title: Genome-wide patterns of differentiation and spatially varying selection between postglacial recolonization lineages of Populus alba (Salicaceae), a widespread forest tree.
abstract: Studying the divergence continuum in plants is relevant to fundamental and applied biology because of the potential to reveal functionally important genetic variation. In this context, whole-genome sequencing (WGS) provides the necessary rigour for uncovering footprints of selection. We resequenced populations of two divergent phylogeographic lineages of Populus alba (n = 48), thoroughly characterized by microsatellites (n = 317), and scanned their genomes for regions of unusually high allelic differentiation and reduced diversity using > 1.7 million single nucleotide polymorphisms (SNPs) from WGS. Results were confirmed by Sanger sequencing. On average, 9134 high-differentiation (≥ 4 standard deviations) outlier SNPs were uncovered between populations, 848 of which were shared by ≥ three replicate comparisons. Annotation revealed that 545 of these were located in 437 predicted genes. Twelve percent of differentiation outlier genome regions exhibited significantly reduced genetic diversity. Gene ontology (GO) searches were successful for 327 high-differentiation genes, and these were enriched for 63 GO terms. Our results provide a snapshot of the roles of 'hard selective sweeps' vs divergent selection of standing genetic variation in distinct postglacial recolonization lineages of P. alba. Thus, this study adds to our understanding of the mechanisms responsible for the origin of functionally relevant variation in temperate trees.
authors: Unit of Ecology and Evolution, Department of Biology, University of Fribourg, Chemin du Musee 10, 1700, Fribourg, Switzerland.
authors: Kai N
authors: KN
authors: Stölting
authors: Unit of Ecology and Evolution, Department of Biology, University of Fribourg, Chemin du Musee 10, 1700, Fribourg, Switzerland.
authors: Margot
authors: M
authors: Paris
authors: Unit of Ecology and Evolution, Department of Biology, University of Fribourg, Chemin du Musee 10, 1700, Fribourg, Switzerland.
authors: Cécile
authors: C
authors: Meier
authors: Department of Forest Genetics, Austrian Research Centre for Forests (BFW), Seckendorff-Gudent Weg 8, 1130, Vienna, Austria.
authors: Berthold
authors: B
authors: Heinze
authors: Department of Chemistry, University of Salerno, 84084, Fisciano, Italy.
authors: Stefano
authors: S
authors: Castiglione
authors: Department of Botany, West-Hungarian University, 9400, Sopron, Hungary.
authors: Denes
authors: D
authors: Bartha
authors: Unit of Ecology and Evolution, Department of Biology, University of Fribourg, Chemin du Musee 10, 1700, Fribourg, Switzerland.
authors: Christian
authors: C
authors: Lexer
mesh_terms: D065928:Forests; D063990:Gene Ontology; D017343:Genes, Plant; D056726:Genetic Association Studies; D014644:Genetic Variation; D018745:Genome, Plant; D006814:Hungary; D046448:Ice Cover; D007558:Italy; D018895:Microsatellite Repeats / Q000235:genetics; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D032107:Populus / Q000235:genetics*; D015203:Reproducibility of Results; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D014197:Trees / Q000235:genetics*
keywords: Populus; adaptation; divergence continuum; divergent selection; population genomics; postglacial recolonization; selective sweep; whole-genome sequencing