Flower shapes, colors, sizes and fragrances are shaped mostly for pollinator attraction. Flower phenotypes are, however, subjected to conflicting selection directed by both pollinators and non-pollinating agents. We investigated flower attractiveness to a model pollinator in the snowdrop (Galanthus nivalis L.) under laboratory conditions. Naïve bumblebees (Bombus terrestris L.) showed strong, innate preferences for experimentally altered upward positioned flowers, suggesting that the natural, downward orientation did not evolve to attract pollinators. Experimentally treated green marks on inner tepals decreased pollinator attraction compared with flowers expressing intact marks, suggesting that green marks serve to guide/attract pollinators. Attractiveness of green marks was significantly compromised by flower orientation; green marks were attractive only for untreated downward-oriented flowers, but they did not improve the attractiveness of upward-oriented flowers. Our results suggest that downward flowers in snowdrop evolved under conflicting selection directed by biotic and abiotic factors, and that green marks on inner tepals could evolve later to enhance flower attractiveness.

花的形状，颜色，大小和香味的形状主要是为了吸引传粉者。然而，花的表型受到授粉媒介和非授粉媒介的直接选择。我们在实验室条件下调查了雪花莲（Garanthus nivalis L.）中的模型传粉者对花的吸引力。天真大黄蜂（Bombus terrestrisL.）对实验改变的向上定位的花朵表现出强烈的先天偏爱，表明自然，向下的方向并没有发展为吸引传粉媒介。与表达完整标记的花朵相比，内部花被上经过绿色处理的绿色标记降低了授粉媒介的吸引力，这表明绿色标记有助于引导/吸引授粉媒介。花朵取向严重损害了绿色标记的吸引力；绿色标记仅对未处理的朝下花朵具有吸引力，但并不能提高朝上花朵的吸引力。我们的结果表明，在由生物和非生物因素指导的相互冲突的选择下，雪花莲中的向下花朵进化了，而内部花被上的绿色标记可以在以后进化以增强花朵的吸引力。