scholarly journals Somatic genetic drift and multi-level selection in modular species

2019 ◽  
Author(s):  
Lei Yu ◽  
Christoffer Boström ◽  
Sören Franzenburg ◽  
Till Bayer ◽  
Tal Dagan ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Genetic Drift ◽  
Purifying Selection ◽  
Cellular Level ◽  
Population Bottlenecks ◽  
Multi Level ◽  
Multiple Levels ◽  
Level Of Selection ◽  
Multicellular Organisms ◽  
Clonal Species

AbstractCells in multicellular organisms are genetically heterogeneous owing to somatic mutations. The accumulation of somatic genetic variation in species undergoing asexual (or clonal) reproduction (termed modular species) may lead to phenotypic heterogeneity among modules. However, abundance and dynamics of somatic genetic variation under clonal growth, a widespread life history in nature, remain poorly understood. Here we show that branching events in a seagrass clone or genet leads to population bottlenecks at the cellular level and hence the evolution of genetically differentiated modules. Studying inter-module somatic genetic variation, we uncovered thousands of SNPs that segregated among modules. The strength of purifying selection on mosaic genetic variation was greater at the intra-module comparing with the inter-module level. Our study provides evidence for the operation of selection at multiple levels, of cell population and modules. Somatic genetic drift leads to the emergence of genetically unique modules; hence, modules in long-lived clonal species constitute an appropriate elementary level of selection and individuality.

scholarly journals Transmission of SARS-CoV-2 in domestic cats imposes a narrow bottleneck

2020 ◽  
Author(s):  
Katarina M. Braun ◽  
Gage K. Moreno ◽  
Peter J. Halfmann ◽  
Emma B. Hodcroft ◽  
David A. Baker ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Monoclonal Antibodies ◽  
Positive Selection ◽  
Genetic Drift ◽  
Purifying Selection ◽  
Amino Acid Position ◽  
Domestic Cats ◽  
Human Monoclonal Antibodies ◽  
Evolutionary Mechanisms ◽  
Context Specific

AbstractThe evolutionary mechanisms by which SARS-CoV-2 viruses adapt to mammalian hosts and, potentially, undergo antigenic evolution depend on the ways genetic variation is generated and selected within and between individual hosts. Using domestic cats as a model, we show that SARS-CoV-2 consensus sequences remain largely unchanged over time within hosts, while dynamic sub-consensus diversity reveals processes of genetic drift and weak purifying selection. We further identify a notable variant at amino acid position 655 in Spike (H655Y), which was previously shown to confer escape from human monoclonal antibodies. This variant arises rapidly and persists at intermediate frequencies in index cats. It also becomes fixed following transmission in two of three pairs. These dynamics suggest this site may be under positive selection in this system and illustrate how a variant can quickly arise and become fixed in parallel across multiple transmission pairs. Transmission of SARS-CoV-2 in cats involved a narrow bottleneck, with new infections founded by fewer than ten viruses. In RNA virus evolution, stochastic processes like narrow transmission bottlenecks and genetic drift typically act to constrain the overall pace of adaptive evolution. Our data suggest that here, positive selection in index cats followed by a narrow transmission bottleneck may have instead accelerated the fixation of S H655Y, a potentially beneficial SARS-CoV-2 variant. Overall, our study suggests species- and context-specific adaptations are likely to continue to emerge. This underscores the importance of continued genomic surveillance for new SARS-CoV-2 variants as well as heightened scrutiny for signatures of SARS-CoV-2 positive selection in humans and mammalian model systems.Author summaryThrough ongoing human adaptation, spill-back events from other animal intermediates, or with the distribution of vaccines and therapeutics, the landscape of SARS-CoV-2 genetic variation is certain to change. The evolutionary mechanisms by which SARS-CoV-2 will continue to adapt to mammalian hosts depend on genetic variation generated within and between hosts. Here, using domestic cats as a model, we show that within-host SARS-CoV-2 genetic variation is predominantly influenced by genetic drift and purifying selection. Transmission of SARS-CoV-2 between hosts is defined by a narrow transmission bottleneck, involving 2-5 viruses. We further identify a notable variant at amino acid position 655 in Spike (H655Y), which arises rapidly and is transmitted in cats. Spike H655Y has been previously shown to confer escape from human monoclonal antibodies and is currently found in over 1000 human sequences. Overall, our study suggests species- and context-specific adaptations are likely to continue to emerge, underscoring the importance of continued genomic surveillance in humans and non-human mammalian hosts.

The Consequences of Accounting Failure for Innovation: A Multi-Level Analysis

2020 ◽  
Vol 34 (2) ◽  
pp. 109-124
Author(s):  
Megan F. Hess ◽  
Andrew M. Hess
Keyword(s):  
Firm Level ◽  
Psychological Response ◽  
Top Executives ◽  
Innovation Activities ◽  
Threat Rigidity ◽  
Multi Level ◽  
Multiple Levels ◽  
Financial Misconduct ◽  
Public Disclosures ◽  
Level Analysis

SYNOPSIS In this study, we investigate the relation between accounting failure and innovation at multiple levels in an organization by developing and testing a model for how top executives and functional managers might change their risk preferences and their innovation investments in response to public disclosures of financial misconduct. At the firm level, we find that accounting failures reduce subsequent investments in R&D, as predicted by a threat rigidity (“play it safe”) psychological response among top executives. At the project level, accounting failures have the opposite effect, resulting in an increase in the number of exploratory projects, as predicted by a failure trap (“swing for the fences”) psychological response among functional managers. Unpacking this relation at multiple levels of analysis helps us to understand the complex ways in which financial misconduct shapes a firm's innovation activities and appreciate the far-reaching consequences of accounting failure.

Genetic variation in allozymes of western larch

1986 ◽  
Vol 16 (5) ◽  
pp. 1013-1018 ◽  
Author(s):  
Lauren Fins ◽  
Lisa W. Seeb
Keyword(s):  
Genetic Variation ◽  
Genetic Drift ◽  
Fire History ◽  
Glacial History ◽  
Geographic Proximity ◽  
Electrophoretic Variation ◽  
Inland Empire ◽  
Genetic History ◽  
Expected Heterozygosity ◽  
History Of

Seed samples from 19 stands of Larixoccidentalis Nutt. were analyzed for electrophoretic variation at 23 loci. Because sample sizes consisted of only 9 or 10 trees per stand (18–20 alleles per locus per stand), samples were grouped by geographic proximity into four larger samples. For all measures of variation, this species scored lower than most, but within the range observed for other western conifers. Most of the variation was found within rather than between the population groups. The single southern sample appeared to be genetically distinct from the others. Although some variation was observed between individual stand samples in expected heterozygosity, the consistently low values for all samples suggest that genetic drift has played a major role in the genetic history of the species in the Inland Empire, both through its glacial history in postulated refugia and through fire history in recent times.

The Causal Structure of Natural Selection

2021 ◽  
Author(s):  
Charles H. Pence
Keyword(s):  
Natural Selection ◽  
Case Studies ◽  
Genetic Drift ◽  
Evolutionary Theory ◽  
Causal Structure ◽  
Philosophy Of Biology ◽  
Philosophy Of Physics ◽  
Potential Value ◽  
Multi Level ◽  
Evolutionary Explanations

Recent arguments concerning the nature of causation in evolutionary theory, now often known as the debate between the 'causalist' and 'statisticalist' positions, have involved answers to a variety of independent questions – definitions of key evolutionary concepts like natural selection, fitness, and genetic drift; causation in multi-level systems; or the nature of evolutionary explanations, among others. This Element offers a way to disentangle one set of these questions surrounding the causal structure of natural selection. Doing so allows us to clearly reconstruct the approach that some of these major competing interpretations of evolutionary theory have to this causal structure, highlighting particular features of philosophical interest within each. Further, those features concern problems not exclusive to the philosophy of biology. Connections between them and, in two case studies, contemporary metaphysics and philosophy of physics demonstrate the potential value of broader collaboration in the understanding of evolution.

scholarly journals Who are "the people" in the German Constitution? A critique of , and contribution to , the debate about the right of foreigners to vote in multilevel democracies

2020 ◽  
Vol 24 ◽  
Author(s):  
Jelena Bäumler
Keyword(s):  
South Africa ◽  
Voting Rights ◽  
Constitutional Court ◽  
Federal States ◽  
The People ◽  
German Constitution ◽  
Multi Level ◽  
Multiple Levels ◽  
Right To Vote ◽  
The Right

ABSTRACT Democracy means power to the people, but it is not always clear who belongs to "the people". The question has become pertinent in the age of migration where large groups of foreigners permanently reside outside their countries of nationality. The economic, cultural, and political integration of these foreigners is one of the pressing problems faced by democratic States in both the developed and developing worlds. One question is : whether resident non-citizens should be granted the right to vote. The answer to this question depends on who belongs to "the people". In federal and quasi-federal States with multiple levels of government the further question arises : whether "the people" is a homogenous concept that applies uniformly across all levels of government. This article contributes to the debate about the right of foreigners to vote in democratic States with multiple levels of government, such as, South Africa and Kenya. It does so by discussing the German response to the problems mentioned above. The dominant view of the German Federal Constitutional Court since the 1990s has been that "the people" only includes "German citizens" , and that attempts by lower levels of government to extend the right to vote to foreigners from Africa and elsewhere are unconstitutional. In this article I explore and critique this conventional view. I then present a positive case for the extension of voting rights to resident non-citizens under the German Constitution. Many of the arguments would apply with equal force to the debate about the right to vote of foreigners in African multi-level democracies, such as, South Africa and Kenya. Keywords: Denizenship, Citizenship, Voting rights, Nationality law, Multi-level government, The people, Foreigners, Residents, Affected persons principle, Democracy.

scholarly journals An organ-based multi-level model for glucose homeostasis: organ distributions, timing, and impact of blood flow

2020 ◽  
Author(s):  
Tilda Herrgårdh ◽  
Hao Li ◽  
Elin Nyman ◽  
Gunnar Cedersund
Keyword(s):  
Blood Flow ◽  
Glucose Homeostasis ◽  
Statistical Tests ◽  
Cellular Level ◽  
Whole Body ◽  
Response Curves ◽  
Future Data ◽  
Level Model ◽  
Multi Level ◽  
Original Cell

AbstractGlucose homeostasis is the tight control of glucose in the blood. This complex control is important and not yet sufficiently understood, due to its malfunction in serious diseases like diabetes. Due to the involvement of numerous organs and sub-systems, each with their own intra-cellular control, we have developed a multi-level mathematical model, for glucose homeostasis, which integrates a variety of data. Over the last 10 years, this model has been used to insert new insights from the intra-cellular level into the larger whole-body perspective. However, the original cell-organ-body translation has during these years never been updated, despite several critical shortcomings, which also have not been resolved by other modelling efforts. For this reason, we here present an updated multi-level model. This model provides a more accurate sub-division of how much glucose is being taken up by the different organs. Unlike the original model, we now also account for the different dynamics seen in the different organs. The new model also incorporates the central impact of blood flow on insulin-stimulated glucose uptake. Each new improvement is clear upon visual inspection, and they are also supported by statistical tests. The final multi-level model describes >300 data points in >40 time-series and dose-response curves, resulting from a large variety of perturbations, describing both intra-cellular processes, organ fluxes, and whole-body meal responses. We hope that this model will serve as an improved basis for future data integration, useful for research and drug developments within diabetes.

scholarly journals Conservation genetics of the threatened plant species Physaria filiformis (Missouri bladderpod) reveals strong genetic structure and a possible cryptic species

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0247586
Author(s):  
Christine E. Edwards ◽  
Brooke C. Tessier ◽  
Joel F. Swift ◽  
Burgund Bassüner ◽  
Alexander G. Linan ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Genetic Variation ◽  
Genetic Structure ◽  
Plant Species ◽  
Genetic Drift ◽  
Rare Species ◽  
Ex Situ ◽  
Ouachita Mountains ◽  
Genetic Diversity And Structure ◽  
Genetic Clusters

Understanding genetic diversity and structure in a rare species is critical for prioritizing both in situ and ex situ conservation efforts. One such rare species is Physaria filiformis (Brassicaceae), a threatened, winter annual plant species. The species has a naturally fragmented distribution, occupying three different soil types spread across four disjunct geographical locations in Missouri and Arkansas. The goals of this study were to understand: (1) whether factors associated with fragmentation and small population size (i.e., inbreeding, genetic drift or genetic bottlenecks) have reduced levels of genetic diversity, (2) how genetic variation is structured and which factors have influenced genetic structure, and (3) how much extant genetic variation of P. filiformis is currently publicly protected and the implications for the development of conservation strategies to protect its genetic diversity. Using 16 microsatellite markers, we genotyped individuals from 20 populations of P. filiformis from across its geographical range and one population of Physaria gracilis for comparison and analyzed genetic diversity and structure. Populations of P. filiformis showed comparable levels of genetic diversity to its congener, except a single population in northwest Arkansas showed evidence of a genetic bottleneck and two populations in the Ouachita Mountains of Arkansas showed lower genetic variation, consistent with genetic drift. Populations showed isolation by distance, indicating that migration is geographically limited, and analyses of genetic structure grouped individuals into seven geographically structured genetic clusters, with geographic location/spatial separation showing a strong influence on genetic structure. At least one population is protected for all genetic clusters except one in north-central Arkansas, which should therefore be prioritized for protection. Populations in the Ouachita Mountains were genetically divergent from the rest of P. filiformis; future morphological analyses are needed to identify whether it merits recognition as a new, extremely rare species.

scholarly journals Direct and indirect effects of chemical contaminants on the behaviour, ecology and evolution of wildlife

2018 ◽  
Vol 285 (1885) ◽  
pp. 20181297 ◽  
Author(s):  
Minna Saaristo ◽  
Tomas Brodin ◽  
Sigal Balshine ◽  
Michael G. Bertram ◽  
Bryan W. Brooks ◽  
...  
Keyword(s):  
Indirect Effects ◽  
Population Level ◽  
Chemical Pollution ◽  
Direct And Indirect Effects ◽  
Chemical Contaminants ◽  
Behavioural Effects ◽  
Sensitive Tool ◽  
Hazard And Risk ◽  
Multi Level ◽  
Multiple Levels

Chemical contaminants (e.g. metals, pesticides, pharmaceuticals) are changing ecosystems via effects on wildlife. Indeed, recent work explicitly performed under environmentally realistic conditions reveals that chemical contaminants can have both direct and indirect effects at multiple levels of organization by influencing animal behaviour. Altered behaviour reflects multiple physiological changes and links individual- to population-level processes, thereby representing a sensitive tool for holistically assessing impacts of environmentally relevant contaminant concentrations. Here, we show that even if direct effects of contaminants on behavioural responses are reasonably well documented, there are significant knowledge gaps in understanding both the plasticity (i.e. individual variation) and evolution of contaminant-induced behavioural changes. We explore implications of multi-level processes by developing a conceptual framework that integrates direct and indirect effects on behaviour under environmentally realistic contexts. Our framework illustrates how sublethal behavioural effects of contaminants can be both negative and positive, varying dynamically within the same individuals and populations. This is because linkages within communities will act indirectly to alter and even magnify contaminant-induced effects. Given the increasing pressure on wildlife and ecosystems from chemical pollution, we argue there is a need to incorporate existing knowledge in ecology and evolution to improve ecological hazard and risk assessments.

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