Tree Genetics & Genomes

, 11:817

Fine-scale environmental variation contributes to introgression in a three-species spruce hybrid complex

  • Jill A. Hamilton
  • Amanda R. De la Torre
  • Sally N. Aitken
Original Paper

DOI: 10.1007/s11295-014-0817-y

Cite this article as:
Hamilton, J.A., De la Torre, A.R. & Aitken, S.N. Tree Genetics & Genomes (2015) 11: 817. doi:10.1007/s11295-014-0817-y


Hybridization is common for many forest trees, where weak barriers to reproduction obscure species boundaries. We characterized the genomic structure of Picea populations comprising three species spanning two well-known contact zones, the Picea sitchensis × Picea glauca and the P. engelmannii × P. glauca hybrid zones, using a set of 71 candidate-gene single nucleotide polymorphisms. The genetic structure of populations suggests a complex genomic architecture shaped by interspecific gene flow and strong environmental selection, with increased genetic diversity in hybrids. The presence of admixture among all three species suggests that three-way hybrids with mixed ancestry occur where species ranges overlap in transitional environments. Significant clinal variation and associations with climatic variables (including continentality, temperature, and precipitation) differ between hybrid zones, indicating that individual species and their hybrids are adapted to distinct environmental niches. Allele–environmental association analysis revealed that most of the candidate genes with evidence of selection were unique to either the Sitka × white or the Engelmann × white hybrid zones, with few shared between these zones. Management of these widespread and diverse gene pools will be best served through development of climate-based seed transfer, with recommended seed sources informed by a combination of genetic and climatic information for future climates.


Spruce Admixture Hybrid zones Climate change Local adaptation 

Supplementary material

11295_2014_817_MOESM1_ESM.xlsx (49 kb)
Table S1(XLSX 49 kb)
11295_2014_817_MOESM2_ESM.xlsx (38 kb)
Table S2(XLSX 37 kb)
11295_2014_817_MOESM3_ESM.docx (130 kb)
Table S3(DOCX 130 kb)
11295_2014_817_MOESM4_ESM.xlsx (50 kb)
Table S4(XLSX 49 kb)
11295_2014_817_MOESM5_ESM.pdf (107 kb)
Fig. S1Population genetic structure analyses based on ten replicate Structure runs for Sitka, white, Engelmann, and admixed spruce. Mean ln P[D] (dotted line) and K genetic clusters (solid line) for K = 1–10. (PDF 106 kb)
11295_2014_817_Fig6_ESM.gif (54 kb)
Fig. S2

Loading plot of SNP contributions to the first discriminant principle component function (a) and second discriminant principle component function (b) based on 71 SNPs across the Sitka, white, Engelmann, and admixed populations. The gray line indicates the 95% quantile. (GIF 54 kb)

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High Resolution Image (TIFF 8154 kb)
11295_2014_817_Fig7_ESM.gif (608 kb)
Fig. S3

(GIF 607 kb)

11295_2014_817_MOESM7_ESM.tif (6.5 mb)
High Resolution Image (TIFF 6641 kb)

Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  • Jill A. Hamilton
    • 1
    • 2
  • Amanda R. De la Torre
    • 1
    • 3
  • Sally N. Aitken
    • 1
  1. 1.Centre for Forest Conservation Genetics, Department of Forest and Conservation SciencesUniversity of British ColumbiaVancouverCanada
  2. 2.Department of Biological SciencesUniversity of AlbertaEdmontonCanada
  3. 3.Department of Ecology and Environmental ScienceUmea UniversityUmeaSweden

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