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 whether 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 because of 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）依靠飞行传粉者完成传粉，但以翅翼作为花粉传播媒介的相关研究报道却较为罕见。火焰杜鹃（Rhododendron calendulaceum）虽有多种昆虫造访，但既往观测仅提示蝶翼可能将花粉传递至柱头。本研究采用实验方法，旨在明确蝶翼是否为火焰杜鹃传粉的主要载体。历经两个季节的野外观测，仅北美大黄凤蝶（Papilio glaucus）与银斑豹蛱蝶（Speyeria cybele）两类蝴蝶同时接触花药与柱头；但因振翅行为存在差异，北美大黄凤蝶的花粉传递效率更高。与之形成鲜明对比的是，蜂类要么特化取食花粉，要么专注于花蜜采集，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结实，而开放授粉的花朵坐果率与人工授粉的花朵并无显著差异。此外，蝴蝶翅翼上携带的杜鹃花粉量是其躯体的56倍，且火焰杜鹃的柱头上同时存在花粉与蝶翼鳞片。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某一类群的访客完成传粉，而借助翅翼传播花粉乃是火焰杜鹃传粉的关键模式。