Energy Allocations in Annual and Perennial Lupines (lupinus: Leguminosae)

Abstract

The energy allocation patterns of 3 species of lupine, an annual, a perennial herb, and a shrub were investigated and related to life cycle differences as well as ecological differences among the species. All 3 species occur along the central California coast but differ in their specific environmental tolerances. The annual, Lupinus nanus, and the shrub, Lupinus arboreus, have high growth rates and photosynthetic rates when compared with the perennial herb, Lupinus variicolor. The 3 species initially have similar energy allocation patterns, but they gradually diverge during the growing season. The annual ultimately devotes up to 61% of its energy to reproductive tissues and 29% to seeds alone, while only 3%—4% ends up in the roots. Its life cycle strategy and energy allocation pattern make it a poor competitor in stable environments, and it is only found in disturbed sites along the coast. The perennial herb may not reproduce in the 1st year, and in the 2nd year devotes only 18% of its energy to reproduction and only 5% to seeds. At least 40% of its energy is invested in its large taproot system where energy for future growth can be stored. Its prostrate growth form and low investment in reproduction are related to its restriction to the climatically stable but fairly harsh environment found on cool, windy bluffs. The shrub also may not reproduce in the 1st year but later devotes at least 20% of its energy to reproduction and 6% to seeds. It typically devotes °50% to stems, and this, along with its high growth rate, makes it a superior competitor, particularly in successional habitats away from the ocean bluffs. Its unusually short life span explains its fairly high reproductive effort as well as its absence from climax coastal communities. The 3 lupines have energy allocation patterns that fall within the patterns found for other plants with similar life cycle strategies, except that the reproductive efforts are at the high ends of the respective ranges. Investments in seeds alone are more in line with previous findings and reveal that the lupines devote an unusually high percentage of their energy budgets to structures ancillary to reproduction.