WPC 2 B V P Z Courier 10cpi ? x x x , Z x 6 X @ 8 ; X @ HP DeskJet 500 HPDES500.PRS x @ x X , , 0 FX @Courier 10cpi 2 @ V P Z #| x ? x x x , Z x 6 X @ 8 ; X @ HP DeskJet 500 HPDES500.PRS x @ x X , , 0 FX @ 9317476 Broyles Hybridization and long distance pollen movement (i.e. gene flow) are important processes that are responsible for introducing and maintaining genetic diversity within plant populations. In the proposed study, I will examine pollen dispersal, gene flow, and effective hybridization between two common North American milkweeds (Poke Milkweed, Asclepias exaltata L.; Common Milkweed, Asclepias syriaca L.). These species occur in the same areas and overlap in flowering time, share pollinators, form viable hybrids, maintain high levels of genetic variation, and possess several unique genetic markers. Together these features make them ideal candidates for examining gene flow and hybridization. Nevertheless, A . exaltata and A . syriaca differ in several reproductive features (e.g., asexual reproduction, investment in pollen producing structures, and inflorescence size) which permits us to examine the effects of these life history traits on gene flow and hybridization. Specifically, gene flow and hybridization will be quantified by identifying pollen parents of seed to examine (1) pollen dispersal, (2) levels of long distance pollen mediated gene flow, and (3) effective hybridization between these species. The results of this study will contribute to our understanding of gene flow and hybridization in the maintenance of genetic diversity in plant populations. These processes are important to study because genetic var iation provides the necessary material for adaptation and long term species conservation. I will examine the underlying pollination mechanisms and plant pollinator interactions that directly affect these evolutionary processes. In addition, this study should lay the foundation for more comprehensive studies on the processes and evolutionary consequences of long distance pollen dispersal and hybridization in natural populations.
