The tallgrass prairie once covered over 22,000,000 acres of Illinois. Degradation of prairie ecosystems began with the European settlement of North America and accelerated as agriculture and development increased, reducing the prairie to its current coverage of 2,000 acres. The remaining prairie consists of isolated and fragmented remnants. Such fragmentation limits gene flow into prairie remnants, which may lead to genetic drift and inbreeding, lower remnant population viability, and even local extinction. Genetic declines also limit a species ability to adapt to changing selection pressures. I will conduct a study of gene flow into and within a population of Asclepias tuberosa (butterfly weed), a native milkweed species that supports many pollinators and serves as a larval food plant of monarch butterflies. My study site is James Woodworth Prairie (JWP), a 5-acre remnant isolated within an urban matrix in the Chicago area. Its isolation from other plant communities makes it an ideal location to study pollen mediated gene flow into a remnant prairie. I will combine DNA microsatellite genotyping and paternity assignment of individual plants and their progeny to assess gene flow and pollen dispersal into the prairie to determine the extent of reproductive isolation. I will also characterize pollen movement within the prairie. The unique pollination system of milkweeds, where pollen is delivered in a packet (pollinium) that likely fertilizes all the seeds in a flower, is expected to facilitate paternity assignment. My results will have important implications for conservation and restoration efforts of native prairies. Data analysis and results are pending.