title: Genetic evidence for hybridization in red oaks (Quercus sect. Lobatae, Fagaceae).
abstract: OBJECTIVE
  Hybridization is pervasive in many plant taxa, with consequences for species taxonomy, local adaptation, and management. Oaks (Quercus spp.) are thought to hybridize readily yet retain distinct traits, drawing into question the biological species concept for such taxa, but the true extent of gene flow is controversial. Genetic data are beginning to shed new light on this issue, but red oaks (section Lobatae), an important component of North American forests, have largely been neglected. Moreover, gene flow estimates may be sensitive to the choice of life stage, marker type, or genetic structure statistic.
  
  
  METHODS
  We coupled genetic structure data with parentage analyses for two mixed-species stands in North Carolina. Genetic structure analyses of adults (including F(ST), R(ST), G'(ST), and structure) reflect long-term patterns of gene flow, while the percentage of seedlings with parents of two different species reflect current levels of gene flow.
  
  
  RESULTS
  Genetic structure analyses revealed low differentiation in microsatellite allele frequencies between co-occurring species, suggesting past gene flow. However, methods differed in their sensitivity to differentiation, indicating a need for caution when drawing conclusions from a single method. Parentage analyses identified >20% of seedlings as potential hybrids. The species examined exhibit distinct morphologies, suggesting selection against intermediate phenotypes.
  
  
  CONCLUSIONS
  Our results suggest that hybridization between co-occurring red oaks occurs, but that selection may limit introgression, especially at functional loci. However, by providing a source of genetic variation, hybridization could influence the response of oaks and other hybridizing taxa to environmental change.
authors.affiliation: National Institute for Mathematical and Biological Synthesis, University of Tennessee, Knoxville, 37996, USA. moranev@nimbios.org
authors.forename: Emily V
authors.initials: EV
authors.lastname: Moran
authors.forename: John
authors.initials: J
authors.lastname: Willis
authors.forename: James S
authors.initials: JS
authors.lastname: Clark
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D051456:Gene Flow; D040342:Genetic Structures; D005828:Genetics, Population; D018745:Genome, Plant / Q000235:genetics; D005838:Genotype; D006824:Hybridization, Genetic; D009657:North Carolina; D010641:Phenotype; D018515:Plant Leaves / Q000033:anatomy & histology / Q000235:genetics; D029963:Quercus / Q000033:anatomy & histology / Q000235:genetics*; D036226:Seedlings / Q000033:anatomy & histology / Q000235:genetics; D013045:Species Specificity; D014197:Trees