INFLORESCENCE SIZE: TEST OF THE MALE FUNCTION HYPOTHESIS |
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Authors: | Diane R Campbell |
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Institution: | Department of Biology, University of Virginia, Charlottesville, Virginia, 22901
Rocky Mountain Biological Laboratory, Crested Butte, Colorado, 81224 |
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Abstract: | One explanation for low fruit sets in plants with hermaphroditic flowers is that total flower production by a plant is controlled primarily by selection through male function. This male function hypothesis presupposes that success in pollen donation increases more strongly with flower number than does seed set. I tested this prediction by measuring male and female components of reproductive success as functions of flower number in natural populations of the self-incompatible, perfect flowered plant, Ipomopsis aggregata. Fruit set in this hummingbird-pollinated plant averaged 4.9 to 40.3% across the 4 years of study. Both the total amount of pollen donated and the total amount received, as estimated by movement of fluorescent powdered dyes, increased linearly with number of flowers on a plant. Total seed production, however, increased disproportionately quickly because plants with larger floral displays were more likely to set at least one fruit. An estimate of the functional femaleness of a plant, based on pollen donation and seed production, increased with flower number. These results do not support the male function hypothesis. |
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