title: Morphology delimits more species than molecular genetic clusters of invasive Pilosella.
abstract: •
  
  
  OBJECTIVE
  Accurate assessments of biodiversity are paramount for understanding ecosystem processes and adaptation to change. Invasive species often contribute substantially to local biodiversity; correctly identifying and distinguishing invaders is thus necessary to assess their potential impacts. We compared the reliability of morphology and molecular sequences to discriminate six putative species of invasive Pilosella hawkweeds (syn. Hieracium, Asteraceae), known for unreliable identifications and historical introgression. We asked (1) which morphological traits dependably discriminate putative species, (2) if genetic clusters supported morphological species, and (3) if novel hybridizations occur in the invaded range.•
  
  
  METHODS
  We assessed 33 morphometric characters for their discriminatory power using the randomForest classifier and, using AFLPs, evaluated genetic clustering with the program structure and subsequently with an AMOVA. The strength of the association between morphological and genotypic dissimilarity was assessed with a Mantel test.•
  
  
  RESULTS
  Morphometric analyses delimited six species while genetic analyses defined only four clusters. Specifically, we found (1) eight morphological traits could reliably distinguish species, (2) structure suggested strong genetic differentiation but for only four putative species clusters, and (3) genetic data suggest both novel hybridizations and multiple introductions have occurred.•
  
  
  CONCLUSIONS
  (1) Traditional floristic techniques may resolve more species than molecular analyses in taxonomic groups subject to introgression. (2) Even within complexes of closely related species, relatively few but highly discerning morphological characters can reliably discriminate species. (3) By clarifying patterns of morphological and genotypic variation of invasive Pilosella, we lay foundations for further ecological study and mitigation.
authors.affiliation: Biodiversity and Landscape Ecology Research Facility, Department of Biology, University of British Columbia, Okanagan Campus, 3187 University Way, Kelowna, British Columbia V1V 1V7 Canada.
authors.forename: Chandra E
authors.initials: CE
authors.lastname: Moffat
authors.affiliation: Biodiversity and Landscape Ecology Research Facility, Department of Biology, University of British Columbia, Okanagan Campus, 3187 University Way, Kelowna, British Columbia V1V 1V7 Canada.
authors.forename: David J
authors.initials: DJ
authors.lastname: Ensing
authors.affiliation: USDA Agricultural Research Service, Northern Plains Agricultural Research Laboratory, 1500 N. Central Avenue, Sidney, Montana 59270 USA.
authors.forename: John F
authors.initials: JF
authors.lastname: Gaskin
authors.affiliation: Agriculture and Agri-Food Canada, Lethbridge Research Centre, 5403 1 Ave South, Lethbridge, Alberta T1J 4B1, Canada.
authors.forename: Rosemarie A
authors.initials: RA
authors.lastname: De Clerck-Floate
authors.affiliation: Biodiversity and Landscape Ecology Research Facility, Department of Biology, University of British Columbia, Okanagan Campus, 3187 University Way, Kelowna, British Columbia V1V 1V7 Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Pither
mesh_terms: D019659:Asteraceae / Q000033:anatomy & histology / Q000145:classification* / Q000235:genetics; D001955:British Columbia; D016000:Cluster Analysis; D004463:Ecology; D035264:Flowers / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics; D014644:Genetic Variation; D005838:Genotype; D005843:Geography; D006824:Hybridization, Genetic; D058865:Introduced Species; D010641:Phenotype; D015203:Reproducibility of Results
keywords: Asteraceae; Hieracium; Pilosella; genetic cluster; invasive; morphological molecular congruence; morphology; morphometric; randomForest; structure