Genetic Structure and Gene Flow in Woody Riparian Plants: Implications for Restoration in the Grand Canyon
 
Emily Palmquist1,2*, Gerard Allan3, Thomas Whitham4, Kiona Ogle5,6, Bradley Butterfield7,
Patrick Shafroth8
 
1U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, Flagstaff, AZ, USA; epalmquist@usgs.gov
2 Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, USA
3 Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, USA; Gerard.allan@nau.edu
4 Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, USA; Thomas.whitham@nau.edu
5 School of Informatics, Computing & Cyber Systems, Northern Arizona University, Flagstaff, AZ, USA; Kiona.ogle@nau.edu
6Center for Ecosystem Science & Society, Northern Arizona University, Flagstaff, AZ, USA
7 Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ, USA; Bradley.butterfield@nau.edu
8U.S. Geological Survey, Fort Collins Science Center, Fort Collins, CO, USA; shafrothp@usgs.gov
 
 
Current restoration initiatives emphasize the utility of selecting local genetic stock for reestablishment of native plants. The limits of what is “local”, however, vary by species, geography, and availability of source populations. Most studies on appropriate transfer zones for plant restoration materials have been conducted using upland species, but species in riparian systems will likely exhibit different patterns of gene flow and genetic structure due to the influence of river corridor connectivity and differing instream flow regimes on gene flow and local adaptation. In geographically complex systems, such as Grand Canyon, a riparian plant species may experience more similar conditions 80 km downstream on the perennial mainstem of the Colorado River compared to an ephemeral, higher elevation tributary that is only 5 km away. Using simple sequence repeats (SSRs) in common woody riparian species (Populus fremontii, Salix gooddingii, and Salix exigua), we examine the genetic structure and gene flow within the complex riparian landscape of the Grand Canyon region. Preliminary results for P. fremontii suggest that populations within Grand Canyon are strongly differentiated from those outside of Grand Canyon and exhibit differentiation among tributaries. Implications of these patterns of genetic structure are discussed within the context of riparian restoration and rehabilitation for each species and compared across species.