DNA Motifs Are Not General Predictors of Recombination in Two Drosophila Sister Species

Meiotic recombination is crucial for chromosomal segregation, and facilitates the spread of beneficial and removal of deleterious mutations. Recombination rates frequently vary along chromosomes and Drosophila melanogaster exhibits a remarkable pattern. Recombination rates gradually decrease towards centromeres and telomeres, with dramatic impact on levels of variation in natural populations. Two close sister species, D. simulans and D. mauritiana do not only have higher recombination rates, but also exhibit a much more homogeneous recombination rate that only drops sharply close to centromeres and telomeres. Because certain sequence motifs are associated with recombination rate variation in D. melanogaster, we tested whether the difference in recombination landscape between D. melanogaster and D. simulans can be explained by the genomic distribution of recombination-rate associated sequence motifs. We constructed the first high resolution recombination map for D. simulans, and searched for motifs linked with high recombination in both sister species. We identified five consensus motifs, present in either species. While the association between motif density and recombination is strong and positive in D. melanogaster, the results are equivocal in D. simulans. Despite the strong association in D. melanogaster, we do not find a decreasing density of these repeat motifs towards centromeres and telomeres. We conclude that the density of recombination-associated repeat motifs cannot explain the large-scale recombination landscape in D. melanogaster, nor the differences to D. simulans. The strong association seen for the sequence motifs in D. melanogaster likely reflects their impact influencing local differences in recombination rates along the genome.