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Exploring genome porosity in the interior spruce hybrid zone

projects_porosityInterspecific hybridization is an important source of genetic variation for many plant species, playing prominent roles in adaptation and speciation. White spruce (Picea glauca) and Engelmann spruce (P. engelmannii) are closely related North American conifers that extensively hybridize over large areas in British Columbia and Alberta where their ranges overlap, forming a stable hybrid zone. The assortment of advanced-generation hybrids and backcrosses are collectively referred to as interior spruce. Recent research suggest that the interior spruce hybrid zone is ancient and has been maintained by hybrids possessing high fitness in environments intermediate to the parent species. While a candidate SNP study found disproportionately high Engelmann spruce ancestry in hybrids within British Columbia, a comprehensive genomic analysis of variation in ancestry across the entirety of the hybrid zone has yet to be performed. Additionally, recent advances in genomic software now allow the identification of alleles with excessive or deficient ancestry in hybrids. This opens up the possibility of identifying loci that may be responsible for maintaining species boundaries between white and Engelmann spruce despite extensive hybridization, as well as identifying alleles that are present across many genomic and geographic backgrounds which may be facilitating hybrid vigour in intermediate environments.

The AdapTree project has generated an extensive genomic dataset covering thousands of genic and regulatory regions in hundreds of hybrid individuals throughout the hybrid zone. This dataset will be utilized to answer several standing questions regarding the genomics of hybridization in the interior spruce hybrid zone.

  1. How freely do alleles move between species via their hybrids i.e. how porous is the interior spruce genome?
  2. Are species boundaries maintained by a few genomic regions of low porosity?
  3. Are alleles which exhibit particularly high or low porosity associated with phenotypic and environmental clines across the hybrid zone i.e. is there evidence of adaptive introgression?
  4. Are non-porous genes enriched for functional categories associated with reproductive isolation?


Funding: NSERC CGS-M Scholarship, UBC Faculty of Forestry Graduate Award, Mary and David Macaree Fellowship

Primary participants: [Degner | Aitken | Rieseberg]

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Centre for Forest Conservation Genetics
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