More than 150 years after Charles Darwin proposed that saxifrages were a group of plants that practiced carnivory, researchers have meticulously gathered the evidence to confirm he was right.
鈥淭alk about an amazing feeling,鈥� says at the University of Florida. 鈥淭o have the opportunity to confirm a prediction of Darwin is both humbling and very exciting.
鈥淚 would like to think Darwin would be pleased [and say] 鈥業 was right 鈥� again.鈥欌��
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To formally qualify as a carnivorous plant, a species must possess adaptations that enable it to attract, capture and digest its prey and absorb nutrients from it. Perhaps the world鈥檚 most renowned carnivorous plant is the Venus flytrap (Dionaea muscipula).
In 1875, four years after detailing his theory of natural selection in his book On the Origin of Species, Darwin wrote about in the genus Saxifraga, which were known to catch insects.
The genus has around 450 species and is found in Arctic and alpine regions of the northern hemisphere as well as in the South American Andes.
However, despite attempting several experiments to prove the plants digested the insects, Darwin was unable to substantiate his hunch.
To take up the challenge, Soltis and his colleagues studied specimens of Saxifraga candelabrum from Wufeng Mountain in Yunnan province, China 鈥� a different species from those studied by Darwin, but in the same genus.
During field surveys, the botanists observed that the Saxifraga candelabrum plants were capable of trapping small insects, using hairs covered with a sticky secretion. Bigger insects 鈥� those more useful to the plants for pollination 鈥� weren鈥檛 captured by the goo.
Mature plants had an average of more than 70 insects stuck to them, primarily various species of gnat, which suggested a potential carnivorous habit, says team member at the Chinese Academy of Sciences.
The team first tested whether the secretions produced by the hair-like structures that trap insects contained digestive enzymes capable of breaking down the prey, and found they did.
Next, by infusing insect prey with a nitrogen isotope, the scientists were able to demonstrate that nutrients from the digested insect had been taken up by the plant.
Finally, genetic studies showed that Saxifraga shares common genes with other carnivorous plants 鈥� a sundew (Drosera spatulata) and a flycatcher bush (Roridula gorgonias) 鈥� that control prey attraction, digestion and nutrient uptake.
鈥淭ogether, these genomic data provide independent evidence that S. candelabrum is a true carnivorous plant,鈥� says Sun.
Soltis expects the team鈥檚 research will lead to a re-examination of other species in the genus, including the ones Darwin studied, and the wider Saxifraga family.
鈥淢any members of the family have these hairs, and I would not be surprised if others are also carnivorous,鈥� Soltis says.
Nature Communications
