G. Kudo et al., Variation in floral sex allocation and reproductive success within inflorescences of Corydalis ambigua (Fumariaceae): pollination efficiency or resource limitation?, J ECOLOGY, 89(1), 2001, pp. 48-56
1 The variation of floral sex allocation with flower position within inflor
escences was investigated in the spring ephemeral, Corydalis ambigua. Inves
tment in female function (pistil), attraction (corolla) and nectar producti
on decreased from bottom to top flowers, whereas male investment (stamen) d
id not differ.
2 This self-incompatible species appears to set seeds as a result of visita
tion by nectar robbing bumblebee queens. The tendency of bees to visit lowe
r flowers first and then move upwards within an inflorescence should result
in directional pollen flow from bottom to top flowers.
3 Naturally pollinated upper flowers set fewer seeds than intermediate and
lower flowers due to pollen limitation. The lack of differences in seed set
and seed mass per pod following artificial outcrossing indicated that reso
urce limitation did not explain the variation in seed production of flowers
in different positions. Pollen viability also did not differ significantly
between flower positions.
4 A model of pollination was developed that incorporated the visitation pat
tern of bumblebees and observed variations in nectar distribution between f
lower positions. This predicted that receipt of outcross pollen would decre
ase from bottom to top flowers, but that pollen export to other plants woul
d not differ between flower positions provided that the pollen exchange rat
e of pollinators was either small or positively correlated with nectar cont
ent of each flower position. The observed pattern of floral sex allocation
would then be parallel to relative success of pollen export and import betw
een flower positions within inflorescences.