Responses of Manduca sexta larvae to heat waves

Climate change is increasing the frequency of heat waves and other extreme weather events experienced by organisms. How does the number and developmental timing of heat waves affect survival, growth and development of insects? Do heat waves early in development alter performance later in development? We addressed these questions using experimental heat waves with larvae of the Tobacco Hornworm, Manduca sexta. The experiments used diurnally fluctuating temperature treatments differing in the number (0-3) and developmental timing (early, middle and/or late in larval development) of heat waves, in which a single heat wave involved three consecutive days with a daily maximum temperature of 42 C. Survival to pupation declines with increasing number of heat waves. Multiple (but not single) heat waves significantly reduced development time and pupal mass; the best models for the data indicated that both the number and developmental timing of heat waves affected performance. In addition, heat waves earlier in development significantly reduced growth and development rates later in larval development. Our results illustrate how the frequency and developmental timing of sublethal heat waves can have important consequences for life history traits in insects.

气候变化正加剧生物体所遭遇的热浪及其他极端天气事件的发生频率。热浪的发生次数与发育时段将如何影响昆虫的存活、生长与发育？发育早期遭遇的热浪是否会改变昆虫后续发育阶段的表现？本研究以烟草天蛾（Manduca sexta）幼虫为实验对象，通过设置人工热浪开展相关实验以解答上述问题。实验采用昼夜波动温度处理方案，设置不同的热浪发生次数（0至3次）与发育时段（幼虫发育的早期、中期和/或晚期），其中单次热浪为连续3天日最高温达42℃的处理。幼虫化蛹前的存活率随热浪次数增加而下降；多次热浪（而非单次热浪）可显著缩短发育时长并降低蛹重；最优拟合模型表明，热浪的发生次数与发育时段均会对昆虫的表现产生影响。此外，发育早期遭遇的热浪会显著降低幼虫后续发育阶段的生长与发育速率。本研究结果阐明了亚致死热浪的发生频率与发育时段，将如何对昆虫的生活史性状产生重要影响。