Maternal age at reproduction drives multigenerational variation in life-history traits
Offspring phenotypes are often influenced by maternal age at reproduction. However, the persistence of such effects across multiple generations remains poorly understood, especially in rare cases where offspring of older mothers exhibit enhanced performance. Using the predatory mite Amblyseius herbicolus, we experimentally tested whether maternal age at reproduction influences offspring life history across two generations under contrasting dietary conditions. We found that grandmaternal (F0) and maternal (F1) age affected offspring (F2) developmental time and body size, but not hatching success, survival, or oviposition. The effect of maternal age on body size depended on grandmaternal age, suggesting that grandmaternal age mediates how mothers adjust offspring provisioning. Diet strongly influenced offspring traits but showed limited interaction with age effects. To our knowledge, this is the first study to demonstrate the persistence of an inverse Lansing effect across generations, whereby enhanced immature development is maintained without detectable trade-offs in reproduction or adult survival. These results identify maternal age as a key driver of transgenerational phenotypic variation, with important implications for population dynamics and responses to environmental change at the population level.