Rates of DNA sequence evolution are not sex-biased in Drosophila melanogaster and D. simulans

To determine whether male- or female-biased mutation rates have affectedthe molecular evolution of Drosophila melanogaster and D. simulans, wecalculated the male-to-female ratio of germline cell divisions ([symbol:see text]) from germline generation data and the male-to-female ratio ofmutation rate ([symbol: see text]) by comparing chromosomal levels ofnucleotide divergence. We found that the ratio of germline cell divisionschanges from indicating a weak female bias to indicating a weak male biasas the age of reproduction increases. The range of [symbol: see text]values that we observed, however, does not lead us to expect much, if any,difference in mutation rate between the sexes. Silent and intron nucleotidedivergence were compared between nine loci on the X chromosome and nineloci on the second and third chromosomes. The average levels of nucleotidedivergence were not significantly different across the chromosomes,although both silent and intron sites show a trend toward slightly moredivergence on the X. These results indicate a lack of sex- orchromosome-biased molecular evolution in D. melanogaster and D. simulans.