A Comparison of Reproductive Effort in the Dioecious Shrub Oemleria cerasiformis Using Nitrogen, Energy and Biomass as Currencies

Abstract

-Energy and nitrogen concentration were determined for reproductive structures of the dioecious shrub Oemleria cerasiformis. We compared reproductive effort for 28 plants of each sex, calculated in terms of energy and nitrogen, with previous estimates of reproductive effort using biomass. Energy concentration was very similar among reproductive structures and among individual plants. The concentration of nitrogen was highest in flowers and flower peduncles of both sexes (3.78-5.20%), much lower in fruits (1.77%) and lowest in fruit peduncles (1.03%). In terms of nitrogen, reproductive effort of females was almost twice that of males; in terms of energy or biomass, the difference was approximately fourfold. Using any of these currencies, the difference between the sexes is sufficient to have important life-history implications.