Variation in floral organ size depends on function: a test with Commelina communis, an andromonoecious species

We measured the size of floral organs in andromonoecious Commelina communis to test the hypothesis that pollinator-mediated selection might regulate variation in the size of floral organs. We compared variation in floral organ size between C. communis perfect flowers, with fertile pistils, and C. communis staminate flowers, with sterile pistils. We hypothesized that variation in size of the sexually functionless pistil would be large. We found supporting evidence from eight C. communis populations. These results suggest that pollinator-mediated selection may have stabilized variation in the style length of perfect flowers. We also found differences in variation in length among three different types of anthers in both perfect and staminate flowers, only two of which produce fertile pollen. This is consistent with our prediction that mating-related organs should vary less in size than attraction-related organs.