Limits to fruit production in a monoecious fig: consequences of an obligate mutualism

The Costa Rican fig tree, Ficus pertusa, is pollinated by a species-specific wasp (Agaonidae) whose female offspring transfer pollen between trees. Pollination success (the proportion of inflorescences pollinated) ranged from 1-100% and averaged only 65%. Resource availability evidently was limiting to fruit set as well: every crop abscised many inflorescences at a predictable point during growth. This abscission period usually preceded the brief but variably timed period of pollinator arrivals; in most cases every pollinated, undamaged inflorescence set fruit. Fruit abortion would not be expected in plants that evolved under conditions of pollen limitation; although pollinators have been thought to be overabunadnt in highly coevolved pollination mutualisms, figs' unique flowering phenology may in fact make pollen limitation common. The fact that future pollen carriers as well as seeds mature within fruits may also help explain these unusual fruit maturation patterns. -from Author