The genetic and social contributions to sex differences in lifespan in Drosophila serrata

Abstract

Sex differences in lifespan remain an intriguing puzzle for evolutionary biologists. A possible explanation for lower lifespan in males is the unconditional expression of recessive deleterious alleles in heterogametic X chromosomes in males (the unguarded X hypothesis). Empirical evidence, however, has yielded controversial results that can be attributed to differences in both genetic and social background. Here, we test the unguarded X hypothesis in Drosophila serrata using a factorial design to quantify the effects of genotype, sex, social environment, and their interactions on phenotypic variation for lifespan. Using an experimental approach, we manipulated two inbred laboratory genotypes and their reciprocal F1s, while controlling for different levels of density and mating status to account for any potential social effects. Our results also show subtle but significant genotype dependent effects for both density and mating, but ultimately find the unguarded X hypothesis insufficient to fully explain sexual dimorphism in D. serrata lifespan.