Resource Gradients and the Distribution and Flowering of Butterwort, a Carnivorous Plant

The transfer of materials such as nutrients from one ecosystem to another can establish gradients that affect the distribution and performance of species. We examined how a natural resource gradient influences the density and flowering of butterwort (Pinguicula vulgaris), a carnivorous plant. Mývatn, a lake in Iceland, produces large midge populations, generating a gradient in midge abundance on shore. The midge gradient was associated with butterwort flowering probability, which decreased by roughly 50% moving away from the shore. In a midge addition experiment, plants receiving midges had a four-fold increase in their subsequent likelihood of flowering, implicating carnivory in the flowering gradient. Nonetheless, the density of butterworts increased with distance from shore, in negative association with soil nutrient content and the abundance of grass species. This suggests that the positive effect of the midge gradient on butterwort flowering is overwhelmed by the negative effect of competition with g...