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A male fly lands next to a fake female fly simulated by a daisy (photo: Roman Kellenberger/ University of Cambridge) it is never easy to survive in the intriguing nature-especially for a fly looking for breeding opportunities. Imagine that when you fly over the flowers, you happen to see a loved one of the opposite sex and want to have a good time with it. But after a while of effort, there was no response-you had to admit that you were cheated and worked for others for free.

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This is the story between the South African daisy Gorteria diffusa and the "fly" Megapalpus capensis who pollinated it: the daisy has dark spots on its petals, and when the male flies think they are females and come to mate, the daisy achieves its goal: pollination.

The usual trick of plants is that reproduction is a race against the clock for many plants growing in Namaqualand, South Africa. Here belongs to the semi-desert environment, the rainy season is very short. Between a few short heavy rains, daisies need to blossom, pollinate and produce seeds. As the main force of pollination, this group of "flies" has become a "hot resource" in the rainy season.

To be exact, M. capensis, one of the protagonists of the story, is not a fly. It belongs to the family Diptera, which is sometimes called "bombyliid fly". At first, these daisies, like many insect-borne flowers, provide nectar and fragrance to attract insects. However, some daisies adopt another strategy-to simulate a "fake wife" for male flies and trick them into mating in order to achieve their own pollination.

It is not uncommon to imitate female and cheat male pollination, but most of them are concentrated in orchids. Australia's Drakaea glyptodon, for example, is one of the best. The saw fly that pollinates the hammer orchid has a special mating habit: before mating, the female will climb to the tip of the grass, and the male will come and hold the female and fly into the air to mate together.

Hammer orchid happens to take advantage of this habit of saw flies. To males, hammer orchid looks like a female fly lying on the tip of a grass waiting to mate-this "female" even releases a similar pheromone. But when the male sawfly hugs the potential mate, it certainly doesn't fly into the air with the male, which keeps trying to take off. In the process, the back of the male fly hits the pollen of the hammer orchid, leaving the pollen firmly attached to its back. When the poor male finally gave up and ran to the next female simulated by Hammer Orchid, Hammer Orchid completed its own breeding career.

Hammer orchid (photo: Mcyster / English Wikipedia, CC BY-SA 3.0) and this daisy is one of the few "liars" found outside Orchidaceae, although it has not yet been proved to be able to use pheromones to lure pollinating insects, but for males, physical simulations alone are deceptive enough.

Not all South African daisies look the same, and at least 15 forms have been found in the daisies. The main difference between them is the spots on the petals. Some of them have a whole circle of dark spots in the middle of the petals. Other spots are more scattered on the petals and do not form a complete circle.

There are a few more, and the spots are extraordinarily delicate: dark spots scattered on the petals, rounded radians, fluff-like protrusions, and even the luster of the body and wings. And these exquisitely designed flower forms are the main force to deceive pollinators. Even though there may be some differences for humans, in the eyes of males, this is a completely irresistible mate.

In 2010, two South African researchers took an in-depth look at how these daisies deceive males. They found that male flies behave differently on different types of daisies. For daisies that are not simulated enough, male flies only actively feed on nectar and pollen, or briefly land on petal spots to check what it is.

Only daisies that really mimic fake females can trick males into mating: males shake their bellies, spin back and forth on spots, and wander back and forth between spots on a flower. Statistics show that up to 75% of the males that visit these flowers try to mate with spots. And these forms do attract more males and get more opportunities for pollination.

Fortunately, for other forms of daisies, even if they cannot attract female flies by simulation, they can still rely on nectar to attract pollinators and use food in exchange for the opportunity to reproduce themselves.

The proportion of male (top) and female (lower) flies feeding (light gray), observing (gray) and mating (black) on flowers of different shapes. In the two simulated forms (buffels and spring), the male flies showed mating behavior. (photo Source: A. G. Ellis & Steven D. Johnson, 2010) the exquisite design of three groups of genetic South African daisies is not only amazing, but also confusing: such a simulation is perfect, and if you want to achieve such a complex structure, it must involve a large number of genetic mutations, so it will take a long time to evolve.

A recent study published in Current Biology found that these daisies evolved in this form in less than 2 million years. They are so fast because they use an efficient technique: instead of waiting for new mutations, they perfectly combine three existing sets of genes to assemble them in the petals in a new way to build such "fake flies".

"they have done something smarter: putting existing genes together," says Beverley Glover of the Department of Biochemistry at the University of Cambridge in the UK. This phenomenon is called co-option, which refers to the process that genes and their products produce new functions in the process of evolution, and then replace the original functions.

The researchers found that when the daisy designed the female fly, a total of three sets of existing genes were used. The first can control the migration of iron ions and adjust the color of the petals so that the spots show a green to black gradient similar to that of female flies; the second gene is related to root hair, which can make the surface of the spots grow furry protuberances, so that the male flies "feel" more texture; the third group of genes can control the flowering time, which can make the spots appear in obvious random positions, rather than in a neat circle.

The "female fly" simulated by the daisy is also dark green and has a similar luster (photo: University of Cambridge) based on different types of genomes, the researchers were able to construct pedigrees and calculate the evolution order of these traits. The researchers speculate that the daisies first evolved the dark green of the spots, then randomly located, and finally the bulges on the spotted surface. Daisies may first attract the attention of males through color and arrangement-males are more efficient at pollination than females, and finally, the touch that resembles females induces pseudo-mating, thus directly using the mating process to pollinate.

Just imagine, when a male fly finds such a flower, its beautiful appearance and furry touch confirm its desire. With the action, the pollen fell on the male fly, but the "female fly" in its eyes did not respond. Until the male fly gives up in frustration and continues to look for the next wife-- it is likely to find a fake wife again-- its own reproductive progress may be zero, but daisies seize the precious rainy season.

I think of a friend who is addicted to paper.

Reference link:

Https://www.journals.uchicago.edu/doi/full/10.1086/656487

Https://www.cell.com/current-biology/fulltext/S0960-9822(23)00270-1?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982223002701%3Fshowall%3Dtrue#

Https://www.eurekalert.org/news-releases/983125

Https://www.science.org/doi/10.1126/science.329.5999.1581-d

This article comes from the official account of Wechat: global Science (ID:huanqiukexue)

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