Offspring quality in relation to excess flowers in Pultenaea gunnii (Fabaceae)

Abstract

The wider choice hypothesis suggests that hermaphroditic plants increase their female fitness by producing excess flowers, exposing more ovaries to the scrutiny of selective abortion, and thereby increasing the offspring quality obtained from the best, which escape abortion. Selective discrimination of fruit maturation has been well documented in many angiosperm species, but there has been no examination of how offspring quality varies in relation to the number of excess flowers. This relation must be positive over the entire range of excess flower number for the wider choice mechanism to be the selective force behind the evolution of very large excess floral displays. I examined offspring quality in relation to natural variation in nonfruiting flowers in 72 plants of Pultenaea gunnii, an Australian bush pea. Maximum seed mass and maximum seedling height at 30 days growth showed a nonlinear, saturating relation to excess flower number that is consistent with a theoretical model of wider choice. But the strongly diminishing marginal benefits of excess flowers in this relation make it unlikely that wider choice plays a major role in the evolution of floral display size in this species.