By Jill Brooke
Heard the expression “fresh as a daisy?” Well, you may want to rethink that phrase and add some naughtiness and flirtation to it.
Turns out that researchers at the University of Cambridge have discovered that resourceful little daisies in drought-filled South Africa are shifting their petals to look like lady flies, in order to seduce male flies. I kid you not. Flowers are SO COOL.
A male fly approaches a flower, lands on top of what he thinks is a female fly, and jiggles around. He’s trying to mate, but it isn’t quite working. He has another go. Eventually, he gives up and buzzes off, unsuccessful. The plant, meanwhile, has got what it wanted: pollen.
The South African daisy, Gorteria diffusa, is the only daisy known to make such a complicated structure resembling a female fly on its petals.
“This daisy didn’t evolve a new ‘make a fly’ gene. Instead, it did something even cleverer – it brought together existing genes, which already do other things in different parts of the plant, to make a complicated spot on the petals that deceives male flies,” said Professor Beverley Glover at the University of Cambridge’s Department of Plant Sciences and Director of the University’s Botanic Garden, senior author of the study.
The study, which is in the journal “Current Biology,” discusses how the mechanism behind this convincing three-dimensional deception, complete with hairy bumps and white highlights, has intrigued scientists for decades. But now these dedicated researchers have identified three sets of genes involved in building the fake fly on the daisy’s petals. The big surprise is that all three sets already have other functions in the plant: one moves iron around, one makes root hairs grow, and one controls when flowers are made.
I won’t look at a daisy the same way anymore, will you? I’ve written a lot about how humans have used flowers to seduce, but flowers are pros at it. They are such inventive entities and adapt for survival. They take flirting to a whole new level.
The researchers say the daisy’s petals give it an evolutionary advantage, by attracting more male flies to pollinate it. The plants grow in a harsh desert environment in South Africa, with only a short rainy season in which to produce flowers, get pollinated, and set seed before they die. This creates intense competition to attract pollinators – and the petals with fake lady flies make the South African daisy stand out from the crowd.
Compared to most living organisms, the group of plants including the sexually deceptive daisy is very young in evolutionary terms at 1.5 to 2 million years old. The earliest daisies of this family tree didn’t have the fake fly spots, which means they must have appeared on the daisy petals very rapidly.
“We’d expect that something as complex as a fake fly would take a long time to evolve, involving lots of genes and lots of mutations. But actually, by bringing together three existing sets of genes, it has happened much more quickly,” said Dr. Roman Kellenberger, a postdoctoral researcher in the University of Cambridge’s Department of Plant Sciences and first author of the study.
To get their results, the researchers compared which genes were switched on in petals with, and without fake flies in the same type of daisy plant. They also compared these to petals from a different type of daisy that produces a simple spot pattern, to work out which genes were specifically involved in making the daisy’s spots so deceptive.
This is the only example of a flower that produces multiple fake flies on top of its petals. Other members of the daisy family make much simpler spots – for example, spots in a ring around all the petals – that aren’t very convincing to real flies. By comparing the different daisies in the family tree, the researchers were able to work out the order in which the fake flies came into being: color first, then random positioning, then texture.
“It’s almost like evolving a whole new organ in a very short time frame. Male flies don’t stay long on flowers with simple spots, but they’re so convinced by these fake flies that they spend extra time trying to mate and rub off more pollen onto the flower – helping to pollinate it,” said Kellenberger.
This research was funded by the Swiss National Science Foundation, the Natural Environment Research Council, and the Biotechnology and Biological Sciences Research Council.