This month’s talk in the Fernkloof Hall was given by Prof Johann du Preez who discussed the pollination strategies of both plants and their animal pollinators.
As birds are major plant pollinators, we invited members of the local bird clubs to join us.
“Nothing on earth is permanent” says Johann at the start of his brilliant overview of life on earth from its emergence to the present. Since the early development of flowering plants about 130 million years ago plants have changed considerably.
Evolution of the sex organs has been most spectacular. Protection from dessication and predation was important, but the changes driven by the necessity for pollination to ensure survival of the species had to co-evolve with the animal pollinators.
Johann asked what might pollinate the world’s largest single flower plant, Rafflesia on the Borneo forest floor? No sunshine penetrates there but flies are attracted to dead animals, Rafflesia has developed a similar smell, to ensure that flies are its pollinators.
The sausage tree (Kigelia africana) of the Kruger National Park opens its blood red flowers at night which attract bats.
Many plants develop long tubular flowers which can only be pollinated by the long curved bills of sunbirds and sugarbirds. Although specialisation comes at a cost there are advantages, floral parts can be reduced, and the nectar is protected deep inside the flower. Trouble comes when a particular specialised bird species becomes rare, then pollination may become impossible and the plant faces extinction.
Johann closed his fascinating talk with illustrations of a sunbird walking up the strong blue stigma of Strelitzia reginae to reach the nectar, and in the process exposes the pollen anthers by its own weight, thus covering its feet with pollen. And the story of the Australian thynnid wasp which, after attempting to mate with the spring-loaded lip of the hammer orchid, flies up, is thrown forward and hits its head on the pollinia had the audience in fits of laughter!
Submitted by Deirdre