Charles Darwin, who established the theory of evolution, suggested in 1875 that some species of Saxifraga that flower in alpine regions might be carnivorous plants. They had glandular hairs that secrete sticky mucus. Although this creates good conditions for trapping insects, decisive evidence to support the hypothesis was not found despite multiple experiments afterward.
Scientists from China and the United States have verified Darwin's claim after 150 years. As Darwin anticipated, they confirmed that the plants use glandular hairs to trap insects and even digest them. Douglas Soltis, a corresponding co-author of the paper and a professor at the Florida Museum of Natural History, said, "Having the opportunity to confirm Darwin's prediction is both humbling and very exciting," adding, "I would like to think Darwin would be delighted and say, 'I was right again.'"
◇Darwin's research after publishing On the Origin of Species
For a plant to be recognized as carnivorous, it must be able to attract and capture prey, digest it, and absorb nutrients from it. Venus flytrap (scientific name Dionaea muscipula), which closes its leaves like a baseball glove to catch insects, is a representative example. Four years after publishing On the Origin of Species, which explained the theory of natural selection, Darwin said two Saxifraga species might be carnivorous plants.
A team led by Hang Sun, director of the Kunming Institute of Botany at the Chinese Academy of Sciences, and Professor Soltis collected and studied Saxifraga candelabrum from Wufeng Mountain in Yunnan Province, China. This plant is a perennial herb in the Saxifraga genus of the Saxifragaceae family and is similar to the plants Darwin mentioned. Because the flower stalk structure resembles a candlestick or a lampstand, it is known in traditional medicine as zhutaohuer cao (燭台虎耳草) or dengjiahuer cao (燈架虎耳草). In Korean, it would be "candlestick beomuigwi" or "lampstand beomuigwi," but since it belongs to the Saxifraga genus, "candlestick saxifrage" is the more accurate name.
The researchers found insects attached to the glandular hairs of 43 out of 45 specimens. Mostly nonbiting midges were caught. Mature plants captured an average of 71 insects. To determine whether insects had simply stuck by chance to the sticky leaves or had been captured and digested, they tracked with a substance that fluoresces when it encounters digestive enzymes found in carnivorous plants. When they applied this substance to the mucus-secreting leaves, the digestive enzymes removed phosphates and emitted light. A congeneric species that does not attract insects (Saxifraga filicaulis) lacked these enzymes.
◇Tracking insect digestion with fluorescent compounds and isotopes
In the next step, the team used nitrogen isotopes to see whether these enzymes actually participate in digesting insects. Isotopes have the same atomic number but different mass. They mixed nitrogen isotope 15, which has an atomic mass of 15, into feed and gave it to fruit flies for two months. Most nitrogen in nature has an atomic mass of 14. Saxifraga candelabrum showed a large increase in the level of nitrogen isotope 15 compared with other plants. This indicates it actually digested the fruit flies.
Finally, they compared genes with other carnivorous plants. They commonly found genes needed to attract and digest prey and regulate nutrient absorption. Sun said, "Taken together, these genomic data provide independent evidence that Saxifraga candelabrum is a true carnivorous plant."
Saxifraga candelabrum is the first carnivorous plant confirmed in the Saxifragaceae family. Scientists do not think it is the only carnivorous plant in this family. It means more carnivorous plants, including the Saxifraga species Darwin identified, may be confirmed using methods like these. Kadeem Gilbert of Michigan State University said, "As with the plant studied this time, there are hundreds or thousands of species with sticky hairs, including tomatoes, and a substantial number of them may be carnivorous."
References
Nature Communications (2026), DOI: https://doi.org/10.1038/s41467-026-75288-y