Abstract

Sexual reproduction in plants is a subject of great complexity. Animal mediated pollen transport leads to the potential for simultaneous deposition of gametes from several different possible mates. Plants that are able to select the pollen that will fertilize their ovules will likely have more fit offspring than plants that have no control over the paternity of their seeds. Inbreeding and outbreeding, the degree of relatedness between two mating individuals, can have a large effect on offspring fitness, both beneficial and deleterious. When a plant suffers from both inbreeding and outbreeding depression there should be some optimal outcrossing distance where offspring fitness is maximized. There is evidence that Erythronium americanum suffers from both inbreeding and outbreeding depression. My study attempted to find the optimal outcrossing distance of a northern Louisiana pop of E. americanum. I excluded pollinators from plants and pollinated E. americanum with pollen from 10 cm, 1 m, and 10 meters away. I also left some plants unmanipulated as a potentially selfing control. In the second year of experimentation I also excavated and measured bulbs before and after the growing season. The data I collected in the cross pollination study shows a trend toward optimal outcrossing distance. In the bulb experiment there was significant change in bulb size throughout the experiment.