More than 150 years after Charles Darwin suspected that certain saxifrage plants caught insects, scientists confirmed he was right. Researchers proved that Saxifraga candelabrum traps gnats with sticky glandular hairs, produces digestive enzymes, and absorbs nutrients, validating the naturalist’s nineteenth-century observations using modern technology.
Charles Darwin spent decades fascinated by the natural world, noting in 1875 that certain flowering plants possessed peculiar hairlike structures that hinted at a hidden appetite. Among them were species in the Saxifraga genus, which features around 450 varieties thriving across the Arctic, alpine regions of the northern hemisphere, and the South American Andes. Darwin suspected these plants were carnivorous, but his nineteenth-century experiments could not conclusively prove they digested their prey.
Field Observations on Wufeng Mountain and Yunnan Province
To test Darwin’s long-standing hypothesis, scientists focused on Saxifraga candelabrum, a flowering mountain plant that grows at high altitudes on the southern part of the Qinghai-Tibet Plateau and in the Hengduan Mountains across China’s Yunnan and Sichuan provinces. Field surveys conducted on Wufeng Mountain revealed that the plants capture small insects using hairs covered with a sticky secretion.
During field observations, botanists noticed that mature plants averaged more than 70 trapped insects, primarily consisting of various species of gnat. Interestingly, larger flies that visited the flowers for pollination were not caught by the sticky goo, indicating that the plants selectively captured ineffective pollinators while sparing the insects necessary for reproduction. Douglas Soltis, a distinguished professor at the Florida Museum of Natural History and the department of biology at the University of Florida, noted that while hairs can serve as defensive structures against herbivores, trapping insects is only the first step toward true carnivory.
Enzymes, Nitrogen Isotopes, and Genomic Evidence
To formally classify a species as carnivorous, researchers must demonstrate that it attracts, captures, and digests prey, subsequently absorbing the resulting nutrients. The research team systematically tested each requirement using modern laboratory techniques. First, biochemical analyses revealed that the secretions produced by the hair-like structures contained an enzyme called phosphatase, which is capable of breaking down insect remains.
Next, the scientists utilized isotope labeling by infusing insect prey with nitrogen-15, a technique that tags atomic weights to trace nutrient transfer. This isotope tracking highlighted a direct path from trapping to digestion, proving that nutrients from the dissolved insects were successfully taken up by the plant. Susan Myers, horticulture and conservation director at the Pittsburgh Botanic Garden, praised the methodological precision of the work.
Finally, genetic sequencing provided independent confirmation. Genetic studies showed that Saxifraga shares common genes with established carnivorous plants—such as a sundew and a flycatcher bush—that control prey attraction, digestion, and nutrient uptake.
Hang Sun of the Chinese Academy of Sciences noted via New Scientist that together, these genomic data provide independent evidence that S. candelabrum is a true carnivorous plant.
Hang Sun, Chinese Academy of Sciences, via New Scientist
Broader Implications for Angiosperms and Future Botanical Discoveries
Botanists point out that carnivorous plants typically evolve in habitats where soil is naturally nitrate-poor. While these plants can photosynthesize to create their own food, capturing insects provides the essential nitrates they need to thrive. When the research team broadened their genetic investigation, they discovered dozens of genes across various plant groups related to digesting insect remains.
Hang Sun, senior study author and director of the Kunming Institute of Botany at the Chinese Academy of Sciences in Beijing, noted that these findings suggest carnivory may be far more widespread among flowering plants than previously documented.
With at least 350,000 species of flowering plants existing globally, more than 750 species are currently recognized as carnivorous. Because different styles of carnivory evolved independently across 14 plant families through convergent evolution, researchers expect this study to prompt a re-examination of other species within the Saxifraga genus—including the exact plants Darwin examined in 1875—as botanists search for undiscovered carnivorous lineages.
Such an effort could ultimately reveal that the capacity for carnivory is far more widespread among these plants than has been previously understood by the scientific community.
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