title: Uniform selection as a primary force reducing population genetic differentiation of cavitation resistance across a species range.
abstract: BACKGROUND
  Cavitation resistance to water stress-induced embolism determines plant survival during drought. This adaptive trait has been described as highly variable in a wide range of tree species, but little is known about the extent of genetic and phenotypic variability within species. This information is essential to our understanding of the evolutionary forces that have shaped this trait, and for evaluation of its inclusion in breeding programs.
  
  
  METHODS
  We assessed cavitation resistance (P(50)), growth and carbon isotope composition in six Pinus pinaster populations in a provenance and progeny trial. We estimated the heritability of cavitation resistance and compared the distribution of neutral markers (F(ST)) and quantitative genetic differentiation (Q(ST)), for retrospective identification of the evolutionary forces acting on these traits.
  
  
  CONCLUSIONS
  In contrast to growth and carbon isotope composition, no population differentiation was found for cavitation resistance. Heritability was higher than for the other traits, with a low additive genetic variance (h(2) (ns) = 0.43±0.18, CV(A) = 4.4%). Q(ST) was significantly lower than F(ST), indicating uniform selection for P(50), rather than genetic drift. Putative mechanisms underlying Q(ST)<F(ST) are discussed.
authors.affiliation: INRA, UMR 1202 BIOGECO, F-33610 Cestas, France.
authors.forename: Jean-Baptiste
authors.initials: JB
authors.lastname: Lamy
authors.forename: Laurent
authors.initials: L
authors.lastname: Bouffier
authors.forename: Régis
authors.initials: R
authors.lastname: Burlett
authors.forename: Christophe
authors.initials: C
authors.lastname: Plomion
authors.forename: Hervé
authors.initials: H
authors.lastname: Cochard
authors.forename: Sylvain
authors.initials: S
authors.lastname: Delzon
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D000465:Algorithms; D005075:Biological Evolution; D055864:Droughts; D040961:Genetic Drift; D014644:Genetic Variation; D005828:Genetics, Population; D008957:Models, Genetic; D028223:Pinus / Q000235:genetics / Q000254:growth & development; D063245:Plant Development; D010944:Plants / Q000145:classification / Q000235:genetics*; D025341:Principal Component Analysis; D012641:Selection, Genetic