Darwin’s 1875 Prediction Confirmed: *Saxifraga candelabrum* Proven Carnivorous

Researchers published a study in *Nature Communications* demonstrating that the alpine plant *Saxifraga candelabrum* meets all criteria for carnivory. The species uses glandular trichomes that exude a sticky secretion to trap insects, emits volatile compounds that attract gnats, produces the digestive enzyme phosphatase to break down prey, and assimilates nitrogen-15 from labeled insects into its tissues. Field observations recorded up to 70 trapped gnats on mature plants, and isotope tracing confirmed direct nutrient transfer.

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In 1875 Charles Darwin described sticky-haired Saxifraga species and hypothesized they might be insect-eating, but his feeding experiments with *S. rotundifolia* and *S. umbrosa* could not prove digestion. Over 150 years later, a multidisciplinary team from the Kunming Institute of Botany (Chinese Academy of Sciences), the Florida Museum of Natural History, and other institutions revisited the question with modern chemical, isotopic, and genetic tools.

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• Altitudinal range of *S. candelabrum*: 8,200–10,800 ft (2,500–3,300 m) on the Qinghai-Tibet Plateau and Hengduan Mountains.

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• Average insect capture: >70 gnats per mature plant in field surveys.

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• Known flowering plant species: ~350,000; documented carnivorous species: >750.

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• Enzyme identified: phosphatase, a hallmark of carnivorous digestion.

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• Genetic analysis revealed dozens of shared carnivory-related genes across unrelated plant families.

Gizmodo

Susan Myers, horticulture and conservation director at the Pittsburgh Botanic Garden, called the study design “brilliant” for linking morphology, enzyme activity, and nitrogen tracing. Douglas Soltis, distinguished professor at the University of Florida, emphasized that the plant’s habitat—rocky, dry, nutrient-poor soils—drives the evolution of insect-derived nitrogen acquisition. Xin-Jian Zhang noted that *S. candelabrum* is not currently endangered, given its stable population and remote alpine environment.

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• “Many members of the family to which Saxifraga belongs have sticky glandular hairs and you often see insects stuck on them,” — Douglas Soltis, at the University of Florida

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• “Together, these genomic data provide independent evidence that S. candelabrum is a true carnivorous plant,” — Sun. Soltis, at the University of Florida

New Scientist

• “Many members of the family have these hairs, and I would not be surprised if others are also carnivorous,” — Douglas Soltis, at the University of Florida

New Scientist

Researchers observed that the plant’s flowers emit scents known to attract small insects, while larger pollinators avoid the sticky hairs, indicating selective trapping of ineffective pollinators. The sticky glandular hairs function both as a defensive barrier and as a prey-capture mechanism.

CNN

The confirmation of carnivory in a Saxifraga species expands the known diversity of plant carnivory beyond the typical bog-dwelling lineages such as Venus flytraps and pitcher plants. Soltis expects the team’s work will prompt re-examination of other Saxifraga members, many of which possess similar glandular hairs. Continued genomic comparisons may uncover additional evolutionary pathways that enable carnivorous behavior across flowering plants.

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