The role of biological interactions in determining the abundance, distribution and persistence of rare plants, and their vulnerability to environmental stress, is poorly known. This study will analyze the consequences of competition and seed predation on the population dynamics of a federally-listed threatened species, Cirsium pitcheri.The proposed research will use field experiments to reduce the impact of biological factors and interactions along a climatic gradient in the dune systems around Lake Michigan. The results of this study will provide critical baseline information on plant population dynamics of a threatened species. In addition, results from this work will contribute to developing useful conservation and management protocols for rare and endangered plant species.
