Flower production in relation to individual plant age and leaf production among different patches of Corydalis intermedia

Abstract

The life history of an organism can be viewed as the combination of allocations made to maintenance, growth, and reproduction. Allocation to these functions are constrained by trade-offs as increased investment to one function may happen at the expense of another. Moreover, because fecundity and survival probabilities are affected by both the state of an individual and by its surrounding environment, optimal allocation to reproduction and growth may vary with both individual size/age and with the habitat in which it lives. In this study we aim to describe how flower production varies with individual plant age and leaf production among different patches of the perennial herb Corydalis intermedia. We take advantage of the construction of the underground storage organ to estimate the age of individual plants which allows us tacitly to relate flower and leaf production to individual age and successional status of the patch. We sampled all individuals present in nine patches from the same forest and estimated their age, flower production and total leaf area. The age distributions showed that each patch was most often dominated by a few and consecutive age classes. In patches where individuals had the oldest mean age, very few or no juvenile age classes were found suggesting that recruitment had ceased. Based on the age distribution of the patches we propose that the dynamics may best be described as metapopulational with colonization of newly formed open forest gaps and a successionally determined extinction as the patch gradually becomes too shaded for recruitment. Both mean flower production, leaf area and age varied significantly among patches. Flower production increased with both increasing age and leaf area. We found no indication of a trade off between reproduction and vegetative growth since flower production showed a positive relation with leaf production even after removing the effect of age. Number of flowers produced by plants of the same age but growing in different patches did not vary indicating that the difference among patches mainly was due to a difference in age distribution. No individuals produced flowers before they reached an estimated age of three years. Production of flowers followed a power function with increasing age. Our data suggests that C. intermedia plants change their allocation strategy with age investing a relatively large amount of energy in flower production immediately after the immature growth phase when recruitment in their patch may be high. Production of flowers then reaches a plateau around the age of 11 years after which number of flowers produced stays constant.