Parental breeding age effects on descendants’ longevity interact over two generations in matrilines and patrilines

Individuals within populations vary enormously in mortality risk and
longevity, but the causes of this variation remain poorly understood. A
potentially important and phylogenetically widespread source of such
variation is maternal age at breeding, which typically has negative
effects on offspring longevity. Here, we show that paternal age can affect
offspring longevity as strongly as maternal age does, and that breeding
age effects can interact over two generations in both matrilines and
patrilines. We manipulated maternal and paternal ages at breeding over two
generations in the neriid fly Telostylinus angusticollis. To determine
whether breeding age effects can be modulated by the environment, we also
manipulated larval diet and male competitive environment in the first
generation. We found separate and interactive effects of parental and
grandparental ages at breeding on descendants’ mortality rate and lifespan
in both matrilines and patrilines. These breeding age effects were not
modulated by grandparental larval diet quality or competitive environment.
Our findings suggest that variation in maternal and paternal ages at
breeding could contribute substantially to intra-population variation in
mortality and longevity.