Compensating for the corolla? Pollen exposure is not associated with pollen-collecting hair length.

Background And Aims: Secondary pollen presentation, the relocation of pollen from the anthers to elsewhere on the flower, has evolved multiple times across many plant families. While hypotheses suggest it evolved to promote outcrossing, a by-product of relocation may be protection of pollen from loss due to abiotic factors. In Campanulaceae pollen is presented on pollen-collecting hairs along the style and the hairs retract over time and release pollen for transfer.

Support for Baker's law: Facultative self-fertilization ability decreases pollen limitation in experimental colonization.

Premise: The ability to self-fertilize is predicted to provide an advantage in colonization because a single individual can reproduce and establish a next generation in a new location regardless of the density of mates. While there is theoretical and correlative support for this idea, the strength of mate limitation as a selective agent has not yet been delineated from other factors that can also select for self-fertilization in colonization of new habitats. We used known mating-system variation in the American bellflower (Campanula americana) to explore how plants' ability to self-fertilize can mitigate density-dependent reproduction and impact colonization success.