WHY SEX - - MONTE-CARLO SIMULATIONS OF SURVIVAL AFTER CATASTROPHES

Using the Penna bit-string model for biological ageing we compare two kinds of reproductive regimes: Sexual reproduction (SR) and meiotic pa rthenogenesis (MP). The last one is a common type of asexual reproduct ion with recombination, found in diploid organisms. We show that altho ugh both regimes present roughly the same survival rates, the diversit y 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.