No long-term costs of meristem allocation to flowering in stoloniferous Trifolium species

Clonal plants propagate by means of clonal growth and sexual reproduction. The commitment of meristems to branching and flowering govern the expressio n of these two mutually exclusive life-history functions. We used a modelli ng and an experimental approach to examine the consequences of a structural trade-off between flowering and clonal growth on future growth and fitness in stoloniferous species with a determinate module architecture. The model revealed negative effects of flowering on vegetative growth due to a struc tural trade-off at the meristem level. Total fecundity was maximized at int ermediate flowering frequencies. In addition, optimal meristem commitment t o flowering depended strongly on the time available for growth and reproduc tion. This indicates an interaction between optimal flowering frequency, th e length of the growing period and the rate of ontogenetic development. The greenhouse study made use of 15 genotypes of two closely related, stolonif erous Trifolium species. Despite the existence of a structural trade-off at the meristem level, we found no evidence for costs of flowering on the who le-plant level. High allocation to flowering did not result in reduced plan t performance (biomass and module production) and total fecundity, indicati ng that there were no demographic costs of meristem investment to different life-history functions. Flowering frequencies never exceeded the model pre diction for optimal commitment of meristems to sexual reproduction, suggest ing strong past selection to eliminate high levels of meristem allocation t o flowering. Hence, clonal growth seems to have evolutionary priority over sexual reproduction in our species.