scholarly journals Does evolution design robust food webs?

2020 ◽  
Vol 287 (1930) ◽  
pp. 20200747
Author(s):  
B. Girardot ◽  
M. Gauduchon ◽  
F. Ménard ◽  
J. C. Poggiale
Keyword(s):  
Food Webs ◽  
Energy Supply ◽  
Ecological Communities ◽  
Short Term ◽  
Trophic Networks ◽  
Crucial Effect ◽  
Community Evolution ◽  
History Of ◽  
Past Conditions

Theoretical works that use a dynamical approach to study the ability of ecological communities to resist perturbations are largely based on randomly generated ecosystem structures. By contrast, we ask here whether the evolutionary history of food webs matters for their robustness. Using a community evolution model, we first generate trophic networks by varying the level of energy supply (richness) of the environment in which species adapt and diversify. After placing our simulation outputs in perspective with present-day food webs empirical data, we highlight the complex, structuring role of this environmental condition during the evolutionary setting up of trophic networks. We then assess the robustness of food webs by studying their short-term ecological responses to swift changes in their customary environmental richness. We reveal that the past conditions have a crucial effect on the robustness of current food webs. Moreover, directly focusing on connectance of evolved food webs, it turns out that the most connected ones appear to be the least robust to sharp depletion in the environmental energy supply. Finally, we appraise the ‘adaptation’ of food webs themselves: generally poor, except in relation to a diversity of flux property.

scholarly journals Interaction Histories and Short-Term Memory: Enactive Development of Turn-Taking Behaviours in a Childlike Humanoid Robot

Philosophies ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 26 ◽  
Author(s):  
Frank Broz ◽  
Chrystopher L. Nehaniv ◽  
Hatice Kose ◽  
Kerstin Dautenhahn
Keyword(s):  
Humanoid Robot ◽  
Short Term Memory ◽  
Social Feedback ◽  
Short Term ◽  
Term Memory ◽  
Human Partner ◽  
Turn Taking ◽  
History Of ◽  
Immediate Experience

In this article, an enactive architecture is described that allows a humanoid robot to learn to compose simple actions into turn-taking behaviours while playing interaction games with a human partner. The robot’s action choices are reinforced by social feedback from the human in the form of visual attention and measures of behavioural synchronisation. We demonstrate that the system can acquire and switch between behaviours learned through interaction based on social feedback from the human partner. The role of reinforcement based on a short-term memory of the interaction was experimentally investigated. Results indicate that feedback based only on the immediate experience was insufficient to learn longer, more complex turn-taking behaviours. Therefore, some history of the interaction must be considered in the acquisition of turn-taking, which can be efficiently handled through the use of short-term memory.

scholarly journals Does evolution design robust food webs ?

2019 ◽  
Author(s):  
B. Girardot ◽  
M. Gauduchon ◽  
F. Ménard ◽  
JC. Poggiale
Keyword(s):  
Food Webs ◽  
Adaptive Dynamics ◽  
Emergent Properties ◽  
Ecological Communities ◽  
Environmental Perturbations ◽  
Richness Condition ◽  
Trophic Network ◽  
Evolutionary Emergence ◽  
Current Paradigm

Theoretical works that use a dynamical approach to study the ability of ecological communities to resist perturbations are largely based on randomly generated ecosystem structures. In contrast, we propose here to asses the robustness of food webs drawn from ecological and evolutionary processes with the use of community evolution models. In a first part, with the use of Adaptive Dynamics theoretical framework, we generate a variety of diversified food webs by solely sampling different richness levels of the environment as a control parameter, and obtain networks that satisfactory compare with empirical data. This allows us to highlight the complex, structuring role of the environmental richness during the evolutionary emergence of food webs. In a second part, we study the short-term ecological responses of food webs to swift changes in their customary environmental richness condition. We reveal a strong link between the environmental conditions that attended food webs evolutionary constructions and their robustness to environmental perturbations. When focusing on emergent properties of our evolved food webs, especially connectance, we highlight results that seem to contradict the current paradigm. Among these food webs, the most connected appear to be the less robust to sudden depletion of the environmental richness that constituted their evolutionary environment. Otherwise, we appraise the “adaptation” of food webs, by examining how they perform after being suddently immersed in an environment of modified richness level, in comparison with a trophic network that experienced this latter environmental condition all along its evolution.

scholarly journals Enron and the California Energy Crisis: The Role of Networks in Enabling Organizational Corruption

2021 ◽  
Vol 95 (4) ◽  
pp. 765-802
Author(s):  
Adam Nix ◽  
Stephanie Decker ◽  
Carola Wolf
Keyword(s):  
Energy Supply ◽  
Point Of View ◽  
Historical Research ◽  
Energy Crisis ◽  
Energy Market ◽  
Interorganizational Network ◽  
Organizational Corruption ◽  
History Of

We provide an analytically structured history of Enron's involvement in the California energy crisis, exploring its emergence as a corrupt organization and its use of an interorganizational network to manipulate California's energy supply markets. We use this history to introduce the concept of network-enabled corruption, showing how corruption, even if primarily enacted by a single dominant organization, is often highly dependent on the support of other organizations. Specifically, we show how Enron combined resources from partner firms with its own capabilities, manipulating the energy market and capitalizing on the crisis. From a methodological point of view, our study emphasizes the growing importance of digital sources for historical research, drawing particularly on telephone and email records from the period to develop a rich, fly-on-the-wall understanding of a phenomenon that is otherwise hard to observe.

The Fossil Record of Predator-Prey Arms Races: Coevolution and Escalation Hypotheses

2002 ◽  
Vol 8 ◽  
pp. 353-374 ◽  
Author(s):  
Gregory P. Dietl ◽  
Patricia H. Kelley
Keyword(s):  
Species Interactions ◽  
Fossil Record ◽  
Top Down ◽  
Short Term ◽  
Arms Races ◽  
Predator Prey ◽  
Long Run ◽  
Selective Agents ◽  
History Of

Arms races between predators and prey may be driven by two related processes—escalation and coevolution. Escalation is enemy-driven evolution. In this top-down view of an arms race, the role of prey (with the exception of dangerous prey) is downplayed. In coevolution, two or more species change reciprocally in response to one another; prey are thought to drive the evolution of their predator, and vice versa. In the fossil record, the two processes are most reliably distinguished when the predator-prey system is viewed within the context of the other species that may influence the interaction, thus allowing for a relative ranking of the importance of selective agents. Detailed documentation of the natural history of living predator-prey systems is recommended in order to distinguish the processes in some fossil systems. A geographic view of species interactions and the processes driving their evolution may lead to a more diverse array of testable hypotheses on how predator-prey systems evolve and what constraints interactions impose on the evolution of organisms. Scale is important in evaluating the role of escalation and coevolution in the evolution of species interactions. If short-term reciprocal adaptation (via phenotypic plasticity or selection mosaics among populations) between predator and prey is a common process, then prey are likely to exert some selective pressure over their predators over the short term (on ecological time scales), but in the long run predators may still exert primary “top-down” control in directing evolution. On the scale of evolutionary time, predators of large effect likely control the overall directionality of evolution due to the inequalities of predator and prey in control of resources.

scholarly journals The Role Of Private And Public Sectors: An Analysis Of Methodological Steps In Understanding Growth Cycles

2008 ◽  
Vol 4 (3) ◽  
pp. 225-233
Author(s):  
Santosh Singh Bais ◽  
Jagannath B. Kukkudi
Keyword(s):  
Developing Countries ◽  
Business Cycles ◽  
21St Century ◽  
Current Fluctuations ◽  
Short Term ◽  
Policy Makers ◽  
Growth Cycles ◽  
Private And Public ◽  
History Of

Though with a very long standing history of a century the growth cycles have once again been in the limelight of thinking of modern economists of 1960 and that of 1995. However, the 21st century growth cycles have been in the focus for policy makers of both developed and developing countries alike. The globalization phenomena has added new  dimension to these business cycles and have been a matter of time to time concerns of the policy makers of the developing countries which by nature have a vivid experience in different sectors of the economy. Indeed in the result years it is the current fluctuations which have occupied a prime place in all the economy which are going to be tied or cemented through trade, what attempts are essential and harmonious so as to control these short term growth fluctuations and what political and economic compromises are needed requires a brief analysis this what had been attempted in the paper.

scholarly journals Cultural and Artistic Journals in Circumstances of Independent Ukraine

2019 ◽  
pp. 104-112
Author(s):  
Petro Nesterenko
Keyword(s):  
General Concept ◽  
Short Term ◽  
Artistic Process ◽  
Typical Situation ◽  
Important Material ◽  
National Characteristics ◽  
The World ◽  
History Of ◽  
Over Time

During the years of independence the diversity in the opinions on many important issues – the role of an artist and art in the world, the solution of the crucial contemporary problems, the understanding of the national characteristics – became particularly acute. This contributed to the revival of some old journals and creation of many new ones. Unfortunately, today’s typical situation with an extravagant appearance of the next new edition and its short-term existence is reminiscent of the events that took place nearly hundred years ago. Numerous periodicals were born at that time and then quickly disappeared and went into oblivion. Over time, when it turned out that outstanding, though hidden from public, artists worked on their design and artistically determined the era, many journal covers were at last evaluated as achievement of Ukrainian art. However, the modern authors of the covers and the general concept of numerous journals remain on the margins of the artistic process as well. As a consequence, the question arises: do we really have to wait decades to properly evaluate their high art? Despite the short age, artistic and other journals added a bright page in the cultural and educational life of independent Ukraine. They objectively covered the achievements of Ukrainian artists and will serve as an important material for further research on the history of the Ukrainian art. A skillfully designed logo accompanied by a well-chosen and composed work of art or its fragment became a true decoration of contemporary journals. In this regard, the author of the paper considers the artistic designs of the covers used in Kyiv journals (from 1980s up to now) and identifies the best masters working in this field. Attention is paid to the time and circumstances of their release, the coordinated work of the authors and editors, the purposes and tasks of the editions. The important role of periodicals in the artistic and educational life of independent Ukraine is highlighted.

scholarly journals Health and environmental applications of gut microbiome: a review

2017 ◽  
Vol 24 (3) ◽  
pp. 467-482 ◽  
Author(s):  
Soumya Chatterjee ◽  
Sibnarayan Datta ◽  
Sonika Sharma ◽  
Sarika Tiwari ◽  
Dharmendra K. Gupta
Keyword(s):  
Microbial Communities ◽  
Gut Microbiome ◽  
Ecological Communities ◽  
Anatomy And Physiology ◽  
Physiological Processes ◽  
Health Related ◽  
History Of ◽  
Subsequent Elimination ◽  
Life On Earth

AbstractLife on Earth harbours an unimaginable diversity of microbial communities. Among these, gut microbiome, the ecological communities of commensal, symbionts (bacteria and bacteriophages) are a unique assemblage of microbes. This microbial population of animal gut helps in performing organism’s physiological processes to stay healthy and fit. The role of these microbial communities is immense. They continually maintain interrelation with the intestinal mucosa in a subtle equilibrium and help the gut for different functions ranging from metabolism to immunologic functions like upgradation of nutrient-poor diets, aid in digestion of recalcitrant food components, protection from pathogens, contribute to inter- and intra-specific communication, affecting the efficiency as disease vectors etc. The microbial diversity in the gut depends upon environmental competition between microbes, their sieving effects and subsequent elimination. Due to wide diversity of anatomy and physiology of the digestive tracts and food habits, the gut microbiome also differs broadly among animals. Stochastic factors through the history of colonization of the microbiome in a species andin situevolution are likely to establish interspecies diversity. Moreover, the microbes offer enormous opportunity to discover novel species for therapeutic and/or biotechnological applications. In this manuscript, we review the available knowledge on gut microbiome, emphasising their role in health and health related applications in human.

Abstract P161: Randomized Trial Of Magnesium Glycinate Supplementation And Blood Pressure In Middle-aged Adults

Hypertension ◽  
2020 ◽  
Vol 76 (Suppl_1) ◽  
Author(s):  
Howard D Sesso ◽  
Trisha Copeland ◽  
Jennifer L Coates ◽  
Olubunmi A Solano ◽  
Allison Clar ◽  
...  
Keyword(s):  
Randomized Trials ◽  
Controlled Trial ◽  
Short Term ◽  
Double Blind ◽  
Subgroup Analyses ◽  
History Of ◽  
Baseline Characteristics ◽  
Middle Aged Adults ◽  
Healthy Participants

Introduction: Magnesium (Mg) intake is inversely associated with BP and hypertension risk in observational studies. However, short-term randomized trials on seated BP have been inconsistent, with few studies measuring 24-h ambulatory BP (ABP). In addition, Mg glycinate, a more easily absorbed form of supplemental Mg, has been largely untested in randomized trials and may serve as a first-line approach for BP reduction among those with elevated, untreated, BP. Methods: We conducted a randomized, double-blind, placebo-controlled trial (NCT03688503) testing 480 mg/d of elemental Mg glycinate versus placebo for 12 weeks among 59 otherwise healthy participants aged 30-74 y with elevated seated BP (systolic BP (SBP) 120-149 mmHg and/or diastolic BP (DBP) 80-94 mmHg) and no history of anti-hypertensive medication use. At baseline, 6 weeks, and 12 weeks, we measured seated BP, monitored 24-h ABP, and collected blood samples. Our primary aim tested Mg glycinate on 12-week changes in seated BP and 24-h ABP, and subgroup analyses considered if sex, age, or baseline BP modified the effect of Mg on BP. Results: Baseline characteristics were equally distributed at randomization (mean age, 57.2 y; 58% men) with mean seated BP of 133.4/82.6 mmHg. Compliance was high (Mg, 87%; placebo, 96%). After 12 weeks, there was no significant effect of Mg glycinate versus placebo on seated SBP (-4.5 vs -1.6 mmHg from baseline; p=0.38) and DBP (-1.9 vs -0.9 mmHg from baseline; p=0.64), nor was there any significant effect on overall, daytime, or nighttime 24-h ambulatory SBP and DBP (all p>0.05). In subgroup analyses, the effect of Mg glycinate on seated SBP was suggestively, but non-significantly, stronger among those with baseline seated SBP ≥130 mmHg (-9.3 vs -2.7 mmHg; p=0.12; p, interaction=0.24) and among women (-9.7 vs -3.1 mmHg; p=0.26; p, interaction=0.29). Age, seated DBP, and mean 24-h ambulatory SBP and DBP did not modify the effects of Mg supplementation. Conclusions: A Mg glycinate supplement did not significantly reduce seated or 24-h BP in adults with elevated, untreated BP. Forthcoming analyses will expand on the role of serum and dietary Mg levels. Larger trials are warranted to elucidate possible effects of Mg glycinate on seated SBP among those with elevated BP and among women.

scholarly journals Community evolution increases plant productivity at low diversity

2017 ◽  
Author(s):  
Sofia J. van Moorsel ◽  
Terhi Hahl ◽  
Cameron Wagg ◽  
Gerlinde B. De Deyn ◽  
Dan F.B. Flynn ◽  
...  
Keyword(s):  
Ecosystem Functioning ◽  
Evolutionary Processes ◽  
Selection History ◽  
Community Evolution ◽  
Low Diversity ◽  
History Of ◽  
Ecological Mechanisms ◽  
Term Field

ABSTRACTSpecies extinctions from local communities can negatively affect ecosystem functioning. Ecological mechanisms underlying these impacts are well studied but the role of evolutionary processes is rarely assessed. Using a long-term field experiment, we tested whether natural selection in plant communities increased the effects of biodiversity on productivity. We re-assembled communities with 8-year co-selection history adjacent to communities with identical species composition but no history of co-selection (“naïve communities”). Monocultures and in particular mixtures of two to four co-selected species were more productive than their corresponding naïve communities over four years in soils with or without co-selected microbial communities. At the highest diversity level of eight plant species, no such differences were observed. Our findings suggest that plant community evolution can lead to rapid increases in ecosystem functioning at low diversity but may take longer at high diversity. This effect was not modified by treatments that simulated additional co-evolutionary processes between plants and soil organisms.

Sign in / Sign up

Export Citation Format

Share Document