scholarly journals Fluctuating environments select for short-term phenotypic variation leading to long-term exploration

2018 ◽  
Author(s):  
Rosangela Canino-Koning ◽  
Michael J. Wiser ◽  
Charles Ofria
Keyword(s):  
Evolutionary Dynamics ◽  
Population Bottlenecks ◽  
Evolutionary Potential ◽  
Short Term ◽  
Phenotypic Properties ◽  
Mutational Landscape ◽  
Changing Environments ◽  
Digital Organisms ◽  
Mutational Step

AbstractGenetic spaces are often described in terms of fitness landscapes or genotype-to-phenotype maps, where each genetic sequence is associated with phenotypic properties and linked to other genotypes that are a single mutational step away. The positions close to a genotype make up its “mutational landscape” and, in aggregate, determine the short-term evolutionary potential of a population. Populations with wider ranges of phenotypes in their mutational neighborhood are known to be more evolvable. Likewise, those with fewer phenotypic changes available in their local neighborhoods are more mutationally robust. Here, we examine whether forces that change the distribution of phenotypes available by mutation profoundly alter subsequent evolutionary dynamics.We compare evolved populations of digital organisms that were subject to either static or cyclically-changing environments. For each of these, we examine diversity of the phenotypes that are produced through mutations in order to characterize the local genotype-phenotype map. We demonstrate that environmental change can push populations toward more evolvable mutational landscapes where many alternate phenotypes are available, though purely deleterious mutations remain suppressed. Further, we show that populations in environments with harsh changes switch phenotypes more readily than those in environments with more benign changes. We trace this effect to repeated population bottlenecks in the harsh environments, which result in shorter coalescence times and keep populations in regions of the mutational landscape where the phenotypic shifts in question are more likely to occur. Typically, static environments select solely for immediate optimization, at the expensive of long-term evolvability. In contrast, we show that with changing environments, short-term pressures to deal with immediate challenges can align with long-term pressures to explore a more productive portion of the mutational landscape.

Evolutionary Stable Strategies for Supply Chains: Selfishness, Fairness, and Altruism

2018 ◽  
Vol 6 (6) ◽  
pp. 532-551 ◽  
Author(s):  
Caichun Chai ◽  
Hailong Zhu ◽  
Zhangwei Feng
Keyword(s):  
Supply Chains ◽  
Evolutionary Dynamics ◽  
Replicator Dynamics ◽  
Management Strategies ◽  
Individual Preference ◽  
Short Term ◽  
Evolutionary Stable Strategies ◽  
Pure Strategies ◽  
The Stability

Abstract The management strategies of a firm are inevitable affected by individual behavior preferences. The effect of individual preference on the evolutionary dynamics for supply chains is studied by employing replicator dynamics. Each firm has three behavior preferences: selfishness, fairness, and altruism. Firstly, the case that the strategy set of manufacturers and retailers including two pure strategies is considered and the effect of preference parameter on the equilibrium outcome in the short-term interaction is discussed. Secondly, the equilibrium state in the short-term is always disturbed because the change of the environment, firm’s structure, and so forth. Using the replicator dynamics, the evolutionary stable strategies of manufacturers and retailers in the long-term interaction are analyzed. Finally, the extend case that the strategy set of manufacturers and retailers include three pure strategies is investigated. These results are found that the strategy profile in which both manufacturer and retailer choose fairness or altruism, or one player chooses fair or altruistic strategy and the other player chooses selfish strategy may be evolutionary stable, the stability of these equilibria depends on the the preference parameters.

scholarly journals Evolutionary dynamics in structured populations under strong population genetic forces

2019 ◽  
Author(s):  
Alison F. Feder ◽  
Pleuni S. Pennings ◽  
Joachim Hermisson ◽  
Dmitri A. Petrov
Keyword(s):  
Population Differentiation ◽  
Evolutionary Dynamics ◽  
Structured Populations ◽  
Short Term ◽  
Migration Rates ◽  
Neutral Equilibrium ◽  
Demographic Processes ◽  
And Migration ◽  
Approximate Bayesian

AbstractHigh rates of migration between subpopulations result in little population differentiation in the long-term neutral equilibrium. However, in the short-term, even very abundant migration may not be enough for subpopulations to equilibrate immediately. In this study, we investigate dynamical patterns of short-term population differentiation in adapting populations via stochastic and analytical modeling through time. We characterize a regime in which selection and migration interact to create non-monotonic patterns of the population differentiation statistic FST when migration is weaker than selection, but stronger than drift. We demonstrate how these patterns can be leveraged to estimate high migration rates that would lead to panmixia in the long term equilibrium using an approximate Bayesian computation approach. We apply this approach to estimate fast migration in a rapidly adapting intra-host Simian-HIV population sampled from different anatomical locations. Notably, we find differences in estimated migration rates between different compartments, all above Nem = 1. This work demonstrates how studying demographic processes on the timescale of selective sweeps illuminates processes too fast to leave signatures on neutral timescales.

scholarly journals The population genetics of sporophytic self–incompatibility in Senecio squalidus L. (Asteraceae): avoidance of mating constraints imposed by low S –allele number

2003 ◽  
Vol 358 (1434) ◽  
pp. 1047-1050 ◽  
Author(s):  
Adrian C. Brennan ◽  
Stephen A. Harris ◽  
Simon J. Hiscock
Keyword(s):  
Evolutionary Dynamics ◽  
Self Incompatibility ◽  
Population Bottlenecks ◽  
Short Term ◽  
Mate Availability ◽  
Allele Number ◽  
Dominance Interactions ◽  
History Of ◽  
Colonization Potential ◽  
S Allele

Senecio squalidus L. (Asteraceae) has been the subject of several ecological and population genetic studies due to its well–documented history of introduction, establishment and spread throughout Britain in the past 300 years. Our recent studies have focused on identifying and quantifying factors associated with the sporophytic self–incompatibility (SSI) system of S. squalidus that may have contributed to its success as a colonist. These findings are of general biological interest because they provide important insights into the short–term evolutionary dynamics of a plant mating system. The number of S –alleles in populations and their dominance interactions were investigated in eight wild British populations using cross–diallel studies. The numbers of S –alleles in British S. squalidus populations are typically low (average of 5.3 S –alleles) and the entire British population is estimated to possess no more than 7–11 S –alleles. Such low numbers of S –alleles are most probably a consequence of population bottlenecks associated with introduction and colonization. Potential evolutionary impacts on SSI caused by a paucity of S –alleles, such as restricted mate availability, are discussed, and we suggest that increased dominance interactions between S –alleles may be an important short–term means of increasing mate availability when S –allele numbers are low.

scholarly journals Cryptic genetic variation defines the adaptive evolutionary potential of enzymes

2017 ◽  
Author(s):  
Florian Baier ◽  
Nansook Hong ◽  
Gloria Yang ◽  
Anna Pabis ◽  
Alexandre Barrozo ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Catalytic Activity ◽  
Directed Evolution ◽  
Molecular Basis ◽  
Initial Activity ◽  
Evolutionary Potential ◽  
Phenotypic Properties ◽  
Changing Environments ◽  
Protein Functions ◽  
Evolution Of Proteins

AbstractGenetic variation among orthologous proteins can cause cryptic phenotypic properties that only manifest in changing environments. Such variation may also impact the evolutionary potential of proteins, but the molecular basis for this remains unclear. Here we perform comparative directed evolution in which four orthologous metallo-β-lactamases were evolved toward a new function. We found that genetic variation between these enzymes resulted in distinct evolutionary outcomes. The ortholog with the lower initial activity reached a 20-fold higher fitness plateau exclusively via increasing catalytic activity. By contrast, the ortholog with the highest initial activity evolved to a less-optimal and phenotypically distinct outcome through changes in expression, oligomerization and activity. We show that the cryptic molecular properties and conformational variation of residues in the initial genotypes cause epistasis, thereby constraining evolutionary outcomes. Our work highlights that understanding the molecular details relating genetic variation to protein functions is essential to predicting the evolution of proteins.

scholarly journals Cryptic genetic variation shapes the adaptive evolutionary potential of enzymes

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Florian Baier ◽  
Nansook Hong ◽  
Gloria Yang ◽  
Anna Pabis ◽  
Charlotte M Miton ◽  
...  
Keyword(s):  
Genetic Variation ◽  
Catalytic Activity ◽  
Active Site ◽  
Protein Function ◽  
Molecular Basis ◽  
Initial Activity ◽  
Active Site Residues ◽  
Evolutionary Potential ◽  
Phenotypic Properties ◽  
Changing Environments

Genetic variation among orthologous proteins can cause cryptic phenotypic properties that only manifest in changing environments. Such variation may impact the evolvability of proteins, but the underlying molecular basis remains unclear. Here, we performed comparative directed evolution of four orthologous metallo-β-lactamases toward a new function and found that different starting genotypes evolved to distinct evolutionary outcomes. Despite a low initial fitness, one ortholog reached a significantly higher fitness plateau than its counterparts, via increasing catalytic activity. By contrast, the ortholog with the highest initial activity evolved to a less-optimal and phenotypically distinct outcome through changes in expression, oligomerization and activity. We show how cryptic molecular properties and conformational variation of active site residues in the initial genotypes cause epistasis, that could lead to distinct evolutionary outcomes. Our work highlights the importance of understanding the molecular details that connect genetic variation to protein function to improve the prediction of protein evolution.

The adaptive advantage of phenotypic memory in changing environments

1995 ◽  
Vol 350 (1332) ◽  
pp. 133-141 ◽  
Keyword(s):  
Adaptive Plasticity ◽  
Adaptive Mechanism ◽  
Time Dimension ◽  
Short Term ◽  
Changing Environments ◽  
Stochastic Environments ◽  
Adaptive Value ◽  
Carry Over ◽  
The Stability

The adaptive value of carry-over effects, the persistence of induced phenotypes for several generations despite the change in the conditions that first induced these phenotypes, is studied in the framework of a simple model. Three different organismal strategies - non-inducible (genetic), completely inducible (plastic), and intermediate (carry-over) - are compared in fitness terms within three different environments. Analytical results and numerical simulations show that carry-over effects can have an advantage in stochastic environments even over organisms with high adaptive plasticity. We argue that carry-over effects represent an adaptive mechanism on the ecological timescale that fills the gap between short-term individual adaptations and long-term evolutionary adaptations. An extension of the concept of plasticity to incorporate the time dimension and include the stability of induced phenotypes through both clonal and sexual generations, is suggested.

scholarly journals The Exploration Advantage: Children’s instinct to explore allows them to find information that adults miss.

2019 ◽  
Author(s):  
Emily Sumner ◽  
Amy Xiangjin Li ◽  
Amy Perfors ◽  
Brett Hayes ◽  
Danielle Navarro ◽  
...  
Keyword(s):  
Human Beings ◽  
Short Term ◽  
Changing Environments ◽  
The World ◽  
Dynamic Version ◽  
The Cost

Humans have a long childhood in comparison to all other species. Across disciplines, researchers agree that humans’ prolonged immaturity is integral to our unique intelligence. The studies presented here support the hypothesis that human beings’ extended childhood pays off in the form of an ability to learn more about changing environments. Across two studies (n = 213), children and adults played a game where they chose among four different cartoon monsters yielding different numbers of star rewards. Adults focused on maximizing reward, while children chose to explore longer, even at the cost of earning fewer stars. As a result, adults won significantly more stars than children did. However, in the ‘dynamic’ version of the task, the rewards given out by the monsters changed halfway through: the monster that had been giving out the fewest stars began giving out the most. Because children continued to explore whereas adults ignored the low-reward monster, children were much more likely than adults to detect the change. This illustrates that while exploration may be costly in the short term, it leads to a more flexible understanding of the world in the long term, particularly when that world is changing.

scholarly journals Evolutionary Dynamics in Structured Populations Under Strong Population Genetic Forces

2019 ◽  
Vol 9 (10) ◽  
pp. 3395-3407 ◽  
Author(s):  
Alison F. Feder ◽  
Pleuni S. Pennings ◽  
Joachim Hermisson ◽  
Dmitri A. Petrov
Keyword(s):  
Population Differentiation ◽  
Evolutionary Dynamics ◽  
Structured Populations ◽  
Short Term ◽  
Migration Rates ◽  
Neutral Equilibrium ◽  
Demographic Processes ◽  
And Migration ◽  
Approximate Bayesian

In the long-term neutral equilibrium, high rates of migration between subpopulations result in little population differentiation. However, in the short-term, even very abundant migration may not be enough for subpopulations to equilibrate immediately. In this study, we investigate dynamical patterns of short-term population differentiation in adapting populations via stochastic and analytical modeling through time. We characterize a regime in which selection and migration interact to create non-monotonic patterns of population differentiation over time when migration is weaker than selection, but stronger than drift. We demonstrate how these patterns can be leveraged to estimate high migration rates using approximate Bayesian computation. We apply this approach to estimate fast migration in a rapidly adapting intra-host Simian-HIV population sampled from different anatomical locations. We find differences in estimated migration rates between different compartments, even though all are above Nem = 1. This work demonstrates how studying demographic processes on the timescale of selective sweeps illuminates processes too fast to leave signatures on neutral timescales.

Conceptual short-term memory (CSTM) supports core claims of Christiansen and Chater

2016 ◽  
Vol 39 ◽  
Author(s):  
Mary C. Potter
Keyword(s):  
Working Memory ◽  
Rapid Serial Visual Presentation ◽  
Language Comprehension ◽  
Short Term Memory ◽  
Visual Presentation ◽  
Long Term Memory ◽  
Short Term ◽  
Term Memory ◽  
Use Of Knowledge

AbstractRapid serial visual presentation (RSVP) of words or pictured scenes provides evidence for a large-capacity conceptual short-term memory (CSTM) that momentarily provides rich associated material from long-term memory, permitting rapid chunking (Potter 1993; 2009; 2012). In perception of scenes as well as language comprehension, we make use of knowledge that briefly exceeds the supposed limits of working memory.

Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

1990 ◽  
Vol 48 (3) ◽  
pp. 374-375
Author(s):  
D.E. Loudy ◽  
J. Sprinkle-Cavallo ◽  
J.T. Yarrington ◽  
F.Y. Thompson ◽  
J.P. Gibson
Keyword(s):  
Antidepressant Drug ◽  
Beagle Dogs ◽  
Long Term Effects ◽  
Short Term ◽  
Platelet Counts ◽  
Toxicological Studies ◽  
Induced Aggregation ◽  
Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

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