The effects of light availability, prey capture, and their interaction on pitcher plant morphology

Carnivorous plants inhabit nutrient-poor environments and supplement nutrient acquisition by capturing prey. Carnivorous adaptations have been hypothesized to be beneficial only in environments with high-light availability. We hypothesized that plant morphology would change in response to resource availability (light and prey capture). In a field experiment in Leon County, Texas, we examined the effects of feeding, shading, and their interaction on pitcher plant (Sarracenia alata) morphology. When light availability was reduced, plants produced pitchers that had smaller diameters. The sum of pitcher heights was significantly lower for unfed plants than fed plants. As the season progressed, competing vegetation reduced light availability to pitchers in all treatments. Plants in all treatments produced pitchers that were blade-like with a small, non-functional opening and a widened keel. This experiment provides support for the theoretical model that carnivorous structures are only beneficial under conditions of high-light availability. It also emphasizes the importance of periodic burns of carnivorous plant bogs to reduce competing vegetation.