scholarly journals Evolutionary rescue in randomly mating, selfing, and clonal populations

2016 ◽  
Author(s):  
Hildegard Uecker
Keyword(s):  
Environmental Change ◽  
Random Mating ◽  
Diploid Species ◽  
Evolutionary Rescue ◽  
Before And After ◽  
Establishment Probability ◽  
Population Survival ◽  
Set Up ◽  
Mutant Homozygote ◽  
Allele Model

AbstractSevere environmental change can drive a population extinct unless the population adapts in time to the new conditions (“evolutionary rescue”). How does bi-parental sexual reproduction influence the chances of population persistence compared to clonal reproduction or selfing? In this paper, we set up a one-locus two-allele model for adaptation in diploid species, where rescue is contingent on the establishment of the mutant homozygote. Reproduction can occur by random mating, selfing, or clonally. Random mating generates and destroys the rescue mutant; selfing is efficient at generating it but at the same time depletes the heterozygote, which can lead to a low mutant frequency in the standing genetic variation and also affects the establishment probability of the mutation. Due to these antagonistic effects, we find a non-trivial dependence of population survival on the rate of sex/selfing, which is strongly affected by the dominance coefficient of the mutation before and after the environmental change. Importantly, since mating with the wildtype breaks the mutant homozygote up, a slow decay of the wildtype population size can impede rescue in randomly mating populations.

scholarly journals Genomic signatures of evolutionary rescue in bats surviving white-nose syndrome

2018 ◽  
Author(s):  
Sarah A. Gignoux-Wolfsohn ◽  
Malin L. Pinsky ◽  
Kathleen Kerwin ◽  
Carl Herzog ◽  
MacKenzie Hall ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Environmental Change ◽  
Rapid Evolution ◽  
Genomic Signatures ◽  
White Nose Syndrome ◽  
Multiple Loci ◽  
Evolutionary Rescue ◽  
Before And After ◽  
Soft Selection ◽  
Little Brown Bat

AbstractRapid evolution of advantageous traits following abrupt environmental change can help populations grow and avoid extinction through evolutionary rescue. Here, we provide the first genetic evidence for rapid evolution in bat populations affected by white-nose syndrome (WNS). By comparing genetic samples from before and after little brown bat populations were decimated by WNS, we identified signatures of soft selection on standing genetic variation. This selection occurred at multiple loci in genes linked to hibernation behavior rather than immune function, suggesting that differences in hibernation strategy have allowed these bats to survive infection with WNS. Through these findings, we suggest that evolutionary rescue can be a conservationrelevant process even in slowly reproducing taxa threatened with extinction.

scholarly journals Evolutionary rescue can maintain an oscillating community undergoing environmental change

2013 ◽  
Vol 3 (6) ◽  
pp. 20130036 ◽  
Author(s):  
Gregor F. Fussmann ◽  
Andrew Gonzalez
Keyword(s):  
Environmental Change ◽  
Community Dynamics ◽  
Ecological Communities ◽  
Evolutionary Response ◽  
Evolutionary Rescue ◽  
Before And After ◽  
Internal Forces ◽  
Frequency Changes ◽  
Response To Environmental Change ◽  
Physiological Acclimation

The persistence of ecological communities is challenged by widespread and rapid environmental change. In many cases, persistence may not be assured via physiological acclimation or migration and so species must adapt rapidly in situ . This process of evolutionary rescue (ER) occurs when genetic adaptation allows a population to recover from decline initiated by environmental change that would otherwise cause extirpation. Community evolutionary rescue (CER) occurs when one or more species undergo a rapid evolutionary response to environmental change, resulting in the recovery of the ancestral community. Here, we study the dynamics of CER within a three-species community coexisting by virtue of resource oscillations brought about by nonlinear interactions between two species competing for a live resource. We allowed gradual environmental change to affect the traits that determine the strength and symmetry of the interaction among species. By allowing the component species to evolve rapidly, we found that: (i) trait evolution can allow CER and ensure the community persists by preventing competitive exclusion during environmental change, (ii) CER brings about a change in the character of the oscillations (period, amplitude) governing coexistence before and after environmental change, and (iii) CER may depend on evolutionary change that occurs simultaneously with or subsequently to environmental change. We were able to show that a change in the character of community oscillations may be a signature that a community is undergoing ER. Our study extends the theory on ER to a world of nonlinear community dynamics where—despite high-frequency changes of population abundances—adaptive evolutionary trait change can be gradual and directional, and therefore contribute to community rescue. ER may happen in real, complex communities that fluctuate owing to a mix of external and internal forces. Experiments testing this theory are now required to validate our predictions.

scholarly journals The effect of habitat choice on evolutionary rescue in subdivided populations

2019 ◽  
Author(s):  
Peter Czuppon ◽  
François Blanquart ◽  
Hildegard Uecker ◽  
Florence Débarre
Keyword(s):  
Environmental Change ◽  
De Novo ◽  
Habitat Choice ◽  
Wild Type ◽  
De Novo Mutations ◽  
Relative Contribution ◽  
Evolutionary Rescue ◽  
Subdivided Populations ◽  
Dynamics Of Population ◽  
Population Survival

AbstractEvolutionary rescue is the process by which a population, in response to an environmental change, successfully avoids extinction through adaptation. In spatially structured environments, dispersal can affect the probability of rescue. Here, we model an environment consisting of patches that degrade one after another, and we investigate the probability of rescue by a mutant adapted to the degraded habitat. We focus on the effects of dispersal and of immigration biases. We find that the probability of evolutionary rescue can undergo up to three phases: (i) starting from low dispersal rates, it increases with dispersal; (ii) at intermediate dispersal rates, it decreases; (iii) finally, at large dispersal rates, the probability of rescue increases again with dispersal, except if mutants are too counter-selected in not-yet-degraded patches. The probability of rescue is generally highest when mutant and wild-type individuals preferentially immigrate into patches that have already undergone environmental change. Additionally, we find that mutants that will eventually rescue the population most likely first appear in non-degraded patches, and that the relative contribution of standing genetic variation vs. de-novo mutations declines with increasing emigration rates. Overall, our results show that habitat choice, when compared to the often studied unbiased immigration scheme, can substantially alter the dynamics of population survival and adaptation to new environments.

Evaluation of Freezing Methods by Low Temperature X-Ray Diffraction

1977 ◽  
Vol 35 ◽  
pp. 330-333
Author(s):  
T. Gulik-Krzywicki ◽  
M.J. Costello
Keyword(s):  
Biological Materials ◽  
Molecular Organization ◽  
X Ray Diffraction ◽  
Glass Capillary ◽  
X Ray ◽  
Rate Dependent ◽  
Before And After ◽  
Freeze Etching ◽  
Diffraction Patterns ◽  
Set Up

Freeze-etching electron microscopy is currently one of the best methods for studying molecular organization of biological materials. Its application, however, is still limited by our imprecise knowledge about the perturbations of the original organization which may occur during quenching and fracturing of the samples and during the replication of fractured surfaces. Although it is well known that the preservation of the molecular organization of biological materials is critically dependent on the rate of freezing of the samples, little information is presently available concerning the nature and the extent of freezing-rate dependent perturbations of the original organizations. In order to obtain this information, we have developed a method based on the comparison of x-ray diffraction patterns of samples before and after freezing, prior to fracturing and replication.Our experimental set-up is shown in Fig. 1. The sample to be quenched is placed on its holder which is then mounted on a small metal holder (O) fixed on a glass capillary (p), whose position is controlled by a micromanipulator.

Research on pull-type multi-AGV system dynamic path optimization based on time window

2021 ◽  
pp. 095440702098271
Author(s):  
Hongying Shan ◽  
Chuang Wang ◽  
Cungang Zou ◽  
Mengyao Qin
Keyword(s):  
Path Planning ◽  
Time Window ◽  
Planning Problem ◽  
Dijkstra Algorithm ◽  
Before And After ◽  
Common Planning ◽  
Planning Algorithm ◽  
Dynamic Path ◽  
Set Up ◽  
Path Planning Algorithm

This paper is a study of the dynamic path planning problem of the pull-type multiple Automated Guided Vehicle (multi-AGV) complex system. First, based on research status at home and abroad, the conflict types, common planning algorithms, and task scheduling methods of different AGV complex systems are compared and analyzed. After comparing the different algorithms, the Dijkstra algorithm was selected as the path planning algorithm. Secondly, a mathematical model is set up for the shortest path of the total driving path, and a general algorithm for multi-AGV collision-free path planning based on a time window is proposed. After a thorough study of the shortcomings of traditional single-car planning and conflict resolution algorithms, a time window improvement algorithm for the planning path and the solution of the path conflict covariance is established. Experiments on VC++ software showed that the improved algorithm reduces the time of path planning and improves the punctual delivery rate of tasks. Finally, the algorithm is applied to material distribution in the OSIS workshop of a C enterprise company. It can be determined that the method is feasible in the actual production and has a certain application value by the improvement of the data before and after the comparison.

scholarly journals Wear and Friction Characteristics of 65Mn Steel for Spike-Tooth Harrow

Coatings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 319
Author(s):  
Zhiguo Lu ◽  
Chuanyu Du ◽  
Qingcai Chen ◽  
Tianying Niu ◽  
Na Wang ◽  
...  
Keyword(s):  
Friction And Wear ◽  
Working Environment ◽  
Manganese Steel ◽  
Wear Loss ◽  
Variable Parameters ◽  
Wear Characteristics ◽  
Before And After ◽  
Set Up ◽  
Worn Surface ◽  
Friction And Wear Characteristics

The friction and wear characteristics of spike-tooth material (65Mn steel) of Spike-Tooth Harrow in a two-stage peanut harvester were studied in this paper. The friction and wear tests of pin and disc on 65 manganese steel were carried out on the tribometer, then the wear loss and the friction coefficient were studied. The wear loss of the pin was acquired by calculating the mass of the pin before and after the experiment using an electronic balance. According to the actual working environment of peanut spring-finger, four variable parameters are set up: load, speed, soil moisture and soil type. The friction and wear characteristics of pins were studied under different loads, speeds and different soil environments. After wearing, the worn surface of the material was observed by scanning microscope and the wear mechanism was studied. The experimental results show that the wear of the pin increases with the increase of load and decreases with the increase of rotational speed in the same rotation number. Especially in the case of the sandy soil with 20% in moisture, a maximum wear loss of the pin is achieved.

scholarly journals Innovative passive reinforcements for the gradual stabilization of a landslide according with the observational method

Landslides ◽  
2021 ◽  
Author(s):  
Lorenzo Brezzi ◽  
Alberto Bisson ◽  
Davide Pasa ◽  
Simonetta Cola
Keyword(s):  
Monitoring System ◽  
Low Cost ◽  
Economic Losses ◽  
Fe Model ◽  
Site Conditions ◽  
Observational Method ◽  
Rainy Period ◽  
Sustainable Solutions ◽  
Before And After ◽  
Set Up

AbstractA large number of landslides occur in North-Eastern Italy during every rainy period due to the particular hydrogeological conditions of this area. Even if there are no casualties, the economic losses are often significant, and municipalities frequently do not have sufficient financial resources to repair the damage and stabilize all the unstable slopes. In this regard, the research for more economically sustainable solutions is a crucial challenge. Floating composite anchors are an innovative and low-cost technique set up for slope stabilization: it consists in the use of passive sub-horizontal reinforcements, obtained by coupling a traditional self-drilling bar with some tendons cemented inside it. This work concerns the application of this technique according to the observational method described within the Italian and European technical codes and mainly recommended for the design of geotechnical works, especially when performed in highly uncertain site conditions. The observational method prescribes designing an intervention and, at the same time, using a monitoring system in order to correct and adapt the project during realization of the works on the basis of new data acquired while on site. The case study is the landslide of Cischele, a medium landslide which occurred in 2010 after an exceptional heavy rainy period. In 2015, some floating composite anchors were installed to slow down the movement, even if, due to a limited budget, they were not enough to ensure the complete stabilization of the slope. Thanks to a monitoring system installed in the meantime, it is now possible to have a comparison between the site conditions before and after the intervention. This allows the evaluation of benefits achieved with the reinforcements and, at the same time, the assessment of additional improvements. Two stabilization scenarios are studied through an FE model: the first includes the stabilization system built in 2015, while the second evaluates a new solution proposed to further increase the slope stability.

Reducing Culture Reporting Errors in the Microbiology Laboratory

2019 ◽  
Vol 152 (Supplement_1) ◽  
pp. S131-S132
Author(s):  
Kathryn Hogan ◽  
Beena Umar ◽  
Mohamed Alhamar ◽  
Kathleen Callahan ◽  
Linoj Samuel
Keyword(s):  
Real Time ◽  
Error Rate ◽  
Reporting System ◽  
Error Rates ◽  
Tracking Errors ◽  
Corrective Measures ◽  
Safety Awareness ◽  
Before And After ◽  
Set Up ◽  
System Errors

Abstract Objectives There are few papers that characterize types of errors in microbiology laboratories and scant research demonstrating the effects of interventions on microbiology lab errors. This study aims to categorize types of culture reporting errors found in microbiology labs and to document the error rates before and after interventions designed to reduce errors and improve overall laboratory quality. Methods To improve documentation of error incidence, a self-reporting system was changed to an automatic reporting system. Errors were categorized into five types Gram stain (misinterpretations), identification (incorrect analysis), set up labeling (incorrect patient labels), procedures (not followed), and miscellaneous. Error rates were tracked according to technologist, and technologists were given real-time feedback by a manager. Error rates were also monitored in the daily quality meeting and frequently detected errors were discussed at staff meetings. Technologists attended a year-end review with a manager to improve their performance. To maintain these changes, policies were developed to monitor technologist error rate and to define corrective measures. If a certain number of errors per month was reached, technologists were required to undergo retraining by a manager. If a technologist failed to correct any error according to protocol, they were also potentially subject to corrective measures. Results In 2013, we recorded 0.5 errors per 1,000 tests. By 2018, we recorded only 0.1 errors per 1,000 tests, an 80% decrease. The yearly culture volume from 2013 to 2018 increased by 32%, while the yearly error rate went from 0.05% per year to 0.01% per year, a statistically significant decrease (P = .0007). Conclusion This study supports the effectiveness of the changes implemented to decrease errors in culture reporting. By tracking errors in real time and using a standardized process that involved timely follow-up, technologists were educated on error prevention. This practice increased safety awareness in our micro lab.

Frey's syndrome: treatment with botulinum toxin

1997 ◽  
Vol 111 (9) ◽  
pp. 839-844 ◽  
Author(s):  
A. Bjerkhoel ◽  
O. Trobbe
Keyword(s):  
Botulinum Toxin ◽  
Botulinum Toxin A ◽  
Surgical Techniques ◽  
Frey’S Syndrome ◽  
Need For Treatment ◽  
Gustatory Sweating ◽  
Parotid Surgery ◽  
Frey's Syndrome ◽  
Before And After ◽  
Set Up

AbstractFrey's syndrome, i.e. gustatory sweating on the cheek, is a fairly common embarrassment after parotid gland surgery. New surgical techniques have been proposed to avoid this complication, but are not widely in use. Hence, there is need for treatment of Frey's syndrome. All surgical and topical treatments have drawbacks. This study was set up in order to evaluate a recently described treatment. One hundred and two patients were interviewed after parotidectomy. Thirty-one of them had noticed gustatory sweating and 15 patients underwent Minor's starch iodine test before, and after, treatment with intracutaneous injections of botulinum toxin A (Botox®, Allergan Inc., USA). Thirteen of the patients did not experience any gustatory sweating at follow-up (one to 13 months). Minor's starch test showed total disappearance of gustatory sweating in 12 of the 15 treated patients. The only side effect was a discreet, transitory affection of the orbicularis oris muscle in one patient. As this treatment is minimally invasive it could be an attractive treatment for Frey's syndrome if the effect is maintained. Complaints of local hypoaesthesia and pain were also common after parotid surgery.

scholarly journals METHOD OF DISCUSSION DURING LESSONS OF SURROUNDING WORLD LEARNING: THEORY, POSSIBILITIES AND RESULTS

2009 ◽  
Vol 6 (2) ◽  
pp. 19-30
Author(s):  
Rita Makarskaitė-Petkevičienė ◽  
Jurgita Pitrėnaitė
Keyword(s):  
Waste Management ◽  
Primary Education ◽  
Teaching Methods ◽  
Waste Dump ◽  
Surrounding World ◽  
Educational Role ◽  
Before And After ◽  
Set Up ◽  
Fourth Form

Discussion in the process of teaching refers to a more sophisticated form of conversation, which is more frequently applied working with senior school learners. Problems rather than facts or phenomena are discussed. The question rises if the method of discussion is relevant in lessons of surrounding world learn-ing and whether it enables school learners to acquire knowledge, facilitates its memorisation or allows to ar-rive at solutions to urgent problems. The research involved 18 second formers, 15 school learners of fourth form and 13 students. All the groups of respondents discussed the same problem. Different roles were assigned to the participants in the discussion (a number of respondents represented heads of waste management company, whereas the rest assumed roles of residents of area where waste dump was being set up) and they involved in discussions of issues related to waste management and waste dump establishment. A considerable difference in the results of questionnaires provided to the participants before and after the discussion was observed. It is obvious that the respondents not only gained knowledge but also acquired a different perception and understanding of the problems analysed in the discussion. However, the compari-son of all the results of the survey revealed a stronger educational role of the discussion teaching fourth for-mers. This confirms theoretical statements that this method is more effective with senior school learners. The group of students also found the discussion useful. Key words: primary education, teaching of surrounding world learning, teaching methods, discussion.

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