scholarly journals When does gene flow facilitate evolutionary rescue?

2019 ◽  
Author(s):  
Matteo Tomasini ◽  
Stephan Peischl
Keyword(s):  
Gene Flow ◽  
Structured Populations ◽  
Migration Rates ◽  
Evolutionary Rescue ◽  
Theoretical Question ◽  
The Impact ◽  
Experimental And Theoretical Studies ◽  
Positive Effect ◽  
Theoretical Results ◽  
Traditional Population

AbstractExperimental and theoretical studies have highlighted the impact of gene flow on the probability of evolutionary rescue in structured habitats. Mathematical modelling and simulations of evolutionary rescue in spatially or otherwise structured populations showed that intermediate migration rates can often maximize the probability of rescue in gradually or abruptly deteriorating habitats. These theoretical results corroborate the positive effect of gene flow on evolutionary rescue that has been identified in experimental yeast populations. The observations that gene flow can facilitate adaptation are in seeming conflict with traditional population genetics results that show that gene flow usually hampers (local) adaptation. Identifying conditions for when gene flow facilitates survival chances of populations rather than reducing them remains a key unresolved theoretical question. We here present a simple analytically tractable model for evolutionary rescue in a two-deme model with gene flow. Our main result is a simple condition for when migration facilitates evolutionary rescue, as opposed as no migration. We further investigate the roles of asymmetries in gene flow and / or carrying capacities, and the effects of density regulation and local growth rates on evolutionary rescue.

scholarly journals Deleterious mutations in a hybrid zone: can mutational load decrease the barrier to gene flow?

2002 ◽  
Vol 80 (3) ◽  
pp. 197-204 ◽  
Author(s):  
NICOLAS BIERNE ◽  
THOMAS LENORMAND ◽  
FRANÇOIS BONHOMME ◽  
PATRICE DAVID
Keyword(s):  
Gene Flow ◽  
Hybrid Zone ◽  
Small Population ◽  
Structured Populations ◽  
Mutational Load ◽  
Deleterious Mutations ◽  
Migration Rates ◽  
Linkage Disequilibria ◽  
Deleterious Alleles ◽  
Population Sizes

The aim of this paper is to investigate the effect of deleterious mutations in a hybrid zone maintained by selection against hybrids. In such zones, linkage disequilibria among hybrid depression loci, resulting from a balance between migration and selection, are crucial in maintaining the barrier because they allow each locus, in addition to its own selection coefficient, to cumulate indirect selective effects from other loci. Deleterious alleles produce heterosis and increase by this means the effective migration rate in structured populations. In a hybrid zone, they therefore contribute to decrease linkage disequilibria as well as the barrier to gene flow imposed by hybrid depression. However, deleterious mutations have no effect: (i) when selection against hybrids is weak, because linkage disequilibria are small even without heterosis in this case, or (ii) when selection against hybrids is so strong that it overwhelms heterosis. On the other hand, with moderate selection against hybrids, the decrease in the strength of the barrier due to heterosis may reach detectable levels, although it requires relatively small population sizes and/or migration rates. The effect is expected to be small and only within small genomes where loci are tightly linked can it become strong. Nevertheless, neglecting mutational load may to some extent obscure the estimations of selective parameters based either on artificial F1 crosses or on cline characteristics.

scholarly journals Defining Species When There is Gene Flow

2020 ◽  
Vol 70 (1) ◽  
pp. 108-119 ◽  
Author(s):  
Xiyun Jiao ◽  
Ziheng Yang
Keyword(s):  
Gene Flow ◽  
Migration Rates ◽  
Multispecies Coalescent ◽  
Hybridization Rate ◽  
Time Migration ◽  
Powerful Approach ◽  
Population Sizes ◽  
History Of ◽  
Definition Of ◽  
The Impact

Abstract Whatever one’s definition of species, it is generally expected that individuals of the same species should be genetically more similar to each other than they are to individuals of another species. Here, we show that in the presence of cross-species gene flow, this expectation may be incorrect. We use the multispecies coalescent model with continuous-time migration or episodic introgression to study the impact of gene flow on genetic differences within and between species and highlight a surprising but plausible scenario in which different population sizes and asymmetrical migration rates cause a genetic sequence to be on average more closely related to a sequence from another species than to a sequence from the same species. Our results highlight the extraordinary impact that even a small amount of gene flow may have on the genetic history of the species. We suggest that contrasting long-term migration rate and short-term hybridization rate, both of which can be estimated using genetic data, may be a powerful approach to detecting the presence of reproductive barriers and to define species boundaries.[Gene flow; introgression; migration; multispecies coalescent; species concept; species delimitation.]

scholarly journals Limited evolutionary rescue of locally adapted populations facing climate change

2013 ◽  
Vol 368 (1610) ◽  
pp. 20120083 ◽  
Author(s):  
Katja Schiffers ◽  
Elizabeth C. Bourne ◽  
Sébastien Lavergne ◽  
Wilfried Thuiller ◽  
Justin M. J. Travis
Keyword(s):  
Climate Change ◽  
Gene Flow ◽  
Habitat Heterogeneity ◽  
Climatic Conditions ◽  
Spatially Explicit ◽  
Evolutionary Potential ◽  
Evolutionary Response ◽  
Evolutionary Rescue ◽  
The Impact ◽  
Rapid Environmental Change

Dispersal is a key determinant of a population's evolutionary potential. It facilitates the propagation of beneficial alleles throughout the distributional range of spatially outspread populations and increases the speed of adaptation. However, when habitat is heterogeneous and individuals are locally adapted, dispersal may, at the same time, reduce fitness through increasing maladaptation. Here, we use a spatially explicit, allelic simulation model to quantify how these equivocal effects of dispersal affect a population's evolutionary response to changing climate. Individuals carry a diploid set of chromosomes, with alleles coding for adaptation to non-climatic environmental conditions and climatic conditions, respectively. Our model results demonstrate that the interplay between gene flow and habitat heterogeneity may decrease effective dispersal and population size to such an extent that substantially reduces the likelihood of evolutionary rescue. Importantly, even when evolutionary rescue saves a population from extinction, its spatial range following climate change may be strongly narrowed, that is, the rescue is only partial. These findings emphasize that neglecting the impact of non-climatic, local adaptation might lead to a considerable overestimation of a population's evolvability under rapid environmental change.

scholarly journals Fragmentation helps evolutionary rescue in highly connected habitats

2020 ◽  
Author(s):  
Matteo Tomasini ◽  
Stephan Peischl
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Environmental Conditions ◽  
Structured Populations ◽  
Adaptive Introgression ◽  
Spatially Structured Populations ◽  
Species Survival ◽  
Evolutionary Rescue ◽  
The Face ◽  
Population Sizes

AbstractGenetic variation and population sizes are critical factors for successful adaptation to novel environmental conditions. Gene flow between sub-populations is a potent mechanism to provide such variation and can hence facilitate adaption, for instance by increasing genetic variation or via adaptive introgression. On the other hand, if gene flow between different habitats is too strong, locally beneficial alleles may not be able to establish permanently. In the context of evolutionary rescue, intermediate levels of gene flow are therefore often optimal for maximizing a species chance for survival in meta-populations without spatial structure. To which extent and under which conditions gene flow facilitates or hinders evolutionary rescue in spatially structured populations remains unresolved. We address this question and show that detrimental effects of gene flow can become negligible in spatially structured populations subject to a gradual deterioration of environmental conditions. If the number of sub-populations is sufficiently large, we find a positive relationship between the amount of gene flow and the survival chance of the population. A counter-intuitive conclusion is that increased fragmentation can facilitate species survival in the face of severe environmental change if migration is common but limited to neighboring sub-populations.

scholarly journals Intermediate Migration Yields Optimal Adaptation in Structured, Asexual Populations

2014 ◽  
Author(s):  
Arthur Covert III ◽  
Claus O Wilke
Keyword(s):  
Genetic Variation ◽  
Gene Flow ◽  
Migration Rate ◽  
Appreciable Effect ◽  
Migration Rates ◽  
Optimal Migration ◽  
Digital Organisms ◽  
Asexual Populations ◽  
The Impact

Most evolving populations are subdivided into multiple subpopulations connected to each other by varying levels of gene flow. However, how population structure and gene flow (i.e., migration) affect adaptive evolution is not well understood. Here, we studied the impact of migration on asexually reproducing evolving computer programs (digital organisms). We found that digital organisms evolve the highest fitness values at intermediate migration rates, and we tested three hypotheses that could potentially explain this observation: (i) migration promotes passage through fitness valleys, (ii) migration increases genetic variation, and (iii) migration reduces clonal interference through a process called “leapfrogging”. We found that migration had no appreciable effect on the number of fitness valleys crossed and that genetic variation declined monotonously with increasing migration rates, instead of peaking at the optimal migration rate. However, the number of leapfrogging events, in which a superior beneficial mutation emerges on a genetic background that predates the previously best genotype in the population, did peak at the optimal migration rate. We thus conclude that in structured, asexual populations intermediate migration rates allow for optimal exploration of multiple, distinct fitness peaks, and thus yield the highest long-term adaptive success.

Impact of Digitalization on Service Work in Knowledge-Intensive Business Services: An Empirical Study in Tax Consultancies

2019 ◽  
Vol 3 (4) ◽  
pp. 209-222
Author(s):  
Philipp K. Görs ◽  
Henning Hummert ◽  
Anne Traum ◽  
Friedemann W. Nerdinger
Keyword(s):  
Work Engagement ◽  
Service Work ◽  
Psychological Consequences ◽  
Business Services ◽  
Knowledge Intensive Business Services ◽  
Positive Effects ◽  
Knowledge Intensive ◽  
The Impact ◽  
Positive Effect ◽  
Special Case

Digitalization is a megatrend, but there is relatively little knowledge about its consequences for service work in general and specifically in knowledge-intensive business services (KIBS). We studied the impact of digitalization on psychological consequences for employees in tax consultancies as a special case of KIBS. We compare two tax consulting jobs with very different job demands, those of tax consultants (TCs) and assistant tax consultants (ATCs). The results show that the extent of digitalization at the workplace level for ATCs correlates significantly positively with their job satisfaction. For TCs, the same variable correlates positively with their work engagement. These positive effects of digitalization are mediated in the case of ATCs by the impact on important job characteristics. In the case of TCs, which already have very good working conditions, the impact is mediated by the positive effect on self-efficacy. Theoretical and practical consequences of these results are discussed.

Comparative study of the impact of two mechanical perforation densities on the behavior of a sandy soil

2012 ◽  
Vol 8 (1) ◽  
pp. 37-48
Author(s):  
S. Chehaibi ◽  
K. Abrougui ◽  
F. Haouala
Keyword(s):  
Soil Water ◽  
Sandy Soil ◽  
Water Infiltration ◽  
Cone Penetration ◽  
Initial State ◽  
Soil Water Infiltration ◽  
Good Improvement ◽  
The Impact ◽  
Positive Effect ◽  
Resistance To Penetration

The effects of mechanical perforation densities by extracting soil cores through an aerator Vertidrain with a working width of 1.6 m and equipped with hollow tines spaced of 65 mm, were studied on a sandy soil of a grassy sward in the Golf Course El Kantaoui in Sousse (Tunisia). The mechanical aeration was performed at two densities: 250 and 350 holes/m2. The cone penetration resistance and soil water infiltration were measured. These parameters were performed at initial state before aeration (E0) and then on the 10th, 20th and 30th day after aeration. These results showed that perforation density of 350 holes/m2 had a positive effect on the soil by reducing its cone resistance to penetration compared to the initial state (Rp = 14.8 daN/cm2). At 5 cm depth the decrease in resistance to penetration was 34% and 43% on the 10th and 20th day after aeration, respectively. However, on the 30th day after aeration the soil resistance to penetration tended to grow and its value compared to the initial state decreased only by 21 and 26%, respectively, at 5 and 15 cm of depth only by 10% and 9% with 250 holes/m2 density. The soil water infiltration made a good improvement after aeration compared to the initial state. This parameter increased from 4.8 cm/h to 8.3, 10.9 and 13.1 cm/h with 250 holes/m2 density and to 10, 12.9 and 14.8 cm/h with 350 holes/m2 density on the 10th, 20th and 30th day following the aeration.

THEORETICAL STUDY OF THE EFFECT OF GEOMETRICAL PARAMETERS AND LOCATION OF ROTOR IMPACT ELEMENTS OF AN IMPACT-CENTRIFUGAL GRINDER ON SPEED AND ANGLES OF CRUSHED PARTICLES FLIGHT

2020 ◽  
Keyword(s):  
Granulometric Composition ◽  
Theoretical Study ◽  
Process Efficiency ◽  
Geometrical Parameters ◽  
Grinding Process ◽  
Main Work ◽  
Impact Element ◽  
The Impact ◽  
Positive Effect ◽  
Efficiency Indicators

One of efficiency indicators of grain grinders is grain granulometric composition. The basis of mixed fodder is crushed grain, the particles of which must have a leveled granulometric composition for subsequent mixing and obtaining a high-quality feed mixture. In agricultural production, hammer crushers are widely used, in which the destruction of grain occurs due to the impact of a hinged hammer. The main disadvantage of these crushers is that not the entire surface of the hammers is involved in grinding, thus reduces grinding process efficiency. A slightly different principle of material destruction is laid down in the basis of the proposed design of the shock-centrifugal grinder. Main work is performed by flat impact elements located on the rotor, which serve to accelerate crushed particles with subsequent impact of them on the bump elements. An important step in the design of new constructions of shock-centrifugal grinders is to determine size and location of the impact elements on the rotor, without which the grinding process is not possible. In the calculation method presented, the dependencies for determining the velocities and angles of a single particle flight from the surface of a flat impact element for its specified dimensions are proposed. Two variants of an impact element location on the rotor are considered and analyzed: radial and at an angle in the direction of rotor rotation. As a result of research carried out, it is noted that in the case of inclined position of an impact element on the rotor an increase in flight speed and flight angles change in crushed particles, which gives the opportunity to have a positive effect on grinding process.

The Impact of Coping Strategies on Situational Coping in Daily Life: An Ecological Momentary Assessment Study with the mHealth application TrackYourStress (Preprint)

2020 ◽  
Author(s):  
Teresa O'Rourke ◽  
Carsten Vogel ◽  
Dennis John ◽  
Rüdiger Pryss ◽  
Johannes Schobel ◽  
...  
Keyword(s):  
Social Support ◽  
Coping Strategies ◽  
Daily Life ◽  
Stress Coping ◽  
Positive Thinking ◽  
Active Stress ◽  
Situational Coping ◽  
Ecological Momentary ◽  
The Impact ◽  
Positive Effect

BACKGROUND It is necessary to cope with situations in daily life to prevent stress-related health consequences. However, coping strategies might differ in their impact on dealing with stressful situations in daily life. Moreover, the effect of coping strategies on situational coping might differ between women and men. OBJECTIVE The aim of this study was to investigate the impact of coping strategies on situational coping in everyday life situations and to investigate gender differences. METHODS An ecological momentary assessment study with the mobile health app TrackYourStress (TYS) was conducted with 113 participants. Coping strategies were measured at baseline with the coping scales Positive Thinking, Active Stress Coping, Social Support, Support in Faith, and Alcohol and Cigarette Consumption of the Stress and Coping Inventory (SCI). Situational coping was assessed by the question “How well can you cope with your momentary stress-level” (slider 0-100) in daily life over four weeks. Multilevel models were conducted to test the effects of the coping strategies on situational coping. Additionally, gender differences were evaluated. RESULTS Positive Thinking (P=.03) and Active Stress Coping (P=.04) had significant positive impacts on situational coping in the total sample. For women, only Social Support had a significant positive effect on situational coping (P=.046). For men, only Active Stress Coping had a significant positive effect on situational coping (P=.001). Women had higher scores on the SCI scale Social Support than men (P=.007). CONCLUSIONS These results suggest that different coping strategies could be more effective in daily life for women than for men, which should be considered in the development of interventions aimed at reducing stress consequences through coping. Interventions taking gender into consideration might lead to better coping-outcomes than generalized interventions.

THE IMPACT OF WORLD WAR II ON COST ACCOUNTING AT THE SPERRY CORPORATION

2003 ◽  
Vol 30 (2) ◽  
pp. 67-104 ◽  
Author(s):  
Richard K. Fleischman ◽  
R. Penny Marquette
Keyword(s):  
World War Ii ◽  
Performance Management ◽  
Scientific Management ◽  
World War ◽  
Military Contractors ◽  
Management Techniques ◽  
Cost Awareness ◽  
The Impact ◽  
Positive Effect ◽  
The U.S

The impact of World War II on cost accountancy in the U.S. may be viewed as a double-edged sword. Its most positive effect was engendering greater cost awareness, particularly among companies that served as military contractors and, thus, had to make full representation to contracting agencies for reimbursement. On the negative side, the dislocations of war, especially shortages in the factors of production and capacity constraints, meant that such “scientific management” techniques as existed (standard costing, time-study, specific detailing of task routines) fell by the wayside. This paper utilizes the archive of the Sperry Corporation, a leading governmental contractor, to chart the firm's accounting during World War II. It is concluded that any techniques that had developed from Taylorite principles were suspended, while methods similar to contemporary performance management, such as subcontracting, emphasis on the design phase of products, and substantial expenditure on research and development, flourished.

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