Does the Dwarf Sundew (Drosera brevifolia) Attract Prey

Charles Darwin first suggested some carnivorous plants attract insects to their leaves for extracting nutrients. Since Darwin, it has been assumed that the ability to lure prey is a characteristic of botanical carnivory and that there is strong selection for carnivorous plants to evolve adaptations to accomplish this. The carnivorous syndrome defines botanical carnivory as having four components that include the ability to: attract prey, retain prey with specialized leaves, dissolve prey with digestive enzymes, and absorb soluble nutrients from prey. Relatively few studies have investigated prey attraction and it has been well documented in only three genera of carnivorous plants. We conducted a series of field and lab experiments on the dwarf sundew (Drosera brevifolia) and found this species to be no better at capturing prey than neutral sticky traps. Thus, no evidence was found suggesting this species lures prey to its leaves. We suggest that, like spider webs, sundews might be better adapted to having adhesive surfaces that passively capture prey. Carnivorous plants face the preypollinator conflict of trying to draw the same insects to flowers for pollination as are being drawn to leaves as prey. By evolving alternative ways of capturing prey without attractants, some taxa of carnivorous plants, like D. brevifolia, may reduce the intensity of the prey-pollinator conflict. If these alternatives prevail in species-rich genera of carnivorous plant, then the carnivorous syndrome may need to be refined.