scholarly journals Escalation of Memory Length in Finite Populations

2017 ◽  
Author(s):  
Kyle Harrington ◽  
Jordan Pollack
Keyword(s):  
Computational Simulations ◽  
Finite Populations ◽  
Arms Races ◽  
Memory Length ◽  
Satisfactory Degree ◽  
Cooperative Strategies ◽  
Population Sizes ◽  
Strategic Complexity ◽  
Counter Argument

AbstractThe escalation of complexity is a commonly cited benefit of coevolutionary systems, but computational simulations generally fail to demonstrate this capacity to a satisfactory degree. We draw on a macroevolutionary theory of escalation to develop a set of criteria for coevolutionary systems to exhibit escalation of strategic complexity. By expanding on a previously developed model of the evolution of memory length for cooperative strategies by Kristian Lindgren, we resolve previously observed limitations to the escalation of memory length. We present long-term coevolutionary simulations showing that larger population sizes tend to support greater escalation of complexity than smaller population sizes. Additionally, escalation is sensitive to perturbation during transitions of complexity. In whole, a long-standing counter-argument to the ubiquitous nature of coevolution is resolved, suggesting that the escalation of coevolutionary arms races can be harnessed by computational simulations.

scholarly journals Escalation of Memory Length in Finite Populations

2019 ◽  
Vol 25 (1) ◽  
pp. 22-32 ◽  
Author(s):  
Kyle Harrington ◽  
Jordan Pollack
Keyword(s):  
Computational Simulations ◽  
Arms Races ◽  
Memory Length ◽  
Satisfactory Degree ◽  
Cooperative Strategies ◽  
Evolutionary Variation ◽  
Population Sizes ◽  
Competitive Coevolution ◽  
Strategic Complexity

The escalation of complexity is a commonly cited benefit of coevolutionary systems, but computational simulations generally fail to demonstrate this capacity to a satisfactory degree. We draw on a macroevolutionary theory of escalation to develop a set of criteria for coevolutionary systems to exhibit escalation of strategic complexity. By expanding on a previously developed model of the evolution of memory length for cooperative strategies by Kristian Lindgren, we resolve previously observed limitations on the escalation of memory length by extending operators of evolutionary variation. We present long-term coevolutionary simulations showing that larger population sizes tend to support greater escalation of complexity than smaller ones do. Additionally, we investigate the sensitivity of escalation during transitions of complexity. The Lindgren model has often been used to argue that the escalation of competitive coevolution has intrinsic limitations. Our simulations show that coevolutionary arms races can continue to escalate in computational simulations given sufficient population sizes.

scholarly journals Recombination Can Evolve in Large Finite Populations Given Selection on Sufficient Loci

Genetics ◽  
2003 ◽  
Vol 165 (4) ◽  
pp. 2249-2258 ◽  
Author(s):  
Mark M Iles ◽  
Kevin Walters ◽  
Chris Cannings
Keyword(s):  
Experimental Evidence ◽  
Genetic Drift ◽  
Finite Population ◽  
Selective Advantage ◽  
Indirect Selection ◽  
Small Populations ◽  
Finite Populations ◽  
Population Sizes ◽  
Population Recombination

AbstractIt is well known that an allele causing increased recombination is expected to proliferate as a result of genetic drift in a finite population undergoing selection, without requiring other mechanisms. This is supported by recent simulations apparently demonstrating that, in small populations, drift is more important than epistasis in increasing recombination, with this effect disappearing in larger finite populations. However, recent experimental evidence finds a greater advantage for recombination in larger populations. These results are reconciled by demonstrating through simulation without epistasis that for m loci recombination has an appreciable selective advantage over a range of population sizes (am, bm). bm increases steadily with m while am remains fairly static. Thus, however large the finite population, if selection acts on sufficiently many loci, an allele that increases recombination is selected for. We show that as selection acts on our finite population, recombination increases the variance in expected log fitness, causing indirect selection on a recombination-modifying locus. This effect is enhanced in those populations with more loci because the variance in phenotypic fitnesses in relation to the possible range will be smaller. Thus fixation of a particular haplotype is less likely to occur, increasing the advantage of recombination.

scholarly journals Estimating population sizes of lions Panthera leo and spotted hyaenas Crocuta crocuta in Uganda's savannah parks, using lure count methods

Oryx ◽  
2013 ◽  
Vol 48 (3) ◽  
pp. 394-401 ◽  
Author(s):  
Edward Okot Omoya ◽  
Tutilo Mudumba ◽  
Stephen T. Buckland ◽  
Paul Mulondo ◽  
Andrew J. Plumptre
Keyword(s):  
National Parks ◽  
Protected Area ◽  
National Park ◽  
Crocuta Crocuta ◽  
Panthera Leo ◽  
Analysis Method ◽  
Conservation Areas ◽  
Conservation Area ◽  
Population Sizes

AbstractDespite > 60 years of conservation in Uganda's national parks the populations of lions and spotted hyaenas in these areas have never been estimated using a census method. Estimates for some sites have been extrapolated to other protected areas and educated guesses have been made but there has been nothing more definitive. We used a lure count analysis method of call-up counts to estimate populations of the lion Panthera leo and spotted hyaena Crocuta crocuta in the parks where reasonable numbers of these species exist: Queen Elizabeth Protected Area, Murchison Falls Conservation Area and Kidepo Valley National Park. We estimated a total of 408 lions and 324 hyaenas for these three conservation areas. It is unlikely that other conservation areas in Uganda host > 10 lions or > 40 hyaenas. The Queen Elizabeth Protected Area had the largest populations of lions and hyaenas: 140 and 211, respectively. It is estimated that lion numbers have declined by 30% in this protected area since the late 1990s and there are increasing concerns for the long-term viability of both species in Uganda.

scholarly journals The business cycle: a definition

2021 ◽  
pp. 205-262
Author(s):  
Tuur Demeester
Keyword(s):  
Business Cycle ◽  
Jel Classification ◽  
Austrian School ◽  
Methodological Framework ◽  
The Core ◽  
Palabras Clave ◽  
The Business Cycle ◽  
Necessary And Sufficient ◽  
Counter Argument

The goal of this article is to properly define the economic phenomenon of the business cycle. The text is rooted in the tradition of the Austrian School of Economics, and the methodological framework builds on concepts developed by Aristotle and Thomas Aquinas. This leads to the development of a few new methodological concepts, such as a re-interpretation of «inflation» and «deflation», and the re-introduction of «imaginary goods» as an important social phenomenon. The core observation of the article is that the business cycle is in fact a subclass of another kind of cycle, the «fraud cycle». Our conclusion is that in order to produce a business cycle, the occurrence of institutional fraud in the sphere of money and banking are both necessary and sufficient. The counter-argument that honest banking can also produce business cycles is refuted in Appendix I. We believe this article is significant in two ways: 1) it provides an unambiguous recipe for the long term extermination of the business cycle; and 2) it helps expand the scope of the Austrian School beyond economics into fields of law and morality. Key words: Business Cycle, Fraud Cycle, Austrian School, money and banking. JEL Classification: B53, B49, D01, K13. Resumen: El objetivo de este artículo es definir apropiadamente el fenómeno económico del ciclo económico. El resto está enraizado en la tradición de la Escuela Austriaca de Economía, y el marco metodológico parte de los conceptos desarrollados por Aristóteles y Tomás de Aquino. Esto conduce al desarrollo de algunos conceptos metodológicos nuevos, tales como la reinterpretación de la «inflación» y la «deflación», y la reintroducción de los «bienes imaginarios» como un fenómeno social importante. La observación central de este artículo es que el ciclo económico es de hecho una subclase de otro tipo de ciclo, el «ciclo del fraude». Nuestra conclusión es que para producir un ciclo económico, la existencia de un fraude institucional en la esfera del dinero y la banca es una condición necesaria y suficiente. El Apéndice I refuta el contra-argumento de que una banca honesta también puede producir ciclos económicos. Creemos que este artículo es significativo por dos motivos: 1) ofrece una receta clara para la eliminación del ciclo económico; y 2) ayuda a expandir el ámbito de la Escuela Austriaca más allá del campo de la Economía hacia los campos del Derecho y la Moralidad. Palabras clave: Ciclo económico, ciclo del fraude, Escuela Austriaca, dinero y banca. Clasificación JEL: B53, B49, D01, K13.

scholarly journals Long-term experimental evolution reveals purifying selection on piRNA-mediated control of transposable element expression

BMC Biology ◽  
2020 ◽  
Vol 18 (1) ◽  
Author(s):  
Ulfar Bergthorsson ◽  
Caroline J. Sheeba ◽  
Anke Konrad ◽  
Tony Belicard ◽  
Toni Beltran ◽  
...  
Keyword(s):  
Natural Selection ◽  
Transcriptional Activation ◽  
Small Rnas ◽  
Active Regions ◽  
Purifying Selection ◽  
Ancestral Population ◽  
Sequence Context ◽  
C Elegans ◽  
Population Sizes

Abstract Background Transposable elements (TEs) are an almost universal constituent of eukaryotic genomes. In animals, Piwi-interacting small RNAs (piRNAs) and repressive chromatin often play crucial roles in preventing TE transcription and thus restricting TE activity. Nevertheless, TE content varies widely across eukaryotes and the dynamics of TE activity and TE silencing across evolutionary time is poorly understood. Results Here, we used experimentally evolved populations of C. elegans to study the dynamics of TE expression over 409 generations. The experimental populations were evolved at population sizes of 1, 10 and 100 individuals to manipulate the efficiency of natural selection versus genetic drift. We demonstrate increased TE expression relative to the ancestral population, with the largest increases occurring in the smallest populations. We show that the transcriptional activation of TEs within active regions of the genome is associated with failure of piRNA-mediated silencing, whilst desilenced TEs in repressed chromatin domains retain small RNAs. Additionally, we find that the sequence context of the surrounding region influences the propensity of TEs to lose silencing through failure of small RNA-mediated silencing. Conclusions Our results show that natural selection in C. elegans is responsible for maintaining low levels of TE expression, and provide new insights into the epigenomic features responsible.

Swiss Cooperation in the Travel and Tourism Sector: Long-term Relationships and Superior Performance

2019 ◽  
Vol 59 (6) ◽  
pp. 1044-1060
Author(s):  
Vu Thi Thao ◽  
Widar von Arx ◽  
Jonas Frölicher
Keyword(s):  
Public Transport ◽  
Research Area ◽  
Superior Performance ◽  
Cooperative Relationships ◽  
Travel And Tourism ◽  
Cooperative Strategies ◽  
Customer Type ◽  
Cooperative Relationship ◽  
High Degree

Despite a growing body of research on the interface and relationship between transport and tourism, this research area remains undeveloped. Using Switzerland as a case study, the present study aims to investigate the level of integration between public transport and tourism companies, the enablers of their long-term cooperative relationship and outstanding performance, seen from the perspective of the public transport companies. A mixed methods approach is used to provide greater insights into how these companies cooperate with each other. Our findings suggest that public transport companies adopt different cooperative strategies with different types of partners. They are able to maintain long-term cooperative relationships due to strong cooperation in sales, a long tradition of cooperation, a high degree of involvement in national public organizations, and their central focus on the customer. Type of partner, sales, product design and pricing, and service provision have statistically significant effects on cooperative performance.

Ethics of Primate Fieldwork: Toward an Ethically Engaged Primatology

2018 ◽  
Vol 47 (1) ◽  
pp. 493-512 ◽  
Author(s):  
Erin P. Riley ◽  
Michelle Bezanson
Keyword(s):  
Best Practices ◽  
Field Research ◽  
Anthropogenic Factors ◽  
Ethical Practice ◽  
Theoretical Frameworks ◽  
Population Sizes ◽  
History Of ◽  
The Impact ◽  
Term Field

Field primatologists have ethical responsibilities that extend beyond study subjects to the local human communities living near primate populations and their surrounding ecosystems. In this review, we explore the history of ethical discussions within anthropological primatology and examine the best practices for an ethically engaged primatology that should be followed and role-modeled by primatologists. An increasing number of primates are showing reduced population sizes and are in imminent danger of extinction; thus, we need to carefully consider the ethics of intervening to ensure the survival of remaining populations, the impact of anthropogenic factors (e.g., climate change), and whether long-term field research results in conservation outcomes that consider local human communities. Because best practices change over time as theoretical frameworks and methodological tools advance and scientific goals change, field primatologists must continually reflect on what constitutes ethical practice and consider how research influences the overlapping dimensions of fieldwork: primates, people, and ecosystems.

scholarly journals Remote sensing and conservation of isolated indigenous villages in Amazonia

2014 ◽  
Vol 1 (3) ◽  
pp. 140246 ◽  
Author(s):  
Robert S. Walker ◽  
Marcus J. Hamilton ◽  
Aaron A. Groth
Keyword(s):  
Remote Sensing ◽  
Satellite Imagery ◽  
Term Survival ◽  
Surveillance Programme ◽  
Non Invasive ◽  
External Threats ◽  
Indigenous Groups ◽  
Order Of Magnitude ◽  
Population Sizes

The vast forests on the border between Brazil and Peru harbour a number of indigenous groups that have limited contact with the outside world. Accurate estimates of population sizes and village areas are essential to begin assessing the immediate conservation needs of such isolated groups. In contrast to overflights and encounters on the ground, remote sensing with satellite imagery offers a safe, inexpensive, non-invasive and systematic approach to provide demographic and land-use information for isolated peoples. Satellite imagery can also be used to understand the growth of isolated villages over time. There are five isolated villages in the headwaters of the Envira River confirmed by overflights that are visible with recent satellite imagery further confirming their locations and allowing measurement of their cleared gardens, village areas and thatch roofed houses. These isolated villages appear to have population densities that are an order of magnitude higher than averages for other Brazilian indigenous villages. Here, we report on initial results of a remote surveillance programme designed to monitor movements and assess the demographic health of isolated peoples as a means to better mitigate against external threats to their long-term survival.

Weak genetic structuring suggests historically high genetic connectivity among recently fragmented urban populations of the scincid lizard, Ctenotus fallens

2015 ◽  
Vol 63 (4) ◽  
pp. 279 ◽  
Author(s):  
Josef Krawiec ◽  
Siegfried L. Krauss ◽  
Robert A. Davis ◽  
Peter B. S. Spencer
Keyword(s):  
Genetic Diversity ◽  
Gene Flow ◽  
Large Population ◽  
Geographic Distance ◽  
Genetic Erosion ◽  
Genetic Connectivity ◽  
Genetic Structuring ◽  
Low Genetic Diversity ◽  
Population Sizes

Populations in fragmented urban remnants may be at risk of genetic erosion as a result of reduced gene flow and elevated levels of inbreeding. This may have serious genetic implications for the long-term viability of remnant populations, in addition to the more immediate pressures caused by urbanisation. The population genetic structure of the generalist skink Ctenotus fallens was examined using nine microsatellite markers within and among natural vegetation remnants within a highly fragmented urban matrix in the Perth metropolitan area in Western Australia. These data were compared with samples from a large unfragmented site on the edge of the urban area. Overall, estimates of genetic diversity and inbreeding within all populations were similar and low. Weak genetic differentiation, and a significant association between geographic and genetic distance, suggests historically strong genetic connectivity that decreases with geographic distance. Due to recent fragmentation, and genetic inertia associated with low genetic diversity and large population sizes, it is not possible from these data to infer current genetic connectivity levels. However, the historically high levels of gene flow that our data suggest indicate that a reduction in contemporary connectivity due to fragmentation in C. fallens is likely to result in negative genetic consequences in the longer term.

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