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Evaluating the genome-wide effects of selective breeding on adaptive diversity in reforestation seedlots for future climates

Currently, over 64% of reforestation seedlots deployed on provincial land in BC are produced from advanced generation selective breeding programs that are required to use locally sourced parental provenances. While we know the effects of this selective breeding on phenotypically expressed genetic gain and neutral molecular diversity, the genome-wide impacts of selective tree breeding on adaptive molecular variation are unknown.

Climate change is predicted to generate climatic envelope shifts for tree species and cause locally adapted provenances to become disconnected from their current climatic optima. It is predicted that short term evolutionary adaptive responses of locally adapted tree populations will be insufficient to match these shifts in local climatic optima, resulting in an adaptive lag and reduced timber production. The use of locally sourced seedlots for selective breeding programs creates the possibility that reforestation seedlots will also suffer an adaptive lag and experience lower productivity. However, we do not know how well selectively bred seedlots are adapted to their local climatic optima, and what degree of adaptive lag they might experience. This limits our ability to evaluate how assisted migration strategies may be used to safely mitigate decreases in forest productivity due to climate change.

AdapTree is a large scale multi-institutional genomics project based at UBC that aims to elucidate the basis of adaptive molecular genetic variation in two conifer species; lodgepole pine and interior spruce. As part of AdapTree my research will compare reforestation seedlots from natural stands and selective breeding programs to investigate how selective breeding impacts upon adaptive genomic diversity and divergence. For each species seedling common gardens containing ~3000 individuals have been established to provide phenotypic data on several climatically and silviculturally relevant traits, and genotypes for a suite of >1500 adaptive SNPs (DNA sequence variations). By making carefully selected phenotypic and population genomic comparisons between seedlot types, my research will determine whether selective breeding causes adaptive deviations from populations under natural selection regimes. This will allow me to assess how well selectively bred reforestation seedlots match their current and future climatic optima. The findings will allow an evaluation of the current provincial seedlot diversity standards, and provide vital information to guide the development of assisted migration policies for selectively bred seedlots that strive to maintain forest productivity in BC and Alberta.

Funding: Genome Canada and Genome BC through the Adaptree Project.

Primary participants: [ MacLachlan | Aitken ]


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