title: Evidence for natural hybridization between native and introduced lineages of Phragmites australis in the Chesapeake Bay watershed.
abstract: OBJECTIVE
  The introduction of nonnative taxa into areas occupied by conspecifics can lead to local extinction of native taxa via habitat modification and competitive dominance, and be exacerbated by outbreeding depression or the formation of invasive hybrid lineages following intraspecific gene flow. The expansion of Eurasian Phragmites australis into tidal wetlands of North America has been accompanied by a dramatic decline of native P. australis, with few relic populations remaining along the Atlantic coastline of the United States, particularly in the Virginia portion of the Chesapeake Bay.
  
  
  METHODS
  We sampled populations from the York River and its two major tributaries to determine the pattern of Phragmites invasion and identify remnant native populations that warrant conservation. We used chloroplast DNA haplotypes and nuclear DNA microsatellite profiles to classify individuals as belonging to the native or introduced lineage.
  
  
  RESULTS
  Although native Phragmites stands were identified in the brackish upstream reaches of the two York River tributaries, the majority of Phragmites stands surveyed contained the introduced lineage. We also identified a single putative hybrid plant, based on its microsatellite profile. This plant possessed the native cpDNA haplotype and was located in an otherwise native Phragmites stand that is adjacent to an isolated patch of introduced Phragmites.
  
  
  CONCLUSIONS
  Although evidence of field hybridization between native and introduced lineages of Phragmites in North America is still relatively rare, the continued encroachment of the introduced lineage into native wetlands may increase the likelihood of future hybrid formation. Careful genetic monitoring to identify remnant native and potential hybrid Phragmites is essential for prioritizing ongoing management efforts.
authors.affiliation: Department of Biology, 28 Westhampton Way, University of Richmond, Virginia 23173 USA.
authors.forename: Carrie A
authors.initials: CA
authors.lastname: Wu
authors.affiliation: Department of Biology, 28 Westhampton Way, University of Richmond, Virginia 23173 USA.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Murray
authors.affiliation: Division of Natural Heritage, Virginia Department of Conservation and Recreation, 600 East Main Street, Richmond, Virginia 23219 USA.
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Heffernan
mesh_terms: D002467:Cell Nucleus / Q000235:genetics; D018742:DNA, Chloroplast / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics*; D006239:Haplotypes; D006824:Hybridization, Genetic; D058865:Introduced Species; D018895:Microsatellite Repeats; D006109:Poaceae / Q000235:genetics*; D014768:Virginia
chemical_list: D018742:DNA, Chloroplast; D018744:DNA, Plant
keywords: Phragmites australis; common reed; cpDNA; distribution; disturbance; intraspecific hybridization; invasive species; microsatellite