Bioclimatic, ecological, and phenotypic intermediacy and high genetic admixture in a natural hybrid of octoploid strawberries

PREMISE OF THE STUDY: 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 SNPs, 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. KEY RESULTS: Significant admixture and little overall maternal bias in chloroplast or nuclear genomes suggest a high degree of inter-fertility among the parental and hybrid species and point...