Effects of floral sexual investment and dichogamy on floral longevity

Aims Floral longevity,the duration that a flower remains open and func-tional,varies greatly among species.Variation in floral longevity has been considered to be optimal strategy for resource allocation under different ecological conditions,mainly determined by the rates of pollination and cost of flower maintenance.However,it is unclear whether an intrinsic factor,floral sexual investment,con-strains evolution of floral longevity.The theoretical model also pre-dicts that dichogamy favors long-lived flowers,but empirical studies to test this prediction remain unexplored.Methods To examine the effect of floral sexual investment on floral longevity,we measured flower size together with pollen and ovule production in 37 sympatric flowering plants in a natural community.The duration of the female and male phase in 21 protandrous species and floral longevity of the other 16 adichogamous species were documented in the field.Important Findings Floral longevity varied from 1 day to 15 days,while pollen num-ber per flower varied from 643 to 710880 and ovule number per flower from 1 to 426 in the 37 species.Flower size was corre-lated with pollen production as well as ovule production.Floral longevity was positively related to pollen production but not to ovule production.Consistent with the prediction that dichogamy favors long-lived flowers,we found the floral longevity of pro-tandrous species was significantly longer than that of adichoga-mous species.in the protandrous species,pollen production per flower was observed to be positively related to male duration,while ovule production was not related to female duration.our analyses of variation in floral longevity and sexual investment among different species suggest that the floral sexual investment could be an intrinsic factor contributing to the selected floral longevity,particularly the male phase,and that high pollen pro-duction could potentially increase pollen removal,i.e.male pro-ductive success.