An inverse Lansing effect: Older mothers produce offspring with improved development and growth efficiency

The Lansing effect predicts a decline in offspring performance with increasing maternal age. Maternal age and diet can influence offspring development and fitness via maternal effects, but how these two factors interact remains poorly understood. We examined how maternal age at oviposition and dietary conditions affect offspring developmental plasticity in a thelytokous predatory mite (Amblyseius herbicolus). Mothers were provided either a restricted or abundant prey diet, and their offspring were exposed to varying prey availability and monitored for hatching success, survival to adulthood, developmental time, size at maturity, and prey consumption. We addressed two main questions: How does maternal age affect offspring developmental time and size at maturity and does maternal diet modify the effect of maternal age on offspring? Our results suggest an inverse Lansing effect. Offspring of older mothers showed increased survival and reduced prey consumption without any compromise in terms of size at maturity. Interactions were found between maternal diet and age on offspring prey consumption and developmental plasticity. Notably, offspring from older, diet-restricted mothers achieved the best overall performance during development. Our study demonstrates that maternal age and diet jointly shape offspring development, and highlights the importance of incorporating maternal age into studies of maternal effects and phenotypic plasticity.