Heatwave types and frequency alter multigenerational ecological response of wheat aphids

Heatwaves are predicted to become more frequent under climate change. However, how different heatwave types and frequencies are linked to multigenerational ecological response remains unclear. Thus, using three heatwave types (34 °C/180 min, 36 °C/30 min, and 38 °C/10 min) and three frequencies (1, 3, and 5 days), we tested the effects of heat stress on the life history traits of Sitobion avenae. Both heatwave type and frequency altered aphid fitness in a generation-specific manner. In maternal generations, at a 1-day frequency, 34℃/180 min exhibited the greatest effects on reproduction and longevity. However, as frequency increased, differences across various heat stress treatments diminished. Conversely, in offspring, 34℃/180 min had minimal effects on demographic parameters. Offspring performance was poorest at the 3-day frequency, indicating that a longer frequency for the mother does not necessarily mean a greater effect on the offspring. Changes in aphid fitness due to heatwave type and frequency are driven by asymmetric effects of heatwaves on aphid life history. Furthermore, understanding how heat stresses affect the life history of aphids is important for predicting the impacts of climate change at the generational level because climate effects on natural populations cannot be predicted simply through changes in mean temperature.