Sequence-dependent effects of heat and pesticide exposure determine synergistic toxicity and transgenerational fitness costs in a major crop pest (Sitobion avenae)
摘要
The interaction between heat events and pesticides is critical in shaping pest population dynamics under climate change, yet the role of stressor sequence remains poorly understood. Here, this study investigated how the sequence of exposure to a short-term heat shock (34 °C for 3 h) and a low lethal dose of imidacloprid (LC₃₀) influences life-history traits and transgenerational fitness in the wheat aphid, Sitobion avenae. Six treatments were established: control (CK), heat alone (H), pesticide alone (P), heat followed by pesticide (HP), pesticide followed by heat (PH), and simultaneous heat and pesticide exposure (H + P). Results revealed that heat-pesticide interactive treatment induced synergistic toxicity, with HP causing the higher maternal mortality (reduction of 22.35% in survival rate) and the strongest suppression of intrinsic rate of increase (rₘ: 52.71% reduction) . Transgenerational effects were also sequence-specific: maternal HP exposure significantly prolonged offspring development time (9.30 ± 0.15 days vs. control 8.40 ± 0.13 days) and reduced offspring rₘ by 14.28%, demonstrating a persistent fitness cost across generations. Our study demonstrates that the interaction between heat and imidacloprid is synergistic and sequence-dependent, with the HP sequence generating the most severe toxicity and transgenerational fitness costs. These findings highlight the critical importance of exposure sequence in ecological risk assessment and integrated pest management under climate warming scenarios, as it strongly shapes pest vulnerability and population dynamics.