Genomic and evolutionary studies of recombination rate variation in the sister species Drosophila yakuba and D. santomea

Meiotic recombination is a crucial biological mechanism because it is necessary for proper chromosome segregation during meiosis and it increases genetic variation, allowing natural selection to act more efficiently. Crossovers, the reciprocal exchange of genetic information, are a hallmark of this evolutionarily conserved process. Notably, the frequency and distribution of crossovers varies between and within species. To investigate the causes and consequences of differences in crossover distribution between species, I generated the first high-resolution crossover maps for the closely related species Drosophila yakuba and D. santomea and performed a comparison to the model system, and more distantly related, D. melanogaster. The analysis reveals that the X chromosome and autosomes have a similar crossover rate in D. santomea whereas D. yakuba and D. melanogaster show crossover rates higher on the X chromosome compared to the autosomes. Analysis of DNA motifs predictive of crossover localization in D. melanogaster show that they are also enriched near crossovers in both D. santomea and D. yakuba, suggesting that there is a general mechanism in Drosophila. Unexpectedly, the analysis of protein evolution suggest that D. melanogaster has recently experienced changes to its crossover landscape. At the same time, these results suggest that the D. yakuba crossover map is informative of ancestral linkage effects in the whole D. melanogaster subgroup of species, including ancestral populations of D. melanogaster.