SD15: Assessing the impact of parental thermal stress on offspring performance in Baltimore checkerspots

Transgenerational effects, in which the environment experienced by the parents affects the phenotype and fitness of their offspring, can have significant effects on butterflies and moths. In some cases, transgenerational effects increase offspring performance by preparing them to face unfavorable conditions. However, negative transgenerational effects, in which exposure to environmental stress in the parental generation results in poor offspring performance are also common. As a result of global change, insects experience an accumulation of stressors, including recurring exposure to thermal stress. Thus, understanding whether thermal stress results in adaptive or maladaptive transgenerational effects is increasingly important as global temperatures continue to rise and heatwaves of greater intensity and duration are expected to occur more frequently. In this study, we investigate transgenerational effects of thermal stress on the Baltimore Checkerspot (Euphydryas phaeton phaeton, Drury). We exposed the parental generation to thermal stress conditions (cold, control, heat, and extreme heat) at the pupal stage, and the offspring generation to different frequencies of winter heatwaves (control, short, and long heatwaves) during the 4th-instar. We found that exposure to heat stress significantly reduced adult longevity, as individuals exposed to extreme heat stress had a 60% shorter lifespan than all other treatments. By contrast, the thermal environment experienced by the parental generation did not affect egg clutch size, caterpillar mass, or offspring survival. Overall we found that thermal stress can significantly reduce fitness of individuals experiencing it, but we found no evidence of adaptive or maladaptive parental effects in response to thermal stress.