EVIDENCE FOR WIDESPREAD POLLEN LIMITATION OF FRUITING SUCCESS IN CAPEWILDFLOWERS

We used spot checks of stigmatic pollen deposition and hand-pollinatio n experiments to test whether fruit production in Cape wildflower popu lations is limited by pollen availability. Natural levels of stigmatic pollen deposition were very low (median = 30.0% of flowers) in popula tions of 33 orchid species. We found similarly low levels of fruit set (median = 32% of flowers per plant) in six Orchidaceae and four Amary llidaceae species. Experimental hand pollination at the whole plant le vel caused significant increases in fruit production in 11 of the 12 s tudy populations. These results indicate that pollen limitation of fru it set may occur frequently among some plant families in the Cape flor a.