Geographical and environmental gradients shape phenotypic trait variation and genetic structure in Populus trichocarpa

• Published in: The New phytologist Vol. 201; no. 4; pp. 1263 - 1276
• Main Authors: McKown, Athena D., Guy, Robert D., Klápště, Jaroslav, Geraldes, Armando, Friedmann, Michael, Cronk, Quentin C. B., El‐Kassaby, Yousry A., Mansfield, Shawn D., Douglas, Carl J.
• Format: Journal Article
• Language: English
• Published: England New Phytologist Trust 01-03-2014; Wiley Subscription Services, Inc
• Subjects: Biomass; British Columbia; Circadian rhythm; Circadian rhythms; Climate; clinal variation; Correlation; Daylength; Ecological genetics; Ecophysiology; Elevation; Environment; Environmental gradient; Evolutionary genetics; Gas exchange; Gene Ontology; Genes; Genes, Plant; Genetic analysis; Genetic diversity; Genetic structure; Genetic variability; Genetic variation; Genotypes; Geography; Gradients; Growth rate; Growth traits; Heat exchange; Heritability; Inheritance Patterns - genetics; Isotopes; landscape genetics; latitude; Nucleotides; Phenology; Phenotype; Phenotypic traits; Phenotypic variation; Phenotypic variations; Photoperiod; Photoperiods; Polymorphism, Single Nucleotide - genetics; poplar (Populus trichocarpa); Population genetics; Population structure; Populus - genetics; Populus trichocarpa; Principal Component Analysis; Principal components analysis; Provenance; Quantitative Trait, Heritable; Single-nucleotide polymorphism; British Columbia; biomass; latitude; phenology; clinal variation; landscape genetics; photoperiod; ecophysiology; poplar (Populus trichocarpa)
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.12601

Populus trichocarpa is widespread across western North America spanning extensive variation in photoperiod, growing season and climate. We investigated trait variation in P. trichocarpa using over 2000 trees from a common garden at Vancouver, Canada, representing replicate plantings of 461 genotypes originating from 136 provenance localities.
We measured 40 traits encompassing phenological events, biomass accumulation, growth rates, and leaf, isotope and gas exchange-based ecophysiology traits. With replicated plantings and 29 354 single nucleotide polymorphisms (SNPs) from 3518 genes, we estimated both broad-sense trait heritability (H
2) and overall population genetic structure from principal component analysis.
Populus trichocarpa had high phenotypic variation and moderate/high H
2 for many traits. H
2 ranged from 0.3 to 0.9 in phenology, 0.3 to 0.8 in biomass and 0.1 to 0.8 in ecophysiology traits. Most traits correlated strongly with latitude, maximum daylength and temperature of tree origin, but not necessarily with elevation, precipitation or heat: moisture indices. Trait H
2 values reflected trait correlation strength with geoclimate variables. The population genetic structure had one significant principal component (PC1) which correlated with daylength and showed enrichment for genes relating to circadian rhythm and photoperiod.
Robust relationships between traits, population structure and geoclimate in P. trichocarpa reflect patterns which suggest that range-wide geographical and environment gradients have shaped its genotypic and phenotypic variability.