While Steiner was conducting fieldwork in South Africa, he noticed that the Redivia bees he was catching had small yellow objects attached to their legs. These turned out to be pollen packets (pollinaria) from orchid flowers. "By matching up the varied shapes and sizes of the different pollinaria found on the bees with those I extracted from the various orchid flowers I encountered, I was able to determine which orchid species these bees were visiting and what the attractant might be," Steiner comments. "For each orchid whose pollinaria the oil-collecting bees carried, I found that the flowers secreted a non-volatile oil rather than nectar as a reward. And, by examining as many orchid flowers as I could find, I discovered that over 100 orchid species in southern Africa produce oil as a pollinator reward and that these species are pollinated by oil-collecting bees."
The scents of these orchids, which are usually described as unpleasant, pungent, cloying, or smelling like soap, fascinated Steiner, and he sent as many scents as he could collect to a well-known authority on orchid scents, Roman Kaiser. According to Steiner, "Once we had a good sample of scents from the different oil-secreting orchids, we could begin to compare them and ask questions regarding whether closely related species had more similar scents than distantly related species and whether species pollinated by the same bee species also shared the same floral scent, even when they were not closely related. In other words, is phylogeny more important than natural selection in determining the composition of floral scents in this group of orchids?"
Steiner and his colleagues, Kaiser and Dtterl, predicted that because these oil-secreting orchids seem so specialized, the scent profiles of species pollinated by the same bee species would be similar regardless of phylogeny. They also predicted that the scents of orchids within a rainfall region (winter vs. summer) would be more similar t
|Contact: Richard Hund|
American Journal of Botany