Disassortative pollination in the distylous plant Jepsonia heterandra

Abstract

Stigmatic pollen loads were analyzed from naturally pollinated intact and emasculated pin- and thrum-form flowers of Jepsonia heterandra. Observed pollen loads on stigmas of emasculated flowers were compared with expected loads based on random pollination. Observed pollen loads indicated that 13.2% disassortative pollination occurred in the pin form and 43.5% disassortative pollination in the thrum form. Pollen loads from intact flowers indicated that much more self pollination and geitonogamy takes place in the pin form than in the thrum form. In this species, distyly effectively promotes phenotypic disassortative pollination.It is suggested that the adaptive significance of distyly m a diallelic self-incompatible species is that the resultant disassortative pollination increases seed set in the population.