Mimicry, Subterfuge and Stealth: The Machiavellian Fertility Rites of Orchids
Orchids are the most highly evolved and diverse flowering plant family on earth. They have fascinated and inspired humans throughout recorded history with their resilience, beauty and exotic shapes and colours. These flowering plants ae considered one of the most successful and adaptable family of plants and it is estimated they date back to nearly 200 million years ago. Today their territory spreads from the equator to the Arctic Circle and from the Himalayas to Australia. These plants belong to the family Orchidaceae, one of the largest families of flowering plants worldwide encompassing about 6-11 percent of all species of seed plants. Way back in history as the world underwent many changes, species of both plant and animal life died out or were replaced. However, the orchid family expanded populating every corner of the world except Antarctica. Today there are more than 28,000 different orchid species living on trees, rocks, in the ground or under it, and in many different terrains including tropical rainforest, high mountains, or bog. Orchids flourish in the bush including: the Donkey, Spider, Cowslip, Greenhood, Pink Fairy, Blue, Sun and Mignonette orchids. The Donkey Orchid was particularly evident at the beginning of spring growing in swathes of bright yellow flowers in their hundreds.
Australia is relatively rich in native orchid population with over 750 different species. Two thirds of the total Australian population grow in the ground and are known as the terrestrials; and one third, known as the epiphytes or lithophytes, grow on trees or rocks. Moisture and sunlight are the critical factors governing their growth and flowering, so they are found in open forests, natural grasslands, coastal heaths and swamplands. Many terrestrial species are endemic to Australia and rely for sustenance on symbiotic relationships with fungi. The terrestrials grow from a fleshy tuber and have an annual cycle controlled mainly by soil moisture. The flower size of Australian orchids is generally small (commonly 50 to 200 mm across). However, this is adequately compensated by their great diversity in shape, colour and delicate perfume. Every colour is represented in the terrestrials including black and blue. Flower count varies from one in some species to over one hundred per stem, and many thousands per specimen plant. Unlike most plants, both male and female productive organs are carried on the same structure of the orchid, the column. The majority of native orchids flower in spring, however there are many that flower at other times and some flower more than once a year. Orchids have tiny dust-like seeds that are wind dispersed. Unusually for flowering plants, the seeds lack food reserves for the embryo. The orchid seeds are dependent on soil fungi for germination and growth. The structure of orchid leaves corresponds to the specific habitat of the plant. Species that bask in the sunlight or grow on very dry sites have thick leathery leaves covered by waxy cuticle to retain their necessary water supply and shade-loving species have long thin leaves.
A salient reason underpinning the extraordinary and expansive survival of orchids worldwide is their crafty approach to pollination which involves mimicry and subterfuge. When it comes to reproduction orchids are extremely versatile and have adapted themselves to use a variety of pollinators with or without their consent. Their colours, shapes and smells have made them cunning attractors of specific insects that will transport their pollen packets from one plant to another. The plant attracts many insects either by smell or mimicry or in some instances even a little stealth. The smell factor is an obvious attraction to a pollinator, but what about mimicry?
When it comes to sex, various insects that do have a brain are no match to an ingenious orchid and millions of years of evolution. The flowers of many orchids are designed to look either like the sexual partner of a pollinator or an aggressor. For example, some male insect species are not only duped into ‘mating’ with an orchid, and thereby pollinating it, but even prefer to mate with the orchid flower instead of with females of their own species. In the case of the Bee Orchid, male bees are attracted to the plant because the flower looks like a receptive female. During a frustrating attempt at mating with the flower, the male bee becomes the unwitting carrier of pollen. The Australian hammer orchid attracts the male wasp with a scent resembling that of his mate. If he tries to fly off before picking up or depositing pollen, he is battered against the column until he does right by the orchid and is then released. Some orchids adopt the lure technique and have long stems with tips bearing their flowers. These can dance effectively in the breeze and look like butterflies. Many orchid flowers provide an ideal landing platform for their pollinator to use. This is usually designed so that the insect has to come into contact with the orchid’s pollinia which sticks like glue to the back of the unwitting messenger, only to be brushed against the reproductive organs on its next port of call. And finally, we come to stealth: in this case the Slipper orchid lures the insect with a promise of a drink from its pouch or attracts it by scent right to the edge of the pouch which is very slippery and polished. The hapless pollinator finds itself stuck at the bottom of the pouch and there is only one way out which is crawling through a small doorway which is so tight that the pollinator is once again pressed firmly against the pollinia as it escapes.
Orchids’ real and imagined qualities are reflected in the folklore of many cultures, much of it relating, not surprisingly, to reproduction and health. The ancient Greeks, whose word orchis means testicle, gave the family its name based on the tuberous roots of the terrestrial species. Early Greek parents believed they could control the sex of their unborn children by eating orchid roots. European scholars believed that orchids sprang from ground on which animals had bred. They were also thought to be the food of satyrs and powerful aphrodisiacs, while in ancient China and Japan they were revered for their aesthetic and artistic value.
Orchids have many uses in the human world. Some orchid species produce potato-like tubers and are consumed by Aboriginal people who locate the plants in habitat by observing where bandicoots have scratched in search of the tubers. The underground tubers of terrestrial orchids are ground to a powder and used for cooking. Worldwide, the scent of orchids is frequently analysed by perfumers to identify potential fragrance chemicals. Orchids are cultivated for the enjoyment of flowers and many societies and clubs have been established worldwide encouraging the cultivation and collection of orchids. Orchids have also been used for medicines, adhesives, aphrodisiacs, and flavourings.
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