Aquilegia. Click for full size.
Columbines have been important in the study of evolution. It was found that Sierra Columbine (A. pubescens) and Crimson Columbine (A. formosa) each have adapted specifically to a pollinator. Bees and hummingbirds are the visitors to A. formosa, while hawkmoths would only visit A. pubescens when given a choice. Such a “pollination syndrome”, being due to flower color and orientation controlled by their genetics, ensures reproductive isolation and can be a cause of speciation.Aquilegia petals show an enormous range of petal spur length diversity ranging from a centimeter to the 15 cm spurs of Aquilegia longissima. Selection from pollinator shifts is suggested to have driven these changes in nectar spur length. Interestingly, it was shown that this amazing spur length diversity is achieved solely through changing cell shape, not cell number or cell size. This suggests that a simple microscopic change can result in a dramatic evolutionarily relevant morphological change. Source.