Demographic and environmental determinants of reproductive success in Synthyris bullii, a rare endemic species

In recent decades, the conversion of natural habitat to human use has proceeded at a greatly accelerated pace. This habitat destruction and degradation has resulted in the loss of much of the world's biodiversity. Some populations have been preserved in remaining habitat reserves, but their persistence may be further threatened by degradation and interruption of historic ecological processes. In the case of plants, the loss of pollinator mutualists and changing abiotic conditions may comprise the ability of plants to reproduce and maintain viable populations. My thesis research examines several aspects of the demographic and environmental factors that may influence the reproductive ecology of Synthyris bullii, a rare perennial species endemic to North American prairies and savannas. In Chapter 1, I explore the relationship between reproductive success and floral quantity versus quality. The results of this study show that inflorescence size correlates positively with population size, and that both factors play important roles in determining reproductive output. Chapter 2 examines the response of reproductive morphology to different habitat conditions, and shows that there are tradeoffs in inflorescence and flower characteristics associated with each habitat type. I continue to explore the importance of habitat type in Chapter 3, using an experimental manipulation to determine pollinator visitation at sites that vary in woody encroachment. The results show that reproduction is positively associated with more open habitats, and that pollen quality may partly explain the reproductive success in these populations. Taken together, the results of these studies show that habitat degradation in North American prairies is associated with changes in flower morphology, reduced pollinator visitation, and loss of reproductive output for S. bullii