Darwin’s Dating Bureau
by Melitta van Bracht & Juul van Dam
Within the world of plants there are many different seduction methods, some of those were described in an article on this subject published in Blijdorp Blad (Rotterdam Zoo Magazine) nr. 2. In this article we tell you more about it. There is a lot of courting going on among plants, sometimes quite ruthlessly. To prove that we take you along to the kinky paradise of Darwin’s dating bureau.
Insects, birds and bats may accept to be made fun of a few times, but in the end they want to be paid down on the mail. These intermediaries of Darwin’s Dating Bureau are contented with payment in kind: nectar and pollen. Some plans even offer bed and breakfast. In Rotterdam Zoo there is a fine example of this phenomenon: the giant water lily Victoria amazonica. Its creamy white flowers open towards evening, spreading a pineapple-like fragrance luring beetles to the hotel room. For beetles a morning curfew applies instead of an evening curfew. At daybreak the flower closes and the beetles are trapped till the next evening. They have full board and are served with a delicious meal rich in protein. When checking out they get pollen into the bargain. At their next visit to a Victoria flower pollination takes place.
Within a balanced relation between plant and animal the pollinator gets a proper reward for services rendered. But there are always competitors in the field that are cunningly to bypass the pay desk. A flower is like a shop were the shopassistant is absent for a moment and the clients walk out without paying. That’s how it is in the world of plants.
killer water lily
With the South American Victoria the beetle gets value for money, but with the South African water lily Nymphaea capensis it is a different story. The first day the flowers are in the female stage. There is a little pond in the heart of the flower, the bottom being the pistil of the flower. Around the pond there are unripe stamen on which hungry insects are unsuspectingly landing. But alas there is no pollen whatsoever! A sink of iniquity is what is in store for them. Because of the low surface tension of the water the insects rapidly vanish under the water level. The pollen soaking off from the body of the insect during the drowning process sinks towards the pistil and pollination takes place. Nevertheless the next morning this ‘coffin’ shows a different face. When the flower opens it shows its ripe pollen. New insects do not know any better and wallow in abundance, but you, dear reader, you now know the flower’s true colours.
For the botanists in Rotterdam Zoo it is still puzzling that so many plants can still get away with this swindle unpunished. In this category stink plants are no better. They attract carrion flies and other insects that are looking for rotting flesh. With the smell of decay and the looks of a delicious piece of meat stink plants lure these insects into their blossoms to lay their eggs. But worse luck their fate is a few days in jail on bread and water. The hairs in the inflorescense of the Dutchman’s pipe (Aristolochia) only allow one-way traffic. During the imprisonment of fly or beetle the stamens ripen and the prisoners are covered with pollen. Thereafter the ‘bars’ wither and the prisoners are free again. Not only plants can be swindlers, don’t forget bumbles! This wolf in sheep’s clothing is a skimmer of comfrey (Symphytum officinale),
drilling a hole in the flower with his jaws. In this way the coiner gets paid with nectar without service in return for the plant.
Sometimes it is the bumble that is deceived. Some orchid flowers have been evolved in such a way that they are the spitting image of a mating partner of a bumble. Many bumbles will take to this sexy bait. Not only bumbles are deceived, also flies, wasps and bees are fooled. Certain Australian wasps are attracted by a succedaneum female. This false female is an orchid of the Drakaea genus which has a unique system to be pollinated. The male wasp plans a nuptial flight but when meeting a Drakaea his hopes are deceived. He clenches the labellum between his paws to fly away. When fiercely attempting to fly off the labellum hinges backwards and a sticky pollen packet is released and will cling to the back of the wasp. In this way the plant has found a free courier.
Love is not always in the air. There are plants with flowers resembling the prey of the insect. A cunning way of the orchid to lure insects. This time it is not about sex but about pollination. The flowers are being attacked and thus pollinated. The Epipactis consimilis is a clear example of this phenomenon. The structure of the flower looks like the structure of a green fly (aphid) a delicious meal for syphid flies. But the syphid flies will have go without their dinner and the orchid is grateful of course.
Love between plant and animal is not always as a matter of course. It can be a life-and-death struggle. Take the female serial murderer Arisaema triphyllum or Jack in the Pulpit. This plant is dioecious, having female and male specimen. The Arisaema spreads a fungus-like scent luring gnats that like to mate and to lay eggs in the inflorescence. Loaded with pollen they escape from the male inflorescence that has an easy exit. However, the female plant is the malefactor. Escaping is impossible because the emergency exit is missing. As soon as the insects land on the inflorescence they tumble in the condemned cell and are dead. But may be this heroic death is not for nothing. When covered in pollen they have at least contributed to descendants.
People love flowers, but beware what you bring home!