Study Confirms Darwin’s Hypothesis on Carnivorous Plants

Botanists have officially confirmed that Saxifraga candelabrum, an alpine plant native to China’s Tibetan Plateau, is carnivorous, resolving a scientific debate that began over 150 years ago when evolutionary biologist Charles Darwin first experimented with the genus. According to research published in the journal Nature Communications, the species uses sticky, reddish glandular hairs to capture, digest, and absorb nutrients from small insects like mosquitoes, surviving in harsh, nutrient-poor rocky environments.

Darwin’s Century-Old Hypothesis on Saxifraga Finally Proven

Charles Darwin dedicated years to studying barnacles and breeding pigeons, but his fascination with meat-eating plants was among his most enduring. In 1875, he published a landmark treatise on carnivorous plants, detailing species such as sundews. During his research, Darwin tested alpine plants from the genus Saxifraga, noting they featured sticky hairs similar to sundews. However, according to historical records cited in the new study, he could not prove they were carnivorous.

During fieldwork on a mountain in Yunnan province, southwestern China, Sun's team observed that mature S. candelabrum specimens were covered in insects, averaging more than 70 trapped bugs per plant. "This indicates that they [carnivorous plants] may be more widespread than we know and that other species conceal the capacity to digest prey," Sun stated.

How Scientists Proved S. candelabrum Digests Insects

Proving a plant is carnivorous requires demonstrating three distinct criteria: it must capture, digest, and absorb nutrients from its prey. To confirm these stages in S. candelabrum, the research team conducted a series of controlled experiments. First, using screen and glass enclosures, the scientists determined that the plant relies on a floral odor to attract insects to its sticky stems.

The trapping mechanism is remarkably selective. According to Sun, the glandular hairs catch small insects like gnats and mosquitoes while keeping larger pollinators safe from harm. To verify digestion, researchers coated the plants with a chemical that fluoresces green in the presence of digestive enzymes, which lit up upon contact with prey. Finally, by tracking nitrogen isotopes from flies placed on the stems, the team confirmed that the plant absorbs nutrients from its captures over a two-week period.

Evolutionary Implications for Hidden Carnivorous Plants

The confirmation of S. candelabrum as a meat-eating species marks the first verified carnivorous plant within the large Saxifragaceae family. Botanists note that this discovery points to a broader evolutionary trend. Kadeem Gilbert, a botanist at Michigan State University who was not involved in the new research, believes hundreds or even thousands of other sticky-haired plant species could be hiding similar predatory traits.

“This shows how it is possible for this form of nutrition to arise at any point in the evolutionary tree of plants,” Gilbert stated. While classic examples like sundews and pitcher plants inhabit waterlogged peat bogs, mountain-dwelling species face parallel nutritional hurdles on arid, rocky cliffs where soil lacks essential minerals.

Frequently Asked Questions

Is S. candelabrum the first carnivorous plant ever discovered?

However, S. candelabrum is the first confirmed carnivorous species within the Saxifragaceae family, resolving Darwin’s 19th-century hypothesis.

How does S. candelabrum catch its prey?

According to the research published in Nature Communications, the plant uses a combination of sweet-smelling floral odors to attract insects and sticky, reddish glandular hairs on its stems to trap small bugs like mosquitoes.

Do carnivorous plants eat their own pollinators?

Generally, no. Researchers found that S. candelabrum is highly selective, targeting only small insects with its sticky hairs while leaving larger flies and bees unharmed to pollinate its yellow flowers.