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Rare Orchid Pollinates By Making Beetles Horny

by hridika ahire

Rare Orchid Pollinates By Making Beetles Horny

April 11, 2021

In order to maintain the balance among all living organisms, reproduction is very important. Which is why, this rare species of Orchid maintains life by making male beetles horny.

Rarest Orchid

Orchids or Orchidaceae, are a family of widespread and diverse flowering plants. These plants are often colourful and fragrant. There are about 28,000 species of Orchids that are currently accepted and known. But the Disa Forficaria species of this family is the most mysterious and also extinct.

Disa Forficaria belongs to the southern African region. It is so rare that researchers can’t even find it to study it. Disa forficaria has been found on very few occasions and was captured in 1966. There had been only 11 specimens of this white and magenta coloured orchid since the 1800s. But to everyone’s surprise, a single Disa forficaria plant appeared in the Fernkloof Nature Reserve, South Africa, in 2016.

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The southern African orchid Disa forficaria attracts male longhorn beetles.

Caught In the Act

The Fernkloof Nature Reserve located in the Cape Floristic Region, a UNESCO World Heritage site due to its incredible plant species’ incredible diversity. The Disa forficaria orchid had to be supervised very carefully for its protection and for studying how it grows and blooms, as not much was known about it. Therefore, when it appeared in the South African reserve, biologists jumped at the opportunity to examine it. When this news reached an orchid enthusiast and biologist from the University of Cape Town’s FitzPatrick Institute of African Ornithology, Callan Cohen visited the site in March 2016, just after the flower had bloomed. While admiring the flower, Cohen noticed an insect that landed on it.

Cohen caught onto the fact that the insect was mating with the flower. “He puts his head down where these other two little antennae (petals) stick up, and the way he was sort of vigorously moving his abdomen made me realize what was going on and that it needed to be studied further.”

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The disguised flower seemed to help them get in the groove—they displayed much more sexual behavior around the flowers than around the beads.

Use and Grow

Cohen thought that the insect was a wasp, which is pretty standard as many species of orchids use sex pheromones to attract bees and wasps in an attempt for pollination. This insect turned out to be a male longhorn beetle. Beetles are the most common group of animals on Earth, with over 350,000 species. But this was the first time that a beetle was seen pollinating with an orchid.

What surprised Cohen, even more, was the yellow pollen that stuck to the underside of the orchid when the beetle flew away. Upon seeing it, Cohen contacted Steven Johnson, a very well-known biologist from the University of KwaZulu-Natal. Johnson specializes in deceptive pollination in orchids. Along with an international team of researchers, they noted how a small but fragrant flower uses the sex drive of a beetle to fulfil its own reproductive needs.

Deceptive Pollination

The only challenge in understanding and studying this flower was that even though it has many buds, only one flower blooms at a time and stay open for merely one or two days. It didn’t help that the flower only blooms every other year. In total, the researchers could only examine the pollinating nature of this flower for eight days in March 2016 and for four days in March 2018.

They noticed that the flower sexually deceived beetles by imitating a beetle’s sex pheromones. The female insects release the same type of pheromones when they are ready to mate, and the male of the same species detect this chemical by their antennae. Surprisingly, over 400 species of orchids have evolved, and it is common for them to take advantage of the male’s sex driven mind by releasing their own type of sex pheromones in order to attract these pollinators.

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When the longhorn beetle pollinates the orchid, the resemblance between the orchid’s purple petals and the beetle’s antennae become clear.

Pheromone Analysis

Disa forficaria deceives the longhorn beetle both physically and chemically. As a beetle lands on the flower, the purple inner structure fits right underneath it. The beetle then bites and stokes the petal, which is a typical mating behaviour in longhorn beetles and then it proceeds to insert its aedeagus, the penis, into the cleft of the flower. Johnson says that the beetles are so sensitive to the pheromones that they are unaware of any signal in the habitat other than that of the sex pheromone.

When the researchers wanted to gain more information on this behaviour, they collected the fragrance of the flower and put them in a tool called a gas chromatograph which separates the chemicals. They snipped the antennas of some longhorn beetles and connected them with the apparatus that had the chemicals. One chemical brought about the same reaction from every antenna, and since the beetle’s antenna detect the sex pheromones, it was safe to bet that this was the orchid’s signal.

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A male longhorn beetle with pollen from Disa forficaria on its underside

The Seed Lives On

Researchers put varieties of synthetic flower fragrance on artificial flowers as well, and the beetles always made the same choice. They flocked to the molecule that researchers have now named “disalactone.” While the researchers tested disalactone’s ability to attract beetles in the Fernkloof Nature Reserve in 2020, after the orchids disappeared again, three beetles arrived with the yellow pollen stuck to them. When DNA tests were done, it was confirmed that the pollen came from Disa forficaria. This gives biologists hope that this near-extinct orchid might not be so extinct after all.

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