Allocation to male function and its effect on fitness returns in the wind pollinated herb, Ambrosia artemisiifolia (Ragweed)

Date of Award

August 2019

Degree Type


Degree Name

Master of Science (MS)




Jannice Friedman


Ambrosia artemisiifolia, Dichogamy, Flowering, Mating System, Sex allocation, Wind pollination

Subject Categories

Life Sciences


How organisms partition limited resources is a central issue in life history research. The optimal investment of resources into reproduction is determined by the fitness returns for a given allocation to each sex function. In wind pollinated plants, sex allocation theory predicts that male fitness increases linearly with investment of resources into male function, because the air is unlikely to become saturated with pollen. However, there have been few empirical tests of this prediction. Therefore, we experimentally manipulated allocation to male function and measured siring success using 7 polymorphic microsatellite markers in Ambrosia artemisiifolia (common ragweed). Our results provide evidence for a linear relationship between allocation to male function and fitness returns, which is in accordance with our prediction. We also find a positive association between plant width and siring success. Interestingly, we find the start of female versus male flowering time has opposite effects on siring success. This research is among the first empirical studies testing the prediction of linear male fitness returns in wind pollinated plants. Understanding the shape of the gain curve, and the factors that might influence fitness can provide insight into why wind pollinated plants make large amounts of pollen, and why wind pollination is often associated with unisexual flowers.


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