Randomness in the evolution of cooperation.

Tag-based ethnocentric cooperation is a highly robust behavior which can evolve and prevail under a wide variety of conditions. Recent studies have demonstrated, however, that ethnocentrism can temporarily be suppressed by other competing strategies, especially in its early evolutionary stages. In a series of computational experiments, conducted with an agent-based evolutionary model of tag-mediated cooperation, we addressed the question of whether a stochastically established and once dominant non-ethnocentric strategy such as indiscriminate altruism can stably persist and permanently outweigh ethnocentrism.

Haplotype complementarity under mutational pressure.

Natural populations do not correspond to Mendelian populations. Effective populations are much smaller, inbreeding higher, and organization of large number of genes into chromosomes connected with relatively low recombination rate invalidates the law of independent gene assortment. Under such conditions, a large number of genes is inherited as clusters and evolves as genetic units.

Simulated self-organization of death by inherited mutations.

An agent-based computer simulation of death by inheritable mutations in a changing environment shows a maximal population, or avoids extinction, at some intermediate mutation rate of the individuals. Our results indicate that death seems needed to allow for evolution of the fittest, as required by a changing environment.

Agent-based computer simulations of language choice dynamics.

We use agent-based Monte Carlo simulations to address the problem of language choice dynamics in a tripartite community that is linguistically homogeneous but politically divided. We observe the process of nonlocal pattern formation that causes populations to self-organize into stable antagonistic groups as a result of the local dynamics of attraction and influence between individual computational agents. Our findings uncover some of the unique properties of opinion formation in social groups when the process is affected by asymmetric noise distribution, unstable intergroup boundaries, and different migratory behaviors.

Altruism and antagonistic pleiotropy in Penna ageing model.

The Penna ageing model is based on mutation accumulation theory. We show that it also allows for self-organization of antagonistic pleiotropy which helps at young age at the expense of old age. This can be interpreted as emergence of altruism.

Why are diploid genomes widespread and dominant mutations rare?

We have used the sexual Penna ageing model to show that the relation between dominance and recessiveness could be a force which optimizes the genome size. While the possibility of complementation of the damaged allele by its functional counterparts (recessiveness) leads to the redundancy of genetic information, the dominant effect of defective genes tends to diminish the number of alleles fulfilling the same function. Playing with the fraction of dominant loci in the genome it is possible to obtain the condition where the diploid state of the genome is optimal.

Superdiffusion in a model for diffusion in a molecularly crowded environment.

We present a model for diffusion in a molecularly crowded environment. The model consists of random barriers in a percolation network. Random walks in the presence of slowly moving barriers show normal diffusion for long times but anomalous diffusion at intermediate times.

Simulation of Rapoport's rule for latitudinal species spread.

Rapoport's rule claims that latitudinal ranges of plant and animal species are generally smaller at low than at high latitudes. However, doubts as to the generality of the rule have been expressed, because studies providing evidence against the rule are more numerous than those in support of it. In groups for which support has been provided, the trend of increasing latitudinal ranges with latitude is restricted to or at least most distinct at high latitudes, suggesting that the effect may be a local phenomenon, for example the result of glaciations.

Diffusion in scale-free networks with annealed disorder.

The scale-free (SF) networks that have been studied so far contained quenched disorder generated by random dilution which does not vary with the time. In practice, if a SF network is to represent, for example, the worldwide web, then the links between its various nodes may temporarily be lost and reestablished again later on. This gives rise to SF networks with annealed disorder.

Evolutionary ecology in silico: Does mathematical modelling help in understanding 'generic' trends?

Motivated by the results of recent laboratory experiments, as well as many earlier field observations, that evolutionary changes can take place in ecosystems over relatively short ecological time scales, several 'unified' mathematical models of evolutionary ecology have been developed over the last few years with the aim of describing the statistical properties of data related to the evolution of ecosystems. Moreover, because of the availability of sufficiently fast computers, it has become possible to carry out detailed computer simulations of these models. For the sake of completeness and to put these recent developments in perspective, we begin with a brief summary of some older models of ecological phenomena and evolutionary processes.

Number of spanning clusters at the high-dimensional percolation thresholds.

A scaling theory is used to derive the dependence of the average number k of spanning clusters at threshold on the lattice size L. This number should become independent of L for dimensions d<6 and vary as ln L at d=6 . The predictions for d>6 depend on the boundary conditions, and the results there may vary between L(d-6) and L0.

Food-web based unified model of macro- and microevolution.

We incorporate the generic hierarchical architecture of foodwebs into a "unified" model that describes both micro- and macroevolutions within a single theoretical framework. This model describes the microevolution in detail by accounting for the birth, ageing, and natural death of individual organisms as well as prey-predator interactions on a hierarchical dynamic food web. It also provides a natural description of random mutations and speciation (origination) of species as well as their extinctions.

Unification of small and large time scales for biological evolution: deviations from power law.

We develop a unified model that describes both "micro" and "macro" evolutions within a single theoretical framework. The ecosystem is described as a dynamic network; the population dynamics at each node of this network describes the "microevolution" over ecological time scales (i.e.

Simple tools for forecasts of population ageing in developed countries based on extrapolations of human mortality, fertility and migration.

Suitable assumptions for the Gompertz mortality law take into account the break in the time development observed recently by Wilmoth et al. They show how a drastic reduction in the birth rate and improved living conditions lead to a drastic increase in the fraction of old people in the population, and how immigration of half a percent of the population per year can mostly stop this increase.

Monte Carlo simulation of genome viability with paralog replacement.

Recent analyses of genome content have revealed that many single functions, even in haploid organisms, can be executed by more than one gene. As a result, experimental disruption of many individual genes does not exert lethal effects on the organism or even any visible change in the phenotype of the organism with a knockedout gene. Our analysis shows that such genetic redundancy allows for an appreciably higher mutation load in the genome simulations before the viability of the whole organism is destroyed.