9610496 McCauley This project will use the plant Silene alba as a model system to investigate how genetic factors influence the persistence of populations. Many species are distributed into numerous small local populations owing to the natural distribution of patches of favorable habitat, or due to human impact on the landscape. Small populations often face a high probability of extinction, and the persistence of the species at large may require that new populations be founded at a rate that offsets local extinctions. Since small or recently established populations often display the harmful effects of inbreeding, it is important to understand the genetic characteristics of newly formed populations. This study will ask whether recently established populations are prone to the harmful effects of inbreeding such that inbreeding influences population persistence. It will also ask whether the movement of genes from population to population by pollen dispersal (gene flow) can offset the effects of inbreeding. Studies of both natural and experimental populations of S. alba will address these issues. Studies of natural populations will use genetic techniques to measure the rate at which new genes enter recently founded populations owing to pollen movement. They will also investigate whether plants formed by this gene flow are more vigorous than their neighbors. In other experiments artificial populations of S. alba will be created in order to investigate the interaction of gene flow by pollen and inbreeding under more controlled conditions. Taken together, the results of these studies should contribute to a more general understanding of how genetic and ecological factors interact to determine the probability that a species can persist in a given landscape.
