Signatures of directional selection in a hybrid yeast population

Meiotic recombination is a fundamental biological process that leads to crossover and gene conversion. High resolution maps of meiotic recombination have been reported in several model organisms. However, few studies have studied how rapidly selection affects the products of meiotic recombination. Here we constructed and sequenced a yeast population of 38 haploid strains derived from hybridizations of two common used strains S288c and YJM789. We identified 20 regions with strong biased allele frequency across the genome, revealing signatures of selection in a rather short period. These regions harbor ample crossovers and gene conversions, which enable us to trace how selection works on the genomic fragments after meiosis. The total length of such regions under selection accounts for 5% of the entire genome, and those regions contain many functional-related genes. In addition, recombination breaks down linkage disequilibrium to half of its maximum within 42 kb and reduces nucleotide diversity significantly in selected regions. Our study thus provides details of directional selection on the outcomes of meiotic recombination using experimental approaches, and will shed light on our understanding of the fast reshaping of population structure by selection, as well as the important roles of recombination.