| Abstract | For a trait to be evolutionarily advantageous, in theory, the benefit from the trait must outweigh the cost. Sarracenia alata is a carnivorous pitcher plant that grows in nitrogen-poor soil and supplements the low quantity of nitrogen (N) acquired from the soil with N absorbed from insect capture. The purpose of this study was to determine whether pitchers (the insect traps) gain sufficient N from insect capture to offset the N cost of pitcher construction. Nitrogen cost was estimated two ways, N content of mature pitchers and N content after translocation (the removal of nutrients during senescence). Benefit was estimated by measuring the total N in captured prey. There was no significant difference between the total N content of mature pitcher tissue, which averaged 2.61mg + 0.42 (mean + SE), and the cumulative N in prey capture, which averaged 1.75mg + 0.89. Therefore, the pitchers capture barely enough N to offset the N construction of a mature pitcher. Pitcher plants can translocate N to rhizomes for use in subsequent growing seasons. Total N remaining in pitchers after translocation represents the quantity of N that cannot be recovered, and therefore the N deficit after building the pitcher. The total N in pitchers after translocation averaged 0.002mg + 0.0004. Therefore, prey capture provided up to 875 times the amount of N that could not be recovered from the pitchers by translocation. |
