Flight-induced transgenerational maternal effects influence butterfly offspring performance during times of drought

Maternal condition can generate resource-related maternal effects through differential egg provisioning that can negatively affect offspring performance especially when offspring growth occurs in stressful or sub-optimal environments. Using the Speckled Wood butterfly, Pararge aegeria (L.) we tested the hypothesis that repeated periods of intensive flight during female oviposition affects egg provisioning and reduces offspring performance when larval development occurs under stressful conditions on drought stressed host plants. We investigated whether (after controlling for egg size) maternal age and flight treatment resulted in changes in egg provisioning and whether this contributed to variation in offspring traits across life stages. Age-related changes in maternal condition were found to generate resource-related maternal effects that influenced offspring traits across all life stages. Flight-induced changes in maternal egg provisioning were found to have direct consequences for offspring development in the egg and larval stages. There were significant interactive effects between maternal age and flight on larval development and growth. Compared to offspring from forced flight mothers, offspring from control (no forced flight) mothers that hatched from eggs laid early in the oviposition period (i.e. by younger mothers) had shorter larval development times and heavier pupal masses, suggesting that offspring from mothers in relatively good condition may be able to buffer some of the costs associated with growth on drought stressed host plants. Our multi-factor study demonstrates the importance of considering the various, and often interacting, mechanisms by which maternal effects may influence offspring performance in stressful environments.