Quality traits of the lady beetle Eriopis connexa (Germar) resistant to pyrethroids over 130 generations of rearing

The efficacy of the natural enemy may decline after numerous generations of laboratory culture. In addition, insects resistant to insecticides might show diminished performance due to the consequences of insecticide resistance. The insecticide-resistant population of the lady beetle Eriopis connexa (Germar) (EcViR) is metabolically resistant to λ-cyhalothrin and has been kept alive in a lab for over 130 generations, resulting in a 260-fold increase in resistance. Therefore, we compared the biological and behavioral characteristics of the EcViR population with those of a field-collected, cyhalothrin-susceptible population (EcCV). Females from both groups had comparable survival rates during 35 days of monitoring, regardless of food scarcity, but EcViR females demonstrated greater fecundity. The adults from both groups showed a type II functional response when they ate the turnip aphid, Lipaphis pseudobrassicae Davis. This happened whether λ-cyhalothrin was present or not. Nonetheless, EcViR individuals exhibited a greater rate of aphid consumption compared to EcCV, irrespective of the λ-cyhalothrin residue. The period of larval growth was comparable among populations when reared at 18, 25, and 32 °C. On the other hand, EcCV females were bigger than EcViR females when they were raised from larvae at 18 and 25 °C, and EcCV females laid more eggs at 25 and 32 °C. The results show that the EcViR individuals kept their ability to hunt and reproduce even after 100 generations of development in the lab. Conversely, the fecundity of EcViR females was diminished when provided ad libitum, grown from larvae, and maintained at 25 and 32 °C. Consequently, the findings support the idea that the predation rate is unaffected in the resistant population following laboratory rearing. Nevertheless, the adaptation cost of resistance influences the fertility in the resistant population, becoming more pronounced at varying temperatures.

捕食性天敌的控害效能经多代实验室繁育后可能出现下降。此外，携带杀虫剂抗性的昆虫可能因抗性演化的适合度代价而出现适合度下降。瓢虫（Eriopis connexa (Germar)）的抗药性种群（EcViR）对高效氯氟氰菊酯（λ-cyhalothrin）具有代谢抗性，该种群已在实验室连续繁育超130代，抗性水平提升了260倍。因此，本研究将该抗药性种群（EcViR）与田间采集的高效氯氟氰菊酯敏感种群（EcCV）的生物学与行为学特征进行了对比。在35天的监测周期内，无论食物是否匮乏，两个种群的雌成虫存活率均无显著差异，但EcViR种群的雌成虫繁殖力更强。两个种群的成虫在取食萝卜蚜（Lipaphis pseudobrassicae Davis）时均表现出II型功能反应，且无论环境中是否存在高效氯氟氰菊酯残留，该反应模式均保持一致。尽管如此，无论是否存在高效氯氟氰菊酯残留，EcViR种群的蚜虫取食速率均高于EcCV种群。在18℃、25℃及32℃三个温度条件下饲养时，两个种群的幼虫发育历期无显著差异。另一方面，在18℃和25℃下由幼虫阶段饲养至成虫的EcCV雌成虫体型大于EcViR雌成虫，且在25℃和32℃条件下，EcCV雌成虫的产卵量更高。研究结果表明，即便在实验室历经100余代繁育，EcViR种群仍保留了捕食与繁殖能力。与之相反，当在25℃和32℃下以充足食物饲养幼虫至成虫时，EcViR雌成虫的繁殖力出现下降。综上，本研究结果证实：实验室繁育并未对抗性种群的捕食速率产生负面影响，但抗性演化的适应代价会影响抗性种群的繁殖力，且该效应在不同温度条件下更为显著。