Nectar robbing impacts pollinator behavior but not plant reproduction

Trait-mediated indirect effects (TMIEs) refer to interactions in which the effect of one species on another is mediated by the behavior of a third species. A mechanistic approach that identifies the direction and impact of TMIEs can shed light on why different net outcomes are observed in the same general phenomena across systems. Nectar robbing has variable net effects through TMIEs on animal-pollinated plants across systems, but the mechanistic steps underlying this range of outcomes are often unclear. To address this knowledge gap, we assessed linkages between nectar robbing, pollinator behavior and plant reproductive success in the Andean tree, Oreocallis grandiflora. We found that robbing in this system led to lower nectar volumes, higher nectar sucrose concentration, and higher nectar viscosity, which together negatively impact nectar quality. This drop in nectar quality was associated with decreased visitation rates by hummingbirds, which might be expected to impact plant reprodu...性状介导的间接效应（Trait-mediated indirect effects, TMIEs）指一类物种间相互作用，即一个物种对另一物种的作用通过第三个物种的行为得以介导。能够明确性状介导间接效应作用方向与影响的机制性研究方法，可帮助阐释为何在不同生态系统的同类普遍现象中会观测到各异的净结果。盗蜜（Nectar robbing）通过性状介导的间接效应对动物传粉植物产生的净效应在不同生态系统间存在差异，但这类结果差异背后的机制性过程往往尚不明确。为填补这一知识缺口，我们针对安第斯树种Oreocallis grandiflora评估了盗蜜、传粉者行为与植物生殖成功之间的关联。研究发现，该系统中的盗蜜行为会导致花蜜体积降低、花蜜蔗糖浓度升高，同时提升花蜜粘度，上述变化共同对花蜜品质产生负面影响。花蜜品质的下降与蜂鸟的访花频率降低相关，而这一变化或可对植物繁殖产生影响……