Summary

Many animal species exhibit sex differences in aging. In the nematode Caenorhabditis elegans, under conditions that minimize mortality, males are the longer-lived sex. In a survey of 12 independent C. elegans isolates, we find that this is a species-typical character. To test the hypothesis that the C. elegans male longevity bias evolved as a consequence of androdioecy (having males and hermaphrodites), we compared sex-specific survival in four androdioecious and four dioecious (males and females) nematode species. Contrary to expectation, in all but C. briggsae (androdioecious), males were the longer-lived sex, and this difference was greatest among dioe-cious species. Moreover, male lifespan was reduced in androdioecious species relative to dioecious species. The evolutionary theory of aging predicts the evolution of a shorter lifespan in the sex with the greater rate of extrin-sic mortality. We demonstrate that in each of eight species early adult mortality is elevated in females/hermaphro-dites in the absence of food as the consequence of internal hatching of larvae (matricide). This age-independent mortality risk can favour the evolution of rapid aging in females and hermaphrodites relative to males