Centaurium erythraea is pollinated primarily by hoverflies. However, when Brys and his colleagues first started working on this species, they noticed an extraordinary thing. "A remarkable characteristic of this species," notes Brys, "is its surprising and elegant way of realizing delayed selfing, in which anthers curl at the end of a flowers' life in order to shed pollen and guarantee self-pollination."
In situations where autonomous self-fertilization occurs after the chance of out-crossed pollination (e.g., at the end of a flower's life), then autonomous selfing ensures that the plant has at least some chance of passing its genes on to the next generation. This delayed selfing may incur no costs of pollen and/or ovule discounting and may provide reproductive assurance when successful pollinator-mediated seed production fails.
To test the reproductive assurance hypothesis under circumstances where plant populations varied in size and pollinator availability, Brys and colleagues used emasculation experiments in 22 C. erythraea populations, and compared the seed set of flowers in which anthers were removed prior to floweringand thus could not self-pollinatewith unmanipulated control flowers that were still able to self-pollinate. For each population they determined plant population size (by counting the number of flowering individuals) and pollinator density (using insect traps), and examined how seed set varied with these factors.
The authors found that pollinator-mediated seed set significantly depended upon population size and pollinator availability. The contribution of autonomous seed set, on the other hand, varied greatly among the populations studied, accounting for 19% to 87% of total seed production. More self-pollinated seeds were produced in plants found in populations that were smaller and/or had fewer pollinators,
|Contact: Richard Hund|
American Journal of Botany