Common Reed

Phragmites australis

Overview

Common reed, Phragmites australis (Cav.), is among the most widespread angiosperms in the world and is found on every continent except Antarctica. Phragmites grows in all aquatic and brackish environments and spreads through both asexual and sexual structures. In North America, an invasive, European genotype of common reed (Phragmites australis (Cav.) Trin. Ex. Steudel) is now abundant in habitats once colonized by native genotypes. Rapid expansion of populations in wetlands along the East Coast was previously thought to be driven by human disturbance, but evidence now suggests that a cryptic invasion of an European genotype has occurred in the eastern United States (and some western locations), and this biotype continues to spread across the continent.The native genotypes (P. australis subspecies americanus) can be distinguished from the exotic genotype based on morphological and genetic characteristics.

Phragmites is represented by three distinct lineages in North America – native P. australis subsp. americanus, which is comprised of several dozen haplotypes, an invasive European haplotype, and P. australis subsp. berlanderi (commonly refered to as the Gulf Coast variety), which is of unknown origin. In the southwestern US, we have detected invasive populations associated with human alteration of wetlands, as well as hybridization between the native and European lineages. Our lab is studying the causes of invasive lineage establishment and hybridization in this arid region and the effects on incipient communities. We are also studying how insect herbivores, both native and introduced, affect growth, reprduction, and competitive interactions among the three lineages.

Introduction

In North America, an invasive, European genotype of common reed (Phragmites australis (Cav.) Trin. Ex. Steudel) is now abundant in habitats once colonized by native genotypes (Saltonstall et. al, 2004). The native genotypes (P. australis subspecies americanum) can be distinguished from the exotic genotype based on morphological and genetic characteristics (Saltonstall, K. 2004). Population decline and local extinctions of the native genotypes may be a result of competitive displacement by the exotic genotype (Meyerson et.al, 2000) and/or anthropogenic disturbance (Chambers et. al, 1999, Bertness et. al, 2002). We found that the few remaining native populations are more susceptible to exotic insect herbivores than exotic P. australis - the vector for exotic insect introductions (Lambert, A.M., 2005). Our objectives for this research include 1) determining the distribution of native and non-native P. australis in New England, 2) assessing differences in susceptibility to native and non-native herbivores among native and non-native P. australis genotypes, and 3) finding a genotype-specific biological control agent that will safely and permanently control non-native P. australis. This is a collaborative research project among the University of Rhode Island Biological Control Lab, Bernd Blossey's lab (Cornell University), and the RIVR Lab at UCSB.