PARASITIC INFESTATION AND CHOICE OF REPRODUCTIVE REGIMES

The Penna model is used to simulate the competition between an asexual parthenogenetic and asexual population inhabiting the same environment represented by a square lattice. With a small probability, a newborn from the sexual population mutates into an asexual one and vice versa. Then, the asexual population rapidly dominates the sexual one, which all but disappears. However, when an infestation by mutating genetically coupled parasites, that mimic trematodes that feed on gonads, is introduced, the outcome may be one in which both populations coevolve or one in which one of the populations overcomes the other, depending on the density of parasites on the lattice.

ANOMALOUS RELAXATION OF THE PENNA MODEL

We simulate the response of an age-structured population face to an abrupt increasing of fertility. Contrary to the exponential decay of original model, as reported by Coe and Mao, we have found that the relaxation to the equilibrium can be algebraic under certain conditions. We show results from computer simulation for a large range of parameters, although the fertility itself seems to be the most relevant factor.

INBREEDING AND OUTBREEDING DEPRESSIONS IN THE PENNA MODEL AS A RESULT OF CROSSOVER FREQUENCY

The population in the sexual Penna aging model is first separated into several reproductively isolated groups. Then, after equilibration, sexual mixing between the groups is allowed. We study the changes in the population size due to this mixing and interpret them through a counterplay of purifying selection and of haplotype complementarity.