European Journal of Forest Research

, Volume 132, Issue 2, pp 195–209 | Cite as

Assignment testing reveals multiple introduced source populations including potential ash hybrids (Fraxinus excelsior × F. angustifolia) in Ireland

  • Muriel Thomasset
  • Juan F. Fernández-Manjarrés
  • Gerry C. Douglas
  • Paola Bertolino
  • Nathalie Frascaria-Lacoste
  • Trevor R. Hodkinson
Original Paper

Abstract

Large-scale reforestation programmes are a major source of unwarranted gene flow and can have profound consequences on local genetic diversity. Recently, ash has been introduced to Ireland from continental Europe to stock plantations but has often exhibited poor stem form. It was not known whether these trees were Fraxinus excelsior, Fraxinus angustifolia or interspecific hybrids that are known to occur in continental Europe. F. excelsior is the only native ash in Ireland, so the introduced populations represent a potential threat for the genetic diversity of native populations. We characterized the introduced trees within two plantations (Clonee and Kildalkey) using morphological characters and six microsatellite markers. Samples from continental Europe were included for comparison. Plantations exhibited higher genetic diversity than control populations because our data suggest they contain a mixture of several provenances. There was a small but significant differentiation between plantations and control populations (ФCT = 0.0211). Bayesian analysis to infer population structure and to assign introduced individuals to reference populations clearly demonstrated the presence of hybrid individuals within the plantations. The percentage of trees detected with potential hybrid origin ranged from 28 to 58 % depending on the plantation and the threshold data analysis level chosen. Most hybrids could be considered cryptic because there was a lack of intermediate morphology for hybrid individuals that mainly clustered with F. excelsior. The results indicated that the source of material at the two plantation sites differed. Management options to minimize the impact of these introduced populations are discussed.

Keywords

Assignment test Cryptic hybrids Fraxinus Hybridization Leaf morphology Microsatellites 

Supplementary material

10342_2012_667_MOESM1_ESM.doc (142 kb)
Supplementary material 1 (DOC 142 kb)

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Copyright information

© Springer-Verlag Berlin Heidelberg 2012

Authors and Affiliations

  • Muriel Thomasset
    • 1
    • 2
  • Juan F. Fernández-Manjarrés
    • 3
    • 4
    • 5
  • Gerry C. Douglas
    • 2
  • Paola Bertolino
    • 3
    • 4
    • 5
  • Nathalie Frascaria-Lacoste
    • 4
    • 3
    • 5
  • Trevor R. Hodkinson
    • 1
    • 6
  1. 1.School of Natural Sciences, Trinity College DublinUniversity of DublinDublin 2Ireland
  2. 2.Kinsealy Research CentreTeagascDublin 17Ireland
  3. 3.CNRS, UMR 8079OrsayFrance
  4. 4.AgroParisTechParisFrance
  5. 5.UMR 8079Université Paris-SudOrsayFrance
  6. 6.Trinity Centre for Biodiversity Research, Trinity College DublinUniversity of DublinDublin 2Ireland

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