Sebastian Bossert

In population genetics, mathematical models are used to study the distributions and changes of allele frequencies. Main evolutionary factors influencing these frequencies are (among others) mutation, selection and recombination. Maynard Smith and Haigh (1974) analysed in a pioneering theoretical framework the process when a new, strongly selected advantageous mutation becomes fixed in a population. They identified that such an evolution, called selective sweep, leads to the reduction of diversity around the selective locus. In the following years other scientists faced the question to what extent this characteristic still holds, when certain assumptions are modified. In this talk a situation is presented where two selective sweeps within a narrow genomic region overlap in a sexually evolving population. For such a competing sweeps situation the probability of a fixation of both beneficial alleles, in cases where these alleles are not initially linked, is examined. To handle this question a graphical tool, the ancestral selection recombination graph, is utilized, which is based on a genealogical view on the population. This approach provides a limit result (for large selection coefficients) for the probability that both beneficial mutations will eventually fix. The analytical examination is complemented by simulation results.