Within- and Across-Generational Effects of Temperature: Exposure of Manduca sexta Larvae to Heat Stress Impacts...

The effects of temperature on reproduction and other key fitness traits are often primarily considered only for the adult thermal environment, but exposure to thermal stress during earlier life stages may carry over to influence adult traits within a generation or even across generations. In this study, we assessed how an acute heat shock event experienced at two different points in Manduca sexta larval development (early and late) impacted adult performance and fitness traits and whether thermal exposure of parents elicited plastic changes in offspring traits. Heat stress during late larval development had significantly greater negative impacts on adult performance and fitness compared to earlier exposure. Adults that experienced a late larval heat shock failed to produce any viable offspring due to complete elimination of egg hatching success. Larval heat stress during the parental generation also reduced larval development times of their offspring in both control and heat shock conditions. The results of this study illustrate the negative consequences of larval heat stress for adult fitness and indicate that the parental early thermal environment can significantly influence some traits in the next generation. The effects of parent environmental conditions during development, and not just at the adult stage, may therefore be an important but often overlooked factor when assessing cumulative fitness impacts across generations and predicting the vulnerability of populations to climate change.