title: Landscape genomics of Populus trichocarpa: the role of hybridization, limited gene flow, and natural selection in shaping patterns of population structure.
abstract: Populus trichocarpa is an ecologically important tree across western North America. We used a large population sample of 498 accessions over a wide geographical area genotyped with a 34K Populus SNP array to quantify geographical patterns of genetic variation in this species (landscape genomics). We present evidence that three processes contribute to the observed patterns: (1) introgression from the sister species P. balsamifera, (2) isolation by distance (IBD), and (3) natural selection. Introgression was detected only at the margins of the species' distribution. IBD was significant across the sampled area as a whole, but no evidence of restricted gene flow was detected in a core of drainages from southern British Columbia (BC). We identified a large number of FST outliers. Gene Ontology analyses revealed that FST outliers are overrepresented in genes involved in circadian rhythm and response to red/far-red light when the entire dataset is considered, whereas in southern BC heat response genes are overrepresented. We also identified strong correlations between geoclimate variables and allele frequencies at FST outlier loci that provide clues regarding the selective pressures acting at these loci.
authors: Department of Botany, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada. geraldes@mail.ubc.ca.
authors: Armando
authors: A
authors: Geraldes
authors: Nima
authors: N
authors: Farzaneh
authors: Christopher J
authors: CJ
authors: Grassa
authors: Athena D
authors: AD
authors: McKown
authors: Robert D
authors: RD
authors: Guy
authors: Shawn D
authors: SD
authors: Mansfield
authors: Carl J
authors: CJ
authors: Douglas
authors: Quentin C B
authors: QC
authors: Cronk
mesh_terms: D051456:Gene Flow; D017343:Genes, Plant; D014644:Genetic Variation; D005828:Genetics, Population; D006824:Hybridization, Genetic; D010641:Phenotype; D058974:Phylogeography; D020641:Polymorphism, Single Nucleotide; D032107:Populus / Q000145:classification* / Q000235:genetics* / Q000502:physiology; D012641:Selection, Genetic
keywords: Adaptation; FST outliers; Populus balsamifera; SNPs; isolation by distance; red/far-red