Darwin was right: science confirms 150 years later that this little plant is an insect-eater

Darwin was right: science confirms 150 years later that this small plant is an insect-eater In 1875, in his famous treatise on carnivorous plants, Charles Darwin observed with fascination the sticky hairs that cover several species of the genus Saxifraga and suggested these plants could be carnivorous and feed on insects. However, neither his experiments nor subsequent studies yielded conclusive results, and the botanical community classified these species as mere “proto-carnivores,” considering the sticky hairs simply defensive mechanisms. Now, in a study published in the journal Nature Communications, a team led by Chinese scientist Hang Sun from the Kunming Institute of Botany and the University of Florida has discovered the elusive mechanism confirming Darwin’s prediction 150 years ago: Saxifraga candelabrum is indeed carnivorous and can attract, trap, and digest insects, as well as absorb nitrogen from them. Moreover, the plant selectively attracts its prey, trapping large numbers of tiny mosquitoes from the family Chironomidae while allowing larger flies and bees, its pollinators, to escape. A high-altitude predator This small plant grows among rocky fissures exposed to sunlight and extremely poor nutrients on the Tibetan Plateau, at elevations between 2,500 and 3,300 meters. For the study, researchers collected specimens from alpine areas of the Qinghai-Tibet Mountains and the Hengduan Mountains in China. They found insects trapped in the glandular hairs of 43 out of 45 studied specimens. Some mature plants had an average of 71 insects trapped, but they needed evidence of digestion and nutrient absorption to solidify their hypothesis. Through field experiments and analysis of herbarium specimens preserved since 1888, the researchers confirmed that the plant actively attracts prey by emitting a floral scent rich in volatile compounds such as eucalyptol. Scientists also examined enzyme activity in its glandular hairs using a specialized fluorescent reagent and revealed that the plant uses phosphatase enzymes to chemically break down its victims' bodies. In contrast, related species that do not trap insects showed no enzymatic activity. In another experiment, after feeding the plants with marked fruit flies (Drosophila melanogaster) containing a stable nitrogen isotope, scientists found that nitrogen from the insects passed directly into the plant's tissues and was preferentially directed toward its flowers and fruits to ensure reproduction. This result officially adds the order Saxifragales to the evolutionary map of plant carnivory, joining 14 families of flowering plants known to exhibit this phenomenon. By comparing their genes with those of other carnivorous lines, such as the Venus flytrap or pitcher plants, the researchers identified notable genomic convergence: natural selection has independently shaped identical gene families dedicated to mucus production, protein digestion, and nutrient transport. This leads them to conclude that the ability to hunt and digest animals might be far more widespread in the plant kingdom than previously thought, and that Darwin’s intuition 150 years ago confirms that evolution has found molecular solutions similar enough to survive in the planet’s harshest environments. “A remarkable discovery” Pablo Vargas, a botanist at the Royal Botanic Garden (RJB-CSIC) who has studied the genus Saxifraga, considers this a very interesting finding. “It is not just a new species with these habits of trapping and digesting insects, it is an entire lineage,” he emphasizes. “With this, there would already be six main lineages.”