BACKGROUND AND AIMS The temporal dimensions of floral adaptation to pollinators are not yet well understood, partly because we lack accurate information on the diel rhythms of flower visitation for many pollinators. We investigated whether diel patterns of pollinator visitation to flowers of the African woodland orchid Bonatea polypodantha are synchronised with rhythms of floral anthesis, scent emission and nectar availability. METHODS Direct observations and motion-activated cameras were used to identify pollinators of B. polypodantha and to document their activity periods. The timing of pollinaria removal from flowers, emission of scent and availability of nectar were also measured. RESULTS We found that B. polypodantha is pollinated exclusively by short-tongued hawkmoths. Pollinaria of the orchid are affixed between the labial palps of the moths and brush over the protruding stigmatic arms. The flowers also receive visits by long-tongued hawkmoths, but these act as nectar thieves. Tracking of pollinaria removal from flowers confirmed that pollination occurs only at night. Camera footage revealed a striking crepuscular pattern of foraging by short-tongued hawkmoths with peaks of activity during the twilight periods at dusk and at dawn. In contrast, long-tongued hawkmoths were found to visit flowers throughout the night. Flowers of B. polypodantha exhibit unimodal peaks of anthesis, scent emission (dominated by nitrogenous aromatics) and nectar availability before or around dusk. CONCLUSIONS Flowers of B. polypodantha are pollinated exclusively by short-tongued hawkmoths which show crepuscular foraging activity at dusk and dawn. Floral phenophases of the orchid are closely synchronised with the peak of pollinator activity at dusk.

中文翻译：

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与天蛾传粉者双峰活动模式相关的非洲兰花的 Diel 气味和花蜜节律

背景和目标 花对传粉媒介的适应的时间维度还不是很清楚，部分原因是我们缺乏关于许多传粉媒介访问花的昼夜节律的准确信息。我们调查了传粉者访问非洲林地兰花 Bonatea polypodantha 花朵的日间模式是否与花期、气味散发和花蜜供应的节奏同步。方法 直接观察和运动激活相机用于识别 B. polypodantha 的传粉者并记录它们的活动期。还测量了从花中去除花粉的时间、气味的散发和花蜜的可用性。结果我们发现 B. polypodantha 完全由短舌天蛾授粉。兰花的花粉贴在飞蛾的唇瓣之间，刷过突出的柱头臂。花也受到长舌天蛾的访问，但它们充当花蜜小偷。从花中去除花粉的追踪证实授粉仅在夜间发生。摄像机镜头显示出一种惊人的黄昏模式，短舌天蛾在黄昏和黎明的黄昏时期活动达到高峰。相比之下，人们发现长舌天蛾整夜都在探访鲜花。B. polypodantha 的花在黄昏前或黄昏前后表现出单峰的开花、气味散发（以含氮芳香剂为主）和花蜜可用性。结论 B. 的花 polypodantha 完全由短舌天蛾授粉，天蛾在黄昏和黎明时分表现出黄昏觅食活动。兰花的花期与黄昏时授粉活动的高峰密切同步。