Abstract
In contrast to other species of the genus, the nectar spur of I. frithii is not curved downwards, but slightly upwards. This apparently small modification significantly affects how pollen is placed on birds' bodies.When a bird forages on nectar, the flower twists as the spur conforms to the shape of the bird's bill.
As a consequence, pollen is placed in an unusual location on the bird's body - the ventral surface of its bill or head. Our observations demonstrate that a minute change in floral morphology can effectively overcome constraints resulting from the basal floral architecture early in the group's evolution.
We assume that such adaptations can not only help the plants avoid interspecific competition, but as the adaptations create strong reproductive barriers, they may also contribute to plant speciation.