Low Frequency Disadvantage in the Exploitation of Pollinators by Corolla Variants in Phlox

Abstract

The propensity of pollinators to feed upon alternative corolla variants of Phlox drummondii was related to relative morph frequency in experimental populations. The amount of service a variant received was measured in terms of the frequency of random outcrossing, because the variants are self-compatible. The frequency of random outcrossing did not differ significantly in populations in which the variant ratio was 3:1, 1:1, or 1:3. However, when the ratios were 9:1, or 1:9, the frequency of outcrossing was significantly lower than that in the other populations. This indicated that the level of pollinator exploitation of a corolla variant is frequency dependent and that the minority phenotype is at a disadvantage. The pollinator behavior inferred from the outcrossing data is consistent with that observed in communities where the alternative phenotypes are species. The consequence of a rare phenotype disadvantage is the elimination of conspicuous variability for the key floral characters.