title: Cryptic introgression into the kidney saxifrage (Saxifraga hirsuta) from its more abundant sympatric congener Saxifraga spathularis, and the potential risk of genetic assimilation.
abstract: OBJECTIVE
  Although hybridization can play a positive role in plant evolution, it has been shown that excessive unidirectional hybridization can result in replacement of a species' gene pool, and even the extinction of rare species via genetic assimilation. This study examines levels of introgression between the common Saxifraga spathularis and its rarer congener S. hirsuta, which have been observed to hybridize in the wild where they occur sympatrically.
  
  
  METHODS
  Seven species-specific single nucleotide polymorphisms (SNPs) were analysed in 1025 plants representing both species and their hybrid, S. × polita, from 29 sites across their ranges in Ireland. In addition, species distribution modelling was carried out to determine whether the relative abundance of the two parental species is likely to change under future climate scenarios.
  
  
  RESULTS
  Saxifraga spathularis individuals tended to be genetically pure, exhibiting little or no introgression from S. hirsuta, but significant levels of introgression of S. spathularis alleles into S. hirsuta were observed, indicating that populations exhibiting S. hirsuta morphology are more like a hybrid swarm, consisting of backcrosses and F2s. Populations of the hybrid, S. × polita, were generally comprised of F1s or F2s, with some evidence of backcrossing. Species distribution modelling under projected future climate scenarios indicated an increase in suitable habitats for both parental species.
  
  
  CONCLUSIONS
  Levels of introgression observed in this study in both S. spathularis and S. hirsuta would appear to be correlated with the relative abundance of the species. Significant introgression of S. spathularis alleles was detected in the majority of the S. hirsuta populations analysed and, consequently, ongoing introgression would appear to represent a threat to the genetic integrity of S. hirsuta, particularly in areas where the species exists sympatrically with its congener and where it is greatly outnumbered.
authors.affiliation: School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK, Institute for Global Food Security, Queen's University Belfast, UK and DBN Plant Molecular Laboratory, National Botanic Gardens, Glasnevin, Dublin 9, Ireland School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK, Institute for Global Food Security, Queen's University Belfast, UK and DBN Plant Molecular Laboratory, National Botanic Gardens, Glasnevin, Dublin 9, Ireland GBeatty03@qub.ac.uk.
authors.forename: Gemma E
authors.initials: GE
authors.lastname: Beatty
authors.affiliation: School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK, Institute for Global Food Security, Queen's University Belfast, UK and DBN Plant Molecular Laboratory, National Botanic Gardens, Glasnevin, Dublin 9, Ireland.
authors.forename: Laura
authors.initials: L
authors.lastname: Barker
authors.affiliation: School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK, Institute for Global Food Security, Queen's University Belfast, UK and DBN Plant Molecular Laboratory, National Botanic Gardens, Glasnevin, Dublin 9, Ireland.
authors.forename: Pei-Pei
authors.initials: PP
authors.lastname: Chen
authors.affiliation: School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK, Institute for Global Food Security, Queen's University Belfast, UK and DBN Plant Molecular Laboratory, National Botanic Gardens, Glasnevin, Dublin 9, Ireland.
authors.forename: Colin T
authors.initials: CT
authors.lastname: Kelleher
authors.affiliation: School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK, Institute for Global Food Security, Queen's University Belfast, UK and DBN Plant Molecular Laboratory, National Botanic Gardens, Glasnevin, Dublin 9, Ireland School of Biological Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast BT9 7BL, UK, Institute for Global Food Security, Queen's University Belfast, UK and DBN Plant Molecular Laboratory, National Botanic Gardens, Glasnevin, Dublin 9, Ireland.
authors.forename: Jim
authors.initials: J
authors.lastname: Provan
mesh_terms: D017753:Ecosystem; D006824:Hybridization, Genetic; D007178:Inbreeding; D007494:Ireland; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide; D031995:Saxifragaceae / Q000145:classification* / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013045:Species Specificity; D061350:Sympatry
keywords: Genetic assimilation; Saxifraga hirsuta; Saxifraga spathularis; hybridization; introgression; kidney saxifrage; population genetics; single nucleotide polymorphisms; species distribution modelling