Increase of male reproductive components with size in an animal‐pollinated hermaphrodite, Narthecium asiaticum (Liliaceae)

Summary1 In animal‐pollinated plants, female function is expected to increase with size because increased pollen production leads to more competition for ovules by pollen grains from the same parent, and a large flower number results in increased geitonogamy and, in turn, increased pollen discounting. To date, many studies have supported this prediction. 2 In Narthecium asiaticum (Maxim), an animal‐pollinated plant, however, male reproductive components in flowers increased with raceme size whereas female reproductive components did not. This was mostly because of the similar trend for middle to upper flowers within racemes. 3 Height above ground for middle to upper flowers was associated with raceme size, and higher flowers attracted more pollinators. Accordingly, more pollen grains were removed from upper flowers in larger racemes. Furthermore, an increased number of flowers may not increase local mate competition and geitonogamy in this species because only a few flowers function as males at any one time, irrespective of raceme size. 4 This may be the reason why male reproductive components of upper flowers increased with size, even though N. asiaticum is an animal‐pollinated plant. Male reproductive components of lower flowers did not increase, probably because the height of lower flowers was not associated with raceme size.