S. Moss de Oliveira

Mutation accumulation and the catastrophic senescence of the Pacific salmon.

The bit-string model of biological aging is used to simulate the catastrophic senescence of Pacific Salmon. We have shown that reproduction occuring only once and at a fixed age is the only ingredient needed to explain the catastrophic senescence according the mutation accumulation theory. Several results are presented, some of them with up to

Monte Carlo simulations of sexual reproduction

10^8

WHY SEX? MONTE CARLO SIMULATIONS OF SURVIVAL AFTER CATASTROPHES

fishes, showing how the survival rates in catastrophic senescence are affected by changes in the parameters of the model.

Simulating the vanishing of northern cod fish

Modifying the Redfield model of sexual reproduction and the Penna model of biological aging, we compare reproduction with and without recombination in age-structured populations. In constrast to Redfield and in agreement with Bernardes we find sexual reproduction to be preferred to asexual one. In particular, the presence of old but still reproducing males helps the survival of younger females beyond their reproductive age.

THE SPIN-S BLUME-CAPEL RG FLOW DIAGRAM

Using the Penna bit-string model for biological ageing we compare two kinds of reproductive regimes: Sexual reproduction (SR) and meiotic parthenogenesis (MP). The last one is a common type of asexual reproduction with recombination, found in diploid organisms. We show that although both regimes present roughly the same survival rates, the diversity generated by SR is much larger, and can prevent the extinction of a population submitted to a natural disaster. The fixation of bad genes inside an MP population, after many generations, explains our results. We also study the consequences of cloning (simple copy) on population diversity.

A small review of the Penna model for biological ageing

Introducing fishing in a recently presented model for biological ageing we show, through computer simulations, how a slight increase of fishing may destroy a whole stable population.

Theoretical approach to biological aging

Using the finite-size scaling renormalization group, we obtain the two-dimensional flow diagram of the Blume-Capel model forS=1 andS=3/2. In the first case our results are similar to those of mean-field theory, which predicts the existence of first- and second-order transitions with a tricritical point. In the second case, however, our results are different. While we obtain in theS=1 case a phase diagram presenting a multicritical point, the mean-field approach predicts only a second-order transition and a critical endpoint.

Computer simulation of sympatric speciation with Penna ageing model

The Penna bit-string model for biological ageing appeared in 1995, and is now by far the most widely used Monte Carlo simulation technique to predict many of the features found in real populations, related to ageing. The purpose of this paper is to give an overview of the most important results that have been obtained using this technique.

Simulated ecology-driven sympatric speciation

We present a model for biological aging that considers the number of individuals whose (inherited) genotype determines the maximum age for death: each individual may die before that age due to some external factor, but never after that limit. The genotype of the offspring is inherited from the parent with some mutations, described by a transition matrix. The model can describe different strategies of reproduction and it is exactly soluble. We applied our method to the bit-string model for aging and the results are in perfect agreement with numerical simulations.

Exact Results of the Bit-String Model for Catastrophic Senescence

One species is simulated to split into two separate species via random mutations, even if both populations live together in the same environment. This speciation is achieved in the Penna bitstring model of biological ageing, with modified Verhulst factors, and in part by additional bitstrings regulating phenotype and mate selection.