The frequency and outcome of biotic interactions commonly vary with environmental conditions, even without changes to community composition. Yet the drivers of such environmentally-mediated change in biotic interactions are poorly understood, limiting our ability to predict how environmental change will impact communities. Studying nectar robbery by stingless bees of Odontonema cuspidatum (Acanthaceae) in a coffee agroecosystem, we documented a temporally consistent difference in nectar robbing intensity between anthropogenic and seminatural habitats. Plants growing in coffee fields (anthropogenic habitat) experienced significantly more nectar robbery than plants growing in forest fragments (seminatural habitat). Using a combination of field surveys and manipulative experiments, we found that nectar robbery was higher in coffee fields primarily due to environmental effects on a) neighborhood floral context and b) O. cuspidatum floral traits. This led to both preferential foraging by nectar robbers in coffee fields, and to changes in foraging behavior on O. cuspidatum that increased robbery. Nectar robbery significantly reduced fruit set in O. cuspidatum. These results suggest that the effects of anthropogenic environmental change on species traits may be more important than its effect on species density in determining how interaction frequency and outcome are affected by such environmental change.

生物相互作用的频率和结果通常随环境条件而变化，即使不改变群落组成也是如此。然而，人们对这种在生物相互作用中由环境介导的变化的驱动因素知之甚少，这限制了我们预测环境变化将如何影响社区的能力。用无刺蜜蜂的齿形昆虫研究花蜜抢劫（棘皮科）在咖啡农业生态系统中，我们记录了人为和半自然生境之间花蜜抢夺强度的时间一致性差异。与在森林碎片（半自然生境）中生长的植物相比，在咖啡田（人为生境）中生长的植物遭受的花蜜抢劫要多得多。通过实地调查和操纵性实验的结合，我们发现咖啡田中的花蜜抢劫率较高，这主要是由于环境对a）邻里花卉环境和b）虎杖的花性状的影响。这不仅导致咖啡田中的花蜜强盗优先觅食，而且导致虎杖的觅食行为发生变化，从而增加了抢劫。花蜜抢劫显着减少了虎杖的坐果。 这些结果表明，在确定这种环境变化如何影响相互作用频率和结果时，人为环境变化对物种性状的影响可能比其对物种密度的影响更为重要。