Sex-related differences in aging rate are associated with sex chromosome system in amphibians

Abstract/Summary

Sex-related differences in mortality are widespread in the living world. Although sexual selection and environmental conditions might drive sex-specific variation in lifespan, recent findings suggest that sex chromosome systems are also involved. However, the influence of sex chromosome systems on aging rate (i.e., the rate of increase of mortality with age), a mortality metric that only partially correlates with lifespan, has not been investigated so far, due to an apparent lack of demographic data from clades including both XY (with heterogametic males) and ZW (with heterogametic females) sex-determination systems. Taking advantage of a unique collection of capture-recapture datasets in amphibians, a vertebrate group where XY and ZW systems have repeatedly switched over the past 200 million years we examine whether sex heterogamety can predict sex-differences in aging rates. We show that variation in aging rate only accounts for a moderate proportion of the variation in lifespan, similarly to what has been reported in mammals. Moreover, our results demonstrate that the system of genetic sex-determination has a critical impact on aging rate in clades that include closely related taxa with XY vs. ZW systems. In both systems the heterogametic sex experiences a higher aging rate compared to the homogametic sex. This new finding suggests that exposed recessive deleterious mutations on the X/Z chromosome (the “unguarded X/Z effect”) or repeat-rich Y/W chromosome (the “toxic Y/W effect”) could accelerate aging in the heterogametic sex.