Variation in Pollen-Dispensing Schedules ofLobelia siphilitica

Abstract

Premise of research. Many mechanisms have evolved that increase the amount of pollen exported and the number of plants that receive this pollen. One such mechanism is pollen presentation, where plants regulate the amount of pollen available to a pollinator during a single visit. Presenting either a constant proportion or an increasing proportion of available pollen should maximize male fitness in most pollinator environments. But for constant or increasing pollen presentation schedules to evolve, variation in these schedules must have a heritable component.Methodology. We measured pollen presentation schedules of Lobelia siphilitica by simulating a sequence of 16 bee visits to flowers produced by progeny of 10 open-pollinated maternal families. A component of the pollen presentation schedule (the amount of pollen remaining in the flower at the end of the visitation sequence) was measured for plants from all of the families. The complete pollen presentation schedule was measured for plants from four of the...