Prebiotikus és mikrobiális kooperatív rendszerek evolúciójának térben explicit modellezése = Spatially explicit models for the evolution of prebiotic and microbial cooperation

A jelen OTKA-pályázati támogatás keretében elvégzett munkánkat 14 cikkben publikáltuk. Ezek közül 8 jelent meg rangos nemzetközi folyóiratokban, 3 az ""Ökológia"" címmel 2009-ben megjelent tankönyv fejezete, és 3 magyar nyelvű ismeretterjesztő cikk, amelyek közül kettő a Magyar Tudomány-ban, más tudományterületek szakértői számára, egy pedig a szélesebb közönség számára íródott. A kutatási program 3 alprogramra osztható, melyek közös foglalata részben koncepcionális, részben módszertani jellegű. Mindhárom al-téma közvetlenül az evolválódó entitások populációinak térbeli és időbeli dinamikájához kapcsolódik. Az említett entitások lehetnek prebiotikus replikátor-molekulák (az RNS-világ fajainak képviselői), ill. mikro- vagy makroorganizmusok. Kérdéseink ezek populációinak együttélési feltételeire, valamint a dinamikából következő (ko-)evolúciós viszonyaikra vonatkoznak, különböző tér- és időbeli léptékekben. Elméleti eredményeink némelyikét laboratóriumban teszteltük, ill. azok tesztelése folyamatban van. | The results of our research supported by this OTKA project have been summarized in 14 papers, of which 8 are published in high-ranking international journals, 3 are textbook chapters and 3 are reviews of our work, intended either for the professional or the general public, in Hungarian. The project is divided into 3 sub-projects, the common framework of which is partly conceptual and partly methodological. All of the three sub-topics are directly related to the spatio-temporal dynamics of evolving entities which may be populations of either prebiotic replicators or of micro- and macroorganisms. Our questions are directed towards the possible coexistence of such entities on different spatial and temporal scales, and the possible (co-)evolution of their populations thereof. Some of our theoretical results have been (and are being) tested int he lab

Prebiotic replicase evolution in a surface-bound metabolic system: parasites as a source of adaptive evolution

<p>Abstract</p> <p>Background</p> <p>The remarkable potential of recent forms of life for reliably passing on genetic information through many generations now depends on the coordinated action of thousands of specialized biochemical "machines" (enzymes) that were obviously absent in prebiotic times. Thus the question how a complicated system like the living cell could have assembled on Earth seems puzzling. In seeking for a scientific explanation one has to search for step-by-step evolutionary changes from prebiotic chemistry to the emergence of the first proto-cell.</p> <p>Results</p> <p>We try to sketch a plausible scenario for the first steps of prebiotic evolution by exploring the ecological feasibility of a mineral surface-bound replicator system that facilitates a primitive metabolism. Metabolism is a hypothetical network of simple chemical reactions producing monomers for the template-copying of RNA-like replicators, which in turn catalyse metabolic reactions. Using stochastic cellular automata (SCA) simulations we show that the surface-bound metabolic replicator system is viable despite internal competition among the genes and that it also maintains a set of mild "parasitic" sequences which occasionally evolve functions such as that of a replicase.</p> <p>Conclusion</p> <p>Replicase activity is shown to increase even at the expense of slowing down the replication of the evolving ribozyme itself, due to indirect mutualistic benefits in a diffuse form of group selection among neighbouring replicators. We suggest possible paths for further evolutionary changes in the metabolic replicator system leading to increased metabolic efficiency, improved replicase functionality, and membrane production.</p

Stability of Localized Wave Fronts in Bistable Systems

Localized wave fronts are a fundamental feature of biological systems from cell biology to ecology. Here, we study a broad class of bistable models subject to self-activation, degradation, and spatially inhomogeneous activating agents. We determine the conditions under which wave-front localization is possible and analyze the stability thereof with respect to extrinsic perturbations and internal noise. It is found that stability is enhanced upon regulating a positional signal and, surprisingly, also for a low degree of binding cooperativity. We further show a contrasting impact of self-activation to the stability of these two sources of destabilization. DOI: 10.1103/PhysRevLett.110.03810

Evolution of sexual asymmetry

BACKGROUND: The clear dominance of two-gender sex in recent species is a notorious puzzle of evolutionary theory. It has at least two layers: besides the most fundamental and challenging question why sex exists at all, the other part of the problem is equally perplexing but much less studied. Why do most sexual organisms use a binary mating system? Even if sex confers an evolutionary advantage (through whatever genetic mechanism), why does it manifest that advantage in two, and exactly two, genders (or mating types)? Why not just one, and why not more than two? RESULTS: Assuming that sex carries an inherent fitness advantage over pure clonal multiplication, we attempt to give a feasible solution to the problem of the evolution of dimorphic sexual asymmetry as opposed to monomorphic symmetry by using a spatial (cellular automaton) model and its non-spatial (mean-field) approximation. Based on a comparison of the spatial model to the mean-field approximation we suggest that spatial population structure must have played a significant role in the evolution of mating types, due to the largely clonal (self-aggregated) spatial distribution of gamete types, which is plausible in aquatic habitats for physical reasons, and appears to facilitate the evolution of a binary mating system. CONCLUSIONS: Under broad ecological and genetic conditions the cellular automaton predicts selective removal from the population of supposedly primitive gametes that are able to mate with their own type, whereas the non-spatial model admits coexistence of the primitive type and the mating types. Thus we offer a basically ecological solution to a theoretical problem that earlier models based on random gamete encounters had failed to resolve

Topográfiai és topológiai kényszerek evolúciós és ökológiai rendszerekben = Topographical and topological constraints in evolutionary and ecological systems

A pályázat keretében végzett kutatásaink a következő elméleti témakörökben történtek: 1) Párosodási típusok evolúciója térben explicit modellel 2) Korai evolúciós problémák vizsgálata 3) A diszperzió és a mutualizmus evolúciója 4) Metapopulációk erősen zajos környezetben 5) Az interferencia-kompetíció szerepe mikrobiális élet-közösségek diverzitásának fenntartásában 6) Táplálékhálózatok szerkezete és stabilitása. Ebben a hat témakörben összesen 38, a pályázat azonosító számának feltüntetésével megjelent publikáció született, melyek összesített impakt faktora 113.86. Mindegyik témában folytatjuk a kutatásokat. | We have accomplished research in the following theoretical topics with the support of the present grant: 1) The evolution of mating types in a spatially explicit model 2) Research on problems of early evolution 3) The evolution of dispersal and mutualism 4) The dynamics of metapopulations in very noisy environments 5) The role of interference competition in the maintenance of the diversity of microbial communities 6) The strucure and the stability of food webs We have published 38 papers on these six topics with the number of the grant mentioned in the Acknowledgements of the papers. The cumulative impact factor of these publications is 113.86. We are planning to continue research in all the six topics

Directional selection coupled with kin selection favors the establishment of senescence

Background Conventional wisdom in evolutionary theory considers aging as a non-selected byproduct of natural selection. Based on this, conviction aging was regarded as an inevitable phenomenon. It was also thought that in the wild organisms tend to die from diseases, predation and other accidents before they could reach the time when senescence takes its course. Evidence has accumulated, however, that aging is not inevitable and there are organisms that show negative aging even. Furthermore, old age does play a role in the deaths of many different organisms in the wild also. The hypothesis of programmed aging posits that a limited lifespan can evolve as an adaptation (i.e., positively selected for) in its own right, partly because it can enhance evolvability by eliminating “outdated” genotypes. A major shortcoming of this idea is that non-aging sexual individuals that fail to pay the demographic cost of aging would be able to steal good genes by recombination from aging ones. Results Here, we show by a spatially explicit, individual-based simulation model that aging can positively be selected for if a sufficient degree of kin selection complements directional selection. Under such conditions, senescence enhances evolvability because the rate of aging and the rate of recombination play complementary roles. The selected aging rate is highest at zero recombination (clonal reproduction). In our model, increasing extrinsic mortality favors evolved aging by making up free space, thereby decreasing competition and increasing drift, even when selection is stabilizing and the level of aging is set by mutation-selection balance. Importantly, higher extrinsic mortality is not a substitute for evolved aging under directional selection either. Reduction of relatedness decreases the evolved level of aging; chance relatedness favors non-aging genotypes. The applicability of our results depends on empirical values of directional and kin selection in the wild. Conclusions We found that aging can positively be selected for in a spatially explicit population model when sufficiently strong directional and kin selection prevail, even if reproduction is sexual. The view that there is a conceptual link between giving up clonal reproduction and evolving an aging genotype is supported by computational results.info:eu-repo/semantics/publishedVersio

Defensive alliances in spatial models of cyclical population interactions

As a generalization of the 3-strategy Rock-Scissors-Paper game dynamics in space, cyclical interaction models of six mutating species are studied on a square lattice, in which each species is supposed to have two dominant, two subordinated and a neutral interacting partner. Depending on their interaction topologies, these systems can be classified into four (isomorphic) groups exhibiting significantly different behaviors as a function of mutation rate. On three out of four cases three (or four) species form defensive alliances which maintain themselves in a self-organizing polydomain structure via cyclic invasions. Varying the mutation rate this mechanism results in an ordering phenomenon analogous to that of magnetic Ising model.Comment: 4 pages, 3 figure

The early evolution of cooperation in humans: On cheating, group identity and group size

The evolution of cooperation is difficult to understand, because cheaters — individuals who profit without cooperating themselves — have a benefit in interaction with cooperators. Cooperation among humans is even more difficult to understand, because cooperation occurs in large groups, making cheating a bigger threat. Restricting cooperation to members of one’s own group based on some tag-based recognition of non-group members (allorecognition) has been shown to stabilise cooperation. We address how spatial structure and group size affect the opportunities for cheating such tag-based cooperation in a spatially explicit simulation. We show that increased group diversity, under conditions of limited dispersal, reduces the selective opportunities for cheaters. A small number can already be sufficient to keep cheating at a low frequency. We discuss how marginal additional benefits of increased group size, above the benefits of local cooperation, can provide the selective pressure to reduce the number of group identities and discuss possible examples

Metabolically Coupled Replicator Systems: Overview of an RNA-world model concept of prebiotic evolution on mineral surfaces

Metabolically Coupled Replicator Systems (MCRS) are a family of models implementing a simple, physico-chemically and ecologically feasible scenario for the first steps of chemical evolution towards life. Evolution in an abiotically produced RNA-population sets in as soon as any one of the RNA molecules become autocatalytic by engaging in template directed self-replication from activated monomers, and starts increasing exponentially. Competition for the finite external supply of monomers ignites selection favouring RNA molecules with catalytic activity helping self-replication by any possible means. One way of providing such autocatalytic help is to become a replicase ribozyme. An additional way is through increasing monomer supply by contributing to monomer synthesis from external resources, i.e., by evolving metabolic enzyme activity. Retroevolution may build up an increasingly autotrophic, cooperating community of metabolic ribozymes running an increasingly complicated and ever more efficient metabolism. Maintaining such a cooperating community of metabolic replicators raises two serious ecological problems: one is keeping the system coexistent in spite of the different replicabilities of the cooperating replicators; the other is constraining parasitism, i.e., keeping "cheaters" in check. Surface-bound MCRS provide an automatic solution to both problems: coexistence and parasite resistance are the consequences of assuming the local nature of metabolic interactions. In this review we present an overview of results published in previous articles, showing that these effects are, indeed, robust in different MCRS implementations, by considering different environmental setups and realistic chemical details in a few different models. We argue that the MCRS model framework naturally offers a suitable starting point for the future modelling of membrane evolution and extending the theory to cover the emergence of the first protocell in a self-consistent manner. The coevolution of metabolic, genetic and membrane functions is hypothesized to follow the progressive sequestration scenario, the conceptual blueprint for the earliest steps of protocell evolution. (C) 2015 Elsevier Ltd. All rights reserved