Ovule discounting in an outcrossing, cryptically dioecious tree.

Ovule discounting denotes the reduction in the number of ovules available for cross-fertilization due to the interference of inferior pollen. Traditionally, ovule discounting has been discussed solely from the perspective of compromised outcrossing opportunities as a result of selfing, but the principle is more general. Here, we extend its applicability beyond the simple contrast between selfing and outcrossing by showing that, in the cryptically dioecious tree species Fraxinus ornus, ovule discounting through frequent outcrossing with inferior fathers also constitutes a substantial cost of mating.

Paternal effects on functional gender account for cryptic dioecy in a perennial plant.

Natural selection operates on the mating strategies of hermaphrodites through their functional gender, i.e. their relative success as male versus female parents.