How Saxifraga Candelabrum Was Confirmed as a Meat-Eater
Chinese scientists have finally proved Charles Darwin right about a flowering plant that has puzzled botanists for over a century. The plant, Saxifraga candelabrum, is a classic alpine species that grows on the Tibet-Qinghai Plateau and the Hengduan Mountains. Back in 1875, Darwin proposed that some members of the Saxifraga genus might be carnivorous because their sticky glandular hairs trap insects. Now, a team led by botanist Hang Sun has gathered conclusive evidence.
The researchers examined 45 specimens and found that 43 had insect prey stuck to their sticky hairs. They then used fluorescence tagging to detect phosphatase, a digestive enzyme common in known carnivorous plants. Finally, they fed the plant Drosophila flies marked with a stable nitrogen isotope and tracked a significant increase in nitrogen levels—identical to the pattern seen in other carnivorous species. This three-step proof shows that S. candelabrum actively digests and absorbs nutrients from its captured insects.
The findings, published in Nature Communications, establish S. candelabrum as a new lineage of carnivorous plant. They also identify genetic similarities with other unrelated carnivorous plants, including genes linked to prey attraction, digestion and nutrient absorption. The discovery adds a major piece to our understanding of how carnivory evolved independently multiple times in the plant kingdom.
Darwin's Prediction: The Saxifraga Carnivorous Link
Evidence from Enzyme Activity and Nitrogen Uptake
The team's experiments leave little doubt. The presence of phosphatase enzymes on the plant's sticky hairs is a hallmark of carnivorous digestion. When they fed the plants nitrogen-labelled flies, the isotopic marker appeared inside the plant tissues, confirming that nutrients are not just trapped but actively taken up. Non-carnivorous plants showed no such absorption.
Genetic Clues to Convergent Evolution
By analysing the plant's genome, the researchers found stretches of DNA previously linked to carnivory in species like sundews and Venus flytraps. These include genes responsible for attracting prey, breaking down insect proteins and shuttling the resulting nitrogen into the plant's metabolism. Because S. candelabrum is not closely related to any other carnivorous group, these shared genetic tools are a classic case of convergent evolution—different lineages independently arriving at the same solution.
A High-Altitude Predator in the Himalayas
The plant's habitat on the world's highest plateau might be key to understanding why it turned to carnivory. Nitrogen-poor soils are common in alpine environments, and evolving the ability to extract nutrients from insects would have offered a clear survival advantage. This ecological pressure likely drove the independent evolution of carnivory in Saxifraga, just as it did for other unrelated plants in similarly harsh settings.
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