| 1. |
- Hammerstein, Peter, 1971-
(författare)
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Stochastic Resonance and Noise-Assisted Signal Transfer : On Coupling Effects of Stochastic Resonators and Spectral Optimization of Fluctuations in Random Network Switches
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recent research shows that noise or random fluctuations must not always be destructive in Nature by degrading system performance. On the contrary, in nonlinear systems they can synchronize systems or enhance the quality of signal transmission. The latter possibility is reported in the thesis.The phenomenon of stochastic resonance (SR) is presented and illustrated by an example of a ferromagnetically coupled spin chain, described by the Glauber's stochastic Ising spin model. It is demonstrated that an optimal strength of the next-neighbor interaction is able to improve the SR-effect. A similar mechanism has further been studied on the stochastic nonlinear dynamics of a ferromagnetic stripe domain in an inhomogeneous thin film. SR and its dependence on the domain stiffness, which is due to the exchange interaction, are presented. Experimental parameters for potential verification on Bi-doped epitaxial garnet-ferrite films are proposed. Further-on, a nonlinear model of a junction in neuronal and road structures is studied using various types of noise (stochastic processes) to generate the incoming traffic. It is shown that random fluctuations are able to enhance signal transmission, whereby the zero crossings of colored (1/fk) Gaussian noise is superior to Poissonian noise and, in certain cases, to deterministic, periodic traffic too. Optimal traffic for k ≈ 1 has been found. In case of Gaussian 1/fk noise modulated periodic input, noise-assisted traffic can be observed as well and demonstrate how random fluctuations can enhance the signal traffic efficiency in a network. The effect of an optimal k has finally been applied to a data package network switch, whereby a stochastic data scheduling algorithm is proposed and investigated numerically and analytically.
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| 2. |
- Kuijper, Bram, et al.
(författare)
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The evolution of social learning as phenotypic cue integration
- 2021
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Ingår i: Philosophical Transactions of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8436 .- 1471-2970. ; 376:1828
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Tidskriftsartikel (refereegranskat)abstract
- Most analyses of the origins of cultural evolution focus on when and where social learning prevails over individual learning, overlooking the fact that there are other developmental inputs that influence phenotypic fit to the selective environment. This raises the question of how the presence of other cue ‘channels’ affects the scope for social learning. Here, we present a model that considers the simultaneous evolution of (i) multiple forms of social learning (involving vertical or horizontal learning based on either prestige or conformity biases) within the broader context of other evolving inputs on phenotype determination, including (ii) heritable epigenetic factors, (iii) individual learning, (iv) environmental and cascading maternal effects, (v) conservative bet-hedging, and (vi) genetic cues. In fluctuating environments that are autocorrelated (and hence predictable), we find that social learning from members of the same generation (horizontal social learning) explains the large majority of phenotypic variation, whereas other cues are much less important. Moreover, social learning based on prestige biases typically prevails in positively autocorrelated environments, whereas conformity biases prevail in negatively autocorrelated environments. Only when environments are unpredictable or horizontal social learning is characterized by an intrinsically low information content, other cues such as conservative bet-hedging or vertical prestige biases prevail.This article is part of the theme issue ‘Foundations of cultural evolution’.
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| 3. |
- Leimar, Olof, et al.
(författare)
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Cooperation for direct fitness benefits
- 2010
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Ingår i: Philosophical transactions of the Royal Society of London. Series B, Biological sciences. - : The Royal Society. - 1471-2970. ; 365:1553, s. 2619-2626
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Tidskriftsartikel (refereegranskat)abstract
- Studies of the evolution of helping have traditionally used the explanatory frameworks of reciprocity and altruism towards relatives, but recently there has been an increasing interest in other kinds of explanations. We review the success or otherwise of work investigating alternative processes and mechanisms, most of which fall under the heading of cooperation for direct benefits. We evaluate to what extent concepts such as by-product benefits, pseudo-reciprocity, sanctions and partner choice, markets and the build-up of cross-species spatial trait correlations have contributed to the study of the evolution of cooperation. We conclude that these alternative ideas are successful and show potential to further increase our understanding of cooperation. We also bring up the origin and role of common interest in the evolution of cooperation, including the appearance of organisms. We note that there are still unresolved questions about the main processes contributing to the evolution of common interest. Commenting on the broader significance of the recent developments, we argue that they represent a justified balancing of the importance given to different major hypotheses for the evolution of cooperation. This balancing is beneficial because it widens considerably the range of phenomena addressed and, crucially, encourages empirical testing of important theoretical alternatives.
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| 4. |
- Leimar, Olof, et al.
(författare)
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Ecological Genetic Conflict : Genetic Architecture Can Shift the Balance between Local Adaptation and Plasticity
- 2019
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 193:1, s. 70-80
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Tidskriftsartikel (refereegranskat)abstract
- Genetic polymorphism can contribute to local adaptation in heterogeneous habitats, for instance, as a single locus with alleles adapted to different habitats. Phenotypic plasticity can also contribute to trait variation across habitats, through developmental responses to habitat-specific cues. We show that the genetic architecture of genetically polymorphic and plasticity loci may influence the balance between local adaptation and phenotypic plasticity. These effects of genetic architecture are instances of ecological genetic conflict. A reduced effective migration rate for genes tightly linked to a genetic polymorphism provides an explanation for the effects, and they can occur both for a single trait and for a syndrome of coadapted traits. Using individual-based simulations and numerical analysis, we investigate how among-habitat genetic polymorphism and phenotypic plasticity depend on genetic architecture. We also study the evolution of genetic architecture itself, in the form of rates of recombination between genetically polymorphic loci and plasticity loci. Our main result is that for plasticity genes that are unlinked to loci with between-habitat genetic polymorphism, the slope of a reaction norm is steeper in comparison with the slope favored by plasticity genes that are tightly linked to genes for local adaptation.
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| 5. |
- Leimar, Olof, et al.
(författare)
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Genes as Cues of Relatedness and Social Evolution in Heterogeneous Environments
- 2016
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Ingår i: PloS Computational Biology. - : Public Library of Science (PLoS). - 1553-734X .- 1553-7358. ; 12:6
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Tidskriftsartikel (refereegranskat)abstract
- There are many situations where relatives interact while at the same time there is genetic polymorphism in traits influencing survival and reproduction. Examples include cheater-cooperator polymorphism and polymorphic microbial pathogens. Environmental heterogeneity, favoring different traits in nearby habitats, with dispersal between them, is one general reason to expect polymorphism. Currently, there is no formal framework of social evolution that encompasses genetic polymorphism. We develop such a framework, thus integrating theories of social evolution into the evolutionary ecology of heterogeneous environments. We allow for adaptively maintained genetic polymorphism by applying the concept of genetic cues. We analyze a model of social evolution in a two-habitat situation with limited dispersal between habitats, in which the average relatedness at the time of helping and other benefits of helping can differ between habitats. An important result from the analysis is that alleles at a polymorphic locus play the role of genetic cues, in the sense that the presence of a cue allele contains statistical information for an organism about its current environment, including information about relatedness. We show that epistatic modifiers of the cue polymorphism can evolve to make optimal use of the information in the genetic cue, in analogy with a Bayesian decision maker. Another important result is that the genetic linkage between a cue locus and modifier loci influences the evolutionary interest of modifiers, with tighter linkage leading to greater divergence between social traits induced by different cue alleles, and this can be understood in terms of genetic conflict.
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| 6. |
- McNamara, John M., et al.
(författare)
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Detection vs. selection : integration of genetic, epigenetic and environmental cues in fluctuating environments
- 2016
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Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 19:10, s. 1267-1276
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Tidskriftsartikel (refereegranskat)abstract
- There are many inputs during development that influence an organism's fit to current or upcoming environments. These include genetic effects, transgenerational epigenetic influences, environmental cues and developmental noise, which are rarely investigated in the same formal framework. We study an analytically tractable evolutionary model, in which cues are integrated to determine mature phenotypes in fluctuating environments. Environmental cues received during development and by the mother as an adult act as detection-based (individually observed) cues. The mother's phenotype and a quantitative genetic effect act as selection-based cues (they correlate with environmental states after selection). We specify when such cues are complementary and tend to be used together, and when using the most informative cue will predominate. Thus, we extend recent analyses of the evolutionary implications of subsets of these effects by providing a general diagnosis of the conditions under which detection and selection-based influences on development are likely to evolve and coexist.
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| 7. |
- Smolla, Marco, et al.
(författare)
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Underappreciated features of cultural evolution
- 2024
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Cultural evolution theory has long been inspired by evolutionary biology. Conceptual analogies between biological and cultural evolution have led to the adoption of a range of formal theoretical approaches from population dynamics and genetics. However, this has resulted in a research programme with a strong focus on cultural transmission. Here, we contrast biological with cultural evolution, and highlight aspects of cultural evolution that have not received sufficient attention previously. We outline possible implications for evolutionary dynamics and argue that not taking them into account will limit our understanding of cultural systems. We propose twelve key questions for future research, among which are calls to improve our understanding of the combinatorial properties of cultural innovation, and the role of development and life history in cultural dynamics. Finally, we discuss how this vibrant research field can make progress by embracing its multidisciplinary nature.
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| 8. |
- Smolla, Marco, et al.
(författare)
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Underappreciated features of cultural evolution
- 2021
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Ingår i: Proceedings of the Royal Society of London. Biological Sciences. - : The Royal Society. - 0962-8452 .- 1471-2954 .- 0962-8436 .- 1471-2970. ; 376:1828
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Tidskriftsartikel (refereegranskat)abstract
- Cultural evolution theory has long been inspired by evolutionary biology. Conceptual analogies between biological and cultural evolution have led to the adoption of a range of formal theoretical approaches from population dynamics and genetics. However, this has resulted in a research programme with a strong focus on cultural transmission. Here, we contrast biological with cultural evolution, and highlight aspects of cultural evolution that have not received sufficient attention previously. We outline possible implications for evolutionary dynamics and argue that not taking them into account will limit our understanding of cultural systems. We propose twelve key questions for future research, among which are calls to improve our understanding of the combinatorial properties of cultural innovation, and the role of development and life history in cultural dynamics. Finally, we discuss how this vibrant research field can make progress by embracing its multidisciplinary nature.
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