Patterns of DNA sequence polymorphism at Sod vicinities in Drosophila melanogaster: unraveling the footprint of a recent selective sweep.

We survey DNA sequence polymorphisms at the Sod locus and four neighboring regions of Drosophila melanogaster, spanning 55,513 base pairs (bp), in 15 strains from a natural population, plus one reference laboratory strain and one strain of Drosophila simulans. Our objective is to characterize a proposed selective sweep that occurred at a locus close to Sod in D. melanogaster and to characterize the strength of the selection event, its time, and the size of the hitchhiked region. Two regions, 1819 and 6kbr3r, show a pattern of polymorphism very similar to the one of Sod, implying that they have been affected by the same evolutionary process that impacted Sod. A third fragment, 2021 seems unaffected by the event. A fourth one, 4039, on the opposite flank of Sod in relation to 2021, is only partially affected. We estimate that the length of the chromosomal segment impacted by the selective sweep is 41-54 kb, the age of the selective sweep is 2,600-22,000 years, and the selective advantage is 0.020 < s < 0.103.