From carnivore to detritivore?: Isotopic evidence for leaf litter utilization by the tropical pitcher plant Nepenthes ampullaria

Nepenthes pitcher plants trap prey in specialized leaves formed into pitchers. Most lowland species live in open, sunny habitats and capture prey to obtain nutrients, principally nitrogen (N). Nepenthes ampullaria is commonly found under closed canopy forest and possesses morphological traits that indicate adaptation to trap leaf litter as a nutrient source. We tested this hypothesis by comparing foliar stable N isotope abundance (delta(15)N) between plants growing under forest canopy at 20 sites (litterfall present) and those growing in 20 open areas (no litterfall) in Borneo. Foliar delta(15)N values were significantly lower and total N concentrations were higher for the plants with access to litterfall. Using a mixing model, we estimated that N. ampullaria plants growing under forest canopy derived 35.7% +/- 0.1% of their foliar N from leaf litter inputs.