South African daisies use mimicry to lure flies
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South African orange daisies have an unusual lure for attracting pollinators. The small structure of the petals resembles a female fly. Male flies land on flower petals in hopes of mating, but end up carrying the flower’s pollen to other plants. The pseudo-fly-like structures appear to have emerged within a relatively short evolutionary timeframe of two million years, according to scientists who identified three gene sets in daisies that were repurposed to evolve lures.
After each winter’s rains, South Africa’s Namaqualand Desert blooms for months with spectacular blooms. Flower abundance creates stiff competition for South African daisies (extensive blood stains), attracting pollinators such as bees (Megapalpus capensis) with fake fly petals.
“Male flies come to the spot and land very specifically, as if they want to mate,” says Beverly Glover of the University of Cambridge.. “Buzzing and bewildered,” she says, flies scatter pollen on themselves and carry it from plant to plant.
To find out which genes are involved in flower forgery, Glover and her team compared genes expressed in fake fly petals with those expressed in normal petals. South African daisies have evolved false flies with slightly different appearances depending on the subpopulations of the species, but most often 1 to 4 with a raised, hair-like texture that mimics female flies. Contains 4 dark black dots. Some flowers have no false female flies at all. The researchers also compared South African daisies to other species of daisies that have simple spots and dark rings that lack false fly details.
They found three sets of genes involved in creating deceptive lures. All of these already performed other functions in the flower. “[These genes] Everything was adopted or adapted to create this amazing fly imitation,” says Glover. “We know that this particular daisy evolved from the last 1.5 million years to make these spots.”
A set of genes that move iron around the plant were recruited to carry a bluish-black pigment to the petals. The group of genes that tell the plant when to bloom causes false flies to appear on different petals.
The study “helps solve one of the major problems in mimicry research,” said Steve Johnson of the University of KwaZulu-Natal, South Africa, who was not involved in the study. Specifically, it helps to elucidate how plants gradually evolve complex structures through stages of gene copying.
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