Hawkmooth pollination and hybridization in Delphinium leroyi (Ranunculaceae) on the Nyika Plateau, Malawi

The large circumboreal genus Delphinium is characterized by short‐spurred blue‐purple flowers pollinated primarily by bees. Two interesting exceptions to this pattern are the long‐spurred red flowers of two western North American species known to be hummingbird‐pollinated, and the long‐spurred evening‐scented white flowers of an east African species, Delphinium leroyi. Observations on the Nyika Plateau, Malawi, showed that flowers of D. leroyi were frequently visited by hawkmoths during a 30 minute period after dusk. The most common visitor, Hippotion celerio , has a mean tongue length of 37 mm, corresponding almost exactly to the floral spur of D. leroyi ; consequently, there is effective placement of pollen on the underside of the moths. The flowers were also visited occasionally by the very long tongued hawkmoth Agrius convolvuli , but this moth does not make effective contact with anthers and appears to act only as a nectar robber. Delphinium leroyi occurs in open grasslands on the Nyika Plateau, while a related species D. dasycaulon which has short‐spurred blue flowers that are visited by bees, occurs in shrubby vegetation associated with old termitaria and forest margins. Although the two species are parapatric, occasional hybrids occur at sites where populations of the two species occur in close proximity. The status of hybrids was established by a morphometric analysis of the hybrids and their parent populations.