Effects of display size and position on individual floral longevity in racemes of Narthecium asiaticum (Liliaceae)

1. We analysed the longevity of individual flowers and the effect on pollination success with respect to floral display size of racemes (number of flowers open at one time) for the sequentially blooming plant Narthecium asiaticum (Liliaceae). The longevity of lower- and middle-positioned flowers (about 7 days in 1998 and 6 days in 1999) was much greater than the length of time required for the completion of male (about 3 days) and female (within 3 days) functions. 2. We suggest that such prolonged longevity benefits the plant in terms of pollinator attraction, because prolonged longevity in lower and middle flowers leads to large display sizes of racemes. Increased display size would not have resulted in an increase of geitonogamy in this species, because most pollinators left racemes after probing only one flower. Rather, large displays attracted more pollinators and increased pollen dispersal from individual flowers. 3. The longevity of upper-positioned flowers (about 4 days in 1998 and 3 days in 1999) was less than that of lower- and middle-positioned flowers - almost the same as the length of time required for the completion of male and female functions. This difference is possibly because upper flowers open later within racemes: if there were no subsequent flowers, prolonged floral longevity would not benefit the plants and would only consume resources used to maintain the flower. 4. Floral longevity within inflorescence should be understood in relation to the effects of floral display size and floral positions, in addition to the accrual rates of male and female functions and the maintenance cost of individual flowers.