Interactive effects of acclimation temperature and short-term stress exposure on resistance traits in the butterfly Bicyclus anynana

The ability to buffer detrimental effects of environmental stress on fitness is of great ecological importance because, in nature, pronounced environmental variation may regularly induce stress. Furthermore, several stressors may interact in a synergistic manner. In the present study, plastic responses in cold, heat and starvation resistance are investigated in the tropical butterfly Bicyclus anynana Butler, 1879, using a full factorial design with two acclimation temperatures (20 and 27 degrees C) and four short-term stress treatments (control, cold, heat, starvation). Warm-acclimated butterflies are more heat-but less cold-tolerant as expected. Short-term cold and starvation exposure reduce cold and heat resistance, and short-term heat exposure decreases cold but increases heat resistance. Starvation resistance is not affected by any of the short-term treatments. Thus, the effects of short-term stress exposure are either neutral or negative, except for a positive effect of heat exposure on heat resistance, indicating the negative effects of pre-exposure to stress. Interestingly, significant interactions between acclimation temperature and short-term stress exposure for heat and cold resistance are found, demonstrating that larger temperature differences incur more damage. Therefore, animals may not generally be able to benefit from pre-exposure to stress (through 'hardening'), depending on their previously experienced conditions. The complex interactions between environmental variation, stress and resistance are highlighted, warranting further investigations.