Phenotypic plasticity: an evolutionary adaptation of Sarracenia purpurea.

Abstract

The objective of this study was to investigate phenotypic plasticity, environmentally induced variation in form and function of individuals, in the carnivorous plant, Sarracenia purpurea. The production of carnivorous organs has been shown to exhibit phenotypic plasticity. The cost-benefit model for the evolution of carnivory, proposed by Givnish (1984), implies that carnivory will not be favored when there is an excess supply of nutrients because of the photosynthetic cost to producing carnivorous structures. Thus, it was hypothesized that the size of carnivorous organs would increase in areas of low soil nitrogen availability and the size of photosynthetic organs would increase in areas of high soil nitrogen availability. While variation among sites was found, this variation could not be considered phenotypic plasticity because it was not linked to the environmental characteristic tested. No relationship was found between conical pitcher volume (indicator of carnivorous organ size) and 15N values, used as a surrogate to test soil nitrogen content, or between relative wing width (indicator of photosynthetic organ size) and 15 N values. However, 15N analysis is not a direct measure of soil nitrogen content and this method may not have been adequate to test our hypothesis.