Plants growing along steep elevational gradients experience variations in abiotic conditions. The elevational gradient also affects the diversity and abundance of pollinators associated with these plants. As a result, plants may have locally adapted floral traits. However, detailed assessments of multiple floral traits along elevational gradients are often neglected despite the traits being important for plant sexual reproduction. We tested the association of floral traits with pollinators in response to elevation by identifying pollinators and measuring morphological and biochemical floral traits as well as studying the breeding systems of ten aggregated Rhododendron species in the Sikkim Himalaya. Corolla length, nectar volume and distance between stamen and stigma significantly decreased with elevation. In contrast, nectar concentrations were positively associated with elevation. Birds, bumblebees and flies were the three dominant pollinator groups. Bird visits showed a strong negative association with elevation while visits by bumblebees and flies increased with elevation. Species with longer corollas and higher nectar volumes showed higher rates of bird visits, while bumblebees were associated with species that had higher nectar concentrations. Fruit set following cross-pollination was high compared to self-pollination, and higher pollen limitation and auto-fertility were observed among species in higher elevations. These observed patterns in the association between floral traits and pollinator groups in response to elevation may help generate testable hypotheses on alpine plant–pollinator responses to climate warming.

中文翻译：

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花卉特征决定了锡金喜马拉雅山中杜鹃花物种在海拔梯度上的传粉媒介访视

沿陡峭海拔梯度生长的植物在非生物条件下会发生变化。海拔梯度还会影响与这些植物相关的传粉媒介的多样性和丰度。结果，植物可能具有局部适应的花性状。然而，尽管这些特征对于植物的有性繁殖很重要，但往往忽略了沿海拔梯度对多个花卉特征的详细评估。我们通过鉴定传粉媒介并测量形态和生化花卉性状以及研究十个杜鹃花的繁殖系统，来测试花卉特征与传粉媒介对海拔的响应锡金喜马拉雅山中的物种。花冠的长度，花蜜的体积以及雄蕊和柱头之间的距离随着海拔的升高而显着降低。相反，花蜜浓度与海拔高度呈正相关。鸟类，大黄蜂和苍蝇是三个主要的授粉媒介。鸟类探访与海拔呈显着负相关，而大黄蜂和苍蝇的探访随海拔升高而增加。花冠更长，花蜜含量更高的物种显示出更高的鸟类探访率，而大黄蜂与花蜜浓度更高的物种相关。与自花授粉相比，异花授粉后的坐果率高，并且在较高海拔的物种中观察到较高的花粉限制和自育性。