title: Adaptation and exogenous selection in a Picea glauca × Picea engelmannii hybrid zone: implications for forest management under climate change.
abstract: The nature of selection responsible for the maintenance of the economically and ecologically important Picea glauca × Picea engelmannii hybrid zone was investigated. Genomic, phenotypic and climatic data were used to test assumptions of hybrid zone maintenance and to model future scenarios under climate change. Genome-wide estimates of admixture based on a panel of 86 candidate gene single nucleotide polymorphisms were combined with long-term quantitative data on growth and survival (over 20 yr), as well as one-time assessments of bud burst and bud set phenology, and cold hardiness traits. A total of 15,498 individuals were phenotyped for growth and survival. Our results suggest that the P. glauca × P. engelmannii hybrid zone is maintained by local adaptation to growing season length and snowpack (exogenous selection). Hybrids appeared to be fitter than pure species in intermediate environments, which fits expectations of the bounded hybrid superiority model of hybrid zone maintenance. Adaptive introgression from parental species has probably contributed to increased hybrid fitness in intermediate habitats. While P. engelmannii ancestry is higher than P. glauca ancestry in hybrid populations, on average, selective breeding in managed hybrid populations is shifting genomic composition towards P. glauca, potentially pre-adapting managed populations to warmer climates.
authors.affiliation: Centre for Forest Conservation Genetics, Department of Forest and Conservation Sciences, University of British Columbia, 3041-2424 Main Mall, Vancouver, BC, V6T1Z4, Canada.|Department of Ecology and Environmental Sciences, Umeå University, Linneaus väg 6, SE-901 87, Umeå, Sweden.
authors.forename: Amanda R
authors.initials: AR
authors.lastname: De La Torre
authors.affiliation: Centre for Forest Conservation Genetics, Department of Forest and Conservation Sciences, University of British Columbia, 3041-2424 Main Mall, Vancouver, BC, V6T1Z4, Canada.
authors.forename: Tongli
authors.initials: T
authors.lastname: Wang
authors.affiliation: Kalamalka Forestry Centre, Tree Improvement Branch, BC Ministry of Forests, Lands & Natural Resource Operations, 3401 Reservoir Rd, Vernon, BC, V1B2C7, Canada.
authors.forename: Barry
authors.initials: B
authors.lastname: Jaquish
authors.affiliation: Centre for Forest Conservation Genetics, Department of Forest and Conservation Sciences, University of British Columbia, 3041-2424 Main Mall, Vancouver, BC, V6T1Z4, Canada.
authors.forename: Sally N
authors.initials: SN
authors.lastname: Aitken
mesh_terms: D000220:Adaptation, Biological; D057231:Climate Change; D016468:Forestry; D018745:Genome, Plant; D006824:Hybridization, Genetic; D010641:Phenotype; D028222:Picea / Q000033:anatomy & histology / Q000235:genetics / Q000502:physiology*; D012641:Selection, Genetic
keywords: adaptive introgression; bounded hybrid superiority; breeding; climate change; exogenous selection