I. Scheuring - Academia.edu (original) (raw)

Papers by I. Scheuring

Ecology Letters, 2011

We review recent work at the interface of economic game theory and evolutionary biology that prov... more We review recent work at the interface of economic game theory and evolutionary biology that provides new insights into the evolution of partner choice, host sanctions, partner fidelity feedback and public goods. (1) The theory of games with asymmetrical information shows that the right incentives allow hosts to screen-out parasites and screen-in mutualists, explaining successful partner choice in the absence of signalling. Applications range from ant-plants to microbiomes. (2) Contract theory distinguishes two longstanding but weakly differentiated explanations of host response to defectors: host sanctions and partner fidelity feedback. Host traits that selectively punish misbehaving symbionts are parsimoniously interpreted as pre-adaptations. Yucca-moth and legume-rhizobia mutualisms are argued to be examples of partner fidelity feedback. (3) The theory of public goods shows that cooperation in multi-player interactions can evolve in the absence of assortment, in one-shot social dilemmas among non-kin. Applications include alarm calls in vertebrates and exoenzymes in microbes.

Community Ecology, 2009

There is increasing evidence that regime shifts occur at several scales in ecosystems (from the s... more There is increasing evidence that regime shifts occur at several scales in ecosystems (from the spatiotemporal alternation of two species to large-scale, ecosystem-level rearrangements). Yet, the theoretical background for understanding these changes is far from clear. Since fishing down in marine ecosystems is well-documented trend, and its top-down cascading effects in food webs have been richly documented, it is a current question whether overfishing, in general, can also influence regime shifts at lower levels. We model simple marine ecosystems by dynamical food webs and investigate the probability of regime shifts emerging among primary consumers. We considered cases where only one of the primary consumers is persistent in the stationary state. By perturbing the death rates in the food web, we studied the circumstances when the previously persistent primary producer is indirectly changed by the previously non-persistent one. Whether and how regime shifts (e.g., change in primary consumers) can occur depends on (1) food web topology (presence of top-predator and alternative producer), (2) the relative strength of perturbation of primary consumers' death rates, and (3) the dynamical parameters of the recovering consumer. We found that overfishing, food web topology and dynamical parameters together determine the probability of regime shifts. Thus, integrative and complex models are needed in multispecies fisheries.

Theoretical Population Biology, 2003

We investigate the effects of spatial heterogeneity on the coexistence of competing species in th... more We investigate the effects of spatial heterogeneity on the coexistence of competing species in the case when the heterogeneity is dynamically generated by environmental flows with chaotic mixing properties. We show that one of the effects of chaotic advection on the passively advected species (such as phytoplankton, or self-replicating macromolecules) is the possibility of coexistence of more species than that limited by the number of niches they occupy. We derive a novel set of dynamical equations for competing populations.

Proceedings of the National Academy of Sciences, 2000

Hydrodynamical phenomena play a keystone role in the population dynamics of passively advected sp... more Hydrodynamical phenomena play a keystone role in the population dynamics of passively advected species such as phytoplankton and replicating macromolecules. Recent developments in the field of chaotic advection in hydrodynamical flows encourage us to revisit the population dynamics of species competing for the same resource in an open aquatic system. If this aquatic environment is homogeneous and well-mixed then classical studies predict competitive exclusion of all but the most perfectly adapted species. In fact, this homogeneity is very rare, and the species of the community (at least on an ecological observation time scale) are in nonequilibrium coexistence. We argue that a peculiar small-scale, spatial heterogeneity generated by chaotic advection can lead to coexistence. In open flows this imperfect mixing lets the populations accumulate along fractal filaments, where competition is governed by an “advantage of rarity” principle. The possibility of this generic coexistence sheds...

Physica A: Statistical Mechanics and its Applications, 1999

We investigate the dynamics of tracer particles in time-dependent open ows. If the advection is p... more We investigate the dynamics of tracer particles in time-dependent open ows. If the advection is passive the tracer dynamics is shown to be typically transiently chaotic. This implies the appearance of stable fractal patterns, so-called unstable manifolds, traced out by ensembles of particles. Next, the advection of chemically or biologically active tracers is investigated. Since the tracers spend a long time in the vicinity of a fractal curve, the unstable manifold, this fractal structure serves as a catalyst for the active process. The permanent competition between the enhanced activity along the unstable manifold and the escape due to advection results in a steady state of constant production rate. This observation provides a possible solution for the so-called "paradox of plankton", that several competing plankton species are able to coexists in spite of the competitive exclusion predicted by classical studies. We point out that the derivation of the reaction (or population dynamics) equations is analog to that of the macroscopic transport equations based on a microscopic kinetic theory whose support is a fractal subset of the full phase space.

Chaos: An Interdisciplinary Journal of Nonlinear Science, 2000

ABSTRACT A pályázat keretében végzett kutatásaink a következő elméleti témakörökben történtek: 1)... more ABSTRACT 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.

Abstract. Here we show a simple mechanism in which changes in the rate of horizontal stirring by ... more Abstract. Here we show a simple mechanism in which changes in the rate of horizontal stirring by mesoscale ocean eddies can trigger or suppress plankton blooms and can lead to an abrupt change in the average plankton density. We consider a single species phytoplankton model with logistic growth, grazing and a spatially non-uniform carrying capac-ity. The local dynamics have multiple steady states for some values of the carrying capacity that can lead to localized blooms as fluid moves across the regions with different prop-erties. We show that for this model even small changes in the ratio of biological timescales relative to the flow timescales can greatly enhance or reduce the global plankton produc-tivity. Thus, this may be a possible mechanism in which changes in horizontal mixing can trigger plankton blooms or cause regime shifts in some oceanic regions. Compari-son between the spatially distributed model and Lagrangian simulations considering temporal fluctuations along fluid ...

This talk discusses some recent results on the interplay between oceanic turbulence and marine ec... more This talk discusses some recent results on the interplay between oceanic turbulence and marine ecosystem functioning, considering both numerical simulations of geophysical turbulence and the analysis of satellite data. Attention will be focussed on the effects of mesoscale structures on nutrient input and on primary productivity in the ocean. I shall also discuss the role of mesoscale vortices as transport barriers, a fact that may have interesting consequences on plankton competition and on marine

Scientific Reports

A better understanding of how the COVID-19 pandemic responds to social distancing efforts is requ... more A better understanding of how the COVID-19 pandemic responds to social distancing efforts is required for the control of future outbreaks and to calibrate partial lock-downs. We present quantitative relationships between key parameters characterizing the COVID-19 epidemiology and social distancing efforts of nine selected European countries. Epidemiological parameters were extracted from the number of daily deaths data, while mitigation efforts are estimated from mobile phone tracking data. The decrease of the basic reproductive number ($$R_0$$ R 0 ) as well as the duration of the initial exponential expansion phase of the epidemic strongly correlates with the magnitude of mobility reduction. Utilizing these relationships we decipher the relative impact of the timing and the extent of social distancing on the total death burden of the pandemic.

We study the transition of an epidemic from growth phase to decay of the active infections in a p... more We study the transition of an epidemic from growth phase to decay of the active infections in a population when lockdown measures are introduced to reduce the probability of disease transmission. While in the case of uniform lockdown a simple compartmental model would indicate instantaneous transition to decay of the epidemic, this is not the case when partially isolated active clusters remain with the potential to create a series of small outbreaks. We model this using a connected set of stochastic susceptible-infected-removed/recovered (SIR) models representing the locked-down majority population (where the reproduction number is less than one) weakly coupled to a large set of small clusters where the infection may propagate. We find that the presence of such active clusters can lead to slower than expected decay of the epidemic and significantly delayed onset of the decay phase. We study the relative contributions of these changes to the additional total infections caused by the ...

Selection

Theoretical ecologists have observed chaotic behavior in population models for decades. However, ... more Theoretical ecologists have observed chaotic behavior in population models for decades. However, in the past few years, several studies indicate that complex dynamics, including chaos, become less probable in biologically more sophisticated models. For example, the inclusion of either sexual reproduction, population structure or dispersal generally increases stability. These results can explain the difference between the dynamical complexity of most theoretical models and the relative stability found within real time series.

Proceedings of The National Academy of Sciences, 2000

Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 1995

Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 1994

Although ecologists have been aware for almost 20 years that population densities may evolve in a... more Although ecologists have been aware for almost 20 years that population densities may evolve in a chaotic way, the evidence for chaos in natuml populations is rather poor. The lack of convincing evidence may have its origin in the difBculty of estimating the efFect of external environmental noise, but it may also re8ect natural regulation processes. In this paper we present a meta-populationdynamical model, in which the nearest neighbor local population &agments interact by applying a threshold condition. Namely, each local population follows its own temporal evolution until a critical population density is reached, which initiates dispersal (migration) events to the neighbors. The type of interaction is common to self-organized critical cellular automaton models. Depending on the threshold level, the global behavior of our model can be characterized either by noisy dynamics with many degrees of &eedom, by a periodical evolution, or by an evolution towards a fixed point. Low dimensional collective chaos does not occur. Moreover, self-organized criticality with power law distributions emerges if the interaction between the neighboring local populations is strong enough.

Origins of Life and Evolution of Biospheres, 2003

The problem of information integration and resistance to the invasion of parasitic mutants in pre... more The problem of information integration and resistance to the invasion of parasitic mutants in prebiotic replicator systems is a notorious issue of research on the origin of life. Almost all theoretical studies published so far have demonstrated that some kind of spatial structure is indispensable for the persistence and/or the parasite resistance of any feasible replicator system. Based on a detailed critical survey of spatial models on prebiotic information integration, we suggest a possible scenario for replicator system evolution leading to the emergence of the first protocells capable of independent life. We show that even the spatial versions of the hypercycle model are vulnerable to selfish parasites in heterogeneous habitats. Contrary, the metabolic system remains persistent and coexistent with its parasites both on heterogeneous surfaces and in chaotically mixing flowing media. Persistent metabolic parasites can be converted to metabolic cooperators, or they can gradually obtain replicase activity. Our simulations show that, once replicase activity emerged, a gradual and simultaneous evolutionary improvement of replicase functionality (speed and fidelity) and template efficiency is possible only on a surface that constrains the mobility of macromolecule replicators. Based on the results of the models reviewed, we suggest that open chaotic flows ('soup') and surface dynamics ('pizza') both played key roles in the sequence of evolutionary events ultimately concluding in the appearance of the first living cell on Earth.