title: Tracing the origin of Gulf Coast Phragmites (Poaceae): a story of long-distance dispersal and hybridization.
abstract: OBJECTIVE
  Long-distance dispersal can affect speciation processes in two opposing ways. Dispersal can promote geographic isolation or it can bring together geographically distant and distantly related genotypes, thus counteracting local differentiation. We used the Gulf Coast of North America (GC), a "hot spot" of reed diversity and evolutionary dynamics, as a model system to study the diversification processes within the invasive, cosmopolitan, polyploid grass Phragmites.
  
  
  METHODS
  Genetic diversity was studied using collections representing all species of the genus and from all continents (except Antarctica). A range of molecular markers, including chloroplast and nuclear sequences, microsatellites, and AFLPs, was analyzed to detect DNA variation from the population to the species level and to infer phylogenetic relationships across continents.
  
  
  RESULTS
  An interspecific hybrid, Phragmites mauritianus × P. australis, and four P. australis cp-DNA haplotypes from Africa, Europe, and North America have been dispersed to the GC and interbreed with each other.
  
  
  CONCLUSIONS
  Long-distance dispersal and weak breeding barriers appear to be recurring phenomena, not only in the GC, but worldwide. We present data strongly suggesting that interspecific hybridization and introgression among different Phragmites species take place and appear to have contributed significantly to the diversification processes within the genus. Hence, the application of traditional species concepts within Phragmites might be inappropriate.
authors.affiliation: Department of Bioscience, Plant Biology, Aarhus University, Ole Worms Allé 1, 8000 Aarhus C, Denmark. carla.lambertini@biology.au.dk
authors.forename: Carla
authors.initials: C
authors.lastname: Lambertini
authors.forename: Irving A
authors.initials: IA
authors.lastname: Mendelssohn
authors.forename: Mats H G
authors.initials: MH
authors.lastname: Gustafsson
authors.forename: Birgit
authors.initials: B
authors.lastname: Olesen
authors.forename: Tenna
authors.initials: T
authors.lastname: Riis
authors.forename: Brian K
authors.initials: BK
authors.lastname: Sorrell
authors.forename: Hans
authors.initials: H
authors.lastname: Brix
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D005075:Biological Evolution; D003710:Demography; D005819:Genetic Markers; D014644:Genetic Variation; D006824:Hybridization, Genetic / Q000235:genetics*; D006109:Poaceae / Q000235:genetics* / Q000502:physiology*; D013045:Species Specificity
chemical_list: D005819:Genetic Markers