Digestive mutualism of a protocarnivorous plant

The protocarnivorous plant Paepalanthus bromelioides (Eriocaulaceae) has a rosette-like structure commonly inhabited by predators such as spiders, whilst their roots are wrapped by a cylindrical termite mound that grows beneath the rosette. Nishi et al. use laboratory and field studies in Brazil to examine nutrient relationships between these various mutulistic partners and find that the natural ¹⁵N signature of P. bromelioides is similar to that of carnivorous plants and higher than that of non-carnivorous plants in the study area. The results suggest a strong nitrogen input derived from the termite mounds, accounting for about two-thirds of total plant N, but also clear input from predators and insects via the rosette. They conclude that despite most of the N being absorbed through their roots, P. bromelioides has all the attributes necessary to be considered as a carnivorous plant in the context of digestive mutualism.