As the teaching of evolution is being challenged in school systems across the United States, it is important for biologists to document cases where natural selection is producing change over time in a single population. It is also essential to connect selection in the past to observed patterns of diversity within and among species. Several studies have shown that natural selection produces change over time in a single population. For example, we know that selection on the beak size of Galapagos finches by seed size has resulted in changes in beak size over time. However, few researchers have linked past selection to present diversity. Diversity among groups of individuals can arise in two ways: 1) by selection favoring different types of characters in separate populations, and 2) by random change in separated populations over time. This study seeks to disentangle these two causes of diversity within a single plant species, Blue-eyed Mary. Populations of Blue-eyed Mary vary in their ability to produce seeds through self-pollination, a function that insures seed production even when insect pollinators are rare. The researchers will test the hypothesis that selfing ability varies across populations because populations have adapted to differences in pollinator abundance in their habitats, and not because the populations have differentiated randomly. Further, they will test the hypothesis that the optimum selfing rate currently varies across populations. This study will contribute to our understanding of how natural selection creates and maintains patterns of diversity, and how selection in the past can be related to selection in the present.
