| In nature,the effects of heat wave and pesticides on insects are not independent,and there are complex interactions.between them.Sitobion avenae,the dominant species of wheat aphids,and imidacloprid,a type of neonicotinoid insecticide which is widely used to control sucking pest,were used as tested insect and pesticide.The key demographic parameters,population fitness and transgenerational life history traits of S.avenae were studied in response to the two stressors by considering heat event type,stress sequence and thermal acclimation condition.Besides,the effects of thermal acclimation on S.avenae resposing to pesticide were also revealed.The results can provide evidence for understanding the interactive effect of climate warming and pesticide on insects and biodiversity protection,as well as theoretical basis for the comprehensive control of wheat aphid under the two stressors in the future.The main conclusions are as follows:1 The negative effect of high temperature duration is greater than that of heat intensity.S.avenae was exposed to three combinations of sublethal heat intensity and behavioral response time(34°C/180min?36°C/30min?38°C/10min)only one day,the moderate and medium sublethal combination 34°C/180 min and 36°C/30 min exert the largest negative effects on the subsequent life history traits of the maternal and the development and survival of the offspring.But with the exposure days increasing,the damage caused by the combination of higher heat intensity 38°C/10 min is the most obvious.2 Different types of heat events combined with imidacloprid will produce complex interaction effects.Mild and medium heat events combined with imidacloprid will produced stronger effect than higher intesity heat event.In addition,compared with individual heat stress,the presence of imidacloprid enhanced the effects of mild and medium heat events on S.avenae.However,the presence of imidacloprid has no effect on higher intensity heat event.3 The combination of heat event and imidacloprid in different sequences have little difference on the maternal performance but have significant maternal effect.Different interactive effects were observed when the interactions between stressors in different sequences,the effect on the subsequent life history of the mother was not significant but on offspring life history traits were significant.In detail,the order of imidacloprid first then treated with heat event would produce stronger survival selection on F1.4 The combination of heat event and imidacloprid cause more serious damage on insect than individual heat stress.Compared with single heat stress,whatever stress sequence,insect was exposed to double stress of heat and pesticide would be produced negative effect on fitness traits of maternal,and can produce significant maternal effects.5 The combination of heat event and imidacloprid of maternal has significant effect on population dynamics of offspring.Whether individual heat event or double stress of heat event and imidacloprid,the negative effect on the offspring are focused on development and survival,but did not continue to the adult performance of offspring.As mentioned above,but the negative effect on the development of offspring would make a greater contribution to the overall intrinsic rate of offspring,which would lead to the overall decline of the growth rate of population.6 The thermal acclimation of nymph stage has an influence on the response of heat and pesticide,and even has significant maternal effect.The high and low intensity acclimation of nymph stage can improve the thermal tolerance and have a complex impact on insecticide resistance of adult.The low intensity thermal acclimation of nymph will increase the imidacloprid resistance of adult and its opposite in high intensity thermal acclimation.Besides,individual imidacloprid stress does not produce maternal effect,but after the thermal acclimation,the influence of imidacloprid will produce maternal effect. |
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