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45 results for “asexual populations”
Data from: Habitat heterogeneity favors asexual reproduction in natural populations of grassthrips
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Data files for: Hazardous loss of genetic diversity through selective sweeps in asexual populations
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Data from: Facultative asexual reproduction and genetic diversity of populations in the humivorous termite Cavitermes tuberosus
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Supplemental data for article: DNA content variation and SNP diversity within a single population of asexual snails
<p>A growing body of research suggests that many clonal populations maintain genetic diversity even without occasional sexual reproduction. The purpose of our study was to document variation in SNP diversity, DNA content, and pathogen susceptibility in clonal lineages of the New Zealand freshwater snail, <em>Potamopyrgus antipodarum</em>. We studied snails that were collected from multiple field sites around a single lake (Lake Alexandrina), as well as isofemale clonal lineages that had been isolated and maintained in the laboratory. We used the KASP method to genotype our samples at 46 nuclear SNP sites, and we used flow cytometry to estimate DNA content. We found high levels of SNP diversity, both in our field samples and in our clonal laboratory lines. We also found evidence of high variation in DNA content among clones, even among clones with identical genotypes across all SNP sites. Controlled pathogen exposures of the laboratory populations revealed variation in susceptibility among distinct clonal genotypes, which was independent of DNA content. Taken together, these results show high levels of diversity among asexual snails, especially for DNA content, and they suggest rapid genome evolution in asexuals.</p>
Data from: Extreme genetic diversity in asexual grass thrips populations
The continuous generation of genetic variation has been proposed as one of the main factors explaining the maintenance of sexual reproduction in nature. However, populations of asexual individuals may attain high levels of genetic diversity through within-lineage diversification, replicate transitions to asexuality from sexual ancestors and migration. How these mechanisms affect genetic variation in populations of closely related sexual and asexual taxa can therefore provide insights into the role of genetic diversity for the maintenance of sexual reproduction. Here, we evaluate patterns of intra- and interpopulation genetic diversity in sexual and asexual populations of Aptinothrips rufus grass thrips. Asexual A. rufus populations are found throughout the world, whereas sexual populations appear to be confined to few locations in the Mediterranean region. We found that asexual A. rufus populations are characterized by extremely high levels of genetic diversity, both in comparison with their sexual relatives and in comparison with other asexual species. Migration is extensive among asexual populations over large geographic distances, whereas close sexual populations are strongly isolated from each other. The combination of extensive migration with replicate evolution of asexual lineages, and a past demographic expansion in at least one of them, generated high local clone diversities in A. rufus. These high clone diversities in asexual populations may mimic certain benefits conferred by sex via genetic diversity and could help explain the extreme success of asexual A. rufus populations.
Data from: Contrasting dynamics of a mutator allele in asexual populations of differing size
Mutators have been shown to hitchhike in asexual populations when the anticipated beneficial mutation supply rate of the mutator subpopulation, NU_b (for subpopulation of size N and beneficial mutation rate U_b) exceeds that of the wild-type subpopulation. Here, we examine the effect of total population size on mutator dynamics in asexual experimental populations of Saccharomyces cerevisiae. Although mutators quickly hitchhike to fixation in smaller populations, mutator fixation requires more and more time as population size increases; this observed delay in mutator hitchhiking is consistent with the expected effect of clonal interference. Interestingly, despite their higher beneficial mutation supply rate, mutators are supplanted by the wild type in very large populations. We postulate that this striking reversal in mutator dynamics is caused by an interaction between clonal interference, the fitness cost of the mutator allele, and infrequent large-effect beneficial mutations in our experimental populations. Our work thus identifies a potential set of circumstances under which mutator hitchhiking can be inhibited in natural asexual populations, despite recent theoretical predictions that such populations should have a net tendency to evolve ever-higher genomic mutation rates.
Data from: Evolutionary rescue of sexual and asexual populations in a deteriorating environment
The environmental change experienced by many contemporary populations of organisms poses a serious risk to their survival. From the theory of evolutionary rescue we predict that the combination of sex and genetic diversity should increase the probability of survival by increasing variation and thereby the probability of generating a type that can tolerate the stressful environment. We tested this prediction by comparing experimental populations of Chlamydomonas reinhardtii that differ in sexuality and in the initial amount of genetic diversity. The lines were serially propagated in an environment where the level of stress caused by salt increased over time from fresh water to the limits of marine conditions. In the long term, the combination of high diversity and obligate sexuality was most effective in supporting evolutionary rescue. Most of the adaptation to high-salt environments in the obligate sexual-high diversity lines had occurred by mid-way through the experiment, indicating that positive genetic correlations of adaptation to lethal stress with adaptation to sublethal stress greatly increased the probability of evolutionary rescue. The evolutionary rescue events observed in this study provide evidence that major shifts in ways of life can arise within short time frames through the action of natural selection in sexual populations.
Data from: Sex in an uncertain world: environmental stochasticity helps restore competitive balance between sexually and asexually reproducing populations
Like many organisms, individuals of the freshwater ostracod species Eucypris virens can have either obligate sexual or asexual reproductive modes. Both types of individual routinely co-occur, including in the same temporary freshwater pond (their natural habitat in which they undergo seasonal diapause). Given the well-known two-fold cost of sex, this begs the question of how sexually reproducing individuals are able to co-exist with their asexual counterparts in spite of such overwhelming costs. Environmental stochasticity in the form of "false dawn" inundations (where the first hydration is ephemeral and causes loss of early hatching individuals) may provide an advantage to the sexual subpopulation, which exhibits greater variation in hatching times following inundation. We explore the potential role of environmental stochasticity in this system using life-history data analysis, climate data and matrix projection models. In the absence of environmental stochasticity, the population growth rate is significantly lower in sexual subpopulations. Climate data reveal that "false dawn" inundations are common. Using matrix projection modeling with and without environmental stochasticity, we demonstrate that this phenomenon can restore appreciable balance to the system, in terms of growth rates. This provides support for the role of environmental stochasticity in helping to explain the maintenance of sex and the occurrence of geographic parthenogenesis.
Data from: Fixation of mutators in asexual populations: the role of genetic drift and epistasis
We study the evolutionary dynamics of an asexual population of nonmutators and mutators on a class of epistatic fitness landscapes. We consider the situation in which all mutations are deleterious and mutators are produced from nonmutators continually at a constant rate. We find that in an infinitely large population, a minimum nonmutator-to-mutator conversion rate is required to fix the mutators but an arbitrarily small conversion rate results in the fixation of mutators in a finite population. We calculate analytical expressions for the mutator fraction at mutation-selection balance and fixation time for mutators in a finite population when the difference between the mutation rate for mutator and nonmutator is smaller (regime I) and larger (regime II) than the selection coefficient. Our main result is that in regime I, the mutator fraction and the fixation time are independent of epistasis but in regime II, mutators are rarer and take longer to fix when the decrease in fitness with the number of deleterious mutations occurs at an accelerating rate (synergistic epistasis) than at a diminishing rate (antagonistic epistasis). Our analytical results are compared with numerics and their implications are discussed.
Data from: Elevated genetic diversity of mitochondrial genes in asexual populations of bark lice ("Psocoptera": Echmepteryx hageni)
Asexual reproduction is commonly thought to be associated with low genetic diversity in animals. Echmepteryx hageni (Insecta: "Psocoptera") is one of several psocopteran species that are primarily parthenogenetic, but also exists in small, isolated sexual populations. We used mitochondrial DNA sequences to investigate the population history and genealogical relationships between the sexual and asexual forms of this species. The asexual population of E. hageni exhibits extremely high mitochondrial haplotype diversity (H = 0.98), whereas the sexual forms had significantly lower haplotypic diversity (H = 0.25, after correcting for sample size). This diversity in asexuals represents one the greatest genetic diversities reported for asexual animals in the literature. Nucleotide diversities were also higher in asexual compared to sexual populations (π = 0.0071 vs. 0.00027). Compared to other reported estimates of π in insects, asexual nucleotide diversity is high, but not remarkably elevated. Three hypotheses might explain the elevated genetic diversity of asexual populations: 1) larger effective population size, 2) greater mutation rate, or 3) possible recent origin of sexuals. In addition, phylogeographic analysis revealed little geographic structure among asexual E. hageni, although specimens from the upper Midwest form a single clade and are genetically differentiated. The mismatch distribution and neutrality tests indicate a historical population size increase, possibly associated with expansion from glacial refugia.
Data from: Elevated genetic diversity of mitochondrial genes in asexual populations of bark lice ("Psocoptera": Echmepteryx hageni)
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Data from: The effect of population bottlenecks on mutation rate evolution in asexual populations
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Data from: Asexual reproduction in introduced and native populations of the ant Cerapachys biroi
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Data from: Variation and correlations between sexual, asexual and natural enemy resistance life-history traits in a natural plant pathogen population
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Data from: Evolutionary rescue of sexual and asexual populations in a deteriorating environment
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Data from: Virus epidemics can lead to a population-wide spread of intragenomic parasites in a previously parasite-free asexual population
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Data from: Evolutionary dynamics of a quantitative trait in a finite asexual population
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Data from: Extreme genetic diversity in asexual grass thrips populations
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Supplemental data for article: DNA content variation and SNP diversity within a single population of asexual snails
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Data from: Fixation of mutators in asexual populations: the role of genetic drift and epistasis
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Allen Brain Atlas
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DANDI Archive for NWB datasets
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International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.