Experimental manipulation of floral display size does not affect the distribution of paternal diversity in Silene...

Various factors, including pollinator visitation patterns and pollen carryover, govern paternal diversity and its distribution within maternal plants. Floral display size may have opposite effects on fruit- and plant-level paternal diversity, because plants with large displays may receive more pollinator visits but also more sequential probes per visit.

To investigate the effect of floral display size on the distribution of paternal diversity in Silene dioica, we genotyped and assigned paternity for 1320 seeds sampled in several fruits per plant in control and manipulated females-whose flower number was artificially increased-in an experimental population exposed to natural pollination. We estimated within-fruit paternal diversity and sire profile dissimilarity among fruits and compared these metrics between control and manipulated plants. We then quantified pollen carryover using controlled pollinator visitation assays and pollen counts.

Most fruits were multiply sired, but we found no effect of floral display size on within-fruit paternal diversity. Sire profiles were more similar between fruits from the same than from different females, but not more so in manipulated than in control plants. The pollen deposition curve was steep, with an increasing carryover fraction throughout the visitation sequence.

Our results suggest that the effect of floral display size on pollinator foraging behavior is too weak to affect paternal diversity and its distribution in S. dioica, or that other processes, such as limited pollen carryover and spatially restricted pollen dispersal, blur the effect of pollinator visitation patterns on sire profiles.