Reproduction inCampanula afra (Campanulaceae): Mating system and the role of the pollen collecting hairs

Abstract

The aim of the present investigation is to compare two geographically well separated populations ofC. afra with different mating systems with emphasis on (1) factors controlling the length of the male phase with special attention paid on the pollen collecting hairs, (2) crossing ability among populations with different mating systems; shouldC. afra be regarded as one or several species?, and (3) correlations between pollen germinability and mating system; how does pollen germinability vary with anthesis and stigma development? From the results it can be concluded that the length of the male phase and the development of the stigma depend on the stimulation of the pollen collecting hairs rather than on the amount of pollen removed. Furthermore, the length of the male phase was found to be correlated with the mating system, i.e., in the population with a mixed mating system, the differences between treated and untreated flowers were less pronounced than in the population being obligately outcrossing. I also found correlations between mating system and pollen germinability, where the population with a mixed mating system had a high germinability at stigma receptivity, whereas for the xenogamous population, the germinability approached zero at stigma development. No crossing incompatibility was found between the two populations ofCampanula afra in any of the combinations.