Sticky alpine flower confirms Darwin's 150-year-old carnivorous plant prediction

A newly discovered flowering plant, Saxifraga candelabrum, has been confirmed as a carnivorous species, validating a prediction made by Charles Darwin over 150 years ago. To be classified as carnivorous, the plant must attract, trap, digest, and absorb nutrients from insects. In 1875, Darwin proposed that certain Saxifraga species, typically found in alpine regions, could be carnivorous due to their sticky glandular hairs that trap insects.

However, prior evidence supporting this hypothesis was lacking. Researchers studied S. candelabrum, which inhabits the Qinghai–Tibet Plateau–Hengduan Mountains in China. Field observations revealed insects on the plant's glandular hairs, with mature plants trapping an average of 71 insects. To test for digestion and nutrient absorption, researchers used fluorescence tagging to detect phosphatase activity, a digestive enzyme common in carnivorous plants.

They also fed Drosophila labeled with nitrogen to the plant and observed a significant increase in labeled nitrogen levels in S. candelabrum and another carnivorous species, compared to noncarnivorous controls. Genetic analysis further supported their findings, showing genomic similarities with other independently evolved carnivorous plants, including genes involved in prey attraction, digestion, and nutrient absorption.

This multidisciplinary evidence confirms Darwin's hypothesis that some Saxifraga species may be carnivorous, providing strong support for his prediction.