanced if selection against deleterious genetic variants operates more strongly in males than females. However, direct empirical support for this tenet is limited, perhaps because traditional quantitative genetic approaches allow dominance and intermediate-frequency polymorphisms to obscure the effects of rare and partially recessive deleterious alleles that make up the main part of a population’s mutation load. Here, we exposed the mutation load of a population of Callosobruchus maculatus seed beetles via successive generations of inbreeding, and quantified its effects by measuring heterosis – the increase in fitness upon the masking of deleterious alleles by heterozygosity – in a fully factorial sex-specific diallel cross among 16 inbred strains. Competitive lifetime reproductive success (i.e. fitness) was measured in male and female outcrossed F1s as well as inbred parental ‘selfs’, and we estimated the 4×4 male-female inbred-outbred genetic covariance matrix (G) for fitness using Bayesian Markov chain Monte Carlo simulations of a custom-made general linear mixed effects model. We found that heterosis estimated in males and females was highly correlated among strains, and that heterosis was strongly negatively correlated to strains’ outcrossed breeding values for male fitness, but not female fitness. This suggests that the additive genetic variation for fitness in the males, but not females, of this population reflect the amount of (partially) recessive deleterious alleles segregating at mutation-selection balance, and that the population’s mutation load therefore has greater potential to be purged via selection in males. These findings contribute to our understanding of the prevalence of sexual reproduction in nature and the maintenance of genetic variation in fitness-related traits.Impact statementA mainstay evolutionary question has been: why do the large majority of eukaryotic species reproduce sexually if such females must spend half of their reproductive effort producing sons, which produce no offspring themselves? In principle, a lineage of a mutant asexual female that simply clones herself into daughters would grow at twice the rate of her sexual competitors (all else equal). What prevents this from being the predominant mode of reproduction throughout eukaryotes? One category of hypotheses regards the role of males in facilitating the purging of deleterious mutations from the population’s genome since very strong selection in males, unlike females, can occur in many species without direct consequence to population offspring numbers. Due to the inherent difficulties of detecting selection on segregating genetic variation, empirical evidence for this theory is limited to indirect evidence from manipulative experiments and experimental evolution studies. Here we demonstrate that the standing deleterious allelic variation in a population of the seed beetle, Callosobruchus maculatus, is selected against strongly in males but not females. Using a fully factorial diallel cross among 16 inbred strains, we measured the degree to which fitness in the outbred offspring of those crosses improved relative to their inbred parents. This measure is known as heterosis and offers an estimate of the relative number of deleterious alleles carried among strains. We then analyzed the relationship between strains’ heterosis values and their sex-specific additive genetic breeding values for fitness, revealing the extent to which those segregating deleterious alleles are selected against in males and females. We found that strains heterosis values were strongly correlated with male fitness, but not female fitness. This demonstrates that the population’s deleterious mutations can be efficiently selected against (i.e. purged) via selection in males. This process would offer a benefit to sexual reproduction that may outweigh its costs, and therefore yields insight to the prevalence of sex in nature.

Designing a CRM Framework for online & offline sports footwear retailers

2015 ◽  
Vol 3 (1) ◽  
Author(s):  
Rodrigo Cueva ◽  
Guillem Rufian ◽  
Maria Gabriela Valdes
Keyword(s):  
Environmental Changes ◽  
Customer Relationship ◽  
Business Strategies ◽  
Economic Sectors ◽  
Running Shoes ◽  
Brick And Mortar ◽  
Key Factor ◽  
On Line ◽  
The Impact

The use of Customer Relationship Managers to foster customers loyalty has become one of the most common business strategies in the past years.  However, CRM solutions do not fill the abundance of happily ever-after relationships that business needs, and each client’s perception is different in the buying process.  Therefore, the experience must be precise, in order to extend the loyalty period of a customer as much as possible. One of the economic sectors in which CRM’s have improved this experience is retailing, where the personalized attention to the customer is a key factor.  However, brick and mortar experiences are not enough to be aware in how environmental changes could affect the industry trends in the long term.  A base unified theoretical framework must be taken into consideration, in order to develop an adaptable model for constructing or implementing CRMs into companies. Thanks to this approximation, the information is complemented, and the outcome will increment the quality in any Marketing/Sales initiative. The goal of this article is to explore the different factors grouped by three main domains within the impact of service quality, from a consumer’s perspective, in both on-line and off-line retailing sector.  Secondly, we plan to go a step further and extract base guidelines about previous analysis for designing CRM’s solutions focused on the loyalty of the customers for a specific retailing sector and its product: Sports Running Shoes.

scholarly journals Long-Term Experimental Evolution in Escherichia coli. VI. Environmental Constraints on Adaptation and Divergence

Genetics ◽  
1997 ◽  
Vol 146 (2) ◽  
pp. 471-479 ◽  
Author(s):  
Michael Travisano
Keyword(s):  
Escherichia Coli ◽  
Genetic Variation ◽  
Experimental Evolution ◽  
Population Genetic ◽  
Environmental Constraints ◽  
Asymmetric Pattern ◽  
Nutrient Environment ◽  
Mean Fitness ◽  
Population Genetic Variation

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.

Past testate amoeba communities in landslide mountain fens (Polish Carpathians): The relationship between shell types and sediment

The Holocene ◽  
2021 ◽  
pp. 095968362199464
Author(s):  
Katarzyna Marcisz ◽  
Krzysztof Buczek ◽  
Mariusz Gałka ◽  
Włodzimierz Margielewski ◽  
Matthieu Mulot ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Testate Amoebae ◽  
Mineral Matter ◽  
Testate Amoeba ◽  
Run Off ◽  
Number Of Factors ◽  
Depth To Water Table ◽  
Polish Carpathians ◽  
The Relationship

Landslide mountain fens formed in landslide depressions are dynamic environments as their development is disturbed by a number of factors, for example, landslides, slopewash, and surface run-off. These processes lead to the accumulation of mineral material and wood in peat. Disturbed peatlands are interesting archives of past environmental changes, but they may be challenging for providing biotic proxy-based quantitative reconstructions. Here we investigate long-term changes in testate amoeba communities from two landslide mountain fens – so far an overlooked habitat for testate amoeba investigations. Our results show that abundances of testate amoebae are extremely low in this type of peatlands, therefore not suitable for providing quantitative depth-to-water table reconstructions. However, frequent shifts of dominant testate amoeba species reflect dynamic lithological situation of the studied fens. We observed that high and stable mineral matter input into the peatlands was associated with high abundances of species producing agglutinated (xenosomic) as well as idiosomic shells which prevailed in the testate amoeba communities in both analyzed profiles. This is the first study that explores testate amoebae of landslide mountain fens in such detail, providing novel information about microbial communities of these ecosystems.

Sign in / Sign up

Export Citation Format

Share Document