A fascinating example of nature's "ingenuity": Researchers report on a South African plant that uses an astonishingly clever concept to depict dummy female flies on its flowers in order to attract males for pollination. The investigations show that, surprisingly, the plant did not have to produce any special hereditary traits for the formation of these “fake flies”. Instead, it cleverly activates conventional genes in the petals that normally perform other functions in the plant, the scientists report.
Bright colors, smells, special patterns and shapes are intended to draw attention to them: In the course of evolution, many plants have developed sophisticated flower characteristics to attract animals that are supposed to help them reproduce. Insects in particular take on the role of bearers of pollen. They often get sweet nectar as a "reward". But there are also plants that use more tricky strategies: their flowers look like possible mates of certain insects and thus tempt them to land and ingest pollen. A plant with a particularly impressive example of this concept was now the focus of the study by researchers led by Roman Kellenberger from the University of Cambridge.
Tempting “fake flies”
Native to arid regions of South Africa, Gorteria diffusa belongs to the daisy family (Asteraceae) and has a structure of radiating petals around a rounded center - similar to that of a daisy. But some of the petals of G. diffusa are special: They are shortened, dark in color and have bumps with tiny hairs. Even at first glance, they look like an insect. In fact, they are designed to mimic females of the Megapalpus capensis fly species and entice the males of these insects to land, the researchers explain. Those who have been tricked then try in vain to mate with the dummies and thereby pick up pollen grains or provide the plant with pollen that they have previously collected from another flower.
It seems clear that in order to be able to produce these extremely complex “fake flies”, the plant must have special building instructions in its genetic system. In order to get to the bottom of this interesting concept, the scientists used genetic methods to compare which genes were switched on in the flower petals with and without fly dummies in the flowers of G. diffusa.
Simple ingenious dummy construction
As the researchers report, they identified three sets of genes that are involved in the formation of the dummy flies on the flower petals. The big surprise was that these are not exotic special programs that only this plant has produced. Instead, all three sets of genes already have other functions in the plant and are only cleverly activated in the petals. One of the sets of genes is therefore normally responsible for shifting iron in the plant, the other causes hair to sprout on the roots, and the third is responsible for controlling development processes in the plant.
The results of the study now show that these three functional units in the plant's petals are activated in a clever combination in order to "tinker" with the fake flies. Specifically, what emerges is that the "iron-shifting" genes add iron to the usual color pigments of the specially designed petals, causing the color to change to a fly-like blue-green. The activated root hair genes ensure that fly-typical hairs develop on the structure in order to give them deceptive structural features. The third group of genes, in turn, ensures that the dummy flies appear in random places on the flowers, the scientists explain.
“One would expect that something as complex as a dummy fly would take a long time to develop and involve many genes and mutations. But by merging three existing sets of genes, this plant was apparently able to pull off the trick very quickly," says Kellenberger. Finally, one can ask oneself why this adaptation has arisen in this plant of all things. The researchers explain: In the habitat of G. diffusa there is only a short rainy season, during which many plants bloom at the same time. This creates intense competition to attract pollinators. So it was obviously worthwhile for the "clever" plant to stand out from the crowd in a sophisticated way.
Source: University of Cambridge, professional article: doi: Current Biology, doi: 10.1016/j.cub.2023.03.003