PHENOTYPIC PLASTICITY IN AGE AND SIZE AT MATURITY AND ITS EFFECTS ON THE INTEGRATED PHENOTYPIC EXPRESSIONS OF LIFE-HISTORY TRAITS OF CARDAMINE FLEXUOSA (CRUCIFERAE)

We analyzed variation in phenotypic plasticity of life history traits between two Cardamine flexuosa populations based on differences in pla sticity of age and size at maturity. C. flexuosa (Cruciferae) is a fac ultative, vernalization-sensitive, long-day annual, and its phenology and the phenotypic expressions of many life history traits are largely controlled by photoperiod and vernalization in natural populations. W e used plants from two populations which differed in their responses t o chilling and photoperiod treatments. The timing of developmental pro cesses was changed by controlling temperature and photoperiod regimes in growth chambers. Plasticity in size at maturity was analyzed as cha nges in a growth trajectory using two parameters, age at maturity (Del ta t) and growth rate (k). Both traits showed plasticity, but differen ces between the populations were found mostly for Delta t. Distinctive differences in size at maturity of individuals in the two populations were mainly due to different amounts of plasticity in Delta t. Variat ions in plasticity of nine other life history traits and their associa tions to age and size at maturity were also analyzed. Variation for ei ght of the traits can be described, at least in part, as a function of age and size at maturity for both populations, and most of the variat ion in the total number of seeds was explained by age and size at matu rity. Only age at maturity had any effect on changes in resource alloc ation. The nine life history traits were integrated through associated character expressions with age and size at maturity. Changes in the a ssociation between a trait and age and/or size at maturity were rather conservative compared to changes in the plasticity of a trait between the two populations. Associations with age and size at maturity are m ostly explicable in terms of inherent relationships in the development al processes, and they may limit the ecological range expansion and th e adaptive evolution of plasticity in C. flexuosa. The negative correl ation between reproductive allocation and age at maturity can be a cos t of delaying maturation in C. flexuosa.