Data from: Reproduction in flame azalea (Rhododendron calendulaceum, Ericaceae): a rare case of insect wing pollination

Although many angiosperms are serviced by flying pollinators, reports of wings as pollen vectors are rare. Flame azalea (Rhododendron calendulaceum) is visited by diverse insects, yet previous observations suggested that only butterfly wings may transfer pollen to stigmas. We used an experimental approach to determine if butterfly wings are the primary vehicle of pollination in flame azalea. Over two seasons of observations, only butterflies (Papilio glaucus and Speyeria cybele) contacted both anthers and stigmas, yet due to differences in wing-flapping behavior, P. glaucus transferred pollen most efficiently. In contrast, bee species specialized either on pollen or nectar, but did not contact both anthers and stigmas. A field experiment revealed that flowers excluding butterflies experienced almost complete fruit failure, whereas fruit set in open flowers did not differ from those that were hand-pollinated. Additionally, butterflies had 56-fold more azalea pollen on their wings than bodies, while azalea stigmas bore both pollen and wing scales. These results suggest that plants with many visitors contacting reproductive organs may still specialize on a single guild of visitors for pollination, and that wing-borne pollen transfer is a key mode of flame azalea pollination.尽管多数被子植物（angiosperms）均有飞行传粉者（pollinators）为之提供传粉服务，但以翅作为花粉载体（pollen vectors）的相关报道却极为罕见。火焰杜鹃（Rhododendron calendulaceum）会被多种昆虫造访，但此前的观测结果仅表明蝴蝶的翅可将花粉传递至柱头（stigmas）。本研究采用实验方法，旨在明确蝴蝶翅是否为火焰杜鹃的主要传粉媒介。在两个观测季中，仅凤蝶类的北美大黄凤蝶（Papilio glaucus）与银纹贝凤蝶（Speyeria cybele）同时接触了花药（anthers）与柱头（stigmas）；但由于二者振翅行为存在差异，北美大黄凤蝶的花粉传递效率更为突出。与之相对，蜂类要么专性采集花粉，要么专性采集花蜜，均未同时接触花药与柱头。田间实验结果显示，排除蝴蝶访问的花朵几乎完全无法坐果，而开放授粉的花朵坐果率与人工授粉的花朵无显著差异。此外，蝴蝶翅上携带的杜鹃花粉量是其躯体的56倍，而火焰杜鹃的柱头上同时存在花粉与蝶翅鳞片。上述结果表明，即便有多种访客接触植物生殖器官，植物仍可能特化依赖单一类群的访客完成传粉；而借助翅传播花粉，正是火焰杜鹃的核心传粉方式。