The scales of pollen movement within and between restored prairie fragments

Background/Question/Methods: Plant-pollinator interactions are fundamental to the persistence of populations in fragmented ecosystems, including prairies of North America. With inadequate rates of pollen dispersal, low rates of gene flow can lead to inbreeding and population declines. Yet, we know little about the scales over which pollen disperses in fragmented prairie landscapes. I studied pollen dispersal of three species commonly sown in restored tallgrass prairies: Coreopsis lanceolata, Heliopsis helianthoides, and Ratibida pinnata. To evaluate pollen dispersal, I placed fluorescent powder on flowers, which was then carried and deposited by pollinators. This enabled me to track the locations and distances pollen moved. I investigated two questions: (1) over what distances is pollen moving within restored prairies?, and (2) does an agricultural field reduce pollen movement rates between, relative to within, fragments?

Results/Conclusions: I demonstrate that for H. helianthoides and R. pinnata, 86% and 92%, respectively, of recovered pollen moved 50m or less along a 150m transect. In addition, the farthest movements recorded within the fragment were 125m, 120m, and 139m for C. lanceolata, H. helianthoides, and R. pinnata, respectively. I also found that an agricultural field impedes rates of dispersal, recording only one deposition occurrence among fields, compared to 19 depositions at a comparable distance within fields. These results improve our understanding of the distances that pollinators transport pollen within fragmented ecosystems. Furthermore, it has implications for land managers- both considering the distance between fragments before planting, and utilizing physical features, such as corridors, to ensure sufficient connectivity and gene flow between fragments.