title: Bioclimatic, ecological, and phenotypic intermediacy and high genetic admixture in a natural hybrid of octoploid strawberries.
abstract: OBJECTIVE
  Hybrid zones provide "natural laboratories" for understanding the processes of selection, reinforcement, and speciation. We sought to gain insight into the degree of introgression and the extent of ecological-phenotypic intermediacy in the natural hybrid strawberry, Fragaria × ananassa subsp. cuneifolia. •
  
  
  METHODS
  We used whole-plastome sequencing to identify parental species-specific (Fragaria chiloensis and F. virginiana) chloroplast single-nucleotide polymorphisms and combined the use of these with nuclear microsatellite markers to genetically characterize the hybrid zone. We assessed the potential role of selection in the observed geographic patterns by bioclimatically characterizing the niche of the hybrid populations and phenotypically characterizing hybrid individuals of known genomic constitution. •
  
  
  RESULTS
  Significant admixture and little overall maternal bias in chloroplast or nuclear genomes suggest a high degree of interfertility among the parental and hybrid species and point to a long history of backcrossing and genetic mixing in the hybrid zone. Even though hybrids were phenotypically intermediate to the parental species, there was a discernible fingerprint of the parental genotype within hybrid individuals. Thus, although the pattern of introgression observed suggests geographic limitations to gene flow, it may be reinforced by selection for specific parental traits in the bioclimatically intermediate habitat occupied by the hybrid. •
  
  
  CONCLUSIONS
  This work uncovered the genetic complexity underlying the hybrid zone of the wild relatives of the cultivated strawberry. It lays the foundation for experimental dissection of the causes of genomic introgression and nuclear-cytoplasmic disassociation, and for understanding other parts of Fragaria evolutionary history.
authors.affiliation: Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
authors.forename: Isabella
authors.initials: I
authors.lastname: Salamone
authors.forename: Rajanikanth
authors.initials: R
authors.lastname: Govindarajulu
authors.forename: Stacey
authors.initials: S
authors.lastname: Falk
authors.forename: Matthew
authors.initials: M
authors.lastname: Parks
authors.forename: Aaron
authors.initials: A
authors.lastname: Liston
authors.forename: Tia-Lynn
authors.initials: TL
authors.lastname: Ashman
mesh_terms: D005075:Biological Evolution; D003710:Demography; D017753:Ecosystem; D031985:Fragaria / Q000235:genetics*; D018745:Genome, Plant; D006824:Hybridization, Genetic; D008969:Molecular Sequence Data
keywords: hybrid zone; introgression; microsatellites; morphology; population genetic structure