Abstract Changing climatic conditions can fundamentally alter the interactions between species with important implications for agriculture. The impacts of shifts in precipitation on trophic interactions have been understudied relative to other climate drivers. We carried out field experiments to examine how precipitation, attack by parasitoid wasps (Bracon cephi (Gahan))(Hymenoptera: Braconidae) and their potential interaction affect the performance of a major pest of wheat, Cephus cinctus Norton (Hymenoptera: Cephidae), and its impact on wheat yield. We independently manipulated insects (no insects, +C. cinctus, or +C. cinctus and B. cephi) and precipitation (-50% to -70%, ambient, +70%) in a factorial design in each of two growing seasons. Crop-herbivore-parasitoid interactions were remarkably robust to our precipitation manipulations with no significant changes in C. cinctus infestation, survival or levels of parasitism observed in the first (wetter) year of the study. Despite slight declines in pest infestation and percent parasitism under precipitation addition relative to reduction in the second year, both insects had strong and significant impacts on crop yield. These effects were consistent across precipitation manipulations, as evidenced by the lack of a significant interaction between insect and precipitation treatments. The results suggest that natural enemy benefits to crop production in this system can be substantial, and are likely to be robust across a relatively wide range of precipitation levels. While rare, studies that examine climate influences within a tri-trophic context are critical to predicting how pest insects will ultimately impact crop production under changing climatic conditions.

中文翻译：

---

三营养相互作用对小麦农业生态系统中降水水平的大幅变化具有弹性

摘要 不断变化的气候条件可以从根本上改变物种之间的相互作用，对农业具有重要意义。相对于其他气候驱动因素，降水变化对营养相互作用的影响尚未得到充分研究。我们进行了田间试验，研究了降水、寄生蜂（Bracon cephi (Gahan)）（膜翅目：蜂科）及其潜在相互作用如何影响小麦主要害虫 Cephus cinctus Norton（膜翅目：Cephidae）的表现，以及对小麦产量的影响。我们在两个生长季节中的每一个的因子设计中独立操纵昆虫（无昆虫，+C. cinctus，或 +C. cinctus 和 B. cephi）和降水（-50% 到 -70%，环境，+70%） . 作物-食草动物-寄生蜂的相互作用对我们的降水操作非常有效，在研究的第一年（较潮湿）观察到的 C. cinctus 侵染、存活或寄生水平没有显着变化。尽管相对于第二年的减少，在降水增加的情况下害虫侵扰和寄生百分比略有下降，但这两种昆虫对作物产量都产生了强烈而显着的影响。这些影响在降水操作中是一致的，正如昆虫和降水处理之间缺乏显着相互作用所证明的那样。结果表明，在该系统中，天敌对作物生产的益处可能是巨大的，并且可能在相对广泛的降水水平范围内保持强劲。虽然很少见，