Quantitative and qualitative aspects of fecundity in Lychnis flos-cuculi

The determination of the reproductive success of individual plants requires insight into both quantitative and qualitative aspects of fecundity. In this study, variation in flowering phenology, seed yield components and potential seed yield were analysed within and among female half sib families in experimental populations of Lychnis fios-cuculi (L.), grown at different levels of nutrient supply. In addition, differences in the quality of seeds from different origins (maternal parent, capsule position) and of different sizes were measured as the rate of germination and the dry matter production of seedlings. The timing of peak ovule production mainly depended on the start of flowering which varied significantly among half sib families. Within individuals, a twofold variation in ovule number per capsule was present, dependent on the position of capsules within an inflorescence. Due to the very regular developmental pattern of inflorescences, this within-plant variation did not contribute to variation in potential seed yield among individuals of similar stature. Between flowering plants, ovule production varied 35-fold, mainly due to the variation in environmental conditions and maternal parent. At low nutrient levels, the total potential seed yield was tightly buffered by negative correlations among yield components, but in nutrient-rich conditions correlations were positive or non-significant. Significant differences in the quality of seeds from different origins were observed, but from a population dynamics point of view we can conclude that they are of minor importance for variation in fecundity compared to quantitative differences in seed yield.