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

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