title: Spatially variable natural selection and the divergence between parapatric subspecies of lodgepole pine (Pinus contorta, Pinaceae).
abstract: OBJECTIVE
  Plant populations arrayed across sharp environmental gradients are ideal systems for identifying the genetic basis of ecologically relevant phenotypes. A series of five uplifted marine terraces along the northern coast of California represents one such system where morphologically distinct populations of lodgepole pine (Pinus contorta) are distributed across sharp soil gradients ranging from fertile soils near the coast to podzolic soils ca. 5 km inland.
  
  
  METHODS
  A total of 92 trees was sampled across four coastal marine terraces (N = 10-46 trees/terrace) located in Mendocino County, California and sequenced for a set of 24 candidate genes for growth and responses to various soil chemistry variables. Statistical analyses relying on patterns of nucleotide diversity were employed to identify genes whose diversity patterns were inconsistent with three null models.
  
  
  RESULTS
  Most genes displayed patterns of nucleotide diversity that were consistent with null models (N = 19) or with the presence of paralogs (N = 3). Two genes, however, were exceptional: an aluminum responsive ABC-transporter with F(ST) = 0.664 and an inorganic phosphate transporter characterized by divergent haplotypes segregating at intermediate frequencies in most populations.
  
  
  CONCLUSIONS
  Spatially variable natural selection along gradients of aluminum and phosphate ion concentrations likely accounted for both outliers. These results shed light on some of the genetic components comprising the extended phenotype of this ecosystem, as well as highlight ecotones as fruitful study systems for the detection of adaptive genetic variants.
authors: Department of Biology, Virginia Commonwealth University, Richmond, 23284, USA. aeckert2@vcu.edu
authors: Andrew J
authors: AJ
authors: Eckert
authors: Hurshbir
authors: H
authors: Shahi
authors: Shannon L
authors: SL
authors: Datwyler
authors: David B
authors: DB
authors: Neale
mesh_terms: D000222:Adaptation, Physiological; D000535:Aluminum / Q000378:metabolism; D001483:Base Sequence; D002140:California; D056426:Genetic Loci; D040342:Genetic Structures; D014644:Genetic Variation; D005828:Genetics, Population; D019015:Geologic Sediments / Q000737:chemistry; D006239:Haplotypes; D015233:Models, Statistical; D008969:Molecular Sequence Data; D010641:Phenotype; D010710:Phosphates / Q000378:metabolism; D028223:Pinus / Q000235:genetics* / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D012987:Soil / Q000737:chemistry; D013312:Stress, Physiological; D014197:Trees
chemical_list: D010710:Phosphates; D010940:Plant Proteins; D012987:Soil; D000535:Aluminum