Partial sweeping of variation at the Fbp2 locus in a West African population of Drosophila melanogaster

Departure of molecular variation from neutral equilibrium was studied in a highly recombining region of the Drosophila genome. A 2.2-kb region including the Fbp2 locus was sequenced for 10 chromosomes from a D. melanogaster sample from West Africa and for the related species D. simulans. Of the 33 variable sites present in the 1.3-kb transcription unit, 32 made up a single haplotype present in half of the D. melanogaster sample. This pattern significantly departed from predictions of the neutral drift-mutation equilibrium model. The major haplotype presented a diagnostic restriction site which was investigated in 226 chromosomes from three distant European and African populations. It was found at a high frequency (31%) in the population from which the sequenced sample originated, but was nearly absent from the other two (below 4%), suggesting that the major haplotype frequency resulted from a local selective sweep event. Partial sweeping of variation in regions of high recombination rates has previously been found for American and European populations of D. melanogaster: Our study shows that this phenomenon also occurs in African populations, which are in the ancestral range of this species.