scholarly journals Selection versus random drift: long–term polymorphism persistence in small populations (evidence and modelling)

1997 ◽  
Vol 352 (1351) ◽  
pp. 381-389 ◽  
Author(s):  
E. Nevo ◽  
V. Kirzhner ◽  
A. Beiles ◽  
A. Korol
Keyword(s):  
Theoretical Models ◽  
Mutation Rates ◽  
Stabilizing Selection ◽  
Small Populations ◽  
Isolated Populations ◽  
Random Drift ◽  
Subterranean Mammal ◽  
Or Gene ◽  
Additive Genes

Our data on a subterranean mammal, Spalax ehrenbergi , and other evidence, indicate that appreciable polymorphism can be preserved in small isolated populations consisting of several dozens of, or a hundred, individuals. Current theoretical models predict fast gene fixation in small panmictic populations without selection, mutation, or gene inflow. Using simple multilocus models, we demonstrate here that moderate stabilizing selection (with stable or fluctuating optimum) for traits controlled by additive genes could oppose random fixation in such isolates during thousands of generations. We also show that in selection–free models polymorphism persists only for a few hundred generations even under high mutation rates. Our multi-chromosome models challenge the hitchhiking hypothesis of polymorphism maintenance for many neutral loci due to close linkage with few selected loci.

scholarly journals Mutator genomes decay, despite sustained fitness gains, in a long-term experiment with bacteria

2017 ◽  
Vol 114 (43) ◽  
pp. E9026-E9035 ◽  
Author(s):  
Alejandro Couce ◽  
Larissa Viraphong Caudwell ◽  
Christoph Feinauer ◽  
Thomas Hindré ◽  
Jean-Paul Feugeas ◽  
...  
Keyword(s):  
Evolutionary Biology ◽  
Mutation Accumulation ◽  
Mutation Rates ◽  
Weak Selection ◽  
Bacterial Genomes ◽  
Random Drift ◽  
Strong Linkage ◽  
Term Experiment ◽  
Long Term Experiment

Understanding the extreme variation among bacterial genomes remains an unsolved challenge in evolutionary biology, despite long-standing debate about the relative importance of natural selection, mutation, and random drift. A potentially important confounding factor is the variation in mutation rates between lineages and over evolutionary history, which has been documented in several species. Mutation accumulation experiments have shown that hypermutability can erode genomes over short timescales. These results, however, were obtained under conditions of extremely weak selection, casting doubt on their general relevance. Here, we circumvent this limitation by analyzing genomes from mutator populations that arose during a long-term experiment with Escherichia coli, in which populations have been adaptively evolving for >50,000 generations. We develop an analytical framework to quantify the relative contributions of mutation and selection in shaping genomic characteristics, and we validate it using genomes evolved under regimes of high mutation rates with weak selection (mutation accumulation experiments) and low mutation rates with strong selection (natural isolates). Our results show that, despite sustained adaptive evolution in the long-term experiment, the signature of selection is much weaker than that of mutational biases in mutator genomes. This finding suggests that relatively brief periods of hypermutability can play an outsized role in shaping extant bacterial genomes. Overall, these results highlight the importance of genomic draft, in which strong linkage limits the ability of selection to purge deleterious mutations. These insights are also relevant to other biological systems evolving under strong linkage and high mutation rates, including viruses and cancer cells.

scholarly journals Determining the factors driving selective effects of new nonsynonymous mutations

2016 ◽  
Author(s):  
Christian D. Huber ◽  
Bernard Kim ◽  
Clare D. Marsden ◽  
Kirk E. Lohmueller
Keyword(s):  
Natural Populations ◽  
Evolutionary Genetics ◽  
Theoretical Models ◽  
Geometrical Model ◽  
Stabilizing Selection ◽  
Fundamental Parameter ◽  
Mutational Robustness ◽  
Medical Genomics ◽  
Multiple Phenotypes

AbstractThe distribution of fitness effects (DFE) of new mutations is a fundamental parameter in evolutionary genetics1–3. While theoretical models have emphasized the importance of distinct biological factors, such as protein folding4, back mutations5, species complexity6,7, and mutational robustness8 at determining the DFE, it remains unclear which of these models can describe the DFE in natural populations. Here, we show that the theoretical models make distinct predictions about how the DFE will differ between species. We further show that humans have a higher proportion of strongly deleterious mutations than Drosophila melanogaster. Comparing four categories of theoretical models, only Fisher’s Geometrical Model (FGM) is consistent with our data. FGM assumes that multiple phenotypes are under stabilizing selection, with the number of phenotypes defining a complexity of the organism. It suggests that long-term population size and cost of complexity drive the evolution of the DFE, with many implications for evolutionary and medical genomics.

scholarly journals Determining the factors driving selective effects of new nonsynonymous mutations

2017 ◽  
Vol 114 (17) ◽  
pp. 4465-4470 ◽  
Author(s):  
Christian D. Huber ◽  
Bernard Y. Kim ◽  
Clare D. Marsden ◽  
Kirk E. Lohmueller
Keyword(s):  
Natural Populations ◽  
Evolutionary Genetics ◽  
Theoretical Models ◽  
Geometrical Model ◽  
Stabilizing Selection ◽  
Mutational Robustness ◽  
Medical Genomics ◽  
Multiple Phenotypes ◽  
Comparative Population

The distribution of fitness effects (DFE) of new mutations plays a fundamental role in evolutionary genetics. However, the extent to which the DFE differs across species has yet to be systematically investigated. Furthermore, the biological mechanisms determining the DFE in natural populations remain unclear. Here, we show that theoretical models emphasizing different biological factors at determining the DFE, such as protein stability, back-mutations, species complexity, and mutational robustness make distinct predictions about how the DFE will differ between species. Analyzing amino acid-changing variants from natural populations in a comparative population genomic framework, we find that humans have a higher proportion of strongly deleterious mutations than Drosophila melanogaster. Furthermore, when comparing the DFE across yeast, Drosophila, mice, and humans, the average selection coefficient becomes more deleterious with increasing species complexity. Last, pleiotropic genes have a DFE that is less variable than that of nonpleiotropic genes. Comparing four categories of theoretical models, only Fisher’s geometrical model (FGM) is consistent with our findings. FGM assumes that multiple phenotypes are under stabilizing selection, with the number of phenotypes defining the complexity of the organism. Our results suggest that long-term population size and cost of complexity drive the evolution of the DFE, with many implications for evolutionary and medical genomics.

Emotion Dysregulation in Autism Spectrum Disorder

2018 ◽  
pp. 282-298
Author(s):  
Emily Neuhaus
Keyword(s):  
Autism Spectrum Disorder ◽  
Social Communication ◽  
Educational Outcomes ◽  
Emotion Dysregulation ◽  
Research Priorities ◽  
Theoretical Models ◽  
Autism Spectrum ◽  
Repetitive Behaviors ◽  
Spectrum Disorder

Autism spectrum disorder (ASD) is defined by deficits in social communication and interaction, and restricted and repetitive behaviors and interests. Although current diagnostic conceptualizations of ASD do not include emotional difficulties as core deficits, the disorder is associated with emotion dysregulation across the lifespan, with considerable implications for long-term psychological, social, and educational outcomes. The overarching goal of this chapter is to integrate existing knowledge of emotion dysregulation in ASD and identify areas for further investigation. The chapter reviews the prevalence and expressions of emotion dysregulation in ASD, discusses emerging theoretical models that frame emotion dysregulation as an inherent (rather than associated) feature of ASD, presents neurobiological findings and mechanisms related to emotion dysregulation in ASD, and identifies continuing controversies and resulting research priorities.

scholarly journals We’re Not That Choosy: Emerging Evidence of a Progression Bias in Romantic Relationships

2021 ◽  
pp. 108886832110258
Author(s):  
Samantha Joel ◽  
Geoff MacDonald
Keyword(s):  
Romantic Relationships ◽  
Mate Selection ◽  
Theoretical Models ◽  
Romantic Partners ◽  
Test Phase ◽  
Relationship Development ◽  
Cultural Narrative ◽  
Relationship Initiation ◽  
Relationship Decisions

Dating is widely thought of as a test phase for romantic relationships, during which new romantic partners carefully evaluate each other for long-term fit. However, this cultural narrative assumes that people are well equipped to reject poorly suited partners. In this article, we argue that humans are biased toward pro-relationship decisions—decisions that favor the initiation, advancement, and maintenance of romantic relationships. We first review evidence for a progression bias in the context of relationship initiation, investment, and breakup decisions. We next consider possible theoretical underpinnings—both evolutionary and cultural—that may explain why getting into a relationship is often easier than getting out of one, and why being in a less desirable relationship is often preferred over being in no relationship at all. We discuss potential boundary conditions that the phenomenon may have, as well as its implications for existing theoretical models of mate selection and relationship development.

Capturing the dynamics of small populations: A retrospective assessment using long‐term data for an island reintroduction

2021 ◽  
Author(s):  
Doug P. Armstrong ◽  
Elizabeth H. Parlato ◽  
Barbara Egli ◽  
Wendy J. Dimond ◽  
Åsa Berggren ◽  
...  
Keyword(s):  
Small Populations ◽  
Retrospective Assessment ◽  
Term Data

scholarly journals Digital curation: the development of a discipline within information science

2018 ◽  
Vol 74 (6) ◽  
pp. 1318-1338 ◽  
Author(s):  
Sarah Higgins
Keyword(s):  
Information Science ◽  
Theoretical Models ◽  
Digital Information ◽  
Content Type ◽  
Digital Curation ◽  
The Usa ◽  
The Uk ◽  
Financial Ecology

Purpose Digital curation addresses the technical, administrative and financial ecology required to ensure that digital information remains accessible and usable over the long term. The purpose of this paper is to trace digital curation’s disciplinary emergence and examine its position within the information sciences domain in terms of theoretical principles, using a case study of developments in the UK and the USA. Design/methodology/approach Theoretical principles regarding disciplinary development and the identity of information science as a discipline are applied to a case study of the development of digital curation in the UK and the USA to identify the maturity of digital curation and its position in the information science gamut. Findings Digital curation is identified as a mature discipline which is a sub-meta-discipline of information science. As such digital curation has reach across all disciplines and sub-disciplines of information science and has the potential to become the overarching paradigm. Practical implications These findings could influence digital curation’s development from applied discipline to profession within both its educational and professional domains. Originality/value The disciplinary development of digital curation within dominant theoretical models has not hitherto been articulated.

Genetic Differentiation in Isolated Populations of Hakea carinata (Proteaceae)

1998 ◽  
Vol 46 (6) ◽  
pp. 671 ◽  
Author(s):  
G. J. Starr ◽  
S. M. Carthew
Keyword(s):  
Gene Flow ◽  
Habitat Fragmentation ◽  
Gene Diversity ◽  
South Australia ◽  
Similar Species ◽  
Isolated Populations ◽  
Plant Populations ◽  
Evolutionary Condition ◽  
Private Alleles

Fragmentation of the landscape by human activity has created small, isolated plant populations. Hakea carinata F. Muell. ex Meissner, a sclerophyllous shrub, is common in isolated fragments of vegetation in South Australia. This study investigated whether habitat fragmentation has caused restrictions to gene flow between populations. Gene diversity (HT = 0.317) is average for similar species but little is held within populations (HS = 0.168) and 46.9% of gene diversity is accounted for between populations. Estimates of gene flow are NM = 0.270 (based on FST) and NM = 0.129 (based on private alleles). Populations are substantially selfing (t = 0.111). Small isolated populations appears to be a long-term evolutionary condition in this species rather than a consequence of habitat fragmentation; however, population extinctions are occurring. Conservation will require the reservation of many populations to represent the genetic variation present in the species.

scholarly journals Evolutionary dynamics of neutral phenotypes under DNA substitution models

2020 ◽  
Author(s):  
Shadi Zabad ◽  
Alan M Moses
Keyword(s):  
Dna Sequences ◽  
Evolutionary Dynamics ◽  
Gc Content ◽  
Stabilizing Selection ◽  
Restoring Force ◽  
Dna Substitution ◽  
Long Term Trends ◽  
The Mean ◽  
Molecular Phenotypes

AbstractWe study the evolution of quantitative molecular traits in the absence of selection. Using a simple theory based on Felsenstein’s 1981 DNA substitution model, we predict a linear restoring force on the mean of an additive phenotype. Remarkably, the mean dynamics are independent of the effect sizes and genotype and are similar to the widely-used OU model for stabilizing selection. We confirm the predictions empirically using additive molecular phenotypes calculated from ancestral reconstructions of putatively unconstrained DNA sequences in primate genomes. We show that the OU model is favoured by inference software even when applied to GC content of unconstrained sequences or simulations of DNA evolution. We predict and confirm empirically that the dynamics of the variance are more complicated than those predicted by the OU model, and show that our results for the restoring force of mutation hold even for non-additive phenotypes, such as number of transcription factor binding sites, longest encoded peptide and folding propensity of the encoded peptide. Our results have implications for efforts to infer selection based on quantitative phenotype dynamics as well as to understand long-term trends in evolution of quantitative molecular traits.

scholarly journals Do Stress Trajectories Predict Mortality in Older Men? Longitudinal Findings from the VA Normative Aging Study

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Carolyn M. Aldwin ◽  
Nuoo-Ting Molitor ◽  
Avron Spiro ◽  
Michael R. Levenson ◽  
John Molitor ◽  
...  
Keyword(s):  
Allostatic Load ◽  
Stressful Life Events ◽  
High Stress ◽  
Theoretical Models ◽  
Growth Mixture Model ◽  
Growth Mixture ◽  
Aging Study ◽  
Health Related ◽  
The Relationship

We examined long-term patterns of stressful life events (SLE) and their impact on mortality contrasting two theoretical models: allostatic load (linear relationship) and hormesis (inverted U relationship) in 1443 NAS men (aged 41–87 in 1985;M= 60.30, SD = 7.3) with at least two reports of SLEs over 18 years (total observations = 7,634). Using a zero-inflated Poisson growth mixture model, we identified four patterns of SLE trajectories, three showing linear decreases over time with low, medium, and high intercepts, respectively, and one an inverted U, peaking at age 70. Repeating the analysis omitting two health-related SLEs yielded only the first three linear patterns. Compared to the low-stress group, both the moderate and the high-stress groups showed excess mortality, controlling for demographics and health behavior habits, HRs = 1.42 and 1.37,ps<.01and<.05. The relationship between stress trajectories and mortality was complex and not easily explained by either theoretical model.

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