Organisms interact with numerous species in their environment, and these interactions can influence a variety of social and ecological processes. Thus, temporal and spatial variation in species interactions is important for understanding the fitness consequences of multi-trophic relationships. Here, we investigate how tritrophic interactions between a host plant generalist sap-feeding insect, host plant species, and ant mutualists vary in a prairie habitat. We used field transects to quantify the abundances of three host plant species, three species of ants, and the treehopper Entylia carinata. We repeated the transects from Spring until late Fall to quantify seasonal changes in abundances, and across three years to investigate stability of tritrophic relationships across years. In the first year of the study, we also measured plant height. Finally, we characterized variation in the tending behavior of the three species of ants. We found that certain plant-ant species combinations are more common than others. While tritrophic associations between plants, ants, and treehoppers changed seasonally, they were largely stable across years. Furthermore, we found pervasive effects of ants on E. carinata, including E. carinata presence and abundance, E. carinata aggregation size and abundance, E. carinata nest presence and abundance, and E. carinata nest-tending behavior. Plant species had fewer effects, but affected E. carinata presence and abundance as well as the likelihood of E. carinata aggregations occurring on a plant. Finally, significant seasonal changes in ant abundances and ant tending rates create dynamic temporal variation in tritrophic interactions. The patterns observed are likely to have significant effects on E. carinata populations, and—due to the importance of ant-treehopper mutualisms in local ecosystems—cascading effects on local communities.

生物体与其环境中的众多物种相互作用，这些相互作用可以影响各种社会和生态过程。因此，物种相互作用的时间和空间变化对于理解多营养关系的适应性后果非常重要。在这里，我们研究了草原栖息地中寄主植物多面性食液昆虫、寄主植物物种和蚂蚁互利共生体之间的三营养相互作用如何变化。我们使用田间横断面来量化三种寄主植物物种、三种蚂蚁和角蝉Entylia carinata的丰度。我们重复了从春季到深秋的横断面，以量化丰度的季节性变化，并在三年内调查三营养关系的稳定性。在研究的第一年，我们还测量了植物的高度。最后，我们描述了三种蚂蚁的抚育行为的变化。我们发现某些植物-蚂蚁物种的组合比其他物种更常见。虽然植物、蚂蚁和角蝉之间的三营养关系随季节变化，但多年来它们基本上保持稳定。此外，我们发现蚂蚁对E. carinata的普遍影响，包括E. carinata 的存在和丰度、E. carinata聚集大小和丰度、E. carinata巢的存在和丰度以及E. carinata巢穴护理行为。植物物种的影响较小，但影响了E. carinata 的存在和丰度以及E. carinata聚集在植物上的可能性。最后，蚂蚁丰度和蚂蚁抚育率的显着季节性变化会导致三营养相互作用的动态时间变化。观察到的模式可能对E. carinata种群产生重大影响，并且由于蚂蚁与角蝉互利共生在当地生态系统中的重要性，对当地社区产生连锁效应。