Confirmation of hawkmoth pollination in Habenaria epipactidea: Leg placement of pollinaria and crepuscular scent emission

Abstract

In his landmark work on the pollination biology of South African plants in 1954, Stefan Vogel described the deposition of Habenaria epipactidea (= H. polyphylla) pollinaria on the forelegs of the hawkmoth Hippotion celerio. The discovery of a large, well-pollinated population of H. epipactidea in the Eastern Cape allowed us to confirm the presence of this unusual pollen placement on a number of species of shorter-tongued hawkmoths. The long-tongued species Agrius convolvuli is likely to function as a nectar thief as the length of the tongue of this species relative to the nectar spur ensures that the forelegs are unlikely to come into contact with the viscidia. The legitimate hawkmoth pollinators removed a large proportion of pollinaria from the flowers and the majority of flowers had pollen deposited on their stigmas. Despite this, pollen transfer efficiency was relatively low at 8.4%. We also examined the scent production of H. epipactidea and show that volatile production increases markedly after 18:00, peaking at around 20:00. The scent of this species is dominated by methyl benzoate which makes up 99.4% of the floral scent at 20:00. The osmophores are located on the lateral petals and labellum, confirming Vogel's observations in the Soutpansberg (Zoutpansberg).