Let’s Talk about Phragmites australis: Native and Nonnative Reed in the Grand Canyon

Let’s Talk about Phragmites australis: Native and Nonnative Reed in the Grand Canyon 

Emily Palmquist1*, Joel B. Sankey2, and Bradley Butterfield3 

1U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, Flagstaff, Arizona, USA; epalmquist@usgs.gov 

2U.S. Geological Survey, Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, Flagstaff, Arizona, USA; jsankey@usgs.gov 

4Northern Arizona University, Department of Biological Sciences, Flagstaff, Arizona, USA; Bradley.butterfield@nau.edu 

Phragmites australis (common reed) has been the focus of extensive management attention over the last three decades as nonnative stands spread across North America, dramatically changing wetlands and riparian areas. The nonnative lineage (subsp. australis, ‘nonnative Phragmites’, hereafter) has spread from the east coast to the west and south, replacing native stands of the species and also moving into ecosystems previously uninhabited by the species. The native lineage (subsp. americanus, ‘native Phragmites’, hereafter) was widespread in North America prior to nonnative Phragmites expansion and is both ecologically and culturally important. Management of native and nonnative Phragmites is increasingly pressing as native stands are now uncommon or extirpated in many regions and could be declining. Phragmites has expanded in recent decades along the Colorado River in the Grand Canyon; though it is not known whether the expansion includes native, nonnative, or both lineages. As such, this expansion could be related to river regulation (specifically dam operations), the arrival of nonnative Phragmites, or a combination of both factors. If this expansion is largely nonnative Phragmites, removals of nonnative Phragmites and restoration with native Phragmites may be implemented. This study aimed to 1) evaluate the distribution of native and nonnative Phragmites in the Glen and Grand Canyon regions, 2) determine the genetic diversity and structure of native Phragmites for restoration planning, and 3) assess the utility of morphological characters to distinguish between native and nonnative Phragmites in southwestern landscapes. Genetic testing with real-time polymerase chain reaction (rtPCR) methods at 84 locations across the Colorado River and tributaries identified four stands of nonnative Phragmites. A combination of k-means cluster analysis, discriminant analysis of principal components, and analysis of molecular variance indicate that native Phragmites exhibits little to no genetic structure across the landscape, so plant material for restoration can be sourced from any native stand. Morphological analyses show that a few features can be used to distinguish native from nonnative Phragmites. Management actions related to the removal of nonnative Phragmites and restoration using native Phragmites are directly related to cultural connections to southwestern rivers. Rivers and reeds – both native and nonnative – are sacred to many cultures, so consultation with regional Tribes on proposed management actions would improve decision-making and management outcomes.