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  • The world’s largest orchid grows several meters tall.

  • The tiniest is practically invisible.

  • Some bloom high up in trees,

  • while others live underground.

  • All in, there are around 28,000 species of orchid on earth

  • about as many as all the bird, mammal and reptile species combined.

  • They grow all over the world,

  • bearing every imaginable colour, shape, and pattern.

  • And there’s a cunning purpose behind these elaborate displays:

  • many orchids trick insects,

  • sometimes even into having sex with them.

  • Like other flowers,

  • most orchids need to attract insects

  • to gather their pollen and carry it between plants.

  • But unlike most flowers,

  • which attract a range of pollinators with sweet nectar,

  • these masters of deception deploy other tactics

  • like pretending to be an insect’s mate,

  • letting off alluring scents,

  • and mimicking the appearance of other species.

  • One of their most intriguing methods is sexual deception.

  • Through a combination of sexy shapes and pheromones,

  • orchids convince insects to mate with them.

  • Take the bee orchid,

  • whose petals look almost exactly like the velvety body of a bee.

  • This disguise is so convincing that male bees land on the orchid

  • and try to have sex with it,

  • picking up pollen as they go.

  • Other orchids have evolved contrasting colours and ultraviolet spots

  • invisible to humans but irresistible to insects.

  • Still others have tactilelove-handles

  • that ensure insects are positioned precisely for pollination.

  • When a male wasp lands on the hammer orchid, for example,

  • his enthusiastic mating motion flips a hinge in the flower,

  • forcing his body into the pollen.

  • At the next flower he visits,

  • that same hinge pushes his pollen-covered body onto the stigma,

  • fertilizing it.

  • Some orchids make such convincing mates

  • that insects even ejaculate on them,

  • wasting valuable sperm.

  • But the most vital component of sexual deception is scent:

  • orchids mimic the precise scent of a single insect species.

  • This is possible because many insects and flowers

  • produce simple organic compounds called hydrocarbons,

  • which form a layer that protects their bodies from drying out.

  • The precise blend of compounds in this layer is species-specific.

  • Its scent can double as a way for insects to attract potential mates,

  • known as a sex pheromone.

  • Over the course of many thousands of years,

  • random compound combinations have given some orchid species

  • precisely the same signature scent as particular insect species.

  • This matching scent allows them to attract male pollinators

  • who fall over and over again

  • for the flowers masquerading as females

  • of their own species.

  • Sexual deception isn’t the only trick orchids have up their sleeves.

  • Their oldest scam is mimicking the shapes and colours

  • of other nectar-producing flowers

  • but without the sweet nectar.

  • Some orchids also masquerade as places where insects lay their eggs.

  • One species not only has the colour and appearance of rotting meat;

  • it emits a scent of decay as well

  • drawing in flies who deposit their eggs on the flower

  • and unwittingly pollinate the plant.

  • Other orchids look and smell just like the fungi on which certain insects

  • lay their eggs.

  • Where do all these bizarre adaptations come from?

  • Random genetic mutations in orchids may result in a trait

  • like a scent or a shape

  • that, by chance, matches the needs of a single insect species.

  • The huge diversity within the insect world also increases the likelihood

  • that an orchid will find a unique audience.

  • Able to make more seeds and offspring with the help of its dedicated pollinators,

  • the orchid successfully reproduces in isolation,

  • and becomes a new species.

  • But because of their dependence on sometimes just one pollinator species,

  • orchids are also vulnerable,

  • and many quickly go extinct.

  • Over time, though,

  • more orchid species have formed than died out,

  • and orchids are some of the most diverse flowering plants.

  • They have such exuberant and otherworldly shapes

  • that they occasionally deceive human senses, too:

  • In their petals we see what appear to be tiny, dancing people,

  • monkey’s faces, spiders,

  • and even birds in flight.

The world’s largest orchid grows several meters tall.

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蘭の性的欺瞞 - アン・ガスケット (The sexual deception of orchids - Anne Gaskett)

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    林宜悉 に公開 2021 年 01 月 14 日
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