Background selection and patterns of genetic diversity inDrosophila melanogaster

Abstract

SummaryTheoretical models of the effects of selection against deleterious mutations on variation at linked neutral sites (background selection) are used to predict the relations between chromosomal location and genetic variability at the DNA level, inDrosophila melanogaster. The sensitivity of the predictions to variation in the mutation, selection and recombination parameters on which they are based is examined. It is shown that many features of the observed relations between chromosomal location and level of genetic diversity inD. melanogastercan be explained by background selection, especially if the weak selective forces acting on transposable elements are taken into account. In particular, the gradient in diversity in the distal portion of the X chromosome, and the lack of diversity on chromosome 4 and at the bases of the major chromosomes, can be fully accounted for. There are, however, discrepancies between predicted and observed values for some loci inD. melanogaster, which may reflect the effects of forces other than background selection.