The potential for mixed mating in a self-incompatible plant

A previous study showed that flowers of Campanula rapunculoides (Campanulaceae) are strongly self-incompatible when the stigma first becomes receptive but are less strongly self-incompatible as the flowers age. We deposited equivalent loads of self and outcross pollen onto either 1-d-old or 4-d-old stigmas and examined seed paternity using the PGI (phospho-gluco-isomerase) genetic locus. Pollen mixtures (50 : 50) on young flowers yielded only outcross progeny, indicating functional self-incompatibility. Pollinations on the older stigmas, however, resulted in progeny arrays that departed significantly ( chi (2) test, from the P < 0.001) expectations from pure outcrosssing, with self-fertilizations estimated at 15%-22%, depending on the cross. The ability to produce both selfed and outcrossed progeny, i.e., mixed mating, coupled with a 6% increase in fruiting success of C. rapunculoides flowers pollinated shortly before floral senescence may provide an opportunity for reproductive assurance in natural populations of this species.