The contribution of insect prey to the total nitrogen content of sundews (Drosera spp.) determined in situ by stable isotope analysis.

Summary • The contribution of insect prey to total N in the carnivorous plants, Drosera rotundifolia and D. intermedia , was quantified in situ and without any experimental manipulation using natural abundance stable isotope analysis. • Samples of D. rotundifolia and D. intermedia , insects and noncarnivorous reference plants were collected from three contrasting locations across Britain. The proportion of Drosera nitrogen obtained from insect prey was calculated by a mixing model using δ 15 N values from the different plant groups. • The mean proportion of Drosera N derived from prey was 50%. There were significant differences in this proportion between sites, and significant differences w…