title: Seed bank dynamics govern persistence of Brassica hybrids in crop and natural habitats.
abstract: OBJECTIVE
  Gene flow from crops to their wild relatives has the potential to alter population growth rates and demography of hybrid populations, especially when a new crop has been genetically modified (GM). This study introduces a comprehensive approach to assess this potential for altered population fitness, and uses a combination of demographic data in two habitat types and mathematical (matrix) models that include crop rotations and outcrossing between parental species.
  
  
  METHODS
  Full life-cycle demographic rates, including seed bank survival, of non-GM Brassica rapa × B. napus F1 hybrids and their parent species were estimated from experiments in both agricultural and semi-natural habitats. Altered fitness potential was modelled using periodic matrices including crop rotations and outcrossing between parent species.
  
  
  RESULTS
  The demographic vital rates (i.e. for major stage transitions) of the hybrid population were intermediate between or lower than both parental species. The population growth rate (λ) of hybrids indicated decreases in both habitat types, and in a semi-natural habitat hybrids became extinct at two sites. Elasticity analyses indicated that seed bank survival was the greatest contributor to λ. In agricultural habitats, hybrid populations were projected to decline, but with persistence times up to 20 years. The seed bank survival rate was the main driver determining persistence. It was found that λ of the hybrids was largely determined by parental seed bank survival and subsequent replenishment of the hybrid population through outcrossing of B. rapa with B. napus.
  
  
  CONCLUSIONS
  Hybrid persistence was found to be highly dependent on the seed bank, suggesting that targeting hybrid seed survival could be an important management option in controlling hybrid persistence. For local risk mitigation, an increased focus on the wild parent is suggested. Management actions, such as control of B. rapa, could indirectly reduce hybrid populations by blocking hybrid replenishment.
authors.affiliation: Centre for Ecology and Hydrology, Benson Lane, Wallingford OX10 8BB, UK, School of Biosciences, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK and National Institute of Agricultural Botany, Huntingdon Rd, Cambridge CB3 0EL, UK dann1@ceh.ac.uk.
authors.forename: Danny A P
authors.initials: DA
authors.lastname: Hooftman
authors.affiliation: Centre for Ecology and Hydrology, Benson Lane, Wallingford OX10 8BB, UK, School of Biosciences, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK and National Institute of Agricultural Botany, Huntingdon Rd, Cambridge CB3 0EL, UK.
authors.forename: James M
authors.initials: JM
authors.lastname: Bullock
authors.affiliation: Centre for Ecology and Hydrology, Benson Lane, Wallingford OX10 8BB, UK, School of Biosciences, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK and National Institute of Agricultural Botany, Huntingdon Rd, Cambridge CB3 0EL, UK.
authors.forename: Kathryn
authors.initials: K
authors.lastname: Morley
authors.affiliation: Centre for Ecology and Hydrology, Benson Lane, Wallingford OX10 8BB, UK, School of Biosciences, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK and National Institute of Agricultural Botany, Huntingdon Rd, Cambridge CB3 0EL, UK.
authors.forename: Caroline
authors.initials: C
authors.lastname: Lamb
authors.affiliation: Centre for Ecology and Hydrology, Benson Lane, Wallingford OX10 8BB, UK, School of Biosciences, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK and National Institute of Agricultural Botany, Huntingdon Rd, Cambridge CB3 0EL, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Hodgson
authors.affiliation: Centre for Ecology and Hydrology, Benson Lane, Wallingford OX10 8BB, UK, School of Biosciences, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK and National Institute of Agricultural Botany, Huntingdon Rd, Cambridge CB3 0EL, UK.
authors.forename: Philippa
authors.initials: P
authors.lastname: Bell
authors.affiliation: Centre for Ecology and Hydrology, Benson Lane, Wallingford OX10 8BB, UK, School of Biosciences, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK and National Institute of Agricultural Botany, Huntingdon Rd, Cambridge CB3 0EL, UK.
authors.forename: Jane
authors.initials: J
authors.lastname: Thomas
authors.affiliation: Centre for Ecology and Hydrology, Benson Lane, Wallingford OX10 8BB, UK, School of Biosciences, University of Exeter, Cornwall Campus, Penryn TR10 9EZ, UK and National Institute of Agricultural Botany, Huntingdon Rd, Cambridge CB3 0EL, UK.
authors.forename: Rosemary S
authors.initials: RS
authors.lastname: Hails
mesh_terms: D000383:Agriculture / Q000379:methods*; D029688:Brassica napus / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029741:Brassica rapa / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D018556:Crops, Agricultural / Q000235:genetics / Q000254:growth & development; D017753:Ecosystem; D051456:Gene Flow; D056084:Genetic Fitness; D040941:Heredity; D006824:Hybridization, Genetic; D008957:Models, Genetic; D012639:Seeds / Q000254:growth & development*
keywords: Brassica napus; Brassica rapa; crop rotation; demography; fitness; gene flow; genetically modified crops; hybridization; introgression; management