Chapter five
Pollination and natural hybridisation

Over the past decade, much has been learnt about the interrelationships between the Cape orchids and their pollinators. This chapter discusses the ways in which orchid flowers are specifically adapted for pollination by various insects and even birds. Strikingly detailed photography portrays examples of various pollination strategies such as mimicry and sexual deception by orchid flowers. The highly specialised pollination of orchids highlights the remarkable interconnection between living organisms and the intricate mechanisms that promote their survival in nature. The partnership between orchid flowers and their pollinators is one of the most compelling and fascinating aspects of natural history. Orchids, like all other plants, are literally rooted to one spot and this means that they face the challenge of how to acquire pollen—the botanical equivalent of sperm—from one flower to another, in order that they can achieve the fertilisation that is needed to produce seeds. Most do so by using animals as couriers of their pollen. Flowers are simply the reproductive organs of the plant cloaked in colourful and often fragrant layers of petals and sepals. It is these allurements that entice animals to visit the flowers and receive and deposit pollen.

Many discoveries have been made in the past ten years and the list of Cape orchids with known pollinators has increased from about five in the early 1990’s, to about 50 species at present—still a small fraction of the total number of orchid species in this region. Clearly, much remains to be revealed . . .
  • Pollination by butterflies
  • Pollination by moths
  • Pollination by flies
  • Pollination by bees (excluding Melittidae)
  • Pollination by oil-collecting bees (Rediviva: Melittidae)
  • Pollination by beetles
  • Pollination by birds
  • Deception and mimicry
  • Self-pollination
  • Natural hybridisation
Clusters of Bonatea speciosa pollinaria are transported from flower to flower, attached to the eyes of the hawkmoth, Theretra capensis. Goukamma Nature Reserve, southern Cape Floristic Region (29 October 2005)
Click to enlarge Possessed with a passion for red, the Mountain Pride butterfly, Aeropetes tulbaghia, alights upon and pollinates a flower of Disa uniflora. Pollinia dangling from its legs deposit pollen massulae onto the large fleshy stigma (February 1997)
The discovery that horseflies pollinate orchids was first made by Celestine du Plessis, a schoolteacher near Porterville. In February 1911 she sent a life-size painting of a long-proboscid horsefly (Philoliche gulosa) and letter to Bolus, explaining that the insect found by one of her students was carrying an orchid pollinarium, possibly of ‘D. draconis’ (D. harveyana subsp. longicalcarata), attached to its proboscis
From the Pollination chapter