Scientists confirm Darwin’s 150-year-old carnivorous plant theory

More than 150 years after Charles Darwin hypothesized that plants in the genus Saxifraga were carnivorous, a team of international researchers has proven him right. A study published Tuesday in the journal Nature Communications demonstrates that Saxifraga candelabrum, a yellow flowering plant native to the rocky mountain crevices of southwestern China, traps, digests, and absorbs nutrients from insects.cbc+1

Darwin first wrote about his suspicions in 1875 after observing tiny insects stuck to the leaves and stems of two European Saxifraga varieties, but he lacked the tools to prove the plants were actively feeding on their prey.cbc

How the Plant Kills

Researchers found that mature S. candelabrum plants, which grow at high altitudes in the Hengduan Mountains, had an average of 71 insects stuck to the sticky, hair-covered branches of their inflorescences. Through a series of experiments, the team demonstrated the plant meets all criteria for carnivory: it attracts prey using scent, captures them on glandular hairs, digests them using an enzyme called phosphatase found in other carnivorous plants, and absorbs their nutrients.newser+1

To confirm nutrient absorption, the researchers fed fruit flies food enriched with a stable nitrogen isotope, then traced the labeled nitrogen as the plants took it up — a technique unavailable in Darwin's era. "You can actually — much as you would do in medicine — trace where those materials are flowing throughout the plant," study co-author Doug Soltis of the University of Florida told CBC.cbc

A Selective Predator

The plant also shows a notable evolutionary refinement: it avoids killing its own pollinators. "The plant only targets small insects and keeps large pollinators safe," co-author Hang Sun of the Chinese Academy of Sciences' Kunming Institute of Botany told the New York Times.smithsonianmag

Genetic analysis revealed that S. candelabrum shares genes with other known carnivorous plants, providing independent molecular evidence of its carnivorous status.smithsonianmag

More Hidden Killers?

The findings suggest carnivory may be far more widespread in plants than previously believed. Soltis told Live Science he would not be surprised if other Saxifraga species with similar sticky hairs are also quietly hunting insects — just as Darwin suspected. Sean Graham, a botanist at the University of British Columbia whose team discovered a similar carnivorous plant in 2021, called the findings "gratifying" and predicted more examples await discovery.smithsonianmag+1

"To have the opportunity to confirm a prediction of Darwin is both humbling and very exciting," Soltis said.smithsonianmag