Apparent vs. effective mating in an experimental population of Raphanus sativus

Effective mating in plant populations need not occur during periods of peak pollinator activity and flowering. We measured seasonal and diurnal patterns of pollinator activity, pollen and ovule availability, and seed production in an experimental population of Raphanus sativus to infer the times of reproductively effective mating. On a seasonal scale, we found that most "effective matings", those resulting in mature seeds, occurred very early in the season, well before the peak of flowering and pollinator activity. At a finer scale, diurnal schedules of flower opening, stigma saturation with pollen, and pollen removal indicated that most effective matings occurred before noon, even though pollinator activity increased later in the day. These patterns may be most common in populations that are not pollen limited, but other ecological factors (e.g. seed predation, resource depletion) could weaken the correspondence between pollination and effective mating.