Prey capture by three Pinguicula species in a subarctic environment

The number and biomass of prey captured were estimated for Pinguicula alpina, P. villosa and P. vulgaris in a subarctic environment. Seasonal captures were estimated for one site per species for 4-5 years. Captures were related to reproductive status (reproductive/non-reproductive) and to leaf area. For one species (P. vulgaris) the catch was also compared across a range of habitats. Of the seasonal catch, 50-75% was obtained during June and less than 5% during August. For P. alpina and P. villosa the seasonal catch varied threefold or more between years (means of 89-329 μg dry matter plant^-1 season^-1 for P. alpina, and 11-91 μg dry matter plant^-1 season^-1 for P. villosa), whereas the between-year variation for P. vulgaris was small (mean c. 600 μg plant^-1 season^-1). Large variations were, however, observed among habitats for P. vulgaris. Captured prey may contribute a substantial amount of nutrients to the most successful individuals (up to 85% of the mean seasonal turnover), but prey capture varied greatly and during any given season many individuals obtained only marginal amounts of nutrients through carnivory. P. vulgaris trapped almost twice as much per unit leaf area and season as the other two species (224 for P. vulgaris versus 127 μg cm^-2 season^-1 for the other two species). Reproductive individuals of P. vulgaris trapped almost twice as much as non-reproductive individuals (after taking differences in leaf area into account). For the other two species no differences were observed between reproductive and non-reproductive individuals.