title: Multi-Phase US Spread and Habitat Switching of a Post-Columbian Invasive, Sorghum halepense.
abstract: Johnsongrass (Sorghum halepense) is a striking example of a post-Columbian founder event. This natural experiment within ecological time-scales provides a unique opportunity for understanding patterns of continent-wide genetic diversity following range expansion. Microsatellite markers were used for population genetic analyses including leaf-optimized Neighbor-Joining tree, pairwise FST, mismatch analysis, principle coordinate analysis, Tajima's D, Fu's F and Bayesian clusterings of population structure. Evidence indicates two geographically distant introductions of divergent genotypes, which spread across much of the US in <200 years. Based on geophylogeny, gene flow patterns can be inferred to have involved five phases. Centers of genetic diversity have shifted from two introduction sites separated by ~2000 miles toward the middle of the range, consistent with admixture between genotypes from the respective introductions. Genotyping provides evidence for a 'habitat switch' from agricultural to non-agricultural systems and may contribute to both Johnsongrass ubiquity and aggressiveness. Despite lower and more structured diversity at the invasion front, Johnsongrass continues to advance northward into cooler and drier habitats. Association genetic approaches may permit identification of alleles contributing to the habitat switch or other traits important to weed/invasive management and/or crop improvement.
authors.affiliation: Plant Genome Mapping Lab., Athens, GA, United States of America.
authors.forename: U Uzay
authors.identifier: http://orcid.org/0000-0002-2988-8790
authors.initials: UU
authors.lastname: Sezen
authors.affiliation: Virginia Tech, Blacksburg, VA, United States of America.
authors.forename: Jacob N
authors.initials: JN
authors.lastname: Barney
authors.affiliation: Virginia Tech, Blacksburg, VA, United States of America.
authors.forename: Daniel Z
authors.initials: DZ
authors.lastname: Atwater
authors.affiliation: USDA-ARS, PGRCU, Griffin, GA, United States of America.
authors.forename: Gary A
authors.initials: GA
authors.lastname: Pederson
authors.affiliation: USDA-ARS and University of Nebraska-Lincoln, Lincoln, NE, United States of America.
authors.forename: Jeffrey F
authors.initials: JF
authors.lastname: Pederson
authors.affiliation: Texas A&M University, College Station, TX, United States of America.
authors.forename: J Mike
authors.initials: JM
authors.lastname: Chandler
authors.affiliation: The Land Institute, Salina, KS, United States of America.
authors.forename: T Stan
authors.initials: TS
authors.lastname: Cox
authors.affiliation: The Land Institute, Salina, KS, United States of America.
authors.forename: Sheila
authors.initials: S
authors.lastname: Cox
authors.affiliation: Texas Tech University, Lubbock, TX, United States of America.
authors.forename: Peter
authors.initials: P
authors.lastname: Dotray
authors.affiliation: University of Arizona, Tucson, AZ, United States of America.
authors.forename: David
authors.initials: D
authors.lastname: Kopec
authors.affiliation: University of Arizona, Tucson, AZ, United States of America.
authors.forename: Steven E
authors.initials: SE
authors.lastname: Smith
authors.affiliation: New Mexico State University, Las Cruces, NM, United States of America.
authors.forename: Jill
authors.initials: J
authors.lastname: Schroeder
authors.affiliation: University of California Davis, Davis CA, United States of America.
authors.forename: Steven D
authors.initials: SD
authors.lastname: Wright
authors.affiliation: State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, China Academy of Sciences, Beijing, China.
authors.forename: Yuannian
authors.initials: Y
authors.lastname: Jiao
authors.affiliation: Plant Genome Mapping Lab., Athens, GA, United States of America.
authors.forename: Wenqian
authors.initials: W
authors.lastname: Kong
authors.affiliation: Plant Genome Mapping Lab., Athens, GA, United States of America.
authors.forename: Valorie
authors.initials: V
authors.lastname: Goff
authors.affiliation: Plant Genome Mapping Lab., Athens, GA, United States of America.
authors.forename: Susan
authors.initials: S
authors.lastname: Auckland
authors.affiliation: Plant Genome Mapping Lab., Athens, GA, United States of America.
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Rainville
authors.affiliation: Plant Genome Mapping Lab., Athens, GA, United States of America.
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Pierce
authors.affiliation: Plant Genome Mapping Lab., Athens, GA, United States of America.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Lemke
authors.affiliation: Plant Genome Mapping Lab., Athens, GA, United States of America.
authors.forename: Rosana
authors.initials: R
authors.lastname: Compton
authors.affiliation: Plant Genome Mapping Lab., Athens, GA, United States of America.
authors.forename: Christine
authors.initials: C
authors.lastname: Phillips
authors.affiliation: Plant Genome Mapping Lab., Athens, GA, United States of America.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Kerr
authors.affiliation: Plant Genome Mapping Lab., Athens, GA, United States of America.
authors.forename: Matthew
authors.initials: M
authors.lastname: Mettler
authors.affiliation: Plant Genome Mapping Lab., Athens, GA, United States of America.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Paterson
mesh_terms: D001499:Bayes Theorem; D003105:Colombia; D017753:Ecosystem; D014644:Genetic Variation; D005838:Genotype; D058865:Introduced Species; D015810:Linkage Disequilibrium; D018895:Microsatellite Repeats / Q000235:genetics; D025341:Principal Component Analysis; D045868:Sorghum / Q000235:genetics* / Q000254:growth & development; D014481:United States