Autosomal and X linked additive genetic variation for lifespan and aging: comparisons within and between the sexes in Drosophila melanogaster

Theory makes several predictions concerning differences in genetic variation between the X chromosome and the autosomes due to male X hemizygosity. The X chromosome should i) typically show relatively less standing genetic variation than the autosomes, ii) exhibit more variation in males compared to females because of dosage compensation, and iii) potentially be enriched with sex-specific genetic variation. Here we address each of these predictions for lifespan and aging in Drosophila melanogaster. To achieve unbiased estimates of X and autosomal additive genetic variance we use 80 chromosome substitution lines; 40 for the X chromosome and 40 combining the two major autosomes, which we assay for sex-specific and cross-sex genetic (co)variation. We find significant X and autosomal additive genetic variance for both traits in both sexes (with reservation for X linked variation of aging in females), but no conclusive evidence for depletion of X linked variation (measured through females). ...